title: Vitamin D deficiency and incident stroke risk in community-living black and white adults.
abstract: BACKGROUND
  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.
  
  
  METHODS
  We examined the association of 25-hydroxyvitamin D with incident stroke in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, a cohort of black and white adults ≥45 years of age. Using a case-cohort study design, plasma 25-hydroxyvitamin D was measured in 610 participants who developed incident stroke (cases) and in 937 stroke-free individuals from a stratified cohort random sample of REGARDS participants (comparison cohort).
  
  
  RESULTS
  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 >30 ng/mL reference; 25-hydroxyvitamin D concentrations 20-30 ng/mL, hazard ratio 1.33, 95% confidence interval (95% CI) 0.89,1.96; 25-hydroxyvitamin D <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 vs. white participants in fully adjusted models (hazard ratio comparing lowest vs. highest 25-hydroxyvitamin D category 2.62, 95% CI 1.18, 5.83 in blacks vs. 1.64, 95% CI 0.83, 3.24 in whites, P(interaction) = 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.
  
  
  CONCLUSIONS
  Vitamin D deficiency is a risk factor for incident stroke and the strength of this association does not appear to differ by race.
authors.affiliation: Department of Biostatistics, University of Alabama at Birmingham, Birmingham, USA.
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Judd
authors.affiliation: Department of Biostatistics, University of Alabama at Birmingham, Birmingham, USA.
authors.forename: Charity J
authors.initials: CJ
authors.lastname: Morgan
authors.affiliation: Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, USA.
authors.forename: Bhupesh
authors.initials: B
authors.lastname: Panwar
authors.affiliation: Department of Epidemiology, University of Alabama at Birmingham, Birmingham, USA.
authors.forename: Virginia J
authors.initials: VJ
authors.lastname: Howard
authors.affiliation: Division of Gerontology, Geriatrics and Palliative Care, Department of Medicine, University of Alabama at Birmingham, Birmingham, USA.
authors.forename: Virginia G
authors.initials: VG
authors.lastname: Wadley
authors.affiliation: Departments of Medicine and Pathology, University of Vermont, Burlington, USA.
authors.forename: Nancy S
authors.initials: NS
authors.lastname: Jenny
authors.affiliation: Department of Neurology, University of Cincinnati, Cincinnati, USA.
authors.forename: Brett M
authors.initials: BM
authors.lastname: Kissela
authors.affiliation: Division of Nephrology, Department of Medicine, University of Alabama at Birmingham, Birmingham, USA Department of Epidemiology, University of Alabama at Birmingham, Birmingham, USA ogutierr@uab.edu.
authors.forename: Orlando M
authors.initials: OM
authors.lastname: Gutiérrez
mesh_terms: D001741:Black or African American; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors; D012737:Sex Factors; D020521:Stroke / Q000208:ethnology*; D014481:United States / Q000453:epidemiology; D014808:Vitamin D Deficiency / Q000208:ethnology*; D044465:White People
keywords: Stroke; epidemiology; vitamin D