Risks of All‐Cause Mortality in Adults With Chronic Kidney Disease With Sarcopenia or Obesity: A Population‐Based Study

ABSTRACT Background The relationship between obesity, sarcopenic obesity and all‐cause mortality in chronic kidney disease (CKD) patients remains controversial. This study aims to investigate the role of low muscle mass and fat mass in the risk of all‐cause mortality in CKD patients in the United States. Methods This study utilized data from the National Health and Nutrition Examination Survey (NHANES) conducted between 1999–2006 and 2011–2018, including 1553 adults with CKD. Multivariable Cox proportional hazards models were constructed to explore the relationship between sarcopenia, fat mass and all‐cause mortality, with nonlinear relationships assessed using restricted cubic splines. Subgroup analyses were conducted based on sex, CKD stages and the presence of sarcopenia. Results The average age of participants was 58.15 ± 18.48 years, with 45% being male. Sarcopenia was more common in men, non‐diabetic individuals and those with lower education levels. During a median follow‐up of 119.5 months, 693 deaths from all causes were recorded. After adjusting for multiple variables, sarcopenia was significantly associated with increased all‐cause mortality risk in CKD patients (HR 1.21; 95% CI 1.00–1.45, p = 0.047). Participants were categorized based on body mass index (BMI) into normal (reference), sarcopenia only, obesity only and sarcopenic obesity groups. Results showed that obesity alone had a protective effect in CKD Stages I–II (HR 0.45, 95% CI 0.28–0.72, p = 0.001) whereas it had an opposite effect in CKD Stages III–V (CKD III: HR 1.67, 95% CI 1.07–2.60, p = 0.024; CKD IV–V: HR 17.51, 95% CI 1.29–238.01, p = 0.032). Further analysis of fat mass data revealed that compared with the lowest quartile (Q1), middle and higher quartiles of fat mass showed significant benefits in male participants (Q2: HR 0.71, 95% CI 0.51–0.99, p = 0.046; Q3: HR 0.62, 95% CI 0.41–0.92, p = 0.019) and those in CKD Stage III (Q2: HR 0.64, 95% CI 0.47–0.88, p = 0.006; Q3: HR 0.62, 95% CI 0.41–0.93, p = 0.021). Conclusions In this longitudinal cohort study, we found that sarcopenia was associated with an increased risk of all‐cause mortality in CKD patients, whereas moderate or higher fat mass might mitigate this risk, particularly in male patients. Prognostic management for CKD patients should focus on increasing muscle mass rather than simply reducing body weight.