Heterogeneous obesity phenotypes and late-life health in China

The heterogeneous nature of obesity phenotypes and their relationship to diseases in older adults, particularly in China, remains poorly understood. This study aimed to examine the distribution of key obesity phenotypes among older Chinese adults and assess their associations with multiple incident health outcomes. This cohort study used data from the China Health and Retirement Longitudinal Study, a nationally representative survey conducted between 2011 and 2020. We analyzed obesity phenotypes, including metabolically unhealthy obesity (MUO), metabolically healthy obesity (MHO), sarcopenic obesity (SO), nonsarcopenic obesity (NSO), inflammatory obesity (IO), and noninflammatory obesity (NIO), in adults aged 60 years or older, and assessed their associations with cardiovascular disease (CVD), stroke, diabetes, and depressive symptoms. Obesity phenotypes were categorized based on body mass index (BMI), waist circumference, and additional criteria related to cardiometabolic health, inflammation, and muscle strength. CVD, stroke, diabetes, and depressive symptoms were the primary outcomes, assessed using self-reported diagnoses and clinical measures. Associations between obesity phenotypes and incident health outcomes were evaluated using Cox proportional hazards regression models. Among 5,971 participants, 42.1% were classified as obese. The obese group had a higher prevalence of diabetes (20.2% vs. 10.6%), CVD (19.8% vs. 12.4%), and stroke (4.3% vs. 2.3%) compared to the non-obese group ( P < 0.05). Obesity phenotypes were distributed as follows: 74.6% had MUO, 47.1% had SO, and 19.6% had IO. MUO was the most prevalent and showed the greatest overlap with other phenotypes. Regional analysis revealed higher obesity prevalence in northern China, with major cities such as Beijing and Shanghai showing lower prevalence of MUO and SO. In fully adjusted Cox models, MUO was associated with higher hazards of incident diabetes (HR = 2.22, 95% CI 1.65–2.98; P < 0.001) and incident stroke (HR = 1.43, 95% CI 1.04–1.94; P = 0.026), whereas SO was associated with a higher hazard of incident CVD (HR = 1.39, 95% CI 1.09–1.77; P = 0.008). MUO and SO were associated with incident diabetes and CVD, respectively. These observational findings do not establish causality. Regional patterns are descriptive and hypothesis-generating.