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Vitamin D status partly explains ethnic differences in blood pressure: The 'Surinamese in the Netherlands: Study on ethnicity and health'
Abstract
To investigate the role of vitamin D in explaining ethnic differences in blood pressure among three ethnic groups in the Netherlands (ethnic Dutch, African Surinamese, and south Asian Surinamese).
Data were derived from the 'Surinamese in the Netherlands: study on ethnicity and health' study, a population-based observational study. We included 1420 participants (505 ethnic Dutch, 330 south Asian Surinamese, and 585 African Surinamese), aged 35-60 years, in whom serum vitamin D (25-hydroxyvitamin D) and SBP and DBP were measured. Data were analyzed by using linear (SBP, DBP) and logistic (hypertension) regression analyses, using ethnicity as independent variable and adjusting for potential confounders. To study the impact of vitamin D, we additionally adjusted for vitamin D in a final model.
South Asian Surinamese had a 5.6 mmHg higher SBP and 4.9 mmHg higher DBP as compared with the Dutch after adjustment for age, sex, season, physical activity, smoking, education, and BMI. Further adjustment for vitamin D explained 14 and 6% of these SBP and DBP differences, respectively. African Surinamese had an 8.9 mmHg higher SBP and 6.8 mmHg higher DBP as compared with the Dutch. Variation in vitamin D explained 7 and 4% of these SBP and DBP differences. South Asian Surinamese and African Surinamese had 2.2 (1.5-3.2) and 3.3 (2.4-4.6) times higher odds of having hypertension compared with ethnic Dutch. Vitamin D explained 25 and 17% of the variations in SBP and DBP, respectively, resulting in odds ratio of 1.9 (1.3-2.9) and 2.9 (2.0-4.3), respectively.
Higher blood pressures and higher hypertension risk in south Asian Surinamese and African Surinamese were partly explained by their poorer vitamin D status. However, even after adjustment, significant ethnic blood pressure differences persisted.
... Recently, the relationship between 25(OH)D levels and genetic polymorphisms of DBP were reported [32] . It was previously known that 25(OH)D concentrations differed between black Americans and whites [33] . Although it was generally thought that nutritional, environmental, and hormonal factors affected racial differences [34] , the detailed mechanisms behind these differences are unknown. ...
Approximately 30%-50% of people are recognized to have low levels of vitamin D, and insufficiency and deficiency of vitamin D are recognized as global health problems worldwide. Although the presence of hypovitamin D increases the risk of rickets and fractures, low vitamin D levels are also associated with hypertension, cancer, and cardiovascular disease. In addition, diabetes mellitus (DM) and chronic kidney disease (CKD) are also related to vitamin D levels. Vitamin D deficiency has been linked to onset and progression of DM. Although in patients with DM the relationship between vitamin D and insulin secretion, insulin resistance, and β-cell dysfunction are pointed out, evidence regarding vitamin D levels and DM is contradictory, and well controlled studies are needed. In addition, vitamin D influences the renin-angiotensin system, inflammation, and mineral bone disease, which may be associated with the cause and progression CKD. There is increasing evidence that vitamin D deficiency may be a risk factor for DM and CKD; however, it remains uncertain whether vitamin D deficiency also predisposes to death from DM and CKD. Although at this time, supplementation with vitamin D has not been shown to improve glycemic control or prevent incident DM, clinical trials with sufficient sample size, study periods, and optimal doses of vitamin D supplementation are still needed. This review focuses on the mechanism of vitamin D insufficiency and deficiency in DM or CKD, and discusses the current evidence regarding supplementation with vitamin D in patients with these diseases.
... Vitamin D is mainly associated with its role in bone homeostasis and calcium metabolism, but there is emerging evidence about its possible roles also in several other biological processes such as modulation of the immune system [1], infections [2] and cardiovascular diseases [3,4]. In vitro experiments have shown that vitamin D may have important roles also in drug metabolism as several cytochrome P450 (CYP) enzymes such as CYP3A4, CYP2C9 and CYP2B6 are induced by vitamin D [5,6]. ...
In vitro studies have shown that vitamin D may induce several cytochrome P450 (CYP) enzymes in general and CYP3A4 in particular. The primary aim of this study was to investigate the relationship between plasma levels of 25-hydroxyvitamin D3 and suggested in vivo markers of CYP3A activity in healthy volunteers from Sweden and Korea.Plasma concentrations of 25-hydroxyvitamin D3 were analysed in samples from three previously performed studies, and the correlation between these levels and suggested in vivo markers of CYP3A activity was investigated by means of non-parametric correlation. In addition, we studied the modulating effects of three vitamin D receptor promoter polymorphisms on the association between 25-hydroxyvitamin D3 and CYP3A enzyme activity in Swedish subjects.The plasma levels of 25-hydroxyvitamin D3 were not significantly associated with CYP3A phenotypes in any of the three studies, but after accounting for the vitamin D receptor polymorphism rs4516035, there was a significant positive association between 25-hydroxyvitamin D3 and CYP3A activity (p=0.004). Swedes (n=65) had significantly higher 25-hydroxyvitamin D3 levels than Koreans (n=67), 75 nmol/L compared to 31 nmol/L (p<0.001). Swedish women taking oral contraceptives (OC) (n=19) had somewhat higher plasma levels of 25-hydroxyvitamin D3 compared to Swedish women not taking oral contraceptives (n=21), 89 and 72 nmol/L, respectively (p=0.02).In conclusion, our results suggest that the overall influence on the CYP3A activity by 25-hydroxyvitamin D3 is of marginal importance.This article is protected by copyright. All rights reserved.
... Childhood diet and nutritional factors could be important; these include sodium and potassium intakes (not available in the present study) and micronutrient status. Vitamin D status is particularly implicated as a determinant of ethnic differences in BP [47]. Prenatal influences, particularly related to fetal under nutrition and low birth weight, have been implicated in the development of high BP [48]. ...
: Compared to UK white European adults, UK black African-Caribbean adults have higher mean SBP and DBP; UK South Asian adults have higher mean DBP but lower SBP. Information on blood pressure (BP) in UK children from different ethnic groups is limited. The aim of this study was to compare BP levels in UK children of black African-Caribbean, South Asian and white European origin.
: BP and body build were measured in 5666 children in a cross-sectional study of UK primary school children of South Asian, black African-Caribbean and white European origin aged 9-10 years. Ethnic and socioeconomic differences in BP were obtained from multilevel linear regression models.
: After adjustment for height and adiposity, black African-Caribbean children had lower mean SBP than white Europeans [difference 1.62 mmHg, 95% confidence interval (CI) 0.86-2.38 mmHg], whereas mean DBP was similar (difference 0.58 mmHg, 95% CI -0.12 to 1.28 mmHg). The lower SBP was particularly marked in black African rather than Caribbean children (P = 0.002). South Asian children had lower mean SBP (difference 1.10 mmHg, 95% CI 0.34-1.86 mmHg) than white Europeans and higher mean DBP (difference 1.07 mmHg, 95% CI 0.37-1.76 mmHg). The higher mean DBP was particularly marked among Indian and Bangladeshi, rather than Pakistani, children (P = 0.01). BP was unrelated to socioeconomic circumstances; ethnic differences in BP were not affected by socioeconomic adjustment.
