Association between trajectories of waist circumference with incidence of type 2 diabetes mellitus, Tehran lipid and glucose study

Abstract Limited research has addressed the association between the dynamic trends of waist circumference (WC) and the incidence of type 2 diabetes mellitus (T2DM). This study aimed to identify the trajectories of WC and evaluate their association with the incidence of T2DM over an 18-year follow-up among the Iranian population. This study was derived from a large prospective cohort (Tehran Lipid and Glucose Study) and included 6,405 participants aged 20–70 years who were followed up every three years for 18 years; this period was divided into two 9-year intervals to track WC trajectories (measurement period) and record T2DM incidence (outcome assessment period). Three WC trajectory patterns were identified using latent class trajectory analysis. The Cox proportional hazards model was used to evaluate the association between WC trajectories and the risk of developing T2DM. Participants were classified into three WC trajectory patterns of low-increasing (n: 2019), moderate-increasing (n: 3248), and high-increasing (n: 1138). The hazard ratio (HR) of T2DM was 2.3 (95% CI 1.7–2.9) for the high-increasing versus the low-increasing WC trajectory class; the HRs were 2.0 (95% CI 1.1–3.7) in men and 2.5 (95% CI 1.8–3.5) in women. The HR of developing T2DM was 2.6 (95% CI 1.6–4.1) in the normoglycemic in comparison with 1.7 (95% CI 1.0–2.7) in the prediabetic high-increasing WC trajectory class. WC trajectory classes were also compared across baseline body mass index (BMI) categories, which high-increasing WC trajectory class showed the highest risk across all BMI groups. The high-increasing WC trajectory class showed a strong association with the development of T2DM independent of BMI and other important risk factors for T2DM which support continuous surveillance of central obesity for prevention of diabetes.