Vitamin D deficiency as a risk factor for cognitive decline in individuals aged 50 or older.

Longitudinal studies provide conflicting evidence regarding the impact of vitamin D deficiency on cognitive performance in older individuals. The present study aimed to investigate whether vitamin D deficiency is a risk factor for poorer trajectories in global cognition and specific cognitive domains over a six-year follow-up period. This cohort study analysed data from 2625 participants aged 50 years or older from the English Longitudinal Study of Ageing. Vitamin D [25-hydroxyvitamin D, 25(OH)D] was classified as sufficient (> 75 nmol/L), insufficient (> 30 and ≤ 75 nmol/L), or deficient (≤ 30 nmol/L). Cognitive performance was assessed using the verbal fluency test, word list test, temporal orientation test, and global cognition, standardised in z-scores by age group and educational level. Generalised linear mixed models, adjusted for sociodemographic, behavioural, and clinical variables, estimated rates of decline in global cognition and cognitive domains based on vitamin D status. Participants with vitamin D deficiency showed greater declines in the z-score of global cognition (- 0.037 standard deviations (SD) per year; 95% CI: - 0.069 to - 0.005) and executive function (- 0.038 SD per year; 95% CI: - 0.071 to - 0.004) compared to those with sufficient vitamin D levels. No significant differences were observed in the trajectories of memory or temporal orientation in relation to vitamin D status. Vitamin D deficiency is a risk factor for declines in global cognition and executive function in individuals aged 50 or older. The assessment and management of vitamin D levels may be crucial strategies for promoting cognitive health.