Seasonal Changes of HbA1c Levels in Type 2 Diabetes Mellitus Patients

There are changes in plasma glucose and HbA1c of type 2 diabetes mellitus (T2DM) patients in different seasons. HbA1c levels may increase during winter season in most T2DM patients without weight gain. In this study, we described the seasonal changes of HbA1c levels in T2DM patients. This analytical cross-sectional study conducted from 2013 to 2017 on 402 patients with T2DM, aged 20–80 years old who referred to Yazd diabetic research center. Body weight, height, waist circumferences (WC), blood pressure (BP), body mass index (BMI), fasting plasma glucose (FPG), 2 hours post-prandial (2hpp), and HbA1c measured and compared during four seasons. Four hundred and two T2DM patients invited and fulfilled this study. Most of them (56%) were women. The mean age of patients was 58.96 (± 11.10) years old. The mean HbA1c, 2hpp, systolic and diastolic blood pressure were significantly different in four seasons (P-value respectively: 0.022, 0.007, 0.001 and 0.005). The mean difference of HbA1c was significant in the warm and cold seasons (P-value: 0.047). The percentage of people who were below 7% had a significant difference between the warm and cold seasons (P-value: 0.015). The results of this study showed that, in Yazd with desert climate, postprandial hyperglycemia is more prominent in summer. The seasonal changes of glycemic status are an important factor in management of T2DM patients.