Twenty-Year Temporal Trends in Sarcopenic Obesity and Mortality Risk: The Evolving Landscape of Body Composition in US Adults

Abstract Body composition changes and sarcopenic obesity represent emerging health concerns with mortality implications. We analyzed 26,829 adults from NHANES 1999–2018 to examine temporal trends in sarcopenic obesity prevalence and mortality associations. Sarcopenic obesity was defined using fat-to-fat-free mass ratio (general) and trunk fat-to-appendicular muscle mass ratio (abdominal). Age- and sex-adjusted analyses revealed overall declining prevalence of general sarcopenic obesity (6.2% to 4.9%) and abdominal sarcopenic obesity (6.2% to 3.6%) from 1999–2018. However, stratified analyses showed increasing prevalence among Asian populations and older adults (≥ 60 years) for abdominal sarcopenic obesity. Multivariable Cox regression demonstrated that general sarcopenic obesity was associated with elevated all-cause mortality [HR: 1.29 (95% CI: 1.13–1.47)] and cardiovascular mortality [HR: 1.57 (95% CI: 1.25–1.97)], while abdominal sarcopenic obesity showed stronger associations with cardiovascular [HR: 1.83 (95% CI: 1.47–2.29)] and cancer mortality [HR: 1.68 (95% CI: 1.27–2.22)]. These findings highlight demographic-specific trends in sarcopenic obesity prevalence and underscore the independent prognostic value of body composition phenotypes for mortality risk assessment.