Association between A Body Shape Index (ABSI) and mortality risk across populations with different sedentary time: a large-scale cohort study

A Body Shape Index (ABSI) is a simple and efficient metric for assessing adiposity, and sedentary behaviour is a common unhealthy practice. Both factors have been demonstrated to be associated with mortality risk. However, research on the influence of sedentary time on the association between ABSI and mortality risk is currently lacking. This cohort study included 81,459 adults aged 35–75 from the ChinaHEART project in Hunan Province (2015–2023). Participants were grouped by sedentary time (≥ 6 h/day [sedentary] vs. <6 h/day [non-sedentary]). ABSI was derived from waist circumference, height, and weight. Mortality data were obtained from the National Mortality Surveillance System and the Vital Registration System of the Chinese Center for Disease Control and Prevention. Multivariable Cox regression models adjusted for confounders estimated hazard ratios (HRs) for all-cause mortality. The interaction between ABSI and sedentary time was tested. Restricted cubic splines were used to assess dose–response relationships, and differences by sedentary time were examined in stratified analyses. Over a median 5.8-year follow-up, 1,314 deaths occurred. Multivariable Cox regression analysis revealed a positive association between ABSI (per 1-SD increase) and all-cause mortality risk (HR 1.14, 95% CI 1.08–1.20, P < 0.001). When ABSI was categorised by interquartile range, compared to the Q1 group, the Q4 (HR 1.34, 95% CI 1.14–1.56, P < 0.001) group was associated with a higher mortality risk. A significant interaction was observed between ABSI and sedentary group ( P for interaction = 0.023), indicating that the association between ABSI (per 1-SD increase) and mortality risk differed between the sedentary and non-sedentary groups (HR 1.39, 95% CI 1.12–1.73, P = 0.003 vs. HR 1.12, 95% CI 1.06–1.19, P < 0.001). Restricted cubic spline analysis indicated a nonlinear association between ABSI and all-cause mortality in the non-sedentary group ( P for overall < 0.001, P for nonlinear = 0.020), whereas an approximately linear association was observed in the sedentary group ( P for overall = 0.012, P for nonlinear = 0.847). ABSI is positively associated with mortality risk among community-dwelling adults, and this association varies by sedentary time levels. This suggests that ABSI may serve as an important predictor and potential intervention target for mortality risk, and reducing sedentary behaviour could be an important intervention strategy.