: A BP pattern similar to that in adults is present in UK South Asian but not in UK black African-Caribbean children at 9-10 years.
Introduction:
Vitamin D is essential for bone health since it stimulates the intestinal absorption of calcium and phosphorus from the gut, both necessary for bone mineralization. However, vitamin D deficiency is highly prevalent among several non-Western immigrant populations in the Netherlands. To date, there are no data available of the vitamin D status in the Chinese population residing in the Netherlands. Therefore, an observational study was performed to determine 25-hydroxyvitamin D (25OH)D concentrations and to assess potential determinants of low vitamin D status.
Methods:
Subjects, aged 18 years and older, with a Chinese background and residing in the Netherlands were invited to participate in the study. A questionnaire was used to assess general characteristics and lifestyle habits. Fasting blood samples were obtained in March 2014 to measure serum 25(OH)D concentration, and analysed by liquid chromatography tandem mass spectrometry.
Results:
418 subjects participated in the study, 104 men and 314 women. The mean age for both men and women was 56 years. Serum 25(OH)D concentration <50 nmol/L was more prevalent in men than in women (67.9% and 53.1%, respectively; p=0.008). The percentage of serum 25(OH)D concentration<25nmol/L in men and women was 5.8% and 10.9%, respectively. Multiple logistic regression analysis, adjusted for age and gender, revealed that non-use of vitamin D supplements and fewer days per week of physical activity were significant predictors of serum 25(OH)D levels below 50nmol/L.
Conclusions:
Within the Chinese population living in the Netherlands, serum 25(OH)D concentration was below 50nmol/L in 68% of men and 53% of women. Use of vitamin D supplements by Chinese people in the Netherlands was highly protective against low 25(OH)D levels.
Vascular calcification and cardiovascular diseases have been associated with altered bone metabolism. We explored the relationships of arterial pressures and carotid intima-media thickness (CIMT) with parathyroid hormone, 25-hydroxycholecalciferol and their ratio (PTH:25(OH)D3) as well as a marker of bone resorption (CTX) in lean and overweight/obese African women. A population of 434 African women older than 46 years was divided into lean and overweight/obese groups. We assessed brachial blood pressure, central pulse pressure (cPP) and CIMT, and determined PTH, 25(OH)D3 and CTX concentrations. Overweight/obese women had elevated PTH and PTH:25(OH)D3 compared with lean women (both P<0.001), whereas lean women had higher CTX (P<0.001). Single, partial and multiple regression analyses indicated that, in lean women CIMT was independently associated with PTH:25(OH)D3 (R(2)=0.22; β=0.26; P=0.003), whereas in obese women cPP was associated with both PTH:25(OH)D3 (R(2)=0.20; β=0.17; P=0.017) and CTX (R(2)=0.20; β=0.17; P=0.025). In conclusion, we found that in African women with increased adiposity, cPP (as a surrogate measure of arterial stiffness), was positively associated with alterations in bone metabolism and calciotropic hormones, whereas CIMT of lean women was positively associated with PTH:25(OH)D3. Our results suggest that alterations in bone and calcium metabolism may contribute to arterial calcification in older African women.Journal of Human Hypertension advance online publication, 14 August 2014; doi:10.1038/jhh.2014.71.
SummaryThis review describes the vitamin D status in different regions of the world with the objective of understanding the scope
of hypovitaminosis D and the factors related to its prevalence that may contribute to the pathogenesis of osteoporosis and
fragility fractures.
IntroductionVitamin D status has been linked to the pathogenesis of hip fractures as well as other skeletal and non-skeletal disorders.
The purpose of this review is to provide a global perspective of vitamin D status across different regions of the world and
to identify the common and significant determinants of hypovitaminosis D.
MethodsSix regions of the world were reviewed—Asia, Europe, Middle East and Africa, Latin America, North America, and Oceania—through
a survey of published literature.
ResultsThe definition of vitamin D insufficiency and deficiency, as well as assay methodology for 25-hydroxyvitamin D or 25(OH)D,
vary between studies. However, serum 25(OH)D levels below 75nmol/L are prevalent in every region studied whilst levels below
25nmol/L are most common in regions such as South Asia and the Middle East. Older age, female sex, higher latitude, winter
season, darker skin pigmentation, less sunlight exposure, dietary habits, and absence of vitamin D fortification are the main
factors that are significantly associated with lower 25(OH)D levels.
ConclusionReports from across the world indicate that hypovitaminosis D is widespread and is re-emerging as a major health problem globally.
Higher prevalence of hypertension among African Americans is a key cause of racial disparity in cardiovascular morbidity and mortality. Explanations for the difference in prevalence are incomplete. Emerging data suggest that low vitamin D levels may contribute.
To assess the contribution of vitamin D to racial disparity in blood pressure.
Cross-sectional analysis.
Adult non-Hispanic Black and White participants from the National Health and Nutrition Examination Survey 2001-2006.
We assessed Black-White differences in systolic blood pressure (SBP) controlling for conventional risk factors, and then additionally, for vitamin D (serum 25[OH]D).
The sample included 1984 and 5156 Black and White participants ages 20 years and older. The mean age-sex adjusted Black-White SBP difference was 5.2 mm Hg. This difference was reduced to 4.0 mm Hg with additional adjustment for socio-demographic characteristics, health status, health care, health behaviors, and biomarkers; adding 25(OH)D reduced the race difference by 26% (95% CI 7-46%) to 2.9 mm Hg. This effect increased to 39% (95% CI 14-65%) when those on antihypertensive medications were excluded. Supplementary analyses that controlled for cardiovascular fitness, percent body fat, physical activity monitoring, skin type and social support yielded consistent results.
In cross-sectional analyses, 25(OH)D explains one quarter of the Black-White disparity in SBP. Randomized controlled trials are required to determine whether vitamin D supplementation could reduce racial disparity in BP.
To explore associations between vitamin D and cardiovascular disease risk factors in young European adults.
This was a cross-sectional analysis of serum 25-hydroxyvitamin D [s25(OH)D], intact parathyroid hormone (iPTH) and biomarkers of cardiovascular disease risk in 195 healthy 20- to 40-year-olds (109 women) with a BMI between 27.5 and 32.5 from Iceland (64° N; n = 82), Ireland (51° N; n = 37) and Spain (42° N; n = 76) during mid-late winter.
The median s25(OH)D was 52.8 nmol/l (IQR 38.1-69.9) or 21.1 ng/ml (IQR 15.2-28.0) with a latitude-dependent gradient (p ≤ 0.0001): Iceland, 41.7 nmol/l (IQR 32.7-54.2) or 16.7 ng/ml (IQR 13.1-21.7); Ireland, 52.9 nmol/l (IQR 35.3-68.6) or 21.2 ng/ml (IQR 14.1-27.4), and Spain, 67.1 nmol/l (IQR 47.1-87.1) or 26.8 ng/ml (IQR 18.8-34.8). Eleven percent of Icelandic participants had s25(OH)D concentrations <25 nmol/l (10 ng/ml) and 66% of Icelandic, 43% of Irish, and 30% of Spanish volunteers had concentrations <50 nmol/l (20 ng/ml), respectively. Overall, 17% met 3 or more of the NCEP/ATP III criteria for cardio-metabolic syndrome (MetS). Participants in the lowest third of s25(OH)D [≤ 42.5 nmol/l (17 ng/ml)] were more likely to have MetS (OR 2.49, p = 0.045) and elevated TAG (OR 3.46, p = 0.019). Individuals with iPTH concentrations in the lowest third [2.34 pmol/l (22.2 pg/ml)] were more likely to have elevated fasting TAG (OR 4.17, p = 0.039), insulin (OR 3.15, p = 0.029) and HOMA-IR (OR 2.15, p = 0.031), and they were less likely to have elevated IL-6 (OR 0.24, p = 0.003).
