Vitamin D Deficiency is Associated with Increased Risk of Fatal Stroke Among Whites but not Blacks: the NHANES-III Linked Mortality

Abstract

Objective

Deficient 25-hydroxyvitamin D [25(OH)D] levels are associated with cardiovascular disease (CVD) events and mortality. Both 25(OH)D deficiency and stroke are more prevalent among blacks. We examined whether low 25(OH)D contributes to the excess risk of fatal stroke in blacks compared to whites.

Research Methods and Procedures

The Third National Health and Nutrition Examination Survey, a probability sample of US civilians, measured 25(OH)D levels and CVD risk factors between 1988–1994. Vital status through December 2006 was obtained via linkage with the National Death Index. Among white and black adults without CVD reported at baseline (n=7981), Cox regression models were fit to estimate hazard ratios (HR) for fatal stroke by 25(OH)D status and race.

Results

During a median of 14.1 years, there were 116 and 60 fatal strokes among whites and blacks respectively. The risk of fatal stroke was greater in blacks compared to whites in models adjusted for socio-economic status and CVD risk factors, [HR 1.60 (95% CI 1.01–2.53)]. Mean baseline 25(OH)D levels were significantly lower in blacks compared to whites (19.4 vs 30.8 ng/mL, respectively). In multivariable-adjusted models, deficient 25(OH)D levels <15 ng/mL were associated with fatal stroke among whites [HR 2.13 (1.01–4.50)] but not blacks [HR 0.93 (0.49–1.80)].

Conclusions

Vitamin D deficiency was associated with increased risk of stroke death in whites but not blacks. Although blacks had a higher rate of fatal stroke compared to whites, the low 25(OH)D levels in blacks were unrelated to stroke incidence and therefore 25(OH)D levels did not explain this excess risk.

Full study:  http://www.ncbi.nlm.nih.gov/

Graham