The distinct impacts of sarcopenic and dynapenic obesity on mortality in middle-aged and older adults based on different adiposity metrics: Results from I-Lan Longitudinal Aging Study

Background & aims: Sarcopenic obesity (SO) and dynapenic obesity (DO) represent two manifestations of excessive fat accumulation concurrent with compromised muscle mass and function, thereby necessitating an examination of their implications for health. This study aims to investigate the relationship between SO/DO and mortality, taking into account various adiposity measures and existing sarcopenia criteria, with further stratified analyses based on age and gender. Methods: The study sample comprised 1779 older adults residing in the community from the I-Lan Longitudinal Aging Study (ILAS). Body composition was assessed via dual-energy X-ray absorptiometry. The diagnosis of sarcopenia was adhered to the 2019 consensus of the Asian Working Group for Sarcopenia, while adiposity was measured by waist circumference (WC), body mass index (BMI), and fat percentage. SO/DO was defined as the coexistence of sarcopenia/dynapenia and obesity. Multivariate Cox proportional hazard regression models were adopted to examine the association between SO or DO, defined by WC, BMI, fat percentage, and mortality. Results: This 11-year follow-up study of 1779 participants aged 63.9 ± 9.2 years involved 15,068 person-years and 229 deaths. WC-defined SO (HR 1.9, 95% CI 1.1–3.3, p = 0.021) and WC-defined DO (HR 1.4, 95% CI 1.1–1.9, p = 0.022) significantly increased mortality risk, whereas definitions employing alternative adiposity metrics exhibited no statistical significance. WC-defined SO was associated with increased risk of mortality among middle-aged adults, while WC-defined DO was associated with increased risk of mortality among older adults. In sex-specific analysis, WC-defined DO was also associated with increased risk of mortality in men (HR 1.6, 95% CI 1.1–2.4, p = 0.019), while defined by other measurements showed no associations in both sexes. Conclusions: The study identified a significant link between SO/DO, defined by WC, and an 11-year mortality risk, advocating for WC-defined adiposity as an obesity measure and personalized interventions considering SO and DO's distinct impacts on mortality in middle-aged and older adults.