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Seasonality of hair loss: a time series analysis of Google Trends data 2004 to 2016

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E.Y. Hsiang
E.Y. Hsiang
E.Y. Hsiang
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Y.R. Semenov
Y.R. Semenov
Y.R. Semenov
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Crystal Aguh at Johns Hopkins Medicine
Crystal Aguh
S.G. Kwatra
S.G. Kwatra
S.G. Kwatra
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Abstract

Hair loss is a frequently encountered dermatologic complaint that often generates psychological distress. Prior studies have demonstrated a seasonal pattern to hair loss. Maximal proportions of telogen hair have been found to occur in the summer, whereas lowest rates of telogen hairs occur in the winter. Additionally, a recent study demonstrated that maximal hair shedding occurs in August and September, and that the percentage of hairs in the anagen phase peaks at the beginning of spring. This article is protected by copyright. All rights reserved.
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MS ESTHER Y HSIANG (Orcid ID : 0000-0003-2825-6975)
Article type : Research Letter
Seasonality of hair loss: a time series analysis of Google Trends data 2004 to 2016
Authors: E.Y. Hsiang1, Y.R. Semenov2, C. Aguh1, S.G. Kwatra1
1 Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore, MD
2 Division of Dermatology, Washington University School of Medicine, St. Louis, MO
Corresponding author: Shawn G. Kwatra,
Johns Hopkins University School of Medicine
601 N Caroline St, Baltimore, MD, 21231
1-410-955-5933
skwatra1@jhmi.edu
Funding: None
Conflict of interest disclosures: The authors have no conflicts to disclose
Hair loss is a frequently encountered dermatologic complaint that often generates
psychological distress. Prior studies have demonstrated a seasonal pattern to hair loss. Maximal
proportions of telogen hair have been found to occur in the summer,1,2 whereas lowest rates of
Accepted Article
This article is protected by copyright. All rights reserved.
telogen hairs occur in the winter.1 Additionally, a recent study demonstrated that maximal hair
shedding occurs in August and September, and that the percentage of hairs in the anagen phase
peaks at the beginning of spring.3 However, these prior analyses are constrained by small sample
sizes or homogenous patient populations in limited geographic locations, and focus on changes
in the hair growth cycle stages. Additional studies are needed to further describe the relationship
between hair loss and seasonality. In this study, we explore the relationship between seasonality
and hair loss at a population level using Google Trends data. As temperature and daylight levels
have been hypothesized to be causative factors of observed seasonal hair loss patterns,3 we also
sought to investigate if temperature plays a role in affecting seasonal variation. We hypothesized
that “hair loss” search volume index (SVI), a proxy measurement for actual hair loss experienced
in the population, would be highest in summer and lowest in spring.
Google Trends is an online, open-access database that aggregates Google search data
since 2004. SVI is a normalized quantification of a search topic relative to all other Google
searches in a given timeframe and is indexed from zero to 100.4 Monthly SVI data were
evaluated worldwide and in eight English-speaking countries. These countries were chosen by
selecting the top four countries by population in the top 15 countries by “hair loss” SVI from
January 2004 to October 2016 in each hemisphere. We chose to use the term “hair loss” in this
analysis, as the mean SVI for this term was more than 25 times higher than that of “hair
shedding.” We assigned each month to a season based on meteorological definitions and
corrected for hemisphere. We obtained monthly temperature data from the National Oceanic and
Atmospheric Administration and 2013 nominal GDP per capita data5 in order to partially account
for the effect of country access to technology. Multivariable Prais-Winsten time series analyses
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were conducted to examine the association between hair loss SVI and seasonality, adjusted for
temperature, hemisphere, and per capita GDP.
Trends in monthly “hair loss” SVI followed a cyclical distribution across all countries
examined, such that patterns of peaks and troughs in SVI repeat annually. Across all eight
countries analyzed in aggregate, summer and fall were associated with greater “hair loss” SVI
compared to spring (coefficient 5.74 [p<0.001], 5.05 [p<0.001], respectively; Table 1), with the
most pronounced increase in SVI occurring in summer. Winter also demonstrated a greater SVI
than spring, albeit to a lesser extent than summer and fall (coefficient 2.63 [p<0.001]. Of the
confounding variables, temperature was a minor contributor to SVI findings (coefficient 0.18
[p=0.020]), while countries with higher per capita GDP were significantly associated with higher
SVI (coefficients 0.62 [p<0.001]) and countries in the southern hemisphere were associated with
lower SVI (20.23 [p<0.001]).
