Introduction
Vitamin D is both a nutrient and hormone and has become increasingly studied as it relates to circulatory and neurological functioning. Vitamin D deficiency has been associated with Parkinson's disease, Alzheimer's disease, stroke, and dementia. It has also been related to hypertension and diabetes. We examined the role of vitamin D intake on incident stroke and incident cognitive impairment in a cohort of middle aged and older adults.
Methods
The Reasons for Geographic And Racial Differences in Stroke (REGARDS), a cohort of 30,239 participants, was recruited between 2003 and 2007 and is comprised of black and white Americans age 45 and older at baseline. Vitamin D intake was measured by the Block 98 food frequency questionnaire and categorized into tertiles. Participants are surveyed every six months for incident strokes which are adjudicated using medical record review. Cognitive functioning is assessed annually using the Six-item Screener (SIS)(score range 0-6). A score of 4 or below indicates impairment. For the incident stroke analysis, we excluded all people with prior history of stroke, and for the incident cognitive impairment analysis we excluded those with SIS scores<5 at baseline.
Results:
26,039 participants were available for this analysis and were followed over a mean of 5 years. Higher intake of vitamin D was more likely for whites but did not differ by gender or age. Compared to the lowest tertile (range: 0-53.1 IU/day vitamin D), the highest tertile (range: 382-1774 IU/day) of vitamin D intake was associated with a 11% reduction in stroke (HR=0.89; 95% CI =0.79, 1.01) and 24% reduction in cognitive impairment (HR=0.76; 95% CI =0.67,0.86) after adjustment for age, race, income, education, hypertension, diabetes, dyslipidemia, history of heart disease, and BMI. When stratifying by race results were similar for both stroke and cognitive decline. Adding dairy intake to the models slightly attenuated the association but did not meaningfully change the interpretation of the results.
Discussion:
Results suggest a potential role of vitamin D in incident stroke and cognitive impairment. Clinical trials could evaluate the potential of Vitamin D as a neuroprotectant.