Age and Gender Differences in the Association between Serum 25-Hydroxyvitamin D and Stroke in the General US Population: The National Health and Nutrition Examination Survey, 2001-2006

Background: Previous findings on the association between serum 25(OH)D level and stroke have been controversial. We aimed to examine whether these controversial findings could be possibly due to difference in study participant characteristics, especially age and gender differences in these studies, by analyzing the data from a representative sample of the general US population. Methods: Data of 13,642 adults 20 years or older who participated in the 2001-2006 National Health and Nutrition Examination Survey were analyzed in this study. Serum 25(OH)D was used to reflect vitamin D status. Stroke history was self-reported using questionnaires. Unadjusted and adjusted logistic regression models were fitted using SAS survey procedures to investigate the associations between 25(OH) D level and stroke for the pooled sample and age-gender subgroups (men versus women, <50 years old versus >= 50 years old), respectively. Results: After adjusting for demographic and lifestyle covariates, vitamin D deficiency (defined as serum 25(OH) D < 12 ng/mL) was significantly associated with increased risk of stroke (adjusted odds ratio [OR] = 1.62, 95% confidence interval [CI] = 1.11, 2.36), and higher vitamin D levels were significantly associated with reduced risk of stroke (adjusted OR = .70, 95% CI = .51,.96). The association between high levels of serum 25(OH) D and stroke was particularly evident among young females (age = 20 years to < 50 years) (adjusted OR = .26, 95% CI = .14, .49). Conclusions: The findings add to the evidence suggesting maintaining ideal 25(OH) D levels may reduce the risk of stroke among US adults, particularly in adult women younger than 50 years.