Sex difference in the association among nutrition, muscle mass, and strength in peritoneal dialysis patients

Many peritoneal dialysis (PD) patients are malnourished, which leads to weakening owing to a decrease in muscle mass. However, this straightforward association could differ based on the sex of individuals. Further, studies on the sex-based association among nutrition, muscle mass, and strength would be helpful in choosing optimal interventions to improve the strength of patients on dialysis. The study aimed to assess the association between these three variables using mediation analysis. This retrospective study included prevalent PD patients (n = 199). Mediation analysis was conducted to investigate the effect of the appendicular lean mass (ALM) index on the association between the geriatric nutritional risk index (GNRI) and handgrip strength (HGS). The numbers of PD patients with a low ALM index, low HGS, or low GNRI score were 121 (60.8%), 109 (54.8%), and 70 (35.2%), respectively. The proportion of patients with a low ALM index was lower in females than in males, and those with a low HGS were less in patients without diabetes than that in those with diabetes. Patients ≥ 65 years old had a higher proportion of low ALM index or HGS than those < 65 years old. Low HGS was significantly associated with mortality in both sexes. In males, the HGS was correlated with the GNRI and ALM index; however, in females, partial correlation did not demonstrate an association among the GNRI, ALM index, and HGS. Mediation analysis showed that, in males, the GNRI was associated with HGS, and the association was partially mediated through the ALM index. These data reveal that the ALM index accounts for some, but not all, of the relationship between GNRI and HGS. There is not only a significant relationship between the ALM index and HGS, but also some direct relationship between GNRI and HGS. In females, there was no significant association between the GNRI or ALM index and HGS. These suggest that, for both sexes, nutritional supplementation and exercise should be recommended as the primary intervention for improving strength; however, other interventions for improving muscle quality could be considered as alternatives for maintaining strength in women undergoing PD.