Comparison of 5-year Incidence of Type 2 Diabetes in Obese and Non-Obese Adult Population: The YaHs Cohort

Background: Obesity is an important predictor of diabetes. Defining the risk of diabetes among obese subjects is important for preventive health strategies. This study aims to compare the 5-year incidence of diabetes in obese and non-obese adult participants aged 20-70 years in a large population sample of central Iran. Methods: In this prospective study, 9964 people aged 20-70 years were selected between 2014 and 2015 using multi-stage cluster sampling from Yazd Greater Area, Iran. Participants with diabetes were excluded and non-diabetic individuals were evaluated for incident diabetes after a five-year follow-up. Logistic regression was used to find the association between obesity and 5-year incidence of diabetes in bivariate, and multivariate adjusted models for age, sex, physical activity, medical history, marital status, smoking, and education. Results: Out of the initial 9964 participants, 1383 (14%) were excluded due to prevalence of diabetes. The remaining 8413 (86.0%) participants were re-examined in 2019-2020. After five years of follow up, diabetes occurred in 6.6% (n=556) of the participants. The incidence of diabetes in obese men and women was 10.4% (n=109) and 9.9% (n=264), respectively; however, it was 4.5% (n=143) and 2.8% (n=40) in their non-obese counterparts (P<0.01). After multivariate analysis, obesity was associated with a higher likelihood of diabetes in men (OR=1.77, 95% CI: 1.33-2.35), women (OR=2.23, 95% CI: 1.55-3.21), and overall (OR=1.99, 95%CI: 1.60-2.48). Similar findings were obtained in participants aged under and over 60 years (P<0.05). Conclusion: There was a positive association between obesity and 5-year incidence of diabetes in an Iranian adult population. Interventions are required to change lifestyle in the adult population especially in younger participants to prevent obesity and diabetes.