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 South 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 the square of height (height²) was 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/1.73 m². Mean follow-up was 5.14 years. Greater SMA/height² and NAMA/height² ratios were associated with a lower risk of mortality (HRs, 0.58 [95% CI, 0.39-0.88] and 0.55 [0.39-0.79], respectively). Greater NAMA/height² ratio was associated with a 26% lower ESKD incidence (HR, 0.74; 95% CI, 0.59-0.92), but a greater LAMA/height² ratio was associated with a higher 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 risks of mortality and progression of chronic kidney disease to ESKD. Plain-Language Summary Low muscle mass is a known health concern, and we aimed to study its impact specifically in patients with autosomal-dominant polycystic kidney disease (ADPKD). We investigated how muscle mass relates to patient survival and progression to end-stage kidney disease. Using computed tomography scans performed on more than 1,400 patients with ADPKD, we measured the amount and quality of their muscle. We discovered that patients with more muscle, especially higher-quality muscle, had a significantly lower risk of death and were less likely to develop end-stage kidney disease. Conversely, lower-quality muscle was associated with an increased risk of death. These findings suggest that maintaining good muscle mass may improve outcomes for patients with ADPKD. These data can inform future strategies for improving outcomes in people with ADPKD.