Association of Obesity and Sarcopenia with Cardiometabolic Outcomes in Older Adults and Sex-Modified Effects: A Study Based on CHARLS

Abstract Background Obesity and sarcopenia are common abnormal body composition phenotypes in the elderly population. Their coexistence can synergistically amplify cardio-metabolic risk, particularly in elderly individuals with diabetes. However, systematic research is still lacking regarding the differential effects of various obesity indicators (body mass index [BMI] and waist circumference) and sarcopenia‑related indicators (muscle strength, physical function, and muscle mass) on cardiometabolic risk in elderly diabetic populations, as well as the sex‑modifying effects and dose–response relationships involved. Methods This study utilized data from the China Health and Retirement Longitudinal Study (CHARLS) from 2015 to 2020. The cross-sectional analysis included 4,130 older adults aged ≥ 65 years, and the longitudinal analysis included 3,116 participants after excluding those with baseline composite cardiovascular disease (CVD). Obesity indicators included BMI and waist circumference; sarcopenia was assessed according to the Asian Working Group for Sarcopenia (AWGS) 2019 criteria, with indicators including maximal grip strength, gait speed, the five-times chair stand test (5-CST), and appendicular skeletal muscle mass adjusted by BMI (ASM/BMI). Outcome measures included diabetes prevalence, metabolic parameters (blood pressure, lipids, and glycated hemoglobin), and incident composite CVD events within 5 years. Statistical analyses were performed using multiple logistic/linear regression models and the Fine-Gray competing risk model, and restricted cubic splines were applied to explore nonlinear relationships. Results Cross-sectional analysis showed that the confirmed sarcopenic obesity group had the highest levels of systolic blood pressure, fasting blood glucose, low-density lipoprotein cholesterol, and CVD prevalence among all groups. In multivariable regression, BMI, waist circumference, and 5-CST were independent risk factors for diabetes in older adults, with significant effect modification by sex: the effect of BMI was stronger in males, while the association with waist circumference was more prominent in females. Among older diabetic patients, BMI and waist circumference were significantly positively correlated with blood pressure, low-density lipoprotein cholesterol, and triglycerides, and significantly negatively correlated with high-density lipoprotein cholesterol; ASM/BMI was significantly negatively correlated with systolic blood pressure (β = − 39.35). During longitudinal follow-up, BMI, waist circumference, and 5-CST all significantly increased the risk of incident composite CVD; restricted cubic splines revealed nonlinear threshold effects for waist circumference with incident composite CVD (86/93 cm). Conclusion Among older adults, the sarcopenic obesity phenotype exhibits the most prominent cardiometabolic risk profile. The effects of obesity indicators on diabetes risk are significantly modified by sex. In older diabetic patients, BMI and waist circumference significantly increase the risks of elevated blood pressure and dyslipidemia, whereas ASM/BMI exerts an independent protective effect on systolic blood pressure. Waist circumference shows a nonlinear threshold effect with incident composite CVD, with risk beginning to rise at 86 cm and accelerating sharply after 93 cm. We recommend "weight loss with muscle preservation" as a core strategy for primary prevention of cardio-metabolic diseases in older adults.