Abdominal obesity-dependent association between composite upper- and lower-body muscle strength index and incident chronic kidney disease: a nationwide multicenter study

Abstract

Background: The relation of composite upper- and lower body-muscle strength index (MSI) with the risk of incident chronic kidney disease (CKD) remains unknown. Our study aims to evaluate the relationship of MSI with new-onset CKD, using longitudinal data from the nationally representative China Health and Retirement Longitudinal Study (CHARLS). Methods: This multicenter observational study enrolled 4786 community-dwelling adults without baseline chronic kidney disease (CKD) in 2011. Upper and lower body muscle strength were assessed using dynamometer-measured handgrip strength (HGS) and timed performance on 5-repetition chair stand (RCS) test, respectively. A composite muscle strength index (MSI) was derived by combining sex-specific thresholds of HGS (female < 18 kg; male < 28 kg) and RCS performance (≥ 12 s). Participants underwent follow-up assessments in 2013, 2015, and 2018 to track CKD incidents. Cox proportional hazards models were employed to analyze associations between MSI and CKD incidence, with sensitivity analyses assessing the time dependent robustness and stratified analyses testing effect modification. Results: This 7-years follow-up study included 4786 community-dwelling adults (mean age 58.1 ± 8.2 years). During follow-up, 582 incident CKD cases were identified. Participants were stratified by abdominal obesity status (AO) defined by waist circumference (male ≥ 90 cm, female ≥ 85 cm). Kaplan-Meier analysis revealed a significant positive association between MSI categories and CKD risk AO subgroup (Log-rank P < 0.0001). Multivariable Cox regression analysis demonstrated that intermediate MSI was independently associated with new-onset CKD in overall cohort (HR = 1.230, 95%CI = 1.022–1.480). Notably, a distinct dose-response gradient relationship was observed​​ in AO subgroup (Intermediate MSI: HR = 1.577, 95%CI = 1.203–2.069; Poor MSI: HR = 2.250, 95%CI = 1.260–4.016). This association was strengthened in middle-aged adults and those without hypertension or diabetes, and with arthritis (P-interaction < 0.05). Conclusions: This prospective cohort study demonstrates a dose-dependent association between declining MSI and incident CKD among middle-aged and older adults with abdominal obesity. These findings highlight the potential of combined muscle-strengthening and visceral fat reduction as a targeted strategy for CKD prevention in this high-risk population.