Abstract T P146: Vitamin D Deficiency is Associated With Stroke in Black and White Participants of the REGARDS Study

Abstract

Objective: Black Americans are at greater risk of both stroke and vitamin D deficiency than white Americans. We have previously shown that both higher dietary vitamin D and sunlight exposure are associated with decreased risk of stroke; however, serum 25(OH) is thought to be a better marker of vitamin D status. Methods: Using a case cohort design, we examined the association of plasma 25(OH)D with incident stroke in the REasons for Geographic and Racial Differences in Stroke (REGARDS) study, a cohort of black and white participants from across the United States enrolled between 2003 and 2007. Medical records were reviewed by physicians and strokes were classified on the basis of symptoms and neuroimaging. Strokes through July 1, 2011 were included. A stratified cohort sample was selected to ensure approximately equal numbers of black and white participants and an equal distribution across ages. We used Cox proportional hazards models weighted back to the original 30,239 participants, excluding those with history of stroke. Serum 25(OH)D was measured by Immunodetection Systems ELISA. Results: Over mean follow-up of 4.4 years, there were 539 ischemic and 71 hemorrhagic strokes. The stroke-free sub-cohort included 939 participants. After adjustment for age, race, sex, education, diabetes, hypertension, smoking, atrial fibrillation, heart disease, physical activity, kidney function, calcium and phosphorous, 25(OH)D level 30 ng/mL. The direction of association was similar for hemorrhagic stroke though not statistically significant (HR=1.59; 95%CI=0.78, 3.24). Vitamin D deficiency was associated with an increased risk of all stroke (HR=1.54; 95%CI=1.05, 2.23). This effect was greater in blacks (HR=2.09; 95%CI=1.09, 3.99) than whites (HR=1.38; 95%CI=0.78, 2.42). Results were not as strong when we modeled 25(OH)D as a continuous variable (HR=0.99 per 1 ng/ml change in 25(OH)D; 95%CI=0.98, 1.01). Discussion: Similar to low vitamin D intake, vitamin D deficiency is a risk factor for incident stroke. These findings support evidence from cardiovascular and cancer epidemiology that treating low 25(OH)D may prevent strokes.