Akademik Veri Yönetim Sistemi
Istanbul Tip Fakultesi Dergisi, cilt.85, sa.1, ss.117-124, 2022 (ESCI, Scopus, TRDizin)
© 2022 Istanbul University Press. All rights reserved.Objective: In this study, the seasonal variations of HbA1c and serum 25(OH) vitamin D were investigated during different seasons in Istanbul. Materials and Methods: The alterations in HbA1c and vitamin D were evaluated concerning age and sex. The study consisted of 86,835 samples, selected from the Istanbul Faculty of Medicine Electronic Medical Records. Results: LC-MS/MS quantified 25(OH)D levels, and HbA1c were measured in HPLC. The HbA1c level in women was significantly lower than in men (p<0.001), and the HbA1c level was higher in summer compared with winter (p<0.001) and autumn (p=0.005). The 25(OH)D levels of all groups was 28.2±15.5 ng/mL with no difference between men and women. The highest vitamin-D levels were in summer, and the lowest were in winter. Conclusion: Studies have shown that in both hemispheres of the world, HbA1c levels decrease when the air is warm and increase when the weather is cold. However, contrary to expectations, we witnessed that HbA1c wa s 0.3% higher in summer than in winter in Istanbul, where the temperature change over a year is 22.5°C, the coldest month is January, and the hottest month is August. A possible explanation of our findings could stem from the occurrence of Ramadan in the summer months between 2015-2017. However, variations between HbA1c and 25(OH)D related to temperature changes during the year and age groups were detected.