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Greying of the human hair: A worldwide survey, revisiting the '50' rule of thumb
Abstract
Summary Background While numerous papers have reported on the biological mechanisms of human hair pigmentation and greying, epidemiological descriptions of both natural hair colour and the greying process, worldwide, remain scarce.
Objectives To assess hair colour and greying in a large world sample of human subjects, and to revisit the validity of the 50/50/50 rule of thumb, which states that ‘at age 50 years, 50% of the population has at least 50% grey hair’.
Methods The natural hair colour of 4192 healthy male and female volunteers was assessed using a sensorial expert evaluation through the comparison of each volunteer’s hair with standard swatches. Hair colour was studied according to age, gender and ethnic or geographical origin.
Results Overall we observed that between 45 and 65 years of age, 74% of people were affected by grey hair with a mean intensity of 27%. Men harboured significantly more grey hair than women. Both age at onset and rate of greying with age appeared to be clearly linked to ethnic/geographical origin. Subjects of Asian and African descent showed less grey hair than those of caucasian origin, at comparable ages, confirming previously reported data.
Conclusions Calculating the percentage of people showing at least 50% grey hair coverage at age 50 years leads to a global range of 6–23%, according to ethnic/geographical origin and natural hair colour: well below that expressed by the ‘50’ rule of thumb.
... This is because the genetic background and natural hair color of different races vary, and the time at which the results of hair graying become apparent varies [73]. Although natural hair color and brightness vary by race, there is no evidence that graying occurs more frequently or intensely in certain races [19]. ...
... In many races, men tend to develop gray hair earlier and more extensively than women of similar age [19]. Graying patterns also vary by gender [19,78]. ...
... In many races, men tend to develop gray hair earlier and more extensively than women of similar age [19]. Graying patterns also vary by gender [19,78]. In men, hair graying tends to occur first and is more prominent in the temporal region (the sides of the head). ...
This review aims to gain insight into the major causes of hair graying (canities) and how plant-derived extracts and phytochemicals could alleviate this symptom. Research articles on human hair graying were searched and selected using the PubMed, Web of Science, and Google Scholar databases. We first examined the intrinsic and extrinsic factors associated with hair graying, such as the reduced capacity of melanin synthesis and transfer, exhaustion of melanocyte stem cells (MSCs) and melanocytes, genetics and epigenetics, race, gender, family history, aging, oxidative stress, stress hormones, systematic disorders, nutrition, smoking, alcohol consumption, lifestyle, medications, and environmental factors. We also examined various plants and phytochemicals that have shown a potential to interfere with the onset or progression of human hair graying at different levels from in vitro studies to clinical studies: the extract of Polygonum multiflorum and its major components, 2,3,5,4′-tetrahydroxystilbene-2-O-β-D-glucoside and emodin; the extract of Eriodictyon angustifolium and its major flavonoid compounds, hydroxygenkwanin, sterubin, and luteolin; the extracts of Adzuki beans (Vigna angularis), Fuzhuan brick tea (Camellia sinensis), and Gynostemma pentaphyllum; bixin, a carotenoid compound found in Bixa orellana; and rhynchophylline, an alkaloid compound found in certain Uncaria species. Experimental evidence supports the notion that certain plant extracts and phytochemicals could alleviate hair graying by enhancing MSC maintenance or melanocyte function, reducing oxidative stress due to physiological and environmental influences, and managing the secretion and action of stress hormones to an appropriate level. It is suggested that hair graying may be reversible through the following tactical approaches: selective targeting of the p38 mitogen-activated protein kinase (MAPK)–microphthalmia-associated transcription factor (MITF) axis, nuclear factor erythroid 2-related factor 2 (NRF2), or the norepinephrine–β2 adrenergic receptor (β2AR)–protein kinase A (PKA) signaling pathway.
... 6,7 Also, Africans are reported to grey later than Caucasians with respect to late-onset hair greying (HG). 1,8 While the average age of onset of HG in Africans is 43.9 years, in Caucasians, it is 34.0 years. 1 The cause of HG is unknown, but it is attributed to decreased melanogenesis and defective melanosomal transfer in hair follicles. 2,9 The risk factors identified for HG include chronological age, smoking, alcohol, oxidative stress, metabolic diseases, trace elements and stress. ...
... 4 Panhard et al in their worldwide survey of HG concluded that, at age 50 years, 6-23% of individuals would have HG. 8 Clinically, the most common anatomical location of HG is the temporal region in 83.7%, followed by the parietal (64.2%), frontal (60.8%) and occipital (58.4%) in descending order. 4 Hair dyeing to camouflage HG is common in individuals with HG, especially if it is PHG.14 Jo et al. ...
... 4,13,14 This study outcome confirms the increase in chronological age as one of the factors responsible for HG. 9 The prevalence of HG was higher in males than females, similar to the study reports from other epidemiological studies. 4,8,13 These studies were conducted in participants of different races and had the same gender outcome. Further studies to ascertain the reasons for a predominant male HG may be required. ...
Objective:
To document the epidemiological, clinical characteristics, believed triggers and associated behaviour in hair greying.
Design:
A community based cross-sectional descriptive study was conducted in February 2020 following ethical approval and written informed consent from participants. All participants were clinically evaluated for hair greying, its pattern and location on the scalp. Socio-demographic data were documented. Data was entered and analyzed using the IBM statistics software version 22. Numerical and categorical variables are presented.
Setting:
The study was conducted at an urban market in Lagos, Nigeria.
Participants:
The study participants comprised 307 adult traders.
Results:
The mean age of the 307 participants studied was 42.7±12.8 years. The prevalence of hair greying was 47.6% (51% in males and 45.9% in females). The median (IQR) age of those with grey hair was 52 (44, 59) years. The prevalence of hair greying was 14.8% in those aged 30-34 years and 97.2% in those aged 60 years and above. The prevalence of premature greying was 17.7% and greying before friends and family members was reported at 19.9% and 13%, respectively. Grey hair was diffuse in 81.5%; localized to the frontal area of the scalp in 55.5%. Use of hair dye was noted in 15.8%.
Conclusion:
Hair greying is common in the study population. The age at onset is 30 years. Premature hair greying is uncommon in Nigeria. More epidemiological studies of hair greying especially of premature hair greying are needed.
Funding:
Funding for this study was provided by the L'Oreal African Hair & Skin Research Grant.
... 5 A large population based study reported that 6 to 23% of people have 50% gray hair by 5th decade of life. 6 Exact etiology of graying remains incompletely understood. PGH can occur as an autosomal dominant primary disease. ...
... Definition of premature graying with respect to the indian population is lacking, we have selected a cut-off age of 25 years; the rationale being that average age of onset of grey hair is in the late 30s among Asian population. 6 Modified and prevalidated questionnaire based on the DLQI proposed by Finley and Kahn, was used to assess the QoL in patients. 10 The questionnaire consisted of 10 questions; each having 4 response options graded from 0 to 3 (0 being no effect; 1-minimal effect; 2-moderate effect; and 3-severe effect). ...
... 11 The average age of onset of grey hair is in the mid-30s among Caucasians, late-30s among Asian population, and in the mid-40s among Africans population. 6 The mean age of the participants in our study was 16 12,13 Majority of affected patients were in the range of 11-20 years. The mean duration of canities was 1.62 years at the time of presentation (SD±1.18) in our study, while Bhat et al noted that average duration of premature canities at time of presentation was less than 5 years; which suggests its impact on QoL and increasing trend of seeking early medical intervention. ...
p> Background: Quality of life in patients with premature graying of hair is an under studied topic in Indian population. Its onset in adolescence may have a significant effect on the developing psyche of an individual sufferer impairing academic and work related performance and can be associated with low self esteem, low confidence which can further be associated with depression. Aim was to objectively evaluate the impact of premature canities on QoL and early identification of patients in need of medical and psychological intervention.
Methods: The impact on QoL was calculated with the help of a modified and prevalidated questionnaire based on the dermatology life quality index proposed by Finley and Kahn. One hundred patients with onset of canities before the age of 25 years were enrolled, after approval by the institutional ethical committee.
Results: The mean modified DLQI score recorded was 14.3±6.76. Total of 71% patients were found to have a very large to extremely large effect on the QoL. Guilt, mood fluctuation and need for medical intervention were reported frequently. The comparison between DLQI scores of boys and girls was not significant.
