Serum 25-Hydroxyvitamin D and Depressive Symptoms in Older Women and Men

Abstract

Hypovitaminosis D is common in older adults. Vitamin D deficiency in this population has been linked to a large number of poor health outcomes. Several investigators have hypothesized that hypovitaminosis D may contribute to depression in older adults. The few small studies that examined the association between vitamin D and depression in the elderly had conflicting results. This prospective population-based study was designed to investigate the longitudinal relationship between vitamin D and depressive symptoms over a 6-year follow-up period in a representative group of older adults. The participants were enrolled in the InCHIANTI (Invecchiare in Chianti, aging in the Chianti area) Study. The study sample was comprised of 954 participants (531 women and 423 men) aged 65 years or older. The primary study outcome measure was 25-hydroxyvitamin D (serum 25[OH]D). Vitamin D insufficiency was defined as a 25(OH)D level of less than 50 nmol/L. The Center for Epidemiological Studies-Depression Scale (CES-D) was used to assess depressive symptoms at baseline and at 3- and 6-year follow-up. A CES-D score of 16 or higher was considered a clinically relevant depressed mood. The data were stratified by gender. Multivariable analysis was used to adjust for relevant biomarkers and covariates related to sociodemographics, somatic health, and functional status. Compared to women with 25(OH)D levels more than 50 nmol/L, those with levels below this threshold had average adjusted increases in CES-D scores at the 3- and 6-year follow-up of 2.1 (P = 0.02) and 2.2 (P = 0.04), respectively. Lower baseline serum levels of 25(OH)D in women were also associated with a significant higher risk of developing depressed mood during the follow-up; the hazard ratio was 2.0, with a 95% confidence interval of 1.2-3.2 (P = 0.005). Compared to men with 25(OH)D levels above the cutoff of 50 nmol/L, men with lower levels at 3- and 6-year follow-up had increases in CES-D scores of 1.9 (P = 0.01) and 1.1 (P = 0.20), respectively. Lower baseline serum 25(OH)D levels among men were associated with an insignificant increase in risk for depression compared with those with higher levels (hazard ratio, 1.6; 95% confidence interval, 0.9-2.8; P = 0.1). These findings provide evidence of a prospective independent association between hypovitaminosis D and new depression over time. The association is stronger in women than in men. The investigators believe that prevention of vitamin D deficiency may become a future strategy to substantially lower the risk of depression in the elderly patients.