Vitamin-D Link to CHD Varies by Race in MESA Analysis

July 10, 2013

SEATTLE, WA — Low serum levels of 25-hydroxyvitamin D (25[OH]D or vitamin D) independently predicted raised long-term risk of coronary heart disease (CHD) events among white but not among African American participants in the multicenter, community-based Multi-Ethnic Study of Atherosclerosis (MESA)[1]. MESA participants, by design, were free of clinical heart disease at baseline.

That means that the significant inverse association between vitamin-D levels and CHD risk observed across the entire MESA cohort "was driven by the association in the white participants," lead author Dr Cassianne Robinson-Cohen (Kidney Research Institute, University of Washington, Seattle) told heartewire .

The analysis also showed a significant vitamin-D/CHD link among Chinese but not Hispanic MESA participants; however, Robinson-Cohen said she and her colleagues are less confident about those findings due to the small numbers of those groups in MESA but are confident that the difference between whites and blacks is real.

The findings appear in the July 10, 2013 issue of the Journal of the American Medical Association, along with an editorial from Dr Keith C Norris (University of California, Los Angeles) and Dr Sandra F Williams (Cleveland Clinic, Weston, Florida) [2]. It states, echoing a major observation from Robinson-Cohen et al, "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."

The analysis included 6436 MESA participants, who enrolled from July 2000 through September 2002, for whom serum 25(OH)D concentrations were known at baseline. They represented 94% of the entire MESA population, which, as heartwire has long described, was intentionally racially and ethnically diverse: 38% white, 28% African American, 22% Hispanic, and 12% Chinese. They were enrolled at six centers across the US.

Overall, during a median follow-up of 8.5 years, decreasing levels of 25(OH)D corresponded to rising risk of adjudicated CHD events (represented mostly by angina and MI but also CHD-related death and resuscitated cardiac arrest). The interaction between CHD events and ethnicity/race was significant at p<0.05.

The group's fully adjusted model showed significantly raised CHD-event risks for MESA participants who were white (26% jump per 10-ng/mL drop in 25(OH)D levels) and Chinese MESA participants (67% risk increase per 10-ng/mL decrement) but not for those who were African American or Hispanic.

Hazard Ratio (95% CI) for CHD Events, Lowest vs Highest 25(OH)D Levels, by Race/Ethnicity in MESA

Cohort <20 ng/mL vs >30 ng/mL Per 10-ng/mL decrement
Whitea 1.85 (1.21-2.81) 1.26 (1.06-1.49)
Chinesea 2.43 (0.81-7.5) 1.67 (1.07-2.61)
Allb 1.32 (0.95-1.83) 1.15 (1.01-1.32)

a. Adjusted for age, sex, study site, body-mass index, smoking status, education, family income, self-reported health status, exercise, "nutritional" vitamin-D intake, diabetes status, systolic BP, use of antihypertensive medication, chronic kidney disease status, lipid-lowering medications, HDL-cholesterol, LDL-cholesterol, "triglyceride cholesterol," parathyroid hormone, and C-reactive protein

b. Further adjusted  for  race/ethnicity

A link between low vitamin-D levels and increased CHD risk has long been observed, but largely in smaller studies or those with a predominance of white subjects, Robinson-Cohen observed. Their analysis, she said, "is the most rigorous study so far looking at this association across race/ethnicity groups."

A number of ongoing studies are attempting to clarify mechanisms behind the link and especially whether vitamin-D supplementation might lower CHD risk, she said; the report refers to one called the Vitamin D and Omega-3 Trial (VITAL) that is attempting to enroll a large, racially diverse population.

"The next step is to look at the genetic variability in individual susceptibility to low vitamin-D levels, and that's what we're going to be working on next."

The study was supported by the National Heart, Lung, and Blood Institute. Robinson-Cohen had no disclosures. Disclosures for the coauthors are listed in the paper. Norris discloses receiving grant support from the National Institutes of Health and payment for lectures and consulting from Abbott, Amgen, Davita, and Takeda. Williams had no disclosures.

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