“Black individuals are at greater risk of stroke and vitamin D deficiency than White individuals. Epidemiologic studies have shown that low 25-hydroxyvitamin D concentrations are associated with increased risk of stroke, but these studies had limited representation of black individuals,” observes Dr. Suzanne E. Judd, associate professor in the department of biostatistics at the University of Alabama at Birmingham. Therefore, Dr. Judd and colleagues assessed the link between 25-hydroxyvitamin D and incident stroke using data from the REasons for Geographic and Racial Differences in Stroke (REGARDS) project, a national observational study of black and white adults aged 45 and older. Using a case-cohort design, plasma 25-hydroxyvitamin D was measured in 610 REGARDS participants who experienced incident stroke and then compared with information regarding 937 stroke-free individuals from a stratified cohort random sample of REGARDS participants.
Study results show that “in multivariable models adjusted for socio-demographic factors, co-morbidities and laboratory values including parathyroid hormone, lower 25-hydroxyvitamin D concentrations were associated with higher risk of stroke (25-hydroxyvitamin D greater than 30 ng/mL reference; 25-hydroxyvitamin D concentrations 20–30 ng/mL, hazard ratio 1.33, 95 percent confidence interval [95% CI] 0.89, 1.96; 25-hydroxyvitamin D less than 20 ng/mL, hazard ratio 1.85, 95% CI 1.17, 2.93). There were no statistically significant differences in the association of lower 25-hydroxyvitamin D with higher risk of stroke in Black versus White participants in fully adjusted models (hazard ratio comparing lowest versus highest 25-hydroxyvitamin D category 2.62, 95% CI 1.18, 5.83 in Blacks versus 1.64, 95% CI 0.83, 3.24 in Whites, Pinteraction = 0.82). The associations were qualitatively unchanged when restricted to ischemic or hemorrhagic stroke subtypes or when using race-specific cut-offs for 25-hydroxyvitamin D categories.” The team concluded that race does not appear to influence the strength of the association between a deficiency of vitamin D and the risk for incident stroke.
UAB co-investigators in the study are Dr. Charity J. Morgan, assistant professor in the department of biostatistics; Dr. Virginia J. Howard, professor in the department of epidemiology; Dr. Bhupesh Panwar, assistant professor, and Dr. Orlando M. Gutierrez, associate professor, in the division of nephrology; and Dr. Virginia G. Wadley, associate professor in the division of gerontology, geriatrics, & palliative care.
“Vitamin D Deficiency and Incident Stroke Risk in Community-Living Black and White Adults” was published in January in the International Journal of Stroke.
Journal article: http://wso.sagepub.com/content/11/1/93.abstract