Effect of body size and body composition on survival in peritoneal dialysis patients

Using 24-hour urinary creatinine excretion as a measure of muscle mass, we examined whether body composition influences the survival of incident peritoneal dialysis (PD) patients. We hypothesized that patients with high body mass index (BMI) and low muscle mass might be considered to have high levels of body fat.

Using serum creatinines and creatinine clearances reported on Medical Evidence Form 2728, 24-hour urinary creatinine was calculated in 10 140 incident PD patients with normal (18.5 - 24.9 kg/m2) or high (> or = 25 kg/m2) BMI. Patients were classified as low and normal/high muscle mass groups based on the 25th percentile of 24-hour urinary creatinine (0.64 g/day).

In multivariable parametric survival models, compared to the normal BMI-normal/high muscle mass patients, high BMI-normal/high muscle mass patients had lower hazard of all-cause [hazard ratio (HR) 0.90, 95% confidence interval (CI) 0.83 - 0.97] and cardiovascular (HR 0.88, 95% CI 0.79 - 0.97) death; high BMI patients with low muscle mass had higher hazard of all-cause (HR 1.29, 95% CI 1.17 - 1.42) and cardiovascular (HR 1.21, 95% CI 1.06 - 1.39) death.

Both body size and body composition influence survival of incident PD patients. As incident PD patients with high BMI and normal or high muscle mass have the best survival, PD patients should be encouraged to gain muscle mass rather than fat mass.