Issue: August 2013
July 10, 2013
3 min read

Study highlights racial differences in association of vitamin D, CHD events

Issue: August 2013
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In a multiethnic group of adults, low serum 25-hydroxyvitamin D concentration was associated with increased risk for CHD events among white and Chinese participants, but not among black and Hispanic participants.

According to researchers, these findings suggest that the risks and benefits of vitamin D supplementation should be evaluated carefully across race and ethnicity.

“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, PhD, of the University of Washington, Seattle, and colleagues wrote in the study.

Cassiane Robinson-Cohen, PhD 

Cassiane Robinson-Cohen

For this study, the researchers examined the association of serum 25(OH)D concentration with incident CHD events in the large, community-based Multi-Ethnic Study of Atherosclerosis (MESA). The analysis included 6,436 participants recruited from July 2000 to September 2002 who were free of known CVD at baseline. At baseline, the participants’ mean age was 62 years and 53% were women. Serum 25(OH)D concentrations were measured at baseline and associations of 25(OH)D with adjudicated CHD events were assessed through May 2012.

Average serum 25(OH)D concentrations varied substantially by race/ethnicity. During a median follow-up of 8.5 years, 361 participants experienced a CHD event (7.38 events per 1,000 person-years), which included MI, angina, cardiac arrest of CHD death, according to a press release.

The researchers found significant heterogeneity in the association of 25(OH)D with CHD risk by race/ethnicity (P<.05). A lower serum 25(OH)D concentration was associated with significantly higher risk for CHD among white participants (26% higher risk) per 10 ng/mL decrement in 25(OH)D concentration and Chinese participants (67% higher risk; n=27 events), according to the release.

However, there was no association between lower serum 25(OH)D concentration and higher risk for CHD events among black 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 researchers wrote.

A complex relationship

In an accompanying editorial, Keith C. Norris, MD, of the University of California, Los Angeles, and Sandra F. Williams, DMD, MD, of the Cleveland Clinic, Weston, Fla., wrote that “…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,” Norris and Williams wrote.

Ongoing evaluation

Robinson-Cohen and colleagues said there is a need for “well-powered” clinical trials to determine the effects of vitamin D supplementation on CHD risk.

“Currently, at least five such trials are underway,” they wrote in the study. “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 trials should be applied cautiously to individuals who are not white.”

For more information:

Norris KC. JAMA. 2013;310:153-154.

Robinson-Cohen. JAMA. 2013;310:179-188.

Disclosure: Norris reports receiving grant support from the NIH and payment for lectures/consulting from Abbott, Amgen, Davita and Takeda. Robinson-Cohen reports no relevant financial disclosures; see the full study for the other researchers’ disclosures. Williams reports no relevant financial disclosures.