There were interactions between s25(OH)D, iPTH and cardio-metabolic risk factors which, given the increasing prevalence of overweight and obesity and a low vitamin D status among adults, require randomised controlled vitamin D intervention studies in overweight persons.
Vitamin D deficiency is very common in non-western immigrants. In this randomized clinical trial, vitamin D 800 IU/day or 100,000 IU/3 months were compared with advised sunlight exposure. Vitamin D supplementation was more effective than advised sunlight exposure in improving vitamin D status and lowering parathyroid hormone levels.
Vitamin D deficiency (25-hydroxyvitamin D [25(OH)D] < 25 nmol/l) is common among non-western immigrants. It can be treated with vitamin D supplementation or sunlight exposure.
To determine whether the effect of vitamin D(3) supplementation (daily 800 IU or 100,000 IU/3 months) or sunlight exposure advice is similar with regard to serum 25(OH)D and parathyroid hormone (PTH) concentrations. Randomized clinical trial in 11 general practices in The Netherlands. Non-western immigrants, aged 18-65 years (n = 232) and serum 25(OH)D < 25 nmol/l were randomly assigned to supplementation (daily 800 IU or 100,000 IU/3 months) or advice for sunlight exposure for 6 months (March-September). Blood samples were collected at baseline, during treatment (3 months, 6 months), and at follow-up (12 months). Statistical analysis was performed with multilevel regression modelling.
The intention-to-treat analysis included 211 persons. Baseline serum 25(OH)D was 22.5 ± 11.1 nmol/l. After 6 months, mean serum 25(OH)D increased to 53 nmol/l with 800 IU/day, to 50.5 nmol/l with 100,000 IU/3 months, and to 29.1 nmol/l with advised sunlight exposure (supplementation vs sunshine p < 0.001). Serum PTH decreased significantly in all groups after 3 months, more in the supplementation groups than in the advised sunlight group (p < 0.05). There was no significant effect on physical performance and functional limitations.
Vitamin D supplementation is more effective than advised sunlight exposure for treating vitamin D deficiency in non-western immigrants.
Hypertension is a major risk factor for cardiovascular disease and treatment and control of hypertension reduces risk. The Healthy People 2010 goal was to achieve blood pressure (BP) control in 50% of the US population.
To assess progress in treating and controlling hypertension in the United States from 1988-2008.
The National Health and Nutrition Examination Survey (NHANES) 1988-1994 and 1999-2008 in five 2-year blocks included 42 856 adults aged older than 18 years, representing a probability sample of the US civilian population.
Hypertension was defined as systolic BP of at least 140 mm Hg and diastolic BP of at least 90 mm Hg, self-reported use of antihypertensive medications, or both. Hypertension control was defined as systolic BP values of less than 140 mm Hg and diastolic BP values of less than 90 mm Hg. All survey periods were age-adjusted to the year 2000 US population.
Rates of hypertension increased from 23.9% (95% confidence interval [CI], 22.7%-25.2%) in 1988-1994 to 28.5% (95% CI, 25.9%-31.3%; P < .001) in 1999-2000, but did not change between 1999-2000 and 2007-2008 (29.0%; 95% CI, 27.6%-30.5%; P = .24). Hypertension control increased from 27.3% (95% CI, 25.6%-29.1%) in 1988-1994 to 50.1% (95% CI, 46.8%-53.5%; P = .006) in 2007-2008, and BP among patients with hypertension decreased from 143.0/80.4 mm Hg (95% CI, 141.9-144.2/79.6-81.1 mm Hg) to 135.2/74.1 mm Hg (95% CI, 134.2-136.2/73.2-75.0 mm Hg; P = .02/P < .001). Blood pressure control improved significantly more in absolute percentages between 1999-2000 and 2007-2008 vs 1988-1994 and 1999-2000 (18.6%; 95% CI, 13.3%-23.9%; vs 4.1%; 95% CI, -0.5% to 8.8%; P < .001). Better BP control reflected improvements in awareness (69.1%; 95% CI, 67.1%-71.1%; vs 80.7%; 95% CI, 78.1%-83.0%; P for trend = .03), treatment (54.0%; 95% CI, 52.0%-56.1%; vs 72.5%; 95% CI, 70.1%-74.8%; P = .004), and proportion of patients who were treated and had controlled hypertension (50.6%; 95% CI, 48.0%-53.2%; vs 69.1%; 95% CI, 65.7%-72.3%; P = .006). Hypertension control improved significantly between 1988-1994 and 2007-2008, across age, race, and sex groups, but was lower among individuals aged 18 to 39 years vs 40 to 59 years (P < .001) and 60 years or older (P < .001), and in Hispanic vs white individuals (P = .004).
Blood pressure was controlled in an estimated 50.1% of all patients with hypertension in NHANES 2007-2008, with most of the improvement since 1988 occurring after 1999-2000. Hypertension control was significantly lower among younger than middle-aged individuals and older adults, and Hispanic vs white individuals.
Vitamin D status of nonwestern immigrants in Europe was poor. Vitamin D status of nonwestern populations in their countries of origin varied, being either similar to the immigrant populations in Europe or higher than in European indigenous populations. Vitamin D concentrations in nonwestern immigrant populations should be improved.
The higher the latitude, the less vitamin D is produced in the skin. Most European countries are located at higher latitudes than the countries of origin of their nonwestern immigrants. Our aim was to compare the serum 25-hydroxyvitamin D (25(OH)D) concentration of nonwestern immigrant populations with those of the population in their country of origin, and the indigenous population of the country they migrated to.
We performed literature searches in the "PubMed" and "Embase" databases, restricted to 1990 and later. The search profile consisted of terms referring to vitamin D or vitamin D deficiency, prevalence or cross-sectional studies, and countries or ethnicity. Titles and abstracts were reviewed to identify studies on population-based mean serum 25(OH)D concentrations among Turkish, Moroccan, Indian, and sub-Sahara African populations in Europe, Turkey, Morocco, India, and sub-Sahara Africa.
The vitamin D status of immigrant populations in Europe was poor compared to the indigenous European populations. The vitamin D status of studied populations in Turkey and India varied and was either similar to the immigrant populations in Europe (low) or similar to or even higher than the indigenous European populations (high).
In addition to observed negative consequences of low serum 25(OH)D concentrations among nonwestern populations, this overview indicates that vitamin D status in nonwestern immigrant populations should be improved. The most efficacious strategy should be the subject of further study.
