July 10, 2013
Association Of Low Vitamin D Levels With Risk Of CHD Events Differs By Race, Ethnicity
In a multiethnic group of adults, low serum 25-hydroxyvitamin D concentration was associated with increased risk of coronary heart disease events among white or Chinese participants but not among black or Hispanic participants, results that suggest that the risks and benefits of vitamin D supplementation should be evaluated carefully across race and ethnicity, according to a study in the July 10 issue of JAMA.
"Low circulating concentrations of 25-hydroxyvitamin D (25[OH]D) have been consistently associated with increased risk of clinical and subclinical coronary heart disease (CHD). Whether this relationship is causal and modifiable with vitamin D supplementation has not yet been determined in well-powered clinical trials, which are ongoing," according to background information in the article. "Most studies of 25(OH)D and risk of CHD have examined populations that are composed largely or entirely of white participants. Results from these studies are frequently extrapolated to multiracial populations. This may not be appropriate because vitamin D metabolism and circulating 25 (OH)D concentrations vary substantially by race/ethnicity."Cassianne Robinson-Cohen, Ph.D., of the University of Washington, Seattle, and colleagues examined the association of serum 25(OH)D concentration with incident CHD events in a large, community-based, multiethnic population of adults. The analysis included 6,436 participants in the Multi-Ethnic Study of Atherosclerosis (MESA), recruited from July 2000 through September 2002, who were free of known cardiovascular disease at the beginning of the study. Serum 25(OH)D concentrations were measured at baseline and associations of 25(OH)D with adjudicated CHD events were assessed through May 2012. Adjudicated CHD event was defined as myocardial infarction (heart attack), angina, cardiac arrest, or CHD death.
At the beginning of the study, the average age was 62 years and 53 percent of participants were women. Average serum 25(OH)D concentrations varied substantially by race/ethnicity. During a median (midpoint) follow-up of 8.5 years, 361 participants had a CHD event.
The researchers found significant heterogeneity in the association of 25(OH)D with CHD risk by race/ethnicity. Lower serum 25(OH)D concentration was associated with significantly higher risks of CHD among white participants (26 percent higher risk) per 10 ng/mL decrement in 25(OH)D concentration and Chinese participants (67 percent higher risk). "However, there was no evidence of association among black participants or Hispanic participants."
"Differences in associations across race/ethnicity groups were consistent for both a broad and restricted definition of CHD and persisted after adjustment for known CHD risk factors," the authors write.
"Well-powered clinical trials are needed to determine whether vitamin D supplements have causal and clinically relevant effects on the risk of CHD. Currently, at least 5 such trials are under way. One of these trials, the Vitamin D and Omega-3 Trial (VITAL), is targeting enrollment of a large multiracial study population, although power may be insufficient to determine whether effects vary by race even in this trial. Our study suggests that the risks and benefits of vitamin D supplementation should be evaluated carefully across race and ethnicity, and that the results of ongoing vitamin D clinical trials should be applied cautiously to individuals who are not white."
(JAMA. 2013;310(2):179-188; Available pre-embargo to the media at http://media.jamanetwork.com)
Editor's Note: This study was supported by grants from the National Heart, Lung, and Blood Institute. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, etc.
Editorial: Race/Ethnicity, Serum 25-Hydroxyvitamin D, and Heart Disease
In an accompanying editorial, Keith C. Norris, M.D., of the University of California, Los Angeles, and Sandra F. Williams, D.M.D., M.D., of the Cleveland Clinic, Weston, Fla., write that "â¦ this large, well-designed, multiethnic study adds important insights to the complex relationships among race/ethnicity, 25(OH)D concentrations, and CHD risk."
"The heterogeneity of the findings underscores the importance of exploring racial differences in clinical research and of not immediately generalizing results from ethnically homogeneous populations to other groups that may differ by race/ethnicity, sex, or age. Although the pooled data demonstrated a significant association between 25(OH)D and CHD, the subgroup analyses revealed marked differences underscoring the importance of examining such cohorts by race/ethnicity and thereby potentially discovering sociocultural or biological mediators that may affect cardiovascular health."
(JAMA. 2013;310(2):153-154; Available pre-embargo to the media at http://media.jamanetwork.com)
Editor's Note: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr. Norris reports receiving grant support from the National Institutes of Health; and payment for lectures and consulting from Abbott, Amgen, Davita, and Takeda. Dr. Williams reported no disclosures.
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