Vitamin D status and its association with gradual decline in cognitive function

Background/aim: To compare plasma vitamin D concentrations among patients with normal cognitive function (control group), mild cognitive impairment (MCI), and Alzheimer disease (AD). Materials and methods: In total, 158 patients with AD, 228 patients with MCI, and 603 control subjects were included. Plasma levels of 25-hydroxyvitamin D were measured after comprehensive geriatric assessment and compared among groups. SPSS 15.0 was used for statistical analysis. Results: Mean levels of 25-hydroxyvitamin D were significantly different among the 3 groups of AD patients, MCI patients, and controls (P < 0.001). Post hoc analysis revealed that the levels were significantly lower in the MCI group than the control group (P = 0.002) and significantly lower in the AD group than the control group (P = 0.003). Multivariate analysis showed that age (OR: 1.070, 95% CI: 1.025-1.116, P = 0.002), instrumental activities of daily living score (OR: 0.920, 95% CI: 0.850-0.995, P = 0.037), 25-hydroxyvitamin D level (OR: 0.959, 95% CI: 0.932-0.987, P = 0.004), and diabetes mellitus (OR: 2.476, 95% CI: 1.153-5.319, P = 0.020) were factors independently associated with AD. Conclusion: This study demonstrated that there is a correlation between plasma 25-hydroxyvitamin D levels and cognitive functions.