Conclusions: Patients of premature canities were found to have profound impact on their QoL, attributable to their perception of the disease. Considering the age group affected, it could have a long‑term detrimental effect on their psychological and social wellbeing.
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... Due to variations in the structural characteristics across different ethnicities, the aging process of hair can vary extensively ( Table 1). A study by Panhard et al. revealed that African, Thai, and Chinese individuals with darker hair tones tend to experience gray hair less frequently and with less intensity compared to individuals with lighter hair shades, such as Caucasians, who are of similar ages [3]. More specifically, the incidence of graying among sub-Saharan African individuals was found to be 43%; among Thai individuals, 67%; and among Chinese individuals, 69%. ...
... More specifically, the incidence of graying among sub-Saharan African individuals was found to be 43%; among Thai individuals, 67%; and among Chinese individuals, 69%. Comparatively, the incidence of graying among Europeanderived Caucasian individuals was found to average 82% [3]. The average age of onset for hair graying varies by ethnicity, with Caucasians generally starting to gray in their mid-30s, Asians in their late 30s, and Africans in their mid-40s [4]. ...
... From an extensive population study of 4,192 males and females aged between 45 and 65 years old from all over the world, Panhard et al. [2012] showed that in men, the temporal region has an incidence of 75% of gray hairs, compared to 67% on the vertex and 58% on the occipital area. The temporal region is the earliest to be affected, spreading to the vertex and then to the rest of the head [Tobin 2008]. ...
... In this case, the hair could have a different appearance than the one provided by our model at the same age. Also, our model does not account for the ethnic origin of our character, a property that could influence the rate of graying, as presented by Panhard et al. [2012]. Finally, we address some limitations of our work. ...
Hair rendering has been a focal point of attention in computer graphics for the last couple of decades. However, there have been few contributions to the modeling and rendering of the natural hair aging phenomenon. We present a new technique that simulates the process of hair graying and hair thinning on digital models due to aging. Given a 3D human head model with hair, we first compute a segmentation of the head using K-means since hair aging occurs at different rates in distinct head parts. Hair graying is simulated according to recent biological knowledge on aging factors for hairs, and hair thinning decreases hair diameters linearly with time. Our system is biologically inspired, supports facial hair, both genders and many ethnicities, and is compatible with different lengths of hair strands. Our real-time results resemble real-life hair aging, accomplished by simulating the stochastic nature of the process and the gradual decrease of melanin.
... The time of onset of hair greying varies between individuals, as well as between individual hair follicles, based on genetic and other biobehavioral factors (Akin Belli et al., 2016;Bernard, 2012). But most people experience depigmentation of a progressively large number of hair shafts (HSs) from their third decade onward, known as achromotrichia or canities (Panhard et al., 2012). The color in pigmented HSs is provided by melanin granules, a mature form of melanosomes continuously supplied to the trichocytes of the growing hair shaft by melanocytes of the hair follicle pigmentary unit (HFPU) (Tobin, 2011). ...
... Scaling this model to hair populations with thousands of hairs, the simulation reports trajectories of greying for individual hairs, as well as a graph with the population distribution of white hairs (shown as frequency distributions) for a theoretical scalp. First, we simulated the average greying trajectory based on data indicating that the average age of onset for greying is age 35 and that white hairs reach a 40% population frequency at age 65 (Panhard et al., 2012). This established a set of default parameters that yielded the greying trajectory shown in Figure 5C. ...
Background: Hair greying is a hallmark of aging generally believed to be irreversible and linked to psychological stress.
Methods: Here, we develop an approach to profile hair pigmentation patterns (HPPs) along individual human hair shafts, producing quantifiable physical timescales of rapid greying transitions.
Results: Using this method, we show white/grey hairs that naturally regain pigmentation across sex, ethnicities, ages, and body regions, thereby quantitatively defining the reversibility of greying in humans. Molecularly, grey hairs upregulate proteins related to energy metabolism, mitochondria, and antioxidant defenses. Combining HPP profiling and proteomics on single hairs, we also report hair greying and reversal that can occur in parallel with psychological stressors. To generalize these observations, we develop a computational simulation, which suggests a threshold-based mechanism for the temporary reversibility of greying.
Conclusions: Overall, this new method to quantitatively map recent life history in HPPs provides an opportunity to longitudinally examine the influence of recent life exposures on human biology.
Funding: This work was supported by the Wharton Fund and NIH grants GM119793, MH119336, and AG066828 (MP).
... Regarding the evolution, the stability of the disease, and the follow-up of the treatment by the patients, the results are essentially similar to the data Skin condition: The appearance of gray hair is frequent in patients with vitiligo and their families (36). A large populationbased study reported that 6-23% of people have 50% gray hair by 50 years of age (37). The presence of gray hair in patients with vitiligo probably is linked to common causes of developing the disease like stress, oxidative stress, autoimmunity, and low B vitamin levels (38,39). ...
Background
In this study, we aimed to investigate and analyze the clinical and sociodemographic features and possible correlation with factors associated with the development of vitiligo in a cohort of patients suffering from this disease in the central region of Romania.
Methods
Patients diagnosed with vitiligo from private outpatient clinics in the region and from the outpatient clinic of the Dermatology Clinic in Târgu Mureş participated in the study. The study period was between March 2021 and March 2022. Both sets of patients adhered to the same specified inclusion and exclusion criteria. Included just patients who received a complete dermatological clinical examination. They were asked by experienced physicians about epidemiological and clinical data of the disease, using the questions about vitiligo from the validated questionnaire edited by the Vitiligo Research Foundation from the United States of America. The patients who were given incomplete responses were excluded. This questionnaire contains 30 questions with multiple answers, about the patients with vitiligo, divided into seven subgroups as follows: group 1. Origins (demographic data), 2. History of vitiligo, 3. Vitiligo description, 4. Vitiligo treatments, 5. Skin condition, 6. Other conditions (comorbidities), 7. Impact (cost of treatments). Our study consisted of 114 patients, all of whom were Caucasians with Fitzpatrick skin types ranging from I–III.
Results
We have analyzed the found data and compared the result with the data found in the literature. Most of the clinical and epidemiological characteristics of vitiligo in our patients were similar to those in other studies. A few of the characteristics linked to the possible appearance of the disease were present in higher percentages like the presence of the disease in the family, lighter color of the eyes, gray colored hair, the presence of the halo naevus, the predisposition to sunburn, the skin trauma as starting cause and the presence of increased level of thyroid disease.
Conclusion
Based on our results, we can conclude a profile of a potential patient who can develop vitiligo. To our knowledge, this study is the first of its kind from our country, however, our inferences remain limited by the single center, a relatively small sample size, recall bias, and a self-decided classification of some clinical aspects, which are potential limitations of this study.
... Few authors have suggested that 25 years can be used as a cut off for people in the Indian subcontinent [2] . A large population-based study reported that 6%-23% of people have 50% grey hair by 50 years of age [3] . The colour of human hair is due to pigment melanin produced by melanocytes which are neural crest derivatives. ...
The term "Premature greying of hair" (PGH) refers to the greying of hair that occurs in Caucasians before the age of 20, and in African Americans before the age of 30. It has the potential to significantly lower an individual's self-esteem. The exact etiopathogenesis is uncertain, but it has been linked to premature ageing problems, atopy, and autoimmune diseases. In the Unani System of Medicine, the exact cause of Shayb (PGH) is the disturbance in the function of Quwwat-e-Ghādhiya (Nutritive Power), Ḍu 'f-e-Hazm (weak digestion) and Predominance of Khilt-e-Balgam etc. A male patient aged 27 years having complained of Premature greying of hair for 12 years, visited GOPD, RRIUM Mumbai. On taking detailed history there was no family history and systemic disorder. The diagnosis of moderate PGH was established based on the Hair whitening Score. Unani Formulation Jawarish Shahi with Kushta-e-Faulad and Itrifal Ustukhuddos were prescribed for ten weeks. The patients show significant improvement in the hair whitening score at the end of the study.