Vitamin D deficiency is common and is primarily caused by a lack of ultraviolet-B (UVB) radiation from reduced sun exposure, and the consequent limiting of vitamin D production in the skin. The vitamin D endocrine system regulates about 3% of the human genome. Observational data support the concept that vitamin D is involved in the pathogenesis of cardiovascular diseases and arterial hypertension. The antihypertensive properties of vitamin D include renoprotective effects, suppression of the renin-angiotensin-aldosterone system, direct effects on vascular cells, and effects on calcium metabolism, including prevention of secondary hyperparathyroidism. The results of clinical studies largely, but not consistently, favor the hypothesis that vitamin D sufficiency promotes lowering of arterial blood pressure. Randomized, placebo-controlled trials are greatly needed to clarify and definitively prove the effect of vitamin D on blood pressure. In general, the antihypertensive effects of vitamin D seem to be particularly prominent in vitamin-D-deficient patients with elevated blood pressure. Thus, in view of the relatively safe and inexpensive way in which vitamin D can be supplemented, we believe that vitamin D supplementation should be prescribed to patients with hypertension and 25-hydroxyvitamin D levels below target values.
Vitamin D insufficiency is associated with suboptimal health. The prevalence of vitamin D insufficiency may be rising, but population-based trends are uncertain. We sought to evaluate US population trends in vitamin D insufficiency.
We compared serum 25-hydroxyvitamin D (25[OH]D) levels from the Third National Health and Nutrition Examination Survey (NHANES III), collected during 1988 through 1994, with NHANES data collected from 2001 through 2004 (NHANES 2001-2004). Complete data were available for 18 883 participants in NHANES III and 13 369 participants in NHANES 2001-2004.
The mean serum 25(OH)D level was 30 (95% confidence interval [CI], 29-30) ng/mL during NHANES III and decreased to 24 (23-25) ng/mL during NHANES 2001-2004. Accordingly, the prevalence of 25(OH)D levels of less than 10 ng/mL increased from 2% (95% CI, 2%-2%) to 6% (5%-8%), and 25(OH)D levels of 30 ng/mL or more decreased from 45% (43%-47%) to 23% (20%-26%). The prevalence of 25(OH)D levels of less than 10 ng/mL in non-Hispanic blacks rose from 9% during NHANES III to 29% during NHANES 2001-2004, with a corresponding decrease in the prevalence of levels of 30 ng/mL or more from 12% to 3%. Differences by age strata (mean serum 25[OH]D levels ranging from 28-32 ng/mL) and sex (28 ng/mL for women and 32 ng/mL for men) during NHANES III equalized during NHANES 2001-2004 (24 vs 24 ng/mL for age and 24 vs 24 ng/mL for sex).
National data demonstrate a marked decrease in serum 25(OH)D levels from the 1988-1994 to the 2001-2004 NHANES data collections. Racial/ethnic differences have persisted and may have important implications for known health disparities. Current recommendations for vitamin D supplementation are inadequate to address the growing epidemic of vitamin D insufficiency.
Vitamin D deficiency is a highly prevalent condition, present in approximately 30% to 50% of the general population. A growing body of data suggests that low 25-hydroxyvitamin D levels may adversely affect cardiovascular health. Vitamin D deficiency activates the renin-angiotensin-aldosterone system and can predispose to hypertension and left ventricular hypertrophy. Additionally, vitamin D deficiency causes an increase in parathyroid hormone, which increases insulin resistance and is associated with diabetes, hypertension, inflammation, and increased cardiovascular risk. Epidemiologic studies have associated low 25-hydroxyvitamin D levels with coronary risk factors and adverse cardiovascular outcomes. Vitamin D supplementation is simple, safe, and inexpensive. Large randomized controlled trials are needed to firmly establish the relevance of vitamin D status to cardiovascular health. In the meanwhile, monitoring serum 25-hydroxyvitamin D levels and correction of vitamin D deficiency is indicated for optimization of musculoskeletal and general health.
While the prevalence of type 2 diabetes mellitus (DM) is high, tailored risk scores for screening among South Asian and African origin populations are lacking. The aim of this study was, first, to compare the prevalence of (known and newly detected) DM among Hindustani Surinamese, African Surinamese and ethnic Dutch (Dutch). Second, to develop a new risk score for DM. Third, to evaluate the performance of the risk score and to compare it to criteria derived from current guidelines.
We conducted a cross-sectional population based study among 336 Hindustani Surinamese, 593 African Surinamese and 486 Dutch, aged 35-60 years, in Amsterdam. Logistic regressing analyses were used to derive a risk score based on non-invasively determined characteristics. The diagnostic accuracy was assessed by the area under the Receiver-Operator Characteristic curve (AUC).
Hindustani Surinamese had the highest prevalence of DM, followed by African Surinamese and Dutch: 16.7, 8.1, 4.2% (age 35-44) and 35.0, 19.0, 8.2% (age 45-60), respectively. The risk score included ethnicity, body mass index, waist circumference, resting heart rate, first-degree relative with DM, hypertension and history of cardiovascular disease. Selection based on age alone showed the lowest AUC: between 0.57-0.62. The AUC of our score (0.74-0.80) was higher than that of criteria from guidelines based solely on age and BMI and as high as criteria that required invasive specimen collection.
In Hindustani Surinamese and African Surinamese populations, screening for DM should not be limited to those over 45 years, as is advocated in several guidelines. If selective screening is indicated, our ethnicity based risk score performs well as a screening test for DM among these groups, particularly compared to the criteria based on age and/or body mass index derived from current guidelines.
In small case-control studies, obesity was associated with worse vitamin D status. Our aim was to assess the association of adiposity (anthropometric measures as well as dual energy x-ray absorptiometry) with serum 25-hydroxyvitamin D (25-OH-D) and serum PTH levels in a large population-based study including older men and women.
Subjects were participants of the Longitudinal Aging Study Amsterdam and were aged 65 yr and older. In 453 participants, serum 25-OH-D and PTH were determined, and body mass index, waist circumference, waist to hip ratio, sum of skin folds, and total body fat percentage by dual energy x-ray absorptiometry were measured.
After adjustment for potential confounders, higher body mass index, waist circumference, and sum of skin folds were statistically significantly associated with lower 25-OH-D (standardized beta values were -0.136, -0.137, and -0.140, respectively; all P < 0.05) and with higher PTH (0.166, 0.113, and 0.114, respectively; all P < 0.05). Total body fat percentage was more strongly associated with 25-OH-D and PTH (-0.261 and 0.287, respectively; both P < 0.001) compared with anthropometric measures. Total body fat percentage remained associated with 25-OH-D after adjustment for PTH, and with PTH after adjustment for 25-OH-D.
Precisely measured total body fat is inversely associated with 25-OH-D levels and is positively associated with PTH levels. The associations were weaker if anthropometric measures were used, indicating a specific role of adipose tissue. Regardless of the possible underlying mechanisms, it may be relevant to take adiposity into account when assessing vitamin D requirements.
