To test the hypothesis that hypovitaminosis D is associated with a higher risk of cognitive decline over a 4.4-year follow-up in a large sample of older adults.
This research was part of the Progetto Veneto Anziani (Pro.V.A.), an Italian population-based cohort study of 1,927 elderly subjects. Serum 25-hydroxyvitamin D (25OHD) levels were measured at the baseline. Global cognitive function was measured with the Mini-Mental State Examination (MMSE); scores lower than 24 were indicative of cognitive dysfunction, and a decline of 3 or more points on the MMSE over the follow-up was considered as clinically significant. Analyses were adjusted for relevant confounders, including health and performance status.
Participants with 25OHD deficiency (<50 nmol/L) or insufficiency (50-75 nmol/L) were more likely to have declining MMSE scores during the follow-up than those who were 25OHD sufficient (≥75 nmol/L). Among participants cognitively intact (baseline MMSE scores ≥24 and without diagnosis of dementia), the multivariate adjusted relative risk (95% confidence interval [CI]) of the onset of cognitive dysfunction was 1.36 (95% CI: 1.04-1.80; p = 0.02) for those with vitamin D deficiency and 1.29 (95% CI: 1.00-1.76; p = 0.05) for those with vitamin D insufficiency by comparison with individuals with normal 25OHD levels.
The results of our study support an independent association between low 25OHD levels and cognitive decline in elderly individuals. In cognitively intact elderly subjects, 25OHD levels below 75 nmol/L are already predictive of global cognitive dysfunction at 4.4 years.