Respiratory sarcopenia as a mortality predictor for chronic kidney disease: a dual-cohort longitudinal study

Chronic kidney disease (CKD) imposes a substantial global health burden. Emerging evidence implicates respiratory sarcopenia as a potential mortality accelerator. This dual-cohort study aimed to clarify the correlation between respiratory sarcopenia and all-cause mortality in CKD populations and evaluate prognostic impacts of longitudinal transitions. We analyzed 1,300 CKD participants without preexisting chronic respiratory conditions from the China Health and Retirement Longitudinal Study (CHARLS) and 1,346 from the U.S. Health and Retirement Study (HRS). Respiratory sarcopenia was defined using surrogate measures, including peak expiratory flow rate for respiratory muscle strength and appendicular skeletal muscle mass index for muscle mass. Multivariable Cox proportional hazards models were employed to assess the associations between respiratory sarcopenia and all-cause mortality. Over median follow-ups of 88 and 96 months, respiratory sarcopenia was associated with a significantly elevated risk of mortality (CHARLS: Hazard Ratio [HR] = 1.61, 95% Confidence Interval [CI] 1.17-2.22; HRS: HR = 1.48, 95% CI 1.07-2.04). Longitudinal progression from non-sarcopenic to respiratory sarcopenic status was associated with an increased risk of mortality (CHARLS: HR = 1.94, 95% CI 1.01-3.76; HRS: HR = 1.82, 95% CI 1.02-3.28), while reversion was associated with a reduced risk of death in the HRS cohort (HR = 0.15, 95% CI 0.03-0.94). Respiratory sarcopenia was independently associated with an increased risk of all-cause mortality in CKD populations using multivariable-adjusted analyses, and reversion from respiratory sarcopenia was associated with a lower risk of mortality. The multi-cohort design strengthens the clinical relevance of these findings, despite limitations from the indirect diagnosis and potential confounding.