Environmental Factors before the Onset of Type 1 Diabetes Mellitus: A Case-Control Study

Objective: The role of environmental factors in the development of type1 diabetes mellitus (T1D) is inconclusive. This study aimed to investigate the associations between selected environmental factors and T1D. Materials and Methods: This group matched case-control study included diabetic and healthy subjects younger than 19 years old in 2017. Cases were diabetic subjects diagnosed before the age of 19 years and controls were healthy subjects with similar distributions of age, sex, and place of living. Information including demographic characteristics, birth season, duration of breastfeeding and major psychological stressors was obtained by a parent-administered questionnaire. Data were analyzed using SPSS version 16 and T-test and chi-square test. Statistical significance was defined as P< 0.05. Results: The mean age of cases was 12.5 (±5.2) years and 13 (±6.7) in controls (P: 0.55). Compared to controls, children with T1D had a higher chance of having a major psychological stressor in the family before the onset of diabetes (P: 0.0001) with odds ratio (OR) 3.3, higher neonatal jaundice (P: 0.01, OR: 2.25), infection leading to hospitalization within the first year of life (P: 0.007, OR: 6.46), and lower family income (P: 0.018). Duration of breastfeeding was shorter inT1D group (P: 0.018, OR: 3.46) and they had started cereals one month earlier (P: 0.015). Conclusion: Certain environmental factors including major psychological stressors, neonatal jaundice, infection leading to hospitalization within first year of birth and shorter duration of breastfeeding were associated with the development of T1D.