Context: Hypovitaminosis D and depressive symptoms are common conditions in older adults.
Objective: We examined the relationship between 25-hydroxyvitamin D [25(OH)D] and depressive symptoms over a 6-yr follow-up in a sample of older adults.
Design and setting: This research is part of a population-based cohort study (InCHIANTI Study) in Tuscany, Italy.
Participants: A total of 531 women and 423 men aged 65 yr and older participated.
Main outcome measure: Serum 25(OH)D was measured at baseline. Depressive symptoms were assessed at baseline and at 3- and 6-yr follow-ups using the Center for Epidemiological Studies-Depression Scale (CES-D). Depressed mood was defined as CES-D of 16 or higher. Analyses were stratified by sex and adjusted for relevant biomarkers and variables related to sociodemographics, somatic health, and functional status.
Results: Women with 25(OH)D less than 50 nmol/liter compared with those with higher levels experienced increases in CES-D scores of 2.1 (P = 0.02) and 2.2 (P = 0.04) points higher at, respectively, 3- and 6-yr follow-up. Women with low vitamin D (Vit-D) had also significantly higher risk of developing depressive mood over the follow-up (hazard ratio = 2.0; 95% confidence interval = 1.2-3.2; P = 0.005). In parallel models, men with 25(OH)D less than 50 nmol/liter compared with those with higher levels experienced increases in CES-D scores of 1.9 (P = 0.01) and 1.1 (P = 0.20) points higher at 3- and 6-yr follow-up. Men with low Vit- D tended to have higher risk of developing depressed mood (hazard ratio = 1.6; 95% confidence interval = 0.9-2.8; P = 0.1).
Conclusion: Our findings suggest that hypovitaminosis D is a risk factor for the development of depressive symptoms in older persons. The strength of the prospective association is higher in women than in men. Understanding the potential causal pathway between Vit- D deficiency and depression requires further research.