Recent evidence supports an association between vitamin D deficiency and hypertension, peripheral vascular disease, diabetes mellitus, metabolic syndrome, coronary artery disease, and heart failure. The effect of vitamin D supplementation, however, has not been well studied. We examined the associations between vitamin D deficiency, vitamin D supplementation, and patient outcomes in a large cohort. Serum vitamin D measurements for 5 years and 8 months from a large academic institution were matched to patient demographic, physiologic, and disease variables. The vitamin D levels were analyzed as a continuous variable and as normal (≥30 ng/ml) or deficient (<30 ng/ml). Descriptive statistics, univariate analysis, multivariate analysis, survival analysis, and Cox proportional hazard modeling were performed. Of 10,899 patients, the mean age was 58 ± 15 years, 71% were women (n = 7,758), and the average body mass index was 30 ± 8 kg/m(2). The mean serum vitamin D level was 24.1 ± 13.6 ng/ml. Of the 10,899 patients, 3,294 (29.7%) were in the normal vitamin D range and 7,665 (70.3%) were deficient. Vitamin D deficiency was associated with several cardiovascular-related diseases, including hypertension, coronary artery disease, cardiomyopathy, and diabetes (all p <0.05). Vitamin D deficiency was a strong independent predictor of all-cause death (odds ratios 2.64, 95% confidence interval 1.901 to 3.662, p <0.0001) after adjusting for multiple clinical variables. Vitamin D supplementation conferred substantial survival benefit (odds ratio for death 0.39, 95% confidence interval 0.277 to 0.534, p <0.0001). In conclusion, vitamin D deficiency was associated with a significant risk of cardiovascular disease and reduced survival. Vitamin D supplementation was significantly associated with better survival, specifically in patients with documented deficiency.
Vitamin D (Vit D) deficiency has been associated with prevalent and incident cardiovascular (CV) disease, suggesting a role for bioregulators of bone and mineral metabolism in CV health. Vitamin D deficiency leads to secondary hyperparathyroidism, and both primary and secondary hyperparathyroidism are associated with CV pathology. Parathyroid hormone (PTH) is an important regulator of calcium homeostasis, and its impact on CV disease risk is of interest. We tested whether elevated PTH is associated with CV disease and whether risk associations depend on Vit D status and renal function.
Patients in the Intermountain Healthcare system with concurrent PTH and Vit D as 25-hydroxy-vitamin D (25[OH]D) levels were studied (N = 9,369, age 63 ± 16 years, 36% male). Parathyroid hormone levels were defined as low (<15 pg/mL), normal (15-75 pg/mL), or elevated (>75 pg/mL). Prevalence and incidence of hypertension, diabetes, hyperlipidemia, coronary artery disease/myocardial infarction, heart failure, stroke, and peripheral vascular disease were determined by the International Classification of Diseases, Ninth Revision codes documented in electronic medical records at baseline and, for incident events, during an average of 2.0 ± 1.5 years (maximum 7.5 years) of follow-up.
Parathyroid hormone elevation at baseline was noted in 26.1% of the study population. Highly significant differential CV prevalence/incidence rates for most CV risk factors, disease diagnoses, and mortality were noted for PTH >75 pg/mL (by 1.25- to 3-fold). Parathyroid hormone correlated only weakly (r = -0.15) with 25(OH)D and moderately with glomerular filtration rate (r = -0.36). 25(OH)D, standard risk factors, and renal dysfunction variably attenuated PTH risk associations, but risk persisted after full multivariable adjustment.
Elevated PTH is associated with a greater prevalence and incidence of CV risk factors and predicts a greater likelihood of prevalent and incident disease, including mortality. Risk persists when adjusted for 25(OH)D, renal function, and standard risk factors. Parathyroid hormone represents an important new CV risk factor that adds complementary and independent predictive value for CV disease and mortality.
Previous research shows serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) are each associated with blood pressure (BP), but it is unclear whether these associations are independent.
Cross-sectional data from the US National Health and Nutrition Examination Surveys (NHANES) during 2003-2006. Analyses were restricted to 7,561 participants aged ≥20 years with measurements of 25(OH)D, PTH, BP, BP treatment, smoking, physical activity, serum calcium, and creatinine. Results were adjusted for these plus demographic variables.
Serum 25(OH)D was more strongly associated (inversely) with systolic than diastolic BP. Adjusted mean (standard error) difference in BP for the lowest 25(OH)D quintile (≤13 ng/ml) was 3.5 (0.7) mm Hg for systolic BP and 1.8 (0.6) mm Hg for diastolic BP, compared with the highest quintile (≥30 ng/ml). In contrast, PTH was positively associated with both systolic and diastolic BP (P < 0.0001). Adjusted mean (standard error) difference in BP for the highest PTH quintile (≥59 ng/l) was 5.9 (0.8) mm Hg for systolic BP and 4.5 (0.5) mm Hg for diastolic BP, compared with the lowest quintile (≤27 ng/l). When both 25(OH)D and PTH were included in the same model, the associations of PTH with systolic and diastolic BP were unchanged. However, the associations between 25(OH)D and BP were attenuated, with mean (standard error) difference between the highest and lowest quintiles being 2.2 (0.6) mm Hg for systolic BP (P < 0.01) and 0.8 (0.6) mm Hg for diastolic BP.
PTH may mediate most of the association between 25(OH)D and BP, which was not significant when also adjusting for body mass index.
The prevalence of hypertension is higher among blacks than whites. However, inconsistent findings have been reported on the incidence of hypertension among middle-aged and older blacks and whites, and limited data are available on the incidence of hypertension among Hispanics and Asians in the United States. Therefore, this study investigated the age-specific incidence of hypertension by ethnicity for 3146 participants from the Multi-Ethnic Study of Atherosclerosis. Participants, age 45 to 84 years at baseline, were followed for a median of 4.8 years for incident hypertension, defined as systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg, or the initiation of antihypertensive medications. The crude incidence rate of hypertension, per 1000 person-years, was 56.8 for whites, 84.9 for blacks, 65.7 for Hispanics, and 52.2 for Chinese. After adjustment for age, sex, and study site, the incidence rate ratio (IRR) for hypertension was increased for blacks age 45 to 54 (IRR: 2.05 [95%CI: 1.47 to 2.85]), 55 to 64 (IRR: 1.63 [95% CI: 1.20 to 2.23]), and 65 to 74 years (IRR: 1.67 [95% CI: 1.21 to 2.30]) compared with whites but not for those 75 to 84 years of age (IRR: 0.97 [95% CI: 0.56 to 1.66]). Additional adjustment for health characteristics attenuated these associations. Hispanic participants also had a higher incidence of hypertension compared with whites; however, hypertension incidence did not differ for Chinese and white participants. In summary, hypertension incidence was higher for blacks compared with whites between 45 and 74 years of age but not after age 75 years. Public health prevention programs tailored to middle-aged and older adults are needed to eliminate ethnic disparities in incident hypertension.
To examine independent associations of serum 25-hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH) and calcium with a range of cardiovascular risk factors in adolescents.
Cross-sectional population-based study.
A nationally representative sample of the US adolescent population.
Healthy adolescents (aged 12-19) participating in the National Health and Nutrition Examination Survey (NHANES) between 2001 and 2006. Numbers varied between 740 and 5609 for given exposure and outcome associations.
Systolic blood pressure (SBP), diastolic blood pressure (DBP), lipids (triglycerides, low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C)), fasting insulin and glucose, postload glucose and glycohaemoglobin (HbA1c).