The results of this secular trend study suggest that hair loss in the population is
significantly correlated with seasonality, and that hair loss occurs most frequently in the summer
and fall. These findings are consistent with prior studies that used trichograms and other hair
samples to find that telogen hair loss occurs maximally in the summer1,2 or the transition
between summer and fall.2 However, the physiology of hair loss as related to seasonal variation
is unknown. Clinical implications of this pattern of hair loss seasonality include the potential for
confounding diagnosis of hair loss conditions or efficacy of treatment started at different months
of the year. While temperature was associated with hair loss seasonality in this study, it did not
contribute significantly to hair loss in multivariate modeling. However, other seasonal trends
were not evaluated. This suggests that other factors are contributive and that future studies
exploring the effect of UV index variation on patterns of hair loss, for example, are warranted.
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A limitation of this analysis is that Google Trends SVI data shift slightly depending on
acquisition date, as relative percentages of total search volume are continuously altered.7
However, data for the same time range acquired on three separate days demonstrated close
correlation (Spearman correlation 0.97). Nevertheless, this is an initial investigation into seasonal
patterns of hair loss worldwide. Further studies evaluating the seasonality and hair loss
relationship, as well as exploring the effect of other potential mediating factors, are needed.
References
1. Kunz M, Seifert B, Trüeb RM. Seasonality of hair shedding in healthy women
complaining of hair loss. Dermatology. 2009;219(2):105-110. doi:10.1159/000216832.
2. Courtois M, Loussouarn G, Hourseau S, Grollier J. Periodicity in the growth and shedding
of hair. Br J Dermatol. 1996;134(1):47-54.
3. Randall VA, Ebling FJG. Seasonal changes in human hair growth. Br J Dermatol.
1991;124:146-151.
4. Rogers S. What is Google Trends data - and what does it mean? Google News Lab.
https://medium.com/google-news-lab/what-is-google-trends-data-and-what-does-it-mean-
b48f07342ee8#.41itaxnv1. Published 2016. Accessed October 18, 2016.
5. EconFactbook. http://econfactbook.org/. Accessed February 21, 2017.
6. Headington JT. Telogen effluvium: New concepts and review. Arch Dermatol.
1993;129(3):356-363.
7. Google. How Trends data is adjusted.
https://support.google.com/trends/answer/4365533?hl=en. Published 2016. Accessed
November 13, 2016.
8. Google. Note: An improvement to our geographical assignment was applied retroactively
from 1/1/2011. https://support.google.com/trends/answer/1383240?hl=en. Accessed
September 4, 2016.
Accepted Article
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TABLE 1. Multivariable Prais-Winsten model of association between “hair loss” SVI and
season
Characteristic
Regression coefficient (95% CI)
P
Spring
Ref1
Ref1
Summer
5.74 (3.91 to 7.58)
<0.001
Fall
5.05 (2.94 to 7.17)
<0.001
Winter
2.63 (0.72 to 4.55)
0.007
Temperature
0.18 (0.03 to 0.33)
0.020
Southern Hemisphere2
-20.23 (-23.71 to -16.76)
<0.001
Nominal GDP per capita3
0.62 (0.55 to 0.70)
<0.001
1Spring used as reference
2Northern hemisphere used as reference
3GDP in thousands
Note: Seasons for countries in the northern hemisphere were defined such that March, April and
May constituted spring; June, July, and August constituted summer; September, October, and
November constituted fall, and December, January, and February constituted winter. Seasons for
countries in the southern hemisphere were defined as the reverse, such that northern hemisphere
spring constituted southern hemisphere fall; northern hemisphere summer constituted southern
hemisphere winter; northern hemisphere fall constituted southern hemisphere spring; and
northern hemisphere winter constituted southern hemisphere summer.
