BACKGROUND/AIMS: Recent studies suggest that vitamin D metabolites may be important for preserving cognitive function via specific neuroprotective effects. No large studies have examined the association between vitamin D status and cognition. METHODS: In this cross-sectional study, we analyzed the serum 25-hydroxyvitamin D(3) levels and Mini-Mental State Examination (MMSE) test scores of 225 older outpatients who were diagnosed as having probable Alzheimer's disease (AD). In addition to the 25-hydroxyvitamin D(3) levels, we analyzed the serum vitamin B(1), B(6) and B(12) levels. RESULTS: An association was found between MMSE test scores and serum 25-hydroxyvitamin D(3) levels, with a beta-coefficient of 0.05 (p = 0.01). Vitamin-D-sufficient patients had significantly higher MMSE scores as compared to vitamin-D-insufficient ones. No association was found with the other serum vitamin levels. CONCLUSIONS: These data support the idea that a relationship exists between vitamin D status and cognition in patients with probable AD. However, given the cross-sectional design of this study, no causality can be concluded. Further prospective studies are needed to specify the contribution of vitamin D status to the onset and course of cognitive decline and AD. (c) 2008 S. Karger AG, Basel.