Background: To classify waist circumference (WC) trajectories and examine each trajectory's association with risk of incident type 2 diabetes mellitus (T2DM).
Methods: In Korean Genome and Epidemiology Study (KoGES 2001-2014), 4992 participants aged 40 years and above who received biennial health examinations from wave 1 to wave 4 (2001-2008) were selected. Five distinct trajectory groups were identified for WC using group-based trajectory modeling methods such as censored normal model. Cox proportional hazards model was used to examine the association of trajectories with risk of T2DM.
Results: During 31,118 person-years of follow-up (mean follow-up duration, 6.2 years), 276 incident cases of T2DM were identified. Through trajectory analysis, 5 distinct WC patterns were found during wave1 to wave 4, which were "Group A" was stable on very low levels, "Group B" was stable on low levels, "Group C" was stable on moderate levels, "Group D" had increasing pattern on elevated levels, "Group E" was shown increasing on high levels. Age-standardized incidences rates per 100,000 person-years were increased with WC expanding trajectory group (193.9 for Group A, 498.4 for Group B, 661.9 for Group C, 1845.9 for Group D, and 2045.0 for Group E). In multivariate analysis after adjusting for confounding variable at wave 4, Group B (Hazard ratio (HR), 2.2; 95% confidence interval (CI), and 1.1-4.6), Group C (HR: 2.5, 95% CI: 1.2-5.0), Group D (HR: 5.4, 95% CI: 2.7-10.9), Group E (HR: 7.3, 95% CI: 3.5-15.4) had a higher risk of T2DM than Group A. After further adjusting for body mass index strongly correlated with WC, the association was attenuated.
Conclusions: WC trajectory was a significant predictor of T2DM risk in increasing trajectories on high level. This finding indicate the importance of WC management across prolong lifespan by assessing the prognosis and prevention strategies of high-risk populations for T2DM in middle-aged adults.
Keywords: Longitudinal study; Trajectory; Type 2 diabetes mellitus; Waist circumference.