... To illustrate this conclusion, the results for the chosen three tensile variables (wet) are summarised in Figure 1 The occurrence of cyclic changes of specific hair properties (daily, monthly, seasonal) [2] and of seasonal effects for hair growth [3,4,5,6] appear well established. This background led us to speculate that the variability of the results in Figure 1 may contain a seasonal component. ...
... The changes of the material properties of hair may also be the response to an environmental trigger (temperature, daylight levels)or both. This may suggest, e.g., an investigation on hair from different ethnicities and/or climates, analogous to those for hair loss [6,29]. ...
A consumer cross‐over trial suggests that there are significant seasonal changes of the tensile properties (wet) of human hair
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  • Int J Cosmet Sci
Objectives Through the cooperation with an industrial partner, we gained a set of data for the tensile properties (wet) of human hair. The hair samples originated from a cross‐over study with two groups of individuals, using for a topical application sequentially two products (A and B). Each phase of the study lasted six months. The phases of the study were by chance covering first largely the winter and then the summer period. Initially, tensile variables were chosen, which not only reflect the mechanical properties of hair (modulus, break strain, break stress) but which are also considered to have a good connection to practice‐relevant hair properties. The initial analysis of the data showed that changes were observed for the variables due to the treatment phases. However, these were either small or difficult to interpret. Methods Against this background and using Two‐Factor Analysis of Variance, we investigated the hypothesis that the tensile properties of hair (wet) may show significant seasonal changes. For this we chose those two independent variables, which reflect the properties of the intermediate filaments (modulus) and the matrix (break strain) in the composite structure of the hair cortex. Results The results support the ‘seasonal’ hypothesis and clearly show that the variables show significant changes from Winter to Summer ( modulus : 10% increase, break strain : 3% decrease). The seasonal effect was thus a major reason, why the first stage of the analysis of the data was inconclusive. Conclusions The tensile properties of the main morphological components of the cortex show distinct seasonal changes. Towards the summer the hair becomes stiffer and more brittle. Furthermore, the results suggest that seasonal effects may need to be taken into account when conducting studies on lengths of hair grown during different seasons.
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... More hairs are shed in the summer when the ambient temperature is high compared to spring and winter when the ambient temperatures are relatively lower. Coincidentally, there is a greater number of hair follicles in the anagen (hair growth phase) compared to that in the spring and winter [31]. Thus, can temperature modulate hair growth during skin aging? ...
THSD4 promotes hair growth by facilitating dermal papilla and hair matrix interactions
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  • thno
Introduction: Aging causes striking changes in the extracellular matrix (ECM) in hair follicles, which has a profound influence on hair growth. How the ECM of dermal papilla (DP), the master regulator of hair growth, changes during aging remains largely unknown. Methods: Herovici staining, Western Blotting and immunofluorescence were used to assess DP ECM and protein expression in hair follicles. Bulk and single cell RNA-sequencing were used to analyze gene expression and predict upstream and downstream regulators of target genes. Skin organoid and mouse models were used for functional validation of molecular mechanisms. Results: Aged follicle DP shows drastic depletion of ECM in which Thrombospondin Type 1 Domain Containing 4 (Thsd4) is highly downregulated. THSD4 is specifically expressed in the interface between DP and hair matrix (HM). It promotes hair growth by enhancing the interaction between dermal (DP) and epithelial cells (HM) through the SDC4-THSD4-CXCL1 signaling axis in both skin organoids and mouse models. Murine dorsal hair follicles show upregulated THSD4, enhanced DP-HM interaction, and hair growth following exposure to low temperature. Conclusions: THSD4 is a key micro-and macro-environmental mediator to promote hair growth by facilitating epidermal-mesenchymal interactions during aging. These findings demonstrate the therapeutic potential of low-temperature treatment for treating unwanted hair loss.
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... The inclusion of a placebo arm in future clinical trials of hair products is especially crucial due to seasonal fluctuations in spontaneous hair shedding observed in humans. In Europe, the rates of hair shedding and telogen hair are highest in late summer and lowest in early spring, a trend documented independently in the UK, France, and Switzerland [66][67][68]. In the USA, the same trends in hair loss are reflected by the volume of Google searches [69]. ...
