Background: Vitamin D, along with parathyroid hormone (PTH) and calcitonin, is an important hormone that affects bone and calcium metabolism.
Objectives: To evaluate the vitamin D status and its seasonal variation in the adult population of Bursa.
Methods: Since there is not enough information about vitamin D levels, 25 OH vitamin D levels were analysed retrospectively from the records of 11,734 adult subjects (9142 women, 2592 men) admitted to 24 family health centres located in different districts of Bursa between 1 December 2017 and 30 November 2018. Some tests that can affect vitamin D levels, demographic features, and accompanying comorbidities were also evaluated. A face-to-face questionnaire was administered to subjects who were willing to answer (n = 2965).
Results: The mean serum vitamin D level was 16.6 ± 11.5 ng/mL in the entire population, 15.8 ± 11.7 ng/mL in women and 19.5 ± 9.9 ng/mL in men. The percentage of subjects with a vitamin D level <20 ng/mL was highest in March-May and lowest in the September-November period (80.7% and 69.9% for women, 77.5% and 32.9% for men, respectively).
Conclusion: Vitamin D levels <20 ng/mL are more prominent in women, and decline in spring, in the adult population of Bursa. These results are meaningful for the population living in Bursa, Turkey and the northern European region.
Keywords: General practice/family medicine; gender; seasonal variation; vitamin D.