Sleep characteristics and sarcopenia in patients undergoing peritoneal dialysis: nonlinear associations and a potential adiposity-related pathway

Sleep disturbances are common in patients undergoing peritoneal dialysis (PD), yet the pathways linking sleep characteristics to sarcopenia remain poorly understood. We examined associations of sleep duration and quality with sarcopenia and whether these associations included an indirect component involving percent body fat (PBF), with albumin and neutrophil-to-lymphocyte ratio (NLR) as potential modifiers. This cross-sectional study included 562 patients receiving PD. Sleep was assessed by the Pittsburgh Sleep Quality Index (PSQI). Sarcopenia was defined by 2025 Asian Working Group criteria; PBF was assessed by bioelectrical impedance. Restricted cubic splines, mediation/moderated mediation analyses, and sensitivity tests (E-values) were used. Sleep duration showed a U-shaped association with sarcopenia (p-nonlinear < 0.001), with the lowest estimated odds at approximately 7.29 h/night. PSQI score was positively associated with sarcopenia (OR = 1.12 per one-point increase). An indirect association involving PBF was observed for PSQI (ACME = 0.002, p = 0.031) and short sleep (ACME = 0.026, p = 0.030), but not for long sleep. Albumin interacted with PBF in the sarcopenia model for the PSQI (p = 0.042) and short-sleep (p = 0.031) pathways, but the indices of moderated mediation were not statistically significant. NLR showed no evidence of interaction. Mediation sensitivity analysis suggested that the observed indirect associations were not readily explained by modest residual confounding. Sleep duration and quality are associated with sarcopenia in PD patients. An indirect association involving PBF was observed for poorer sleep quality and short sleep, but not for long sleep. Albumin interacts with PBF, yet does not significantly modify the overall indirect pathway. Due to the cross-sectional design, findings are hypothesis-generating and not causal.