Caffeine as an Active Ingredient in Cosmetic Preparations Against Hair Loss: A Systematic Review of Available Clinical Evidence
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Background/Objectives: Hair loss (alopecia or effluvium) can significantly affect the self-esteem and psychosocial well-being of patients, resulting in a reduced quality of life. It may herald a systemic disease, nutritional deficiency, or side effects of pharmacotherapy. Current therapeutic options for hair loss are not always satisfactory and may be associated with considerable side effects; therefore, new solutions are still sought. Caffeine seems to be an effective agent against hair loss thanks to its stimulating effects on cell growth and good penetration into the hair follicle. The aim of this study was to systematically review published clinical trials of topical caffeine preparations against hair loss. Methods: We searched PubMed, Scopus, and Web of Science for clinical trials investigating the efficacy of topical caffeine products in hair loss, published until 29 November 2024. The quality of evidence was assessed using the GRADE classification. Results: The query returned 1121 articles, of which 9 ultimately met the inclusion criteria. In total, 684 people with androgenetic alopecia, excessive hair loss, or hair thinning were included in these trials. In all studies, conclusions were in favor of topical caffeine treatment; however, the level of scientific evidence was medium in 3 studies, low in 1, and very low in the remaining 5. Their major flaws included the lack of randomization and placebo and control groups, as well as the lack of information on the caffeine concentration in the topical products. Conclusions: Results from studies published to date suggest that topical caffeine preparations are safe and effective against hair loss. Nevertheless, better-designed clinical trials of well-defined caffeine products are required for an ultimate statement. Commercial hair products with caffeine offered on the market nowadays may be worth a try, but due to incomplete scientific data and product information, satisfactory outcomes are not guaranteed.
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... Many medical conditions display seasonality in terms of presenting with a first episode or exacerbation of an existing medical problem [6][7][8][9][10][11]. Clinical observations pointed to the same pattern in psoriasis with deterioration or first episodes starting mainly in cold months [12][13][14]. ...
Does the effectiveness of biological medications in the treatment for psoriasis depend on the moment of starting therapy? A preliminary study
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Introduction It is well known that biological medications acting on selected elements of the immune response are highly effective in psoriasis treatment. It is a common perception that psoriasis is a seasonal disorder with improvement in warmer months, however it has not been unequivocally confirmed. It is not known whether the time of year of starting systematic therapy for psoriasis influences treatment outcomes. Material and methods Changes in psoriasis severity scores during treatment with biologics were investigated. The scores were recorded for 62 patients with moderate to severe psoriasis at the beginning, after 1, 4 and 7 months of the therapy. Patients were divided into two groups: those beginning the treatment in the cold period of the year (November-March) and in the warm period (May-September). The seasonal groups were also divided into subgroups according to the type of biologics used: interleukin inhibitors and tumor necrosis factor α (TNF-α) inhibitors. Results of the treatment were analysed using standard statistical tests of differences between samples. Results After 1 and 4 months of the therapy, better efficacy of interleukin inhibitors was found in patients starting treatment in summer. The course of psoriasis improvement in patients taking TNF-α inhibitors resulted in consistent improvement regardless of the season. The outcome of the treatment after 7 months was similar for both seasonal groups and types of biologics used. Conclusions Our understanding of the effectiveness of the treatments depending on the time of the year combined with the type of biologics used, may further improve results of the therapy.
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... Seasonality may reflect oscillatory changes in infectiousness, contact patterns, pathogen survival, or host susceptibility. Google Trends has been shown to be suitable for studying seasonal patterns of various skin problems including infectious diseases or conditions such as hair loss [47][48][49][50][51][52], but few studies have used eHealth tools to assess the seasonal variations of a cutaneous viral infection. ...
