Seasonal Variability of Serum 25-Hydroxy-Vitamin D Levels in the adult population living in Bilecik Province: A Follow-up Study from Turkey

Abstract

Aim: Vitamin D is one of the major hormones involved in phosphorus metabolism in the secosteroid structure. Studies have shown that low serum vitamin D levels are associated with chronic diseases such as autoimmune diseases, diabetes mellitus, hypertension and cancer. The aim of this study was to investigate the seasonal variability of serum 25-hydroxyvitamin D levels in the adult population (18-98) according to age and gender in Bilecik province, Turkey. Methods: The medical records of the patients admitted to hospital between January 2016 and December 2017 were retrospectively screened. The medications of the patients were evaluated. Serum vitamin D levels of 22205 patients were evaluated according to age, gender and seasons. Results: According to the data, serum vitamin D were analyzed from the sera of 17070 females (76,9%) and 5135 males (23.1%). The median values of serum vitamin D levels of the participants were 17.2 ng/ml (4.2-137.9 ng/ml) in females and 22.9 ng/ml (4.3-144.0 ng/ml) in males. According to the seasonal classification, deficient serum 25-OH vitamin D levels were detected in all seasons in females and in males (p<0.001). Unlike men, vitamin D deficiency was detected in women during the spring (p<0.001). For all subjects, median serum 25-OH vitamin D levels were 20.2 ng/mL (4.33-127.2 ng/mL), 16.3 ng/mL (4.23-144.0 ng/mL), 18.6 ng/mL (4.20-129.0 ng/mL) and 19.6 ng/mL (4.30-137.9 ng/mL) for autumn, spring, winter, and summer seasons , respectively. Conclusion: Vitamin D deficiency is prevalent among adults in Bilecik. The serum 25-Hydroxy-Vitamin D Levels were higher in the males than in the females for all seasons (p<0.001). We recommend vitamin D supplementation for adults with additional sunlight exposure.