Depression and serum 25-hydroxyvitamin D in older adults living at northern latitudes - AGES-Reykjavik Study

Low vitamin D status may be associated with depression. Few studies have examined vitamin D and depression in older adults living at northern latitudes. The present study cross-sectionally investigated serum 25-hydroxyvitamin D (25(OH) D) status and depression among 5006 community-dwelling older persons (66-96 years) living in Iceland (latitudes 64-66 degrees N). Depressive symptoms were measured by the fifteen-item Geriatric Depression Scale (GDS-15). Current major depressive disorder was assessed according to Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) criteria. Serum 25(OH) D was analysed using chemiluminescence immunoassay and categorised into three groups: deficient (<30 nmol/l); inadequate (30-49.9 nmol/l); and adequate (>= 50 nmol/l). There were twenty-eight (2%) men and fifty (1%) women with current major depressive disorder. Mean GDS-15 scores for men and women with adequate vitamin D concentrations were 2.1 and 2.2, respectively. Men and women with deficient v. adequate vitamin D status had more depressive symptoms (higher GDS-15 scores) (difference 0.7 (95 % CI 0.4, 0.9) and 0.4 (95 % CI 0.1, 0.6), respectively). Furthermore, men with deficient vitamin D status were more likely to have current major depressive disorder (adjusted OR 2.51; 95 % CI 1.03, 6.13) compared with men with adequate vitamin D status. Associations among women were not significant. In this older population living at northern latitudes, deficient vitamin D status may be associated with depression. Further investigations are warranted to evaluate the pathways that may be associated with risk of depression among older adults.