ASSOCIATION BETWEEN QUADRICEPS ISOMETRIC STRENGTH AND SLEEP DISTURBANCES AMONG PATIENTS ON HEMODIALYSIS

Abstract Background and Aims The muscle strength of patients on hemodialysis (HD) is lower than that of community-dwelling older adults. Because decreased muscle strength, especially quadriceps isometric strength (QIS), has been reported to be a risk factor for increased mortality rate among patients undergoing HD, the prevention and correction of decreased QIS are very important in this population. Although some factors associated with decreased QIS among patients on HD have been reported, these factors remain unclear because patients on HD have many comorbidities with increasing age and prolonged HD vintage. In community-dwelling older adults, sleep disturbance is reported to be a factor associated with reduced muscle strength. In addition, the prevalence of sleep disturbance is higher in patients on HD. Therefore, it is necessary to investigate these associations in this population. We examined the association between QIS and sleep disturbances among patients receiving HD. Method This cross-sectional study included 211 outpatients undergoing HD three times a week. To evaluate QIS, a handheld dynamometer (μtas F