... Also in natural aging there is a "50" rule of thumb (at least 50% of individuals have 50% gray hair by the age of 50 years) published in 2012. [20] The cause of premature graying is more correlated with the release of oxidants, which can also be released from stress, which cause damage to bulge region and as well to melanocyte precursor cells like SOX10PAX3, SOX10, DCT and their receptors like TYR, TYRP1, MITF, PAX3, POMC, KIT. [26,31] This was shown in mice as markedly decreased cells and receptors in un-pigmented mid-segments of hair compared with their pigmented segments by Ying Shi et al. [21] Among 250 cases of androgenic alopecia 7.2 percent had anxiety and 11.2 percent had depression. ...
INTRODUCTION: World Health Organization (W.H.O.) defines health as a complete state of physical, mental and social well-being not merely an absence of disease or infirmity. Functional or psychological disorders are on a rise with the modernization and industrialization. In this study we have correlated anxiety and depression which are the two most important psychological diseases with four common hair disorders alopecia areata, androgenic alopecia, telogen effluvium and premature graying of hair. BODY TEXT: We took five hundred cases between the age of 18 and 45 years, of the four hair disorders alopecia areata, androgenic alopecia, telogen effluvium and premature graying of hair and screened them for anxiety and depression by Hospital Anxiety and Depression Score (HADS) for anxiety and depression. Scale is reprinted in table 1. We also analysed anxiety and depression in otherwise healthy population of same area after eliminating regional, age and sex bias and tabulated and compared the result. Data were analyzed by SPSS ver. 22.0 software, independent T-test, multi variate analysis of covariance (MANCOVA) and chi-square test for comparison the quantitative and ordinal data, respectively; with α < = 0.05. RESULT AND DISCUSSION: There was significant correlation of anxiety and depression with the above four common hair disorders correlating with the p of value less than 0.05. Brain- hair follicle axis and stress-skin system are still being studied. Many theories have been given by studies in mice. Hereby, clinical implications of these theories corroborate with our study of five hundred subjects. CONCLUSION: Any patient should be treated as a whole and skin and hair can be important signs of mental illness which decrease the quality of life and work efficiency. Hence, in common disorders like androgenic alopecia, telogen effluvium, premature graying of scalp hair and alopecia areata, a vigilant approach is needed to diagnose and treat anxiety and /or depression as well.
... Males were observed to be prone to canities more often than females though the association with sex has shown that there are no gender differences which implies that the prevalence of canities is not sexual based but rather males were observed more with both premature and nonpremature canities. The finding is consistent with the previous study by Panhard et al., [15] who in their report on the African population have stated no sexual differences. ...
Background: Canities, or graying or whitening hair, is a natural part of aging caused by reduced melanin production. Premature canities occur in humans or animals at a young age, with factors such as genetics, lifestyle, and environmental influences contributing. The study aims to evaluate the relationship between ABO Blood type, rhesus Factor, Genotype, Lifestyle, and Premature canities. Methods: 259 respondents were involved and a cross-sectional descriptive study design was used to generate data. The respondents were selected using a multi-stage random sampling techniques and data collection was via descriptive questionnaire. Data obtained were analyzed using IBM SPSS version 25. Results: A study of 259 participants found no significant association between premature canities and ABO blood type, rhesus, and genotype while lifestyle factors like smoking, and alcohol intake showed an association. Canities were found in various head regions, with no differences between sexes. Smoking and alcohol intake were more common in males. Depression was negatively associated with non-premature and premature canities. Nutrition intake was similar, but high carbohydrate and vegetable consumption was found to be statistically different. Conclusion: No association between ABO blood type, rhesus factor, genotype with premature canities, and lifestyle (alcohol intake and smoking) showed possible association with premature canities.
... Epidemiological studies have shown that the prevalence of hair graying increases with age, with a substantial proportion of individuals experiencing some degree of graying by their 50s or 60s. While hair graying is predominantly associated with chronological aging, there is considerable variation, both inter-individual and based on genetic background, in the onset and progression of graying [5,6]. Hair graying is a multifaceted process influenced by a combination of genetic, environmental, and age-related factors [7][8][9][10][11][12]. ...
Hair graying, also known as canities or achromotrichia, is a natural phenomenon associated with aging and is influenced by external factors such as stress, environmental toxicants, and radiation exposure. Understanding the mechanisms underlying hair graying is an ideal approach for developing interventions to prevent or reverse age-related changes in regenerative tissues. Hair graying induced by ionizing radiation (γ-rays or X-rays) has emerged as a valuable experimental model to investigate the molecular pathways involved in this process. In this review, we examine the existing evidence on radiation-induced hair graying, with a particular focus on the potential role of radiation-induced cellular senescence. We explore the current understanding of hair graying in aging, delve into the underlying mechanisms, and highlight the unique advantages of using ionizing-irradiation–induced hair graying as a research model. By elucidating the molecular pathways involved, we aim to deepen our understanding of hair graying and potentially identify novel therapeutic targets to address this age-related phenotypic change.
... Recent epidemicologic studies of men and women of different ethnicities found that 74% of adults between the ages of 45 and 65 had grey hair, with a mean intensity of 27%. . (1) ...
... Physiological hair graying may follow the "three-fifty rule"; specifically, approximately 50% of patients at the age of 50 years have at least 50% white hair. 28 The general mechanism of melanin synthesis involves a complicated chemical reaction, 29 during which a large number of ROS are produced. 30 As aging progresses, antioxidant substances, including catalase, glutathione and SOD, are downregulated. ...
Objectives:
To explore the relationship between melanocyte stem cells in the hair follicle bulge and hair graying so as to fully understand their key role in the pathogenesis of hair graying.
Methods:
The published articles about "hair graying, hair color, pigmentation disorders" and "melanocyte stem cells, melanocyte" were searched and analyzed in PubMed to explore their relationship.
Results:
Melanocytes in hair bulb are involved in the pathogenesis of hair graying as well as the melanocyte stem cells in hair follicle bulge also play important roles in the formation of hair graying through some ways.
Conclusion:
Loss of melanocyte stem cells in hair follicle bulge is one of the main reasons of hair graying, and more researches are needed to explain the underlying mechanisms of ectopic differentiation of melanocyte stem cells in different individual.
... Hair greying is a common and ubiquitous feature of human aging. 1 Although the rate of hair greying varies among individuals, almost all males and females experience depigmentation of hair shafts with age. Because the color in hair shafts is provided by melanin granules, which are supplied to the trichocytes of growing hair shafts by melanocytes, 2 agerelated hair greying is thought to involve some dysfunction to these processes. ...
Depigmentation of hair shafts is a hallmark of human aging. However, it remains unclear how aging causes human hair to grey. Here, we found that a single session of hair plucking via waxing causes hair to grey in castrated mice. Moreover, this hair greying continued for several hair cycles. Given that androgen secretion decreases with age in both male and female humans, the present result suggests that this decrease may contribute to age-related hair greying. In addition, our experimental procedure may represent an effective way to generate a new mouse model of hair greying without the need for genetic engineering.
... Typically, white people start going grey in their mid-30s, Asians in their late 30s and African-Americans in their mid-40s. [8] Hair is said to grey prematurely, only if greying occurs before the age of 20 years in Whites, before 25 years in Asians and before 30 years in Africans. [9] Greying is believed to have a multifactorial etiology which includes genetic component, environmental factors, nutritional factors, oxidative stresses etc. ...
Background and objectives:
Greying of hair is a regular feature of chronological aging that occurs in all regions and races. Premature canities is defined as minimum of five grey hairs in a person less than 20 years in Whites, 25 years in Asians, and 30 years in Africans. Premature canities is a common yet incompletely understood dermatological entity. This study aims at finding any association between premature hair greying (PHG) and parameters like hemoglobin (Hb), ferritin and calcium levels as well as its clinical profile.
Methodology:
This was a hospital-based cross-sectional analytical study conducted in the Department of Dermatology and Venereology, Trivandrum over one and half years. The study population consisted of 40 cases and 40 controls. Severity assessment, calculation of body mass index, and estimation of hemoglobin, serum ferritin, calcium, Random blood sugar, Anti Thyroid Peroxidase antibody, T3, T4, and TSH were done.
