Associations of Serum 25-Hydroxyvitamin D Concentrations With Quality of Life and Self-Rated Health in an Older Population

Context: Vitamin D deficiency has been associated with impaired physical functioning, depression, and several chronic diseases and might thereby affect quality of life and self-rated health. Objective: The aim of this study was to assess relationships of serum 25-hydroxyvitamin D[25(OH)D] with quality of life and self-rated health and to examine whether physical performance, depressive symptoms, and number of chronic diseases mediate these relationships. Design: Weanalyzed data from the Longitudinal Aging Study Amsterdam, an ongoing populationbased cohort study of older Dutch individuals. Main Outcome Measures: Serum 25(OH) D was classified into the following categories: less than 25, 25-50, and 50 nmol/L or greater. We assessed quality of life (QOL) using the Short Form-12 Health Survey (SF-12; n = 862) and self-rated health (SRH) with a single question, dichotomized into good vs poor SRH (n = 1248). Results: Individuals with serum 25(OH) D less than 25 nmol/L scored lower on the physical component score of the SF-12 and had a lower odds on good SRH score compared with individuals with serum 25(OH) D greater than 50 nmol/L (beta (95% confidence interval) -3.9 (-6.5 to -1.3) for SF-12, and odds ratio [95% confidence interval) 0.50 (0.33-0.76) for SRH]. Physical performance, depressive symptoms, and the number of chronic diseases were associated with vitamin D status, QOL, and SRH. Adding all these potential mediators to regression models attenuated associations of 25(OH) D less than 25 nmol/L with QOL with 78% and SRH with 32%. Conclusion: Lower 25(OH) D status is related to lower scores on QOL and SRH. A large part of the association with QOL can statistically be explained by physical performance, depressive symptoms, and the number of chronic diseases.