25(OH)D was inversely associated with SBP (-0.068 standard deviations (SD), 95% CI -0.118 to -0.018), and positively associated with HDL-C (0.101; 0.040 to 0.162) and HbA1c (0.073; 0.021 to 0.125) after adjustment for gender, age, ethnicity, socioeconomic status and waist circumference. In adjusted models, PTH was inversely associated with triglycerides (-0.115; -0.188 to -0.042) and LDL-C (-0.133; -0.207 to -0.060). In adjusted models, calcium was positively associated with fasting insulin (0.110; 0.060 to 0.160), postload glucose (0.116; 0.000 to 0.232), HbA1c (0.079; 0.035 to 0.123), triglycerides (0.182; 0.122 to 0.242), HDL-C (0.049; 0.010 to 0.088) and LDL-C (0.137; 0.080 to 0.195). The associations of each exposure with risk factors remained after mutual adjustment for each other.
Higher calcium levels might be a more important predictor of increased cardiovascular risk in adolescents than lower 25(OH)D levels or PTH levels, but the findings require replication in additional studies and examination in prospective studies.
Increasing evidence indicates that vitamin D may influence the risk of hypertension, which is a major risk factor for cardiovascular disease. We conducted a meta-analysis to quantitatively review and summarize the results on the association between blood 25-hydroxyvitamin D concentrations and hypertension.
Relevant studies were identified by a search of PubMed and EMBASE databases until November 2010. We also reviewed the references of retrieved articles. We included prospective and cross-sectional studies with blood 25-hydroxyvitamin D concentrations as the exposure and hypertension as the outcome. Studies had to report results as a relative risk or an odds ratio. We used random-effects model.
Of the 18 studies included in the meta-analysis, 4 were prospective studies and 14 were cross-sectional studies. The pooled odds ratio of hypertension was 0.73 [95% confidence interval (CI) 0.63-0.84] for the highest versus the lowest category of blood 25-hydroxyvitamin D concentration. In a dose-response meta-analysis, the odds ratio for a 40 nmol/l (16 ng/ml) (approximately 2 SDs) increment in blood 25-hydroxyvitamin D concentration was 0.84 (95% CI 0.78-0.90).
Findings from this meta-analysis indicate that blood 25-hydroxyvitamin D concentration is inversely associated with hypertension.
Vitamin D deficiency is highly prevalent and may contribute to arterial hypertension. The antihypertensive effects of vitamin D include suppression of renin and parathyroid hormone levels and renoprotective, anti-inflammatory and vasculoprotective properties. Low 25-hydroxyvitamin D levels, which are used to classify the vitamin D status, are an independent risk factor for incident arterial hypertension. Meta-analyses of randomized controlled trials showed that vitamin D supplementation reduces systolic blood pressure by 2-6 mmHg. However, further studies are needed before drawing a final conclusion on the effect of vitamin D therapy on blood pressure and cardiovascular risk. In our current clinical practice we should take into account the high prevalence of vitamin D deficiency, the easy, cheap and safe way by which it can be supplemented and the promising clinical data suggesting that vitamin D might be useful for the treatment of arterial hypertension as well as other chronic diseases. Therefore, we recommend that testing for and treating vitamin D deficiency in patients with arterial hypertension should be seriously considered.
to study seasonal variation in prevalence of hypertension.
the study was carried out in the year 2006, in Gokulpuri, an urban slum located in eastern part of Delhi. 275 females 18-40 years of age were examined in summer. Blood pressure was measured in two seasons, summer and winter. Nutritional status of each individual was assessed by BMI.
the prevalence of hypertension based on SBP was 12.72% in summer which increased to 22.22% in winter. The prevalence of hypertension, using DBP criteria increased to more than double (summer vs. winter, 11.27% vs. 26.59%, P< 0.001). Overall prevalence of hypertension (SBP ≥ 140 or DBP ≥ 90 mm of Hg) was 1.9 times during winter compared to summer (P<0.001). Greater increase in prevalence of hypertension during winter among older females and underweight as well as normal females was observed.
Significant increase in prevalence of hypertension during winter compared to summer indicates need for considering this factor while comparing prevalence reported in different studies as well as interpreting the surveillance data based on repeat surveys.
Vitamin D has been reported to lower blood pressure in vivo by regulating the renin-angiotensin system; however, there are limited clinical studies to support this finding in humans. We investigated the effect of vitamin D treatment on hypertension in a three-arm randomized placebo controlled pilot and feasibility study. We tested placebo with two forms of vitamin D: cholecalciferol (vitamin D(3)) and the active form of vitamin D, calcitriol. Subjects were recruited from the Atlanta Veterans Affairs Medical Center in Decatur, GA between April and August 2008. Subjects received 200,000IU of vitamin D(3) (n=3) weekly for 3 weeks or matching placebo (n=3) weekly for 3 weeks (n=3) or 0.5mug calcitriol (n=2) taken twice daily for one week. Our primary endpoint was blood pressure measured by 24h ambulatory blood pressure monitor. Subjects receiving calcitriol experienced a 9% decrease in mean systolic blood pressure (SBP) compared placebo (p<0.001). One week after conclusion of calcitriol therapy SBP returned to pre-treatment levels. There was no reduction in blood pressure in the placebo or vitamin D(3) groups. Results from this pilot study suggests that active vitamin D therapy may be an effective short-term intervention for reducing blood pressure and needs to be explored further in larger controlled studies.
The purpose of the present study was to examine seasonal blood pressure variation and its relationship to environmental temperature in healthy elderly Japanese, as studied by home measurements. Fifteen healthy elderly Japanese (79.3 +/- 5.9 yrs) measured their blood pressure at home each morning for more than 25 times per month for 3 years. Monthly mean outdoor temperatures were obtained from the Takamatsu meteorological Observatory. The highest levels of systolic and diastolic blood pressure measured at home were observed in February (129 +/- 14 and 81 +/- 13 mmHg). The lowest levels of systolic and diastolic blood pressure measured at home were observed in August (117 +/- 11 and 73 +/- 10 mmHg). Likewise, the lowest and highest means of outdoor temperature were observed in February (5.0 degrees C) and August (29.2 degrees C), respectively. Hence, both systolic and diastolic blood pressure demonstrated a close inverse correlation with the means of outdoor temperature (r = -0.973, p < 0.001 and r = -0.985, p < 0.001, respectively). A 1 degree C decrease in the mean outdoor temperature was associated with rises of 0.43 mmHg in systolic blood pressure (SBP) and 0.29 mmHg in diastolic blood pressure (DBP). Seasonal variations in home blood pressure and outdoor temperature showed complete correspondence in healthy elderly Japanese, with the blood pressures being inversely related to the ambient temperature. These seasonal home blood pressure variations should be kept in mind when controlling blood pressure in elderly patients.