Results:
The mean age of the 40 patients was 17.14 years and most patients had onset of greying between 16 and 20 years. The male to female ratio was 1.2:1. A positive family history with a paternal predominance was noted. Vertex was the most common site of onset (42.5%), diffuse pattern was the most common clinical pattern (47.5%) and 60% had involvement of mild grade. Fourteen patients (35%) had abnormal investigations reports, in terms of low ferritin levels in 7 (17.5%), low calcium in 4 (10%) and a low Hb levels in 3 (7.5%) patients. Six (15%) patients had raised Anti TPO values. The association of PHG with low ferritin and raised anti-TPO levels were statistically significant.
Conclusion:
Low serum ferritin and raised Anti TPO levels may have a role in premature hair greying.
... [2] Access this article online A recent study reported that 6-23% of people develop 50% of gray hair by 50 years of age. [3] In Ayurveda, Palitam (graying) which occurs in early stages of life can be termed as Akala Palitam (premature graying). It is a pathological condition where discolouration of hair is attributed by the predominant Dosha. ...
Hair color reflects the health of an individual and the discolored hair indicates the pathological state. Palitam is a physiological process when it occurring in old age. Whereas Akala Palitam (premature graying) is a pathological condition manifests in early stages of life. It is characterized byVivarna Kesha (discolored hair) along with altered hair texture and the predominant Dosha attributes Vivarnata to Kesha. Hair color is determined by a pigment called melanin (relative proportions of eumelanins and phaeomelanins) in hair follicles. Diffuse loss of hair melanin during early stages of liferesults in premature graying. In Ayurveda, Bhrajaka Pitta, one among the five types of Pitta located in skin is responsible for the attribution of hair colour. Thus it performs the function similar to melanin pigment in hair follicles. When there is Pitta dosha Vridhi in Rasadhatu along with vitiation of other two Doshas it leads to manifestation of Vivarna Kesha with altered hair texture thus results in Akala Palitam. It is a type of Raspradoshajavikara in which the signs and symptoms varies based on the predominant Dosha. Treatment option for Akala Palitam is also specific based on predominant Dosha. So a critical evaluation on Akala Palitam is essential to understand the etio-pathogenesis of the disease for its better management.
... In a more recent large survey, however, Panhard et al. reported that only 6-23% of the people have 50% hair by the age of 50 years. [1] e term premature hair graying (PHG) is generally used in different literature reviews when the onset of graying is before the age of 20-25 years in Caucasians, 25-30 years in Asians including Indians, and late 30's in Blacks. PHG is determined by genetic factors, i.e., hypothesized to be inherited as an autosomally dominant trait, [2] environmental factors, and can also be seen in nutritional disorders, or pathological conditions such as osteopenia, cardiac disorders among others. ...
Authors have attempted to provide a short concise and clinically relevant review on premature graying of hairs with the focus of updated pathogenesis, rational investigations, and treatment options. Premature graying of hairs is a fairly common clinical condition faced by dermatologists, however, very scarce therapeutic options are available for successful management of gray hairs. The role of antioxidants is not yet established firmly in the therapeutic armamentarium of premature graying of hairs. Authors have summarized the currently available therapeutic options for the treatment of premature graying of hairs.
... The mean age of senile graying for Caucasians (whites) is mid-30s; for Asians of the late 30's; and for Africans of mid-40s. There is a practical declaration which states that at the age of 50, 50% of the population has 50% gray hair (rule of thumb) [4]. The gray of age varies according to race and ethnicity. ...
BACKGROUND: Gray hair is a physiological process of aging that occurs in everyone. Premature hair graying (PHG) is the term when early hair gray at an unusual age. The causes of PHG are multifactorial, genetic, nutritional, and environmental, including oxidative stress. Free radicals caused interference with cellular responses that cause direct damage to various proteins and DNA in the long term. The body’s defense mechanisms likely antioxidant enzymes, including catalase, glutathione peroxidase (GPx), and superoxide dismutase (SOD) was activated against free radicals. AIM: We aimed to evaluate markers of oxidative stress and associated with severe graying at young age. MATERIALS AND METHODS: We recruited consecutive 40 respondents with PHG and healthy controls, male sex and aged <25 years. The severe graying was graded with total of gray hair. The serum samples were collected to detect oxidative stress markers through malondialdehyde (MDA), SOD, catalase, and GPx measurement with enzyme-linked immunosorbent assay. RESULTS: Serum MDA concentration was higher but not significantly (p > 0.05), while serum SOD, catalase, and GPx level, indicators of antioxidant were significantly lower (p < 0.001, p = 0.017 and p < 0.001, respectively) in PHG compared to controls. The correlation between oxidative stress and graying severity was not significant (p > 0.05), but the association between onset and severity of graying was significant (p < 0.001). CONCLUSIONS: Respondents with PHG had increased of pro-oxidants and decreased of antioxidants compared than controls. The severity of graying is equivalent to the level of oxidative stress. The supplement of antioxidants is likely recommended in PHG.
Hair is an important personal attribute defined by the person’s natural hair shape, form and colour as well as by age and health. The hair of Black women has a specific curly texture that has been commonly manipulated to resemble straighter European hair, following centuries of oppressive beauty norms. The biological hair aging also presents challenges to some women due to the traditional social constructs of beauty and the persistent pressure on women to maintain their appearance. This interdisciplinary study explores the evolution of hair management practices of Black women from age-related biological, personal, social and well-being perspectives. A mixed methods approach was adopted, based on an online survey (n = 46) followed by in depth semi-structured interviews (n = 10). A statistically significant shift towards less frequent use of complex hair styles and visits to the hairdressers over a 30-year period was found, but frequency of hair colouring was not impacted. Three main qualitative themes were identified: 1) managing hair greying represented an important age-related negotiation of personal and social identity; 2) curly hair texture remained a strong personal and cultural identity symbol in light of historical dominance of Eurocentric hair beauty standards and hair-based discrimination; and 3) subjective well-being was strengthened by increased confidence in one’s personal hair aesthetics and better-informed choices about hair management. Overall, age did not diminish the desire to maintain good hair. Increasing the visibility of older Black women’s hair will further support their capacity to negotiate their presence and participation in social and professional contexts and to enhance their subjective well-being.
Premature hair graying (PHG) is the early loss of natural hair color, influenced by genetic, biological, and environmental factors. This review discusses the significant psychological impacts of PHG and explores its underlying mechanisms, related health conditions, and available treatments. The review examines the roles of genetics, oxidative stress, and lifestyle factors such as smoking and diet in premature graying. It also considers associated medical conditions and current and emerging treatment options. This overview aims to improve understanding of PHG and its broader implications.
Human hair, particularly on the scalp, serves as a significant aspect of social identity and well-being. The exposome, encompassing both intrinsic and extrinsic factors, plays a fundamental role in hair weathering. Intrinsic factors include genetic predispositions and physiological changes within the body, while extrinsic factors comprise environmental exposures such as UV radiation, pollution, humidity, temperature variations, lifestyle choices, and chemical treatments. These elements collectively contribute to the cumulative damage experienced by hair over time. Understanding the comprehensive impact of the exposome on hair health and hair aging necessitates an exploration of various environmental conditions, lifestyle factors, and technical artifacts. Despite advancements in research, the intricate mechanisms underlying the exposome influence on hair remain incompletely understood. Through a comprehensive review of current literature and emerging research findings, this study aims to enhance the understanding of exposome impact on hair health.
People nowadays are very much concerned about their appearance and personality traits. Among these, hair colour plays an imperative role in overall look and adds to aesthetic value in this modern era of cosmetology mutiny. Hair graying whether timely or premature has a direct pessimistic impact on one’s social well-being. However, in latter the management of hair graying is believed to have significant and direct impact on the quality of life in adolescents. The hair cycle responsible for pigmentation of hairs is dependent on multiple factors viz. enzymes, pH, excessive stress, hormones, hereditary causes, sedentary lifestyle and nutritional deficiencies. Of these, if considered carefully, macronutrients and micronutrients obtained from diet in human body are playing an immense role directly or indirectly in normal hair cycle. A caloric deprivation or deficiency of these dietary components can lead to structural abnormalities in hair as well as pigmentation changes. In this review, an effort is being made to understand the role of various vitamins, minerals, proteins and antioxidants in canities. A broad literature search of PubMed and Google Scholar was performed to compile the information available in research as well as review articles. As per the available data, it can be suggested that there is direct relationship between the low levels of copper, iron and vitamin B12 and PHG. However, reaching a defined conclusion seemed unlikely because of limitations in studies related to the above-mentioned scenario.
