Seasonal incidence of type I diabetes mellitus in the north of Iran

Background: Type I diabetes mellitus (T1DM) with growing frequency which is considered as a world health threatening problem is an autoimmune disease with insulinupenia. Considering the relationship between the incidence of T1DM and environmental factors, the aim of this study was to assess seasonal incidence of T1DM and its association with birth season. Methods: This cross-sectional study was conducted on 112 diabetic patients (66 males, 46 females) less than 18 years, referred to Pediatric Endocrine Clinic (Amirkola Children's Hospital) during 2011-2017. All the needed information was extracted from the patient's files and asking questions of their parents. Data were collected in a checklist. Comparison between different seasons and age groups was done by Pearson's chisquare test. Data were analyzed using SPSS 19 and p0.05 was considered significant level. Results: The mean age of the patients during diagnosis of T1DM was 7.34±3.70 years. The incidence of T1DM was significantly increased in the cold seasons (especially winter) (P<0.008). A more increased incidence was seen in cold seasons in the aged group of 5-9 years old compared to other groups. However, no significant difference was found in all groups in terms of birth season. Conclusions: The results of this study suggest the effects of season as an environmental factor on diabetes incidence. This seasonal diversity is more prominent in the age less than 10 years. So, attention to maintaining the public health and to preventing from viral infections in cold seasons is recommended.