Impact of Fat Mass on Osteoporosis, Sarcopenia, and Osteosarcopenia in Peritoneal Dialysis Patients

The relationship between fat mass and osteoporosis, sarcopenia, and osteosarcopenia is complex. While higher fat mass generally has a negative impact on bone and muscle health in the general population, the impact in peritoneal dialysis (PD) patients is less well understood.

In this study of 359 PD patients, sarcopenia was identified using appendicular skeletal muscle per square meter (ASM/m2), with cut-off values of <7.0 kg/m2 for men and <5.5 kg/m2 for women. Fat tissue index (FTI) and lean tissue index (LTI) were determined using body composition monitoring, with the lowest tertile classified as low FTI and low LTI. Bone mineral density was measured, with a T-score below -2.5 indicating osteoporosis.

The prevalence of osteoporosis, sarcopenia, and osteosarcopenia was 25%, 32%, and 15%, respectively. Notably, 60% of osteoporotic patients had sarcopenia, and about 45% of sarcopenic patients had osteoporosis. Patients with osteoporosis were older and had significantly lower LTI (15.3 vs. 12.7 kg/m2, p < 0.001) and ASM (7.3 vs. 5.8 kg/m2, p < 0.001). Osteoporotic patients also had lower FTI, but this was more pronounced in men than in women. Patients with both sarcopenia and osteoporosis had the lowest LTI and FTI compared to those with only one or neither condition. Low FTI was a significant determinant for osteoporosis (OR, 2.34; 95% CI, 1.43-3.85; p = 0.001), sarcopenia (OR, 2.91; 95% CI, 1.82-4.64; p < 0.001), and osteosarcopenia (OR, 2.34; 95% CI, 1.30-4.24; p = 0.005) in univariate analysis, and these associations remained significant after adjustment for age and body mass index.

Osteoporosis and sarcopenia are common and interrelated in PD patients. Low fat mass, but not normal/high fat mass, was significantly associated with these conditions, suggesting the importance of maintaining adequate fat mass in PD patients.