The review highlights the available published data on the etiopathogenesis of early graying, hair involution and restoration methods. Early graying of hair is defined as settlement before the age of 20 in Caucasians, before the age of 25 in Asians and before the age of 30 in Africans. In etiopathogenesis, an imbalance between oxidative stress and the antioxidant system is considered as the leading mechanism, a significant role is played by genetic predisposition, hormonal disorders of the thyroid gland, acute stress; the causes may also be deficiency of vitamin B12, copper, iron. Currently, the active molecule palmitoyl tetrapeptide-20 is used to prevent pigment loss and restore it. The endocannabinoid system in the hair follicle is also considered as a target for stimulation during the restoration of hair growth.
This chapter reviews acquired hair disorders, including common scarring and non‐scarring alopecia presentations, conditions characterised by excessive body hair growth and acquired hair shaft disorders. We also describe the biology of normal hair follicles, including structure, hair cycle control and immunity, to better understand the mechanisms underlying these conditions. We present methods for clinical assessment, recommended investigation and management of each disease, and present summaries of frequently used therapeutics and cosmetic options employed when treating these problems.
This study aims to investigate human hair color perception through two empirical studies in the context of colored hair. The preliminary study was intended to establish a numerical representation of perceptually meaningful brightness levels. It identified that the brightness level was proportional to the power of 0.766 of L*. In the visual assessment, participants (N = 47) categorized 246 hair color samples into eight color hue groups aligned with the Munsell system. Hue judgment was conducted by visually comparing dyed hair tresses with natural black hair. Based on the L*, a*, and b* values of hair tresses and visual assessments thereof, we observed the ranges of hue categories for hair color alongside the brightness levels. Additionally, the differences between the Munsell hue names and the assessment results were compared. Predominantly influenced by the dark brown hair color, the neutral orientation was shifted to the first quadrant of the a*-b* plane. The study contributes to an understanding of human hair color perception and provides insights into color categorization and labeling, especially when the context is confined.
Background
Considering the paramount significance of hair in life, greying hair at a young age can be extremely distressing. In addition, an incompletely understood aetiology and scarcity of treatment options make premature hair greying (PHG) noteworthy.
Aims
We aimed to estimate the prevalence of PHG in medical college students from Rajasthan, India, and any sociodemographic and lifestyle correlates of PHG and to determine its effect on the quality of life (QOL).
Patients and Methods
A cross-sectional study was conducted amongst 295 students of a medical college in western Rajasthan, India, under the age of 25 years. A scalp examination was done to count grey hair. All factors were investigated using structured, pre-validated questionnaires.
Results
The prevalence of premature greying of hair was 41.4%. Sociodemographic factors such as older age, rural residence and positive family history were significantly associated with PHG. The number of meals, fruit consumption and irregularity of meals were the lifestyle factors associated with PHG. The QoL of 54.1% of students with grey hair was poor; males and rural residents were more affected.
Conclusions
Premature greying of hair is a fairly prevalent condition in medical college students affecting their QoL. Factors such as family history, age, residence and eating habits may predispose students to PHG.
Aging is a complex natural process that leads to a decline in physiological functions, which is visible in signs such as hair graying, thinning, and loss. Although hair graying is characterized by a loss of pigment in the hair shaft, the underlying mechanism of age-associated hair graying is not fully understood. Hair graying and loss can have a significant impact on an individual's self-esteem and self-confidence, potentially leading to mental health problems such as depression and anxiety. Omics technologies, which have applications beyond clinical medicine, have led to the discovery of candidate hair biomarkers and may provide insight into the complex biology of hair aging and identify targets for effective therapies. This review provides an up-to-date overview of recent omics discoveries, including age-associated alterations of proteins and metabolites in the hair shaft and follicle, and highlights the significance of hair aging and graying biomarker discoveries. The decline in hair follicle stem cell activity with aging decreased the regeneration capacity of hair follicles. Cellular senescence, oxidative damage and altered extracellular matrix of hair follicle constituents characterized hair follicle and hair shaft aging and graying. The review attempts to correlate the impact of endogenous and exogenous factors on hair aging. We close by discussing the main challenges and limitations of the field, defining major open questions and offering an outook for future research.
A case of gray hair nearly 99% was seen to be converted to more than 99% of the pigmented hair, after using full sleeves shirts for 2 years, with 1-year follow-up, with the same results, and on screening the literature, we find it first such case in the world literature of almost complete repigmentation of both the forearms after using full sleeves shirts for 2 years and a follow-up of 1 year.
Hair graying is an early and obvious phenotypic and physiological trait with age in humans. Several recent advances in molecular biology and genetics have increased our understanding of the mechanisms of hair graying, which elucidate genes related to the synthesis, transport, and distribution of melanin in hair follicles, as well as genes regulating these processes above. Therefore, we review these advances and examine the trends in the genetic aspects of hair graying from enrichment theory, Genome-Wide association studies, whole exome sequencing, gene expression studies, and animal models for hair graying with age, aiming to overview the changes in hair graying at the genetic level and establish the foundation for future research. Meanwhile, by summarizing the genetics, it's of great value to explore the possible mechanism, treatment, or even prevention of hair graying with age.
Hair loss in elderly patients is a common complaint. It can be related to different conditions that affect patients' quality of life and represents a challenge for dermatologists. It affects both men and women during the aging process with an estimated percentage of balding after 65 years of age of 53% and 37%, respectively. Androgenetic alopecia, frontal fibrosing alopecia, senile alopecia, and erosive pustular dermatosis of the scalp are the hair diseases most frequently described in this age group. The objective of this review is to summarize the current knowledge about alopecia affecting elderly patients, differentiating between chronological hair aging signs and pathological changes, to help clinicians, offer an adequate management of these disorders to their patients.
Anthropogeny is a classic term encompassing transdisciplinary investigations of the origins of the human species. Comparative Anthropogeny is a systematic comparison of humans and other living non-human hominids (so-called "Great Apes"), aiming to identify distinctly human features in health and disease, with the overall goal of explaining human origins. We begin with a historical perspective, briefly describing how the field progressed from earliest evolutionary insights to the current emphasis on in-depth molecular and genomic investigations of "human-specific" biology and an increased appreciation for cultural impacts on human biology. While many such genetic differences between humans and other hominids have been revealed over the last two decades, this information remains insufficient to explain most distinctive phenotypic traits distinguishing humans from other living hominids. Here we undertake a complementary approach of "comparative physiological anthropogeny", along the lines of the preclinical medical curriculum, i.e., beginning with anatomy and considering each physiological system, and in each case considering genetic and molecular components that are relevant. What is ultimately needed is a systematic comparative approach at all levels from molecular to physiological to sociocultural, building networks of related information, drawing inferences, and generating testable hypotheses. The concluding section will touch on distinctive considerations in the study of human evolution, including the importance of gene-culture interactions.
As one of the earliest and most visible phenomenon of aging, gray hair makes it a unique model system for investigating the mechanism of aging. Ionizing radiation successfully induces gray hair in mice, and also provides a venue to establish an organ-cultured human gray hair model. To establish a suitable organ-cultured human gray HF model by IR, which imitates gray hair in the elderly, and to explore the mechanisms behind the model. By detecting growth parameters, melanotic and senescence markers of the model, we found that the model of 5 Gy accords best with features of elderly gray hair. Then, we investigated the formation mechanisms of the model by RNA-sequencing. We demonstrated that the model of organ-cultured gray HFs after 5 Gy irradiation is closest to the older gray HFs. Moreover, the 5 Gy inhibited the expression of TRP-1, Tyr, Pmel17, and MITF in hair bulbs/ORS of HFs. The 5 Gy also significantly induced ectopically pigmented melanocytes and increased the expression of DNA damage and senescence in HFs. Finally, RNA-seq analysis of the model suggested that IR resulted in cell DNA damage, and the accumulation of oxidative stress in the keratinocytes. Oxidative stress and DNA damage caused cell dysfunction and decreased melanin synthesis in the gray HFs. We found that HFs irradiated at 5 Gy successfully constructed an appropriate aging HF model. This may provide a useful model for cost-effective and predictable treatment strategies to human hair graying and the process of aging.
