Seasonal variation of serum vitamin D among Greek female patients with osteoporosis.

Abstract

BACKGROUND/AIM: Vitamin D (vitD) levels are positively associated with bone health and seasonality affects serum vit D. The aim of the study was to investigate the degree of seasonal variation on 25-hydroxyvitamin D (25(OH)D) serum levels in a population-based cohort of post-menopausal women with osteoporosis. PATIENTS AND METHODS: Serum levels of 25(OH)D were assessed in 596 patients (mean age=65.3 years; standard deviation (SD)=9.4) in different time points over a period of 2.5 years. RESULTS: The minimum 25(OH)D serum levels were observed in March (13.4±9.5 ng/ml) and the maximum levels in August, September and October (29.1±16.1, 28.9±12 and 28.4±8.9 ng/ml, respectively). The prevalence of vitD deficiency, insufficiency and sufficiency in March was 76.5, 15.7 and 7.8%, respectively. On the contrary, the highest prevalence of vitD sufficiency was observed in August, September and October (38.1%, 45.3% and 46.5%, respectively). CONCLUSION: Seasonal variations should be considered when measuring for 25(OH)D serum levels and treating vitD deficiency.