Worldwide evolution of vaccinable and non-vaccinable viral skin infections: a Google Trends analysis (Preprint)
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Full-text available
  • Nov 2021
Background Most common viral skin infections are not reportable conditions. Studying the population dynamics of these viral epidemics using traditional field methods is costly and time-consuming, especially over wide geographical areas. Objective This study aimed to explore the evolution, seasonality, and distribution of vaccinable and nonvaccinable viral skin infections through an analysis of Google Trends. Methods Worldwide search trends from January 2004 through May 2021 for viral skin infections were extracted from Google Trends, quantified, and analyzed. Results Time series decomposition showed that the total search term volume for warts; zoster; roseola; measles; hand, foot, and mouth disease (HFMD); varicella; and rubella increased worldwide over the study period, whereas the interest for Pityriasis rosea and herpes simplex decreased. Internet searches for HFMD, varicella, and measles exhibited the highest seasonal patterns. The interest for measles and rubella was more pronounced in African countries, whereas the interest for HFMD and roseola was more pronounced in East Asia. Conclusions Harnessing data generated by web searches may increase the efficacy of traditional surveillance systems and strengthens the suspicion that the incidence of some vaccinable viral skin infections such as varicella, measles, and rubella may be globally increasing, whereas the incidence of common nonvaccinable skin infections remains stable.
View
... The search behavior patterns using Google Trends have been studied previously in the context of dermatologically related topics such as atopic dermatitis, psoriasis, chilblains, cutaneous infestations with arthropods, hair loss and human papilloma virus [27][28][29][30][31][32][33][34]. We prepared a table that compares the clinical symptoms of common dermatological disorders, their seasonality based on the previous literature and our research (Table 2). ...
Seasonal Patterns and Trends in Dermatoses in Poland
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Full-text available
Background: The amount of data available online is constantly increasing, including search behavior and tracking trends in domains such as Google. Analyzing the data helps to predict patient needs and epidemiological events more accurately. Our study aimed to identify dermatology-related terms that occur seasonally and any search anomalies during the SARS-CoV-2 pandemic. Methods: The data were gathered using Google Trends, with 69 entries between January-2010 and December-2020 analyzed. We conducted the Seasonal Mann-Kendal Test to determine the strength of trends. The month with the highest seasonal component (RSV) and the lowest seasonal component (RSV) was indicated for every keyword. Groups of keywords occurring together regularly at specific periods of the year were shown. Results: We found that some topics were seasonally searched in winter (e.g., herpes, scabies, candida) and others in summer (e.g., erythema, warts, urticaria). Conclusions: Interestingly, downward trends in searches on sexually transmitted diseases in comparison with increased infection rates reported officially show a strong need for improved sexual education in Poland. There were no significant differences in trends for coronavirus-related cutaneous symptoms during 2020. We have shown that the seasonality of dermatologically related terms searched in Poland via Google did not differ significantly during SARS-CoV-2 pandemic.
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Alopecia: A Google Trends Analysis of the Past 5 Years (2018–2023)
Article
  • Nov 2024
Introduction: The study aimed to evaluate recent trends in public interest regarding various alopecia associated diagnoses using Google trends. Method: Data generated through Google trends for the relative search volumes (RSVs) of the following diagnostic-related terms: “Alopecia”; “Alopecia areata”; “Androgenetic alopecia”; “Central centrifugal cicatricial alopecia”; “Folliculitis decalvans”; “Frontal fibrosing alopecia”; “Telogen effluvium”; “Traction alopecia” [disease]”. Analysis has been performed worldwide from July 29th, 2018 to July 16th, 2023. Results: Between 2018 and 2023, mean RSVs by 12 months period have remained stable for “alopecia” and “alopecia areata”. “Telogen effluvium” has increased peak search during 2020-2022. “Androgenetic alopecia” and “frontal fibrosing alopecia” display an increase for the past 5 years. There were differences in geographic distribution. For alopecia areata, all the countries were from Middle East; for telogen effluvium, eight of top 10 countries were Latin American or Spanish speaking, Western countries had mainly searched for frontal fibrosing alopecia. Conclusions: Google trends is not a real epidemiological tool. It can be only used by individuals who have access to the Internet, but it does not presume the person or the reason for the search. We observed different geographical distribution according to the disease. Infodemiology provides a better understanding of alopecia needs in different countries and continents.