Numerous cross-sectional studies demonstrate an inverse association between plasma 25-hydroxyvitamin D [25(OH)D] and blood pressure or hypertension. Prospective data, however, are limited. Among 1484 women aged 32 to 52 years who did not have hypertension at baseline, we prospectively analyzed the association between plasma levels of 25(OH)D and the odds of incident hypertension using a nested case-control study design. We matched cases and controls on age, race, and month of blood collection and further adjusted for body mass index, physical activity, family history of hypertension, oral contraceptive use, and plasma levels of parathyroid hormone, calcium, phosphorous, creatinine, and uric acid. Median plasma 25(OH)D levels were lower in the cases (25.6 ng/mL) than in the controls (27.3 ng/mL; P<0.001). Women in the lowest compared with highest quartile of plasma 25(OH)D had an adjusted odds ratio for incident hypertension of 1.66 (95% CI: 1.11 to 2.48; P for trend=0.01). Compared with women with sufficient levels, those with vitamin D deficiency (<30 ng/mL; 65.7% of the study population) had a multivariable odds ratio of 1.47 (95% CI: 1.10 to 1.97). Plasma 25(OH)D levels are inversely and independently associated with the risk of developing hypertension.
African Americans have lower serum 25-hydroxyvitamin D concentrations and a lower risk of fragility fractures than do other populations. I review the evidence on factors other than vitamin D that might explain this paradox and the calcium economy in different life stages. Researchers are actively trying to explain this genetically programmed advantage. Factors that could protect African Americans against fracture include their higher peak bone mass, increased obesity rates, greater muscle mass, lower bone turnover rates, and advantageous femur geometry. In addition, bone histomorphometry in young adults shows longer periods of bone formation. Although African Americans fall as frequently as do whites, the direction of their falls and their manner of breaking falls could protect them from fractures. African American girls accrue more calcium than do white girls during adolescence as the result of increased calcium absorption and superior renal calcium conservation. In adulthood, higher parathyroid hormone concentrations do not result in increased bone loss in African Americans because of their skeletal resistance to parathyroid hormone, and their superior renal conservation of calcium persists. These advantages diminish in the elderly, in whom further increases in parathyroid hormone result in increased bone turnover and bone loss. Ultimately, I explain the paradox by multiple factors associated with fracture risk and calcium economy in African Americans. Despite African Americans' reduced risk of osteoporotic fractures, such fractures remain an important public health problem for this population that vitamin D intervention studies have not addressed.
Seasonal changes in 25-hydroxyvitamin D concentrations were studied in 51 black and 39 white women aged 20-40 y from Boston. Individual measurements were made in February or March (February-March), June or July (June-July), October or November (October-November), and the following February or March (February-March). Samples from the four visits were analyzed in batches at the end of the study. Plasma 25-hydroxyvitamin D was substantially lower in black than in white women at all the time points, including February-March when values were lowest (30.2 +/- 19.7 nmol/L in black and 60.0 +/- 21.4 nmol/L in white women) and June-July when they were highest (41.0 +/- 16.4 nmol/L in black and 85.4 +/- 33.0 nmol/L in white women). Although both groups showed seasonal variation in 25-hydroxyvitamin D concentrations, the mean increase between February-March and June-July was smaller in black women (10.8 +/- 14.0 nmol/L compared with 25.4 +/- 29.8 nmol/L in white women, P = 0.006) and their overall amplitude of seasonal change was lower (P = 0.001). Concentrations of serum parathyroid hormone in February-March were significantly higher (P < 0.005) in black women (5.29 +/- 2.32 pmol/L) than in white women (4.08 +/- 1.41 pmol/L) and were significantly inversely correlated with 25-hydroxyvitamin D in blacks (r = -0.42, P = 0.002) but not in whites (r = -0.19, P = 0.246). Although it is well established that blacks have denser bones and lower fracture rates than whites, elevated parathyroid hormone concentrations resulting from low 25-hydroxyvitamin D concentrations may have negative skeletal consequences within black populations.
The renin-angiotensin system (RAS) plays a central role in the regulation of blood pressure, electrolyte, and volume homeostasis. Epidemiological and clinical studies have long suggested an association of inadequate sunlight exposure or low serum 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] levels with high blood pressure and/or high plasma renin activity, but the mechanism is not understood. Our recent discovery that 1,25(OH)(2)D(3) functions as a potent negative endocrine regulator of renin gene expression provides some insights into the mechanism. The concept of vitamin D regulation of blood pressure through the RAS opens a new avenue to our understanding of the physiological functions of the vitamin D endocrine system, and provides a basis for exploring the potential use of vitamin D analogues in prevention and treatment of hypertension.
The purpose of this study is to determine reproducibility and relative validity of the Short QUestionnaire to ASsess Health-enhancing physical activity (SQUASH).
Participants (36 men and 14 women, aged 27-58) were asked to complete the SQUASH twice with an inbetween period of approximately 5 weeks. In addition, participants wore the Computer Science and Applications (CSA) Activity Monitor for a 2-week period following the first questionnaire.
The Spearman correlation for overall reproducibility of the SQUASH was 0.58 (95%-CI 0.36-0.74). Correlations for the reproducibility of the separate questions varied between 0.44 and 0.96. Spearman's correlation coefficient between CSA readings and the total activity score was 0.45 (95%-CI 0.17-0.66).
In conclusion, the SQUASH is a fairly reliable and reasonably valid questionnaire and may be used to order subjects according to their level of physical activity in an adult population. Because the SQUASH is a short and simple questionnaire, it may proof to be a very useful tool for the evaluation of health enhancing physical activity in large populations.
To assess ethnic differences in prevalence, levels of awareness, treatment and control of hypertension among Dutch ethnic groups and to determine whether these differences are consistent with the UK findings.
Cross-sectional survey.
South-east Amsterdam, The Netherlands.
A random sample of 1383 non-institutional adults aged 35-60 years. Of these, 36.7% were White, 42% were Black and 21.3% were South Asian people.
Prevalence of hypertension, rates of awareness, treatment, and control of hypertension.
The Black and South Asian subjects had a higher prevalence of hypertension compared with White people. After adjustments for age, the odds ratios (95% confidence interval) for being hypertensive were 2.2 (1.4-3.4; P < 0.0001) and 3.8 (2.6-5.7; P < 0.0001) for Black men and women, respectively, and 1.7 (1.0-2.6; P = 0.039) and 2.8 (1.8-4.5; P < 0.0001) for South Asian men and women, compared with White people. There were no differences in awareness and pharmacological treatment of hypertension between the groups. However, Black hypertensive men 0.3 (0.1-0.7; P < 0.01) and women 0.5 (0.3-0.9; P < 0.05) were less likely to have their blood pressure adequately controlled compared with White people.
The higher prevalence of hypertension found among Black and South Asian people in The Netherlands is consistent with the UK studies. However, the lower control rates and the similar levels of awareness and treatment of hypertension in Black Surinamese contrast with the higher rates reported in African Caribbeans in the UK. The rates for the South Asians in The Netherlands were relatively favourable compared to similar South Asian groups in the UK. These findings underscore the urgent need to develop strategies aimed at improving the prevention and control of hypertension, especially among Black people, in The Netherlands.
