Association of 25-hydroxyvitamin D with incident coronary heart disease in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study.

Background Low circulating 25-hydroxyvitamin D (25[OH]D) has been associated with increased risk of coronary heart disease (CHD), but whether this association differs by race is unclear. Methods We examined the association of 25[OH]D with incident CHD in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a prospective cohort study of black and white adults >= 45 years of age enrolled between 2003 and 2007 with follow-up through December 31, 2011. Using a case-cohort design, we measured 25[OH]D in 829 participants who developed incident CHD (cases) and in 813 participants without CHD randomly selected from the REGARDS cohort (comparison subcohort). Cox proportional hazards models were used to examine associations of 25[OH]D with incident CHD adjusting for established CHD risk factors in the study sample overall and stratified by race. Results In the fully adjusted model, lower quintiles of 25[OH]D were associated with a greater risk of incident CHD (25 [OH]D > 33.6 ng/ml reference; 25[OH]D > 27.1-33.6 ng/ml, hazard ratio [HR] 2.79, 95% CI 1.64-4.76; 25[OH] D > 22.4-27.1 ng/ml, HR 2.77, 95% CI 1.57-4.89; 25[OH]D > 16.5-22.4 ng/ml, HR 5.52, 95% CI 3.21-9.50; 25[OH] D <= 16.5 ng/ml, HR 7.46, 95% CI 4.19-13.25). The results were similar when 25[OH]D was examined on a continuous scale (HR per 10-ng/mL decrement in 25[OH]D 2.04, 95% CI 1.65-2.52). The results did not statistically differ by race whether 25[OH]D was examined as a categorical or continuous variable (P-interaction > .10). Conclusions Lower plasma 25(OH)D concentrations were associated with higher risk of incident CHD. In contrast to prior studies, these associations did not differ by race.