The Association between Serum Uric Acid and Appendicular Skeletal Muscle Mass and the Effect of Their Interaction on Mortality in Patients on Peritoneal Dialysis

<b><i>Background:</i></b> Serum uric acid (SUA) has been revealed to be positively associated with the body composition parameters in hemodialysis patients, but few studies have investigated that in patients on peritoneal dialysis (PD). The aim of this study was to identify the relationship between SUA and appendicular skeletal muscle mass (ASM) and the effect of their interaction on mortality in PD patients. <b><i>Methods:</i></b> This was a single-center retrospective cohort study. Patients who underwent multifrequency bioelectrical impedance analysis between January 1, 2013, and December 31, 2016, and had data on SUA values were enrolled. All patients were followed up until December 31, 2019. <b><i>Results:</i></b> In total, 802 prevalent PD patients (57.9% male), with mean age of 46.2 ± 14.2 years were enrolled. The average SUA and ASM were 6.8 ± 1.3 mg/dL and 21.2 ± 4.9 kg. According to multiple linear regression models, SUA was positively associated with relative ASM in middle-aged and older PD patients (standardized coefficients [β] 0.117; 95% confidence interval [CI] 0.027, 0.200; <i>p</i> = 0.010). Further sex-stratified analysis showed that the association existed only in males (β 0.161; 95% CI 0.017, 0.227; <i>p</i> = 0.023). Moreover, the presence of hyperuricemia was found to predict lower risk of all-cause mortality (hazard ratio [HR] 0.514, 95% CI 0.272, 0.970; <i>p</i> = 0.040) only in patients with lower relative ASM. And, the adjusted HR of every 1 mg/dL elevated SUA level was 0.770 (95% CI 0.609, 0.972; <i>p</i> = 0.028) for all-cause mortality in the lower relative ASM subgroup. <b><i>Conclusions:</i></b> There exists a positive association between the SUA and ASM, and the ASM significantly affected the association between SUA and all-cause PD mortality.