Vitamin D status: effects on quality of life in osteoporosis among Turkish women

Background and objectives Vitamin D deficiency causes muscle weakness, impairs bone formation and neuromuscular coordination thus leading to an increase in fracture risk. It has been found that inadequate levels of vitamin D are present in most of the osteoporosis patients. However, very few studies investigate the association between vitamin D status and quality of life (QOL). The aim of this study is to investigate the effects of vitamin D on QOL among Turkish women with osteoporosis. Methods 259 patients (61.0 +/- 8.9 years) with osteoporosis were evaluated by physical activity level, back pain, bone turnover markers, 25-hydroxyvitamin D [25(OH)D], parathyroid hormone levels and bone mineral density. QOL was assessed using QOL Questionnaire of the European Foundation for Osteoporosis (QUALEFFO). 25(OH)D levels below 20 ng/ml was defined as vitamin D insufficiency, below 12 ng/ml as vitamin D deficiency. Results Mean 25(OH)D level was 22.7 +/- 12.6 ng/ml and mean total QUALEFFO score was 43.3 +/- 14.9. Vitamin D levels were significantly correlated with all subscales and total score of QUALEFFO (r = -0.25, P = 0.0001). Vitamin D insufficiency was determined in 132 patients (51%). In vitamin D deficient (< 12 ng/ml) group all subscales and total QOL were found to be poorer when compared with the groups whose vitamin D levels were >= 12 and < 20 ng/ml and >= N20 ng/ml (effect sizes 0.41 and 0.62 respectively, P = 0.0001 for total QOL). Vitamin D level, education, concomitant diseases, physical activity level and pain severity were found to be significantly associated with QOL in multiple linear regression analysis model. Conclusion Vitamin D insufficiency affects physical, social and mental functions of osteoporosis patients and impairs QOL. Vitamin D was found to be one of the factors affecting QOL.