Associations of Skeletal Muscle Mass and Body Mass Index With Clinical Outcomes in Autosomal Dominant Polycystic Kidney Disease: An Observational Study.

RATIONALE & OBJECTIVE Low muscle mass is a risk factor for chronic kidney disease. In this study, we examined the relationship between muscle mass and mortality, as well as end-stage kidney disease (ESKD), in patients with autosomal dominant polycystic kidney disease (ADPKD). STUDY DESIGN Retrospective cohort study. SETTING & PARTICIPANTS 1,443 patients with ADPKD from eight tertiary-care hospitals in Korea between 2006 and 2020. EXPOSURES Computed tomography images were obtained at the third lumbar vertebra to measure the skeletal muscle area (SMA) using an artificial intelligence system. SMA indexed for w a height2 s classified as low-attenuation muscle area (LAMA) or normal-attenuation muscle area (NAMA) based on muscle quality. OUTCOMES All-cause mortality and ESKD. ANALYTICAL APPROACH Cox proportional hazards regression, adjusted for sex, age, creatinine, glucose, and height-adjusted total kidney volume, was used to investigate the associations of muscle indices with all-cause mortality and ESKD. Subgroup analyses were conducted based on body mass index categories: low or normal (<25 kg/m2) and overweight or obese (≥25 kg/m2). RESULTS The study population included more than half female patients, and the mean estimated glomerular filtration rate was 68.4 ml/min/1.73m2. Mean follow-up was 5.14 years. Greater SMA/height2 and NAMA/height2 were associated with a lower risk of mortality (HRs 0.58 (95% CI 0.39-0.88) and 0.55 (95% CI, 0.39-0.79), respectively). Greater NAMA/height2 was associated with a 26% lower ESKD incidence (0.74 (0.59,0.92), but a greater LAMA/height2 was associated with a lower ESKD incidence (HR 1.18, 95% CI 1.01-1.37). A higher NAMA/LAMA ratio was associated with a lower ESKD incidence (HR 0.74, 95% CI 0.60-0.92). Greater muscle mass was associated with a lower risk of mortality among overweight individuals and a lower risk of ESKD in underweight individuals. LIMITATIONS Lack of details about muscle strength and performance. CONCLUSIONS Among individuals with ADPKD, greater and higher-quality muscle mass were associated with lower risk of mortality and progression of CKD to ESKD.