Metabolic Syndrome Complexity among Older Adults in Southwest China: An In-Depth Study Using Heterogeneous Linear Mixed Models

Abstract Objective: To identify distinct longitudinal trajectories of metabolic syndrome (MetS) and their determinants among older adults in Southwest China using a Heterogenous Linear Mixed Model (HLMM), addressing the heterogeneous nature of MetS progression. Methods: This longitudinal study analyzed health records from a tertiary hospital in Chengdu (2018-2023). MetS was defined per Chinese guidelines (2017). HLMM was applied to identify latent trajectory classes based on AIC/BIC criteria. Cox regression determined predictors of trajectory class membership. Results: 868 participants (3,233 observations) were included in the study. Three distinct MetS trajectories were identified: stable (β=0.002, P=0.042), progressive (β=0.043, P<0.001). regressive (β=-0.179, P<0.001). Baseline MetS prevalence was 22.9%, significantly higher in males (35.2% vs. 20.1%, P<0.001). Cox regression revealed that progression was primarily driven by high triglycerides (HR=3.19, 95%CI: 2.41-4.21), central obesity (HR=2.52, 95%CI: 1.92-3.31), and hyperglycemia (HR=2.48, 95%CI: 1.91-3.23). Regression was strongly associated with reductions in central obesity (HR=3.78, 95%CI: 1.69-8.46) and high triglycerides (HR=2.92, 95%CI: 1.34-6.37). Conclusion: MetS exhibits heterogeneous longitudinal patterns in older adults. Central obesity and dyslipidemia are critical determinants, with central obesity playing a dual role—significantly driving progression but offering even greater potential for driving regression when targeted. These findings underscore the need for trajectory-stratified management strategies focusing on visceral adiposity and lipid control to mitigate MetS burden.