Vitamin D insufficiency is more prevalent among African Americans (blacks) than other Americans and, in North America, most young, healthy blacks do not achieve optimal 25-hydroxyvitamin D [25(OH)D] concentrations at any time of year. This is primarily due to the fact that pigmentation reduces vitamin D production in the skin. Also, from about puberty and onward, median vitamin D intakes of American blacks are below recommended intakes in every age group, with or without the inclusion of vitamin D from supplements. Despite their low 25(OH)D levels, blacks have lower rates of osteoporotic fractures. This may result in part from bone-protective adaptations that include an intestinal resistance to the actions of 1,25(OH)2D and a skeletal resistance to the actions of parathyroid hormone (PTH). However, these mechanisms may not fully mitigate the harmful skeletal effects of low 25(OH)D and elevated PTH in blacks, at least among older individuals. Furthermore, it is becoming increasingly apparent that vitamin D protects against other chronic conditions, including cardiovascular disease, diabetes, and some cancers, all of which are as prevalent or more prevalent among blacks than whites. Clinicians and educators should be encouraged to promote improved vitamin D status among blacks (and others) because of the low risk and low cost of vitamin D supplementation and its potentially broad health benefits.
Hydroxylation of 25(OH)D to 1,25-dihydroxyvitamin D and signaling through the vitamin D receptor occur in various tissues not traditionally involved in calcium homeostasis. Laboratory studies indicate that 1,25-dihydroxyvitamin D suppresses renin expression and vascular smooth muscle cell proliferation; clinical studies demonstrate an inverse association between ultraviolet radiation, a surrogate marker for vitamin D synthesis, and blood pressure. We prospectively studied the independent association between measured plasma 25-hydroxyvitamin D [25(OH)D] levels and risk of incident hypertension and also the association between predicted plasma 25(OH)D levels and risk of incident hypertension. Two prospective cohort studies including 613 men from the Health Professionals' Follow-Up Study and 1198 women from the Nurses' Health Study with measured 25(OH)D levels were followed for 4 to 8 years. In addition, 2 prospective cohort studies including 38 388 men and 77 531 women with predicted 25(OH)D levels were followed for 16 to 18 years. During 4 years of follow-up, the multivariable relative risk of incident hypertension among men whose measured plasma 25(OH)D levels were <15 ng/mL (ie, vitamin D deficiency) compared with those whose levels were >or=30 ng/mL was 6.13 (95% confidence interval [CI]: 1.00 to 37.8). Among women, the same comparison yielded a relative risk of 2.67 (95% CI: 1.05 to 6.79). The pooled relative risk combining men and women with measured 25(OH)D levels using the random-effects model was 3.18 (95% CI: 1.39 to 7.29). Using predicted 25(OH)D levels in the larger cohorts, the multivariable relative risks comparing the lowest to highest deciles were 2.31 (95% CI: 2.03 to 2.63) in men and 1.57 (95% CI: 1.44 to 1.72) in women. Plasma 25(OH)D levels are inversely associated with risk of incident hypertension.
Vitamin D inadequacy is pandemic among rehabilitation patients in both inpatient and outpatient settings. Male and female patients of all ages and ethnic backgrounds are affected. Vitamin D deficiency causes osteopenia, precipitates and exacerbates osteoporosis, causes the painful bone disease osteomalacia, and worsens proximal muscle strength and postural sway. Vitamin D inadequacy can be prevented by sensible sun exposure and adequate dietary intake with supplementation. Vitamin D status is determined by measurement of serum 25-hydroxyvitamin D. The recommended healthful serum level is between 30 and 60 ng/mL. 25-Hydroxyvitamin D levels of >30 ng/mL are sufficient to suppress parathyroid hormone production and to maximize the efficiency of dietary calcium absorption from the small intestine. This can be accomplished by ingesting 1000 IU of vitamin D(3) per day, or by taking 50,000 IU of vitamin D(2) every 2 weeks. Vitamin D toxicity is observed when 25-hydroxyvitamin D levels exceed 150 ng/mL. Identification and treatment of vitamin D deficiency reduces the risk of vertebral and nonvertebral fractures by improving bone health and musculoskeletal function. Vitamin D deficiency and osteomalacia should be considered in the differential diagnosis of patients with musculoskeletal pain, fibromyalgia, chronic fatigue syndrome, or myositis. There is a need for better education of health professionals and the general public regarding the optimization of vitamin D status in the care of rehabilitation patients.
Populations with low vitamin D status, such as blacks living in the US or UK, have increased blood pressure (BP) compared with whites. We analyzed the association between serum 25-hydroxyvitamin D (25OHD) and BP to determine whether low 25OHD explains any of the increased BP in blacks.
The Third US National Health and Nutrition Examination Survey (NHANES III) is a cross-sectional survey representative of the US civilian population during 1988 to 1994. Analyses were restricted to 12,644 people aged > or =20 years with measurements of BP and 25OHD, after excluding those on hypertensive medication.
Adjusted mean serum 25OHD was lowest in non-Hispanic blacks (49 nmol/L), intermediate in Mexican Americans (68 nmol/L), and highest in non-Hispanic whites (79 nmol/L). When participants were divided into 25OHD quintiles, mean (standard error) systolic BP was 3.0 (0.7) mm Hg lower (P = .0004) and diastolic BP was 1.6 (0.6) mm Hg lower (P = .011) for participants in the highest quintile (25OHD > or =85.7 nmol/L) compared with the lowest (25OHD < or =40.4 nmol/L), adjusting for age, sex, ethnicity, and physical activity. Further adjustment for body mass index (BMI) weakened the inverse association between 25OHD and BP, which remained significant for systolic BP (P < .05). The inverse association between 25OHD and systolic BP was stronger in participants aged > or =50 years than younger (P = .021). Ethnic differences in 25OHD explained about half of the increased hypertension prevalence in non-Hispanic blacks compared with whites.
Vitamin D status, which is amenable to intervention by safely increasing sun exposure or vitamin D supplementation, was associated inversely with BP in a large sample representative of the US population.
To test whether a single large dose of vitamin D2 can improve endothelial function in patients with Type 2 diabetes mellitus and low serum 25-hydroxyvitamin D levels.
Double-blind, parallel group, placebo-controlled randomized trial. A single dose of 100,000 IU vitamin D2 or placebo was administered to patients with Type 2 diabetes over the winter, when levels of circulating 25-hydroxyvitamin D were likely to be lowest. Patients were enrolled if their baseline 25-hydroxyvitamin D level was < 50 nmol/l. Endothelial function and blood pressure were measured and fasting blood samples were taken at baseline and 8 weeks after administration of vitamin D.
Forty-nine per cent of subjects screened had 25-hydroxyvitamin D levels < 50 nmol/l. Thirty-four subjects completed the study, with a mean age of 64 years and a baseline 25-hydroxyvitamin D level of 38.3 nmol/l. Vitamin D supplementation increased 25-hydroxyvitamin D levels by 15.3 nmol/l relative to placebo and significantly improved flow mediated vasodilatation (FMD) of the brachial artery by 2.3%. The improvement in FMD remained significant after adjusting for changes in blood pressure. Vitamin D supplementation significantly decreased systolic blood pressure by 14 mmHg compared with placebo; this did not correlate with change in FMD.
Vitamin D insufficiency is common in patients with Type 2 diabetes during winter in Scotland. A single large dose of oral vitamin D2 improves endothelial function in patients with Type 2 diabetes and vitamin D insufficiency.