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Seasonality of Hair Shedding in Healthy Women Complaining of Hair Loss
Article
  • May 2009
  • DERMATOLOGY
A number of otherwise healthy women with or without clinical alopecia complain of recurrent hair loss, presumably reflecting seasonality in the growth and shedding of hair. Objective: To test the hypothesis that periodicity in hair shedding reflects seasonal changes in human hair growth. Retrospective case study over a period of 6 years of apparently healthy women with the complaint of hair loss. All underwent biochemical investigations, and trichograms were made. After exclusion of patients with a disease or on drugs known to cause hair loss, 823 women remained. Analysis of trichograms demonstrated annual periodicity in the growth and shedding of hair, manifested by a maximal proportion of telogen hairs in summer. A second peak seems to exist, though it is less pronounced, in spring. The telogen rates were lowest in late winter. These results confirm the findings of former authors who have indicated seasonal changes in human hair growth, though this is the first study performed systematically in a representative number of women.
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Randall VA, Ebling FJSeasonal changes in human hair growth. Br J Dermatol 124:146-151
Article
  • Mar 1991
Various parameters of hair growth were determined every 28 days for 18 months in 14 healthy Caucasian men aged 18-39 with indoor occupations in Sheffield, U.K. (latitude 53.4 degrees N). In the scalp the proportion of follicles in anagen reached a single peak of over 90% in March, and fell steadily to a trough in September. The number of shed hairs reached a peak around August/September, when least follicles were in anagen. At this time the average loss of hairs was about 60 per day, more than double that during the preceding winter. The rate of growth of the beard was lowest in January and February and increased steadily from March to July to reach a peak about 60% above the winter level. The rate of growth of thigh hair showed a similar pattern though with less pronounced differences. No seasonal fluctuations in finger- or toenail growth were detected.
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Periodicity in the growth and shedding of hair
Article
  • Feb 1996
Summary Ten men, with or without alopecia, were observed for a period of between 8 and 14 years using phototrichograms on a precisely located zone on the vertex of the scalp. Among the various parameters observed, we chose the percentage of hairs in telogen as the criterion for assessment of hair shedding. Mathematical analysis of the variations in this telogen percentage was carried out for each individual subject and for the whole group, as represented by the population mean (or the ‘average subject’). This analysis demonstrated the existence of overall annual periodicity, manifested by a maximal proportion of telogen hairs at the end of summer and the beginning of autumn. Some subjects also exhibited a periodicity approximately corresponding to two annual peaks. In those subjects with a very low proportion of hairs in telogen, no periodicity was demonstrated. In another group of subjects, it has been shown that the variations in telogen percentage reflect those observed in hair shedding, assessed in a standardized manner. Periodicity of the telogen percentage, and hence of hair fall, is not independent of climatic factors (sunshine hours), and these must be taken into account when assessing the treatment or prevention of hair loss.
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Seasonality of hair shedding in healthy women complaining of hair loss Periodicity in the growth and shedding of hair
  • Jan 1996
  • 105-11047
  • M Kunz
  • B Seifert
  • Rm Trüeb
  • G Loussouarn
  • S Hourseau
  • J Grollier
Kunz M, Seifert B, Trüeb RM. Seasonality of hair shedding in healthy women complaining of hair loss. Dermatology. 2009;219(2):105-110. doi:10.1159/000216832. 2. Courtois M, Loussouarn G, Hourseau S, Grollier J. Periodicity in the growth and shedding of hair. Br J Dermatol. 1996;134(1):47-54.
What is Google Trends data -and what does it mean? Google News Lab
  • Oct 2016
  • S Rogers
Rogers S. What is Google Trends data -and what does it mean? Google News Lab. https://medium.com/google-news-lab/what-is-google-trends-data-and-what-does-it-mean-b48f07342ee8#.41itaxnv1. Published 2016. Accessed October 18, 2016.
Telogen effluvium: New concepts and review
  • Jan 1993
  • 356-363
  • J T Headington
Headington JT. Telogen effluvium: New concepts and review. Arch Dermatol. 1993;129(3):356-363.
How Trends data is adjusted
  • Google
Google. How Trends data is adjusted.
Note: An improvement to our geographical assignment was applied retroactively from 1/1/2011
  • Sep 2016
  • Google
Google. Note: An improvement to our geographical assignment was applied retroactively from 1/1/2011. https://support.google.com/trends/answer/1383240?hl=en. Accessed September 4, 2016.
What is Google Trends data - and what does it mean?Available at
  • Rogerss
Seasonal changes in human hair growth
  • Jan 1991
  • 146
  • Randall