Relationship Between Lower Extremity Muscle Strength and All-Cause Mortality in Japanese Patients Undergoing Dialysis

Background. Skeletal muscle wasting is common and insidious in patients who are undergoing hemodialysis. However, the association between lower extremity muscle strength and all-cause mortality remains unclear in this population. Objective. The purpose of this study was to investigate the prognostic significance of lower extremity muscle strength on 7-year survival in a cohort of patients who were clinically stable and undergoing hemodialysis. Design. A prospective cohort study was conducted. Methods. A total of 190 Japanese outpatients who were undergoing maintenance hemodialysis 3 times per week at a hemodialysis center were followed for up to 7 years. Lower extremity muscle strength was evaluated using a handheld dynamometer at the time of patient enrollment in the study. Muscle strength data were divided by dry weight and expressed as a percentage. A Cox proportional hazards regression model was used to assess the contribution of lower extremity muscle strength to all-cause mortality. Results. The median age (25th and 75th percentiles) of this study population was 64 years (57 and 72 years), 53.2% of the patients were women, and the time on hemodialysis was 39.0 months (15.9 and 110.5 months) at baseline. During a median follow-up of 36.0 months, there were 30 deaths. With a multivariate Cox model, the hazard ratio in the group with a knee extensor strength of <40% was 2.73 (95% confidence interval = 1.14 - 6.52) compared with that in the >= 40% group. Limitations. This was a small-scale observational study, and the mechanisms underlying the higher mortality risk in patients with poor muscle strength undergoing hemodialysis than in other patients undergoing hemodialysis remain to be elucidated. Conclusions. Decreased lower extremity muscle strength was strongly associated with increased mortality risk in patients undergoing hemodialysis.