25-Hydroxyvitamin D levels and cognitive performance and decline in elderly men

The prevalence of 25 hydroxyvitamin D [25(OH)D] deficiency, defined as 25(OH)D level less than 20 ng/mL, is high, especially among the elderly, with 25% to 65% affected.1–6 While much research has focused on the adverse effect of 25(OH)D deficiency on bone health,5,7 associations between 25(OH)D deficiency and non–bone health outcomes, including hypertension,8 cardiovascular morbidity,9 diabetes,10,11 and cancer,12,13 have also been reported. In addition, there is a growing body of literature to support the role of vitamin D in brain function and development.14–25 Despite the experimental and animal evidence supporting an important role for vitamin D in mood and cognition, epidemiologic studies testing this hypothesis are scarce. Cross-sectional studies that examined the association between 25(OH)D levels and cognition were limited by small sample size,26–28 did not control for potential confounding factors,28 had suboptimal analytic methods to measure 25(OH)D levels,6,26–31 or reported conflicting results.30 To our knowledge, there are no prospective cohort studies examining the association between 25(OH)D level and cognitive decline. To test the hypothesis that lower 25(OH)D levels are associated with a greater likelihood of cognitive impairment and risk of cognitive decline, we measured 25(OH)D and assessed cognitive function using the Modified Mini-Mental State Examination (3MS) and Trail Making Test Part B (Trails B) in a cohort of 1,604 community-dwelling men aged 65 years or older who were enrolled in the Osteoporotic Fractures in Men (MrOS) Study and followed them prospectively for an average of 4.6 years for changes in cognitive function.