Age-stratified association of weight-adjusted waist index with grip strength in community-dwelling older adults in China: The mediating effect of appendicular skeletal muscle mass

The weight-adjusted waist index (WWI) serves as an emerging metric for evaluating body fat distribution, but its association with muscle strength in older adults and the potential mediating role of appendicular skeletal muscle mass (ASM) remain unclear, particularly across different age groups. This research sought to elucidate the association between WWI and grip strength in the elderly community population, with a particular focus on determining whether ASM mediates this relationship and how these dynamics differ by age. This cross-sectional, community-based study recruited 204 adults aged ≥60 years from communities in Hohhot, China. The study population was divided into 2 age-based strata: 60 to 70 years, n = 137 and >70 years, n = 67. The WWI was derived by normalizing waist circumference against the square root of total body mass. ASM was estimated utilizing bioelectrical impedance analysis, while grip strength of the dominant hand was quantified via an electronic dynamometer. To evaluate whether ASM acted as a mediator, mediation analysis was carried out using the PROCESS macro with 5000 bootstrap iterations. In the 60- to 70-age group, a positive correlation linking WWI to grip strength was found, which was completely driven by ASM (indirect effect = 1.739, 95% confidence interval: 1.028-2.611). In the >70 age group, ASM partially accounted for the inverse relationship observed between WWI and grip strength (indirect effect = -0.507, 95% confidence interval: -1.313 to -0.006). ASM acts as a crucial intermediary in the age-dependent link between central adiposity and muscle strength among older adults living in the community.WWI may be a practical, age-specific indicator for sarcopenia risk screening in community health settings.