Vitamin D and Risk of Cognitive Decline in Elderly Persons

Abstract

The findings of a report published in 2007 suggested that over 40% of older, community-living adults in the United States and Europe were vitamin D deficient. There is clinical evidence for a relationship between low serum 25-hydroxyvitamin D (25[OH]D) levels and cognitive dysfunction with aging. Although data in several small clinical studies showing such an association were equivocal, 3 of 4 large population-based cross-sectional studies reported a relationship between levels of serum 25(OH)D and cognitive dysfunction in the elderly. No prior prospective population-based studies have investigated the possible association between vitamin D status and incident dementia or cognitive decline. This prospective population-based study was designed to determine whether low serum levels of 25(OH)D were associated with an increased risk of substantial cognitive decline in an elderly population. Data were obtained from a sample of elderly individuals enrolled in the InCHIANTI study, a large, prospective cohort study conducted in Italy to identify risk factors for late-life disability. The study participants were 858 adults aged 65 years or older who had completed 1 or more follow-up cognitive assessment between 1998 and 2006, with follow-up every 3 years. Cognitive decline was assessed using 2 tests of cognitive function: the Mini-Mental State Examination (MMSE) and the Trail-Making Tests A and B; both were administered at baseline, with follow-up at 3 and 6 years. Substantial cognitive decline was defined with MMSE as a decrease in score of 3 or more points, and with Trails A and Trails B as scoring in the worst 10% of cognitive decline or having the testing discontinued. In multivariate logistic regression fully adjusted models, the relative risk (RR) of substantial cognitive decline on the MMSE among participants who were severely 25(OH)D deficient was 60% greater compared with those who were 25(OH)D sufficient (RR, 1.60; 95% confidence interval [CI], 1.19–2.00; Pvalue for linear trend < 0.02). In fully adjusted random-effects models, the MMSE score declined by an additional 0.3 points per year more among severely 25(OH)D deficient participants compared with those who were 25(OH)D sufficient. With the Trails B, severely vitamin D deficient participants were 31% more likely of having a substantial decline in cognitive performance scores compared to those with sufficient levels of vitamin D; the RR was 1.31, with a 95% CI of 1.03–1.51 (Pvalue for linear trend < 0.04). No significant association was found between 25(OH)D levels and cognitive performance on Trails A. These findings are the first to show in a prospective study that low levels of vitamin D are associated with increased risk of substantial cognitive decline in an elderly population. The data suggest that tests of cognitive function may be useful in future prospective trials of vitamin D supplementation in the elderly.