Hair graying in mice is caused by various injuries such as X-ray radiation and repeated plucking that ultimately damage melanocytes and their stem cells (McSCs). In X-ray-induced hair graying, injuries first manifest as a loss-of-niche function of hair follicular keratinocyte stem cells (HFKSCs) to maintain McSCs. Thus, we hypothesized that HFKSCs could be a practical target to prevent hair graying. Here, we investigated the in vivo effect of the flavonoid hydroxygenkwanin (HGK), which has been shown to exert the best protection on human epidermal keratinocytes against in vitro X-ray-induced cytological effects, using X-ray-induced and repeated hair plucking-induced hair graying mice models. We found that HGK exerted a remarkable effect in preventing hair graying; however, when receptor tyrosine kinase Kit-mutant mice were used, no prevention effect was observed. Therefore, we propose that Kit signaling might be involved in the HGK-induced protective effect against hair graying.
As humans grow older, signs of aging become evident in all the organs of the human body. The first visible signs of aging appear on the skin. The aging skin changes due to a combination of endogenous factors (gene mutations, cellular metabolism, hormonal environment) and exogenous ones (chemicals, toxins, pollutants, UV radiation, smoking, diet, lifestyle). Sun-exposed skin areas will be mostly affected by exogenous factors, presenting as “extrinsic aging”. In contrast, typical changes resulting from endogenous factors are most visible in sun-protected areas and are primarily attributed to individual genetic and epigenetic mechanisms with interindividual variation. This process is coined “intrinsic aging”.
Transcriptomic, proteomic, and methylation aging clocks demonstrate that aging has a predictable preset program, while Transcriptome Trajectory Turning Points indicate that the 20 to 40 age range in humans is the likely stage at which the progressive loss of homeostatic control, and in turn aging, begins to have detrimental effects. Turning points in this age range overlapping with human aging clock genes revealed five candidates that we hypothesized could play a role in aging or age-related physiological decline. To examine these gene’s effects on lifespan and health-span, we utilized whole body and heart specific gene knockdown of human orthologs in Drosophila melanogaster. Whole body Loxl2, fz3, and Glo1 RNAi positively affected lifespan as did heart-specific Loxl2 knockdown. Loxl2 inhibition concurrently reduced age-related cardiac arrythmia and collagen (Pericardin) fiber width. Loxl2 binds several transcription factors in humans and RT-qPCR confirmed that a conserved transcriptional target CDH1 (Drosophila CadN2), has expression levels which correlate with Loxl2 reduction in Drosophila. These results point to conserved pathways and multiple mechanisms by which inhibition of Loxl2 can be beneficial to heart health and organismal aging.
BACKGROUND: Aging is an unavoidable biological process with many influencing factors, accounting for a multitude of visible manifestations on the hair as well as the skin. As the population ages while becoming more diverse, it is increasingly important to better understand the hair aging process. METHODS: A literature search was performed to review what is known about changes in hair structure over time, focusing on the differences in hair aging according to ethnic background. RESULTS: Sixty-nine publications were selected and information regarding hair structure, aging characteristics, and responses to extrinsic damage together with differences between races and ethnicities was collected. Hair-graying onset varies with race, with the average age for Caucasians being mid-thirties, that for Asians being late thirties, and that for Africans being mid-forties. Caucasians and Asians typically experience damage to the distal hair shaft, while African-Americans see damage occurring closer to the hair root. Postmenopausal changes include decreased anagen hairs in the frontal scalp, lower growth rates, and smaller hair diameters. CONCLUSION: There is a paucity of literature examining the characteristics of hair aging across all races. The unique characteristics of hair aging in different ethnicities provides information that will aid in a culturally sensitive approach and recommendations.
Background:
There are several ways by which aging is identified, of which graying of hair is perhaps the most common way. Nowadays, graying of hairs, which was expected to occur after 40s, can be easily observed among younger age group, even before 20s. The present study aims to estimate the prevalence of graying of hairs and its correlates among young adults in Srinagar, Uttarakhand, India.
Methodology:
A community-based cross-sectional study was conducted among 384 young adults between 15 and 30-year age group in the urban area of Srinagar tehsil of Pauri district. Graying of hair was assessed on the basis of the number of white hairs on examination of scalp.
Results:
The prevalence of premature graying of hairs (PMGHs) was found to be 27.3%. Binary logistic regression analysis showed that a paternal history of PMGH, history of smoking, maternal history of PMGH, sunlight exposure, and body mass index were significant predictors of PMGH.
Limitations:
The factors found associated could be better determined through a follow-up study which could not be done in the current study. The present study was carried in a tehsil of one district of Uttarakhand therefore has limited external validity.
Conclusion:
The present study highlights the importance of maintaining a healthy lifestyle as well as adequate exposure to sunlight in preventing PMGH.
Hair is a defining feature of mammals. In other species hair confers important functions that affect survival. Most have been lost or are irrelevant in humans but the role of hair in social and sexual signalling in women and in men survives and thrives. Departures from cultural norms, either physiological or due to pathology, can therefore cause much concern and anxiety. Following an introduction to hair biology, this chapter considers the approach to the diagnosis and management of the patient with hair loss before discussing specific hair disorders. These include the various forms of hair loss due to hair follicle pathology, disturbances in hair cycling and hair shaft dystrophies, and disorders associated with excessive hair growth. The chapter concludes with a discussion of acquired alterations in hair pigmentation.
Background:
The etiology of premature hair graying (PHG) remains incompletely understood with limited treatment options, although has profound impacts on patient's quality of life.
Aims:
To assess demographic and clinical profiles of Egyptian PHG patients and explore association of various epidemiological risk factors and serum vitamin D and ferritin levels with PHG.
Materials and methods:
300 PHG patients and equal number of controls, aged ‹30 years were included. Assessment of epidemiological and clinical characteristics, biometric data and stress perception using perceived stress scale (PSS- 10) was done, with measurement of serum vitamin D and ferritin levels for all subjects. PHG was graded into mild, moderate and severe if ‹10, 10-100 and › 100 gray hairs respectively. Statistical significance for various compared parameters was done employing suitable tests, with p-value≤ 0.05 considered significant.
Results:
Results reported significant positive relation of PHG with family history, sedentary life style and stress (p= 0.001, 0.029 & 0.001 respectively), while no significant relation with smoking, body mass index or frequent hair dyes use (›3 per year) (p= 0.425, 0.5 and 0.65 respectively). No significant difference was found in mean vitamin D between patients and controls (23.79± 13.01 ng/ml vs. 24.85± 13.19 ng/ml, p= 0.701), while low serum ferritin (‹20 ng/ml) was significantly associated with PHG (14.7 % patients vs. 2.7% controls, p= 0.017).
Conclusions:
PHG in Egyptian population is significantly associated with positive family history, stress, sedentary life style and low serum ferritin level, while role of vitamin D deficiency should be further evaluated.
EM, epidermal melanocyte; HFM, hair follicle melanocyte; SOD, superoxide dismutase
The desire of many to look young for their age has led to the establishment of a large cosmetics industry. However, the features of appearance that primarily determine how old women look for their age and whether genetic or environmental factors predominately influence such features are largely unknown. We studied the facial appearance of 102 pairs of female Danish twins aged 59 to 81 as well as 162 British females aged 45 to 75. Skin wrinkling, hair graying and lip height were significantly and independently associated with how old the women looked for their age. The appearance of facial sun-damage was also found to be significantly correlated to how old women look for their age and was primarily due to its commonality with the appearance of skin wrinkles. There was also considerable variation in the perceived age data that was unaccounted for. Composite facial images created from women who looked young or old for their age indicated that the structure of subcutaneous tissue was partly responsible. Heritability analyses of the appearance features revealed that perceived age, pigmented age spots, skin wrinkles and the appearance of sun-damage were influenced more or less equally by genetic and environmental factors. Hair graying, recession of hair from the forehead and lip height were influenced mainly by genetic factors whereas environmental factors influenced hair thinning. These findings indicate that women who look young for their age have large lips, avoid sun-exposure and possess genetic factors that protect against the development of gray hair and skin wrinkles. The findings also demonstrate that perceived age is a better biomarker of skin, hair and facial aging than chronological age.
ACTH, adrenocartico trophic hormone; Eso, sombre; Etob, tobacco; Fk, forskolin; MC1r, melanocortin 1 receptor; Mitf-M, microphtalmia transcription factor-M; POMC, proopiomelanocortin;; α-MSH, α-melanocyte-stimulating hormone; TRP-1, tyrosinase-related protein-1; TRP-2, tyrosinase-related protein-2
The most comprehensive source on the subject, this Second Edition is completely revised and expanded to reveal the most recent advances, technologies, and trends in hair and hair care science-tracking the development of hair care products, the emergence of new regulatory practices, and the latest methods in product safety and efficacy assessment.
The editor, recognizing the indisputable interrelation between cosmetology and dermatology, has prepared a textbook designed to bridge the gap between these two disciplines. Physicians, in particular dermatologists, primarily provide such care as it relates to the treatment of diseases of the scalp and hair; cosmetologists are primarily concerned with enhancing the beauty of hair and scalp and improving hair hygiene.
For many years a distinct line separated the types of care rendered by these professionals to their patients or clients. For obvious reasons, a fundamental understanding of scalp and hair pathology by cosmetologists and of the various hair-grooming and hygienic techniques by dermatologists is imperative, so that each group may render optimum care. However, the editor does not propose that cosmetologists administer treatment for diseases of the scalp and hair, nor does he intend for physicians and dermatologists to become proprietors of hair-care salons.
I suspect such a textbook as
The melanocortin 1 receptor, a seven pass transmembrane G protein coupled receptor, is a key control point in melanogenesis. Loss-of-function mutations at the MC1R are associated with a switch from eumelanin to phaeomelanin production, resulting in a red or yellow coat colour. Activating mutations, in animals at least, lead to enhanced eumelanin synthesis. In man, a number of loss-of-function mutations in the MC1R have been described. The majority of red-heads (red-haired persons) are compound heterozygotes or homozygotes for up to five frequent loss-of-function mutations. A minority of red-heads are, however, only heterozygote. The MC1R is, therefore, a major determinant of sun sensitivity and a genetic risk factor for melanoma and non-melanoma skin cancer. Recent work suggests that the MC1R also shows a clear heterozygote effect on skin type, with up to 30% of the population harbouring loss-of-function mutations. Activating mutations of the MC1R in man have not been described. The MC1R is particularly informative and a tractable gene for studies of human evolution and migration. In particular, study of the MC1R may provide insights into the lightening of skin colour observed in most European populations. The world wide pattern of MC1R diversity is compatible with functional constraint operating in Africa, whereas the greater allelic diversity seen in non-African populations is consistent with neutral predictions rather than selection. Whether this conclusion is as a result of weakness in the statistical testing procedures applied, or whether it will be seen in other pigment genes will be of great interest for studies of human skin colour evolution.
Although we have made significant progress in understanding the regulation of the UVR-exposed epidermal-melanin unit, we know relatively little about how human hair follicle pigmentation is regulated. Progress has been hampered by gaps in our knowledge of the hair growth cycle's controls, to which hair pigmentation appears tightly coupled. However, pigment cell researchers may have overly focused on the follicular melanocytes of the nocturnal and UVR-shy mouse as a proxy for human epidermal melanocytes. Here, I emphasize the epidermis-follicular melanocyte pluralism of human skin, as research models for vitiligo, alopecia areata and melanoma, personal care/cosmetics innovation. Further motivation could be in finding answers to why hair follicle and epidermal pigmentary units remain broadly distinct? Why melanomas tend to originate from epidermal rather than follicular melanocytes? Why multiple follicular melanocyte sub-populations exist? Why follicular melanocytes are more sensitive to aging influences? In this perspective, I attempt to raise the status of the human hair follicle melanocyte and highlight some species-specific issues involved which the general reader of the pigmentation literature (with its substantial mouse-based data) may not fully appreciate.
Synopsis
Skin and hair colour contribute significantly to our overall visual appearance and to social/sexual communication. Despite their shared origins in the embryologic neural crest, the hair follicle and epidermal pigmentary units occupy distinct, although open, cutaneous compartments. They can be distinguished principally on the basis of the former’s stringent coupling to the hair growth cycle compared with the latter’s continuous melanogenesis. The biosynthesis of melanin and its subsequent transfer from melanocyte to hair bulb keratinocytes depend on the availability of melanin precursors and on a raft of signal transduction pathways that are both highly complex and commonly redundant. These signalling pathways can be both dependent and independent of receptors, act through auto‐, para‐ or intracrine mechanisms and can be modified by hormonal signals. Despite many shared features, follicular melanocytes appear to be more sensitive than epidermal melanocytes to ageing influences. This can be seen most dramatically in hair greying/canities and this is likely to reflect significant differences in the epidermal and follicular microenvironments. The hair follicle pigmentary unit may also serve as an important environmental sensor, whereby hair pigment contributes to the rapid excretion of heavy metals, chemicals and toxins from the body by their selective binding to melanin; rendering the hair fibre a useful barometer of exposures. The recent availability of advanced cell culture methodologies for isolated hair follicle melanocytes and for intact anagen hair follicle organ culture should provide the research tools necessary to elucidate the regulatory mechanisms of hair follicle pigmentation. In the longer term, it may be feasible to develop hair colour modifiers of a biological nature to accompany those based on chemicals.
Melanin pigmentation plays an important part in adaptation to the environment. It protects against the carcinogenic effects of actinic radiation. As man migrated away from the tropics, the lightening of the species might have been due to a decreased need for this protection as well as to the need of a lighter skin to allow proper synthesis of vitamin D. New adaptations to sunnier climates might be accompanied by reverse darkening. The reason for the darkening of hair from infancy into adulthood needs studying as well as the differences in texture and coloring between scalp and beard hair. The sociological implications of skin pigmentation are serious. Sufferers from pigmentary disturbances need strong emotional support in addition to the standard forms of treatment.
GREYING of hair is probably the most obvious sign of ageing in man. To
determine whether or not its onset and progress are influenced by hair
colour we have examined a sample of Australians.
Some of the physical and chemical properties of the melanins isolated from human black and red hair were compared. Some of these properties were also compared with those of synthetic dopa melanin. Five samples each of black and red hair were used for isolating melanin by extraction with 2.5 M NaOH, and purification by repeated precipitation with HCl and redissolution in NaOH. The proteins associated with the melanins were hydrolyzed by refluxing the melanoproteins in 6 M HCl. The melanoproteins from black and red hair had 55.8 ± 2.0% and 41.5 ± 2.5% melanin, respectively. There was no statistically significant difference between the amino acid compositions of the hydrolysates from black and red hair melanoproteins. The ultraviolet and visible spectra of red hair melanin showed significant differences from those of black hair melanin and dopa melanin. Even though the overall spectra of red hair melanin showed some differences from those of black hair and dopa melanins, the results indicate a close similarity in the groups identifiable by the IR spectra. The compositions of C, H, N, S, and O in these melanins were determined. Red hair melanin contained more S than black hair melanin; dopa melanin did not contain any S. Black and red hair melanins oxidized NADH at approximately the same rate. Ultraviolet irradiation increased the oxidation of NADH by red hair melanin to a greater extent than that by black hair melanin. These results show that although there are general similarities, there are significant differences in the physical and chemical properties of melanins isolated from black and red hair.
The color variants of mammalian hair, including spotting and albinism, are the result of melanocyte activity and have been shown to be determined by the action of multiple genes, some of which operate through the milieu in which the pigment cell resides; others appear to act intracellularly to control the type of melanogenesis. Although there has been much descriptive work on the mode of action of these genes, it has only been with the recent advances in the chemistry and molecular biology of melanin pigmentation that some progress is being made in understanding the nature and origin of hair color. It is the purpose of this article to provide an integrated overview of the major advances so made and to draw attention to certain peculiarities of the melanization processes of hair with respect to those underlying skin pigmentation. Key words: melanins, melanocytes, melanogenesis, hair.
The melanocortin 1 receptor, a seven pass transmembrane G protein coupled receptor, is a key control point in melanogenesis. Loss-of-function mutations at the MC1R are associated with a switch from eumelanin to phaeomelanin production, resulting in a red or yellow coat colour. Activating mutations, in animals at least, lead to enhanced eumelanin synthesis. In man, a number of loss-of-function mutations in the MC1R have been described. The majority of red-heads (red-haired persons) are compound heterozygotes or homozygotes for up to five frequent loss-of-function mutations. A minority of redheads are, however, only heterozygote. The MC1R is, therefore, a major determinant of sun sensitivity and a genetic risk factor for melanoma and non-melanoma skin cancer. Recent work suggests that the MC1R also shows a clear heterozygote effect on skin type, with up to 30% of the population harbouring loss-of-function mutations. Activating mutations of the MC1R in man have not been described. The MC1R is particularly informative and a tractable gene for studies of human evolution and migration. In particular, study of the MC1R may provide insights into the lightening of skin colour observed in most European populations. The world wide pattern of MC1R diversity is compatible with functional constraint operating in Africa, whereas the greater allelic diversity seen in non-African populations is consistent with neutral predictions rather than selection. Whether this conclusion is as a result of weakness in the statistical testing procedures applied, or whether it will be seen in other pigment genes will be of great interest for studies of human skin colour evolution.
The visual appearance of humans derives predominantly from their skin and hair color. The phylogenetical pathway underling this phenomenon is called melanogenesis and results in the production of melanin pigments in neural crest-derived melanocytes, followed by its transfer to epithelial cells. While melanin from epidermal melanocytes clearly protects human skin by screening harmful ultraviolet radiation, the biologic value of hair pigmentation is less clear. In addition to important roles in social/sexual communication, one potential benefit of pigmented scalp hair in humans may be the rapid excretion of heavy metals, chemicals, toxins from the body by their selective binding to melanin.
The biological importance and/or significance of human hair colour is unknown even though greying is obviously associated with ageing. In order to further characterise hair pigmentation in relation with hair growth variables we evaluated 3 scalp sites (top of the head (T): left and right and occipital(O)) in 12 untreated menopausal women (age range: 49-66 years: average 59.63 +/- 5.66) who presented complaining of hair loss and/or diffuse alopecia. Controls were 12 non menopausal sexually mature woman (7 age range 15-21 and 5 age range 38-48) not complaining of hair loss. One hair sample (whenever possible n = 60) was taken one month after clipping from T and O on each person; menopausal women were sampled twice. The following measures were performed with a light microscope: diameter (average min-max., microm), medulla (0% = absent to 100% = fully developed) and linear hair growth rate (mm/day). The hairs were categorised as pigmented (P) or non-pigmented (white, W) as compared with a black and white reference card. A total of 3343 hairs were analysed with 2-factor analysis of variance (ANOVA). A global comparison (all hairs) showed that the average diameter of W hair (67.68 microm) exceeded that of P hair (57.41 microm) (p = 0.0001) and this was maintained on all 3 scalp sites. In addition, the medulla of W hair (23.91%) appeared more developed than the medulla of P hair (12.21%) (p = 0.0001) and was more expressed in W T hairs as compared with W O hairs (p = 0.0325). There was also a significant interaction between site and pigmentation (p = 0.0074). Growth rate of W hairs (0.38 mm/d) was higher than that of P hairs (0.35 mm/d) (p = 0.0001) and there was a significant variation according to scalp sites (p = 0.0001). There was also a significant interaction between site and pigmentation (p = 0.0062) with the following rank order: O W (0.40 mm/d), T W (0.37 mm/d), O P (0.37 mm/d) and T P (0.34 mm/d). Subgroups of W and P of paired thickness in the range of 50 to 80 pm consistently showed a 10% faster growth rate of W. Previous studies have shown that growth rate and diameter declines in age and alopecia i.e. in hair thinning. Our data shows that the reduced growth rate of terminal hairs is in fact limited to the pigmented hairs. The mechanisms by which white hairs are spared these ageing changes are not yet understood. Less pigmented hairs are usually undetected by photo- graphic techniques used for drug trials. The potential role of drug induced modifications of hair pigmentation should be taken into account during the interpretation of efficacy except if contrast-enhancement has been applied.
Although hair greying is a very common phenomenon characterized by loss of pigment in the hair shaft, the events that cause and control natural hair whitening with age in humans are still unclear.
To decipher the origin of natural hair whitening.
Human hair melanocytes were immunohistochemically characterized at different stages of whitening.
Loss of hair shaft melanin was found to be associated with a decrease in both bulb melanin content and bulb melanocyte population. Although few melanocytes were present in the bulbs of grey hair, they still expressed tyrosinase and tyrosinase-related protein-1, synthesized and transferred melanins to cortical keratinocytes as seen by the presence of melanin granules. In white hair bulbs, no melanocytes could be detected either with pMel-17 or vimentin labelling. Pigmented hair follicles are known to contain inactive melanocytes in the outer root sheath (ORS), and grey and white hairs were also found to contain some of these quiescent melanocytes. However, their population was decreased compared with pigmented hair follicles, ranging from small to nil. This depletion of melanocytes in the different areas of white hairs was detected throughout the hair cycle, namely at telogen and early anagen stages. In contrast, the infundibulum and sebaceous gland of both pigmented and white hairs showed a similar distribution of melanocytes. Furthermore, other distinct cell populations located in the ORS, namely putative stem cells, Merkel cells and Langerhans cells were equivalently identified in pigmented and white hairs.
Thus, hair greying appears to be a consequence of an overall and specific depletion of bulb and ORS melanocytes of human hair.
Skin and hair colour mostly depend on the activity of melanogenic melanocytes. Numerous proteins involved in melanocyte function have been identified including pMel-17, Mitf-M, Sox10, tyrosinase, tyrosinase related proteins-1 (TRP-1) and -2 (TRP-2). In the hair, melanogenic activity occurs only during the anagen phase of the hair cycle. In order to evaluate the implications of some known melanogenic proteins in human hair pigmentation, we performed immunohistochemical studies to reveal the expression of pMel-17, Mitf-M, tyrosinase, TRP-1 and TRP-2 in active bulb melanocytes of eumelanic brown and black anagen hairs of different ethnic origins, e.g. brown Caucasian, black Asian and African hairs. The labelling was compared with that observed in Caucasian and African scalp epidermis (interfollicular epidermis) melanocytes. We found that while pMel-17, TRP-1 and TRP-2 were expressed in epidermal melanocytes irrespective of ethnic origin and melanin content of the scalp epidermis, Mitf-M and tyrosinase expression were clearly evidenced only in pigmented epidermis, e.g. African scalps. Regarding human hair, pMel-17, Mitf-M, tyrosinase and TRP-1 were detected in a similar manner in active bulb melanocytes of brown and black hairs. In contrast and unexpectedly, TRP-2 could not be detected in hair bulb melanocytes, whatever the hair colour and ethnic origin. The lack of TRP-2 was further confirmed by western blot analyses. Reverse transcriptase-polymerase chain reaction (RT-PCR) performed on hair bulb mRNA demonstrated that Mitf-M, tyrosinase and TRP-1 amplimer signals were easily detected, whereas the TRP-2 amplimer signal was barely detectable. Furthermore Sox10 was not detected in hair bulb. Altogether our results suggest that the absence of detectable level of TRP-2 is due to transcriptional control in active melanocytes of human eumelanic hair bulbs. According to the absence of TRP-2 in melanin-producing melanocytes of brown and black hair bulbs, one must consider that eumelanogenesis as well as brown and black colour do not require TRP-2 expression in human hair.
TRP-2 (dopachrome tautomerase) is a melanogenic enzyme whose expression was recently reported to modulate melanocyte response to different cytotoxic events. Here we studied a possible role of TRP-2 in the oxidative stress response in the amelanotic WM35 melanoma cell line. Cell viability assays showed that TRP-2 overexpression in WM35 cells reduced their sensitivity to oxidative stress. Comet assays linked TRP-2 expression to DNA damage protection, and high-performance liquid chromotography-tandem mass spectrometry experiments showed an increase in intracellular glutathione in TRP-2-overexpressing cells. These effects were specifically reversed when TRP-2 was silenced by RNA interference. Nevertheless, these properties appeared to depend on a particular cell environment because expression of TRP-2 failed to rescue HEK epithelial cells exposed to similar treatments.
The cell biology of human hair follicle pigmentation
- Tobin
Contribution to understanding the nature of hair color
- Albrecht
Beobachtungen beim Ergrauen der Haare im Hinblick auf die zurzeit herrschenden theoretischen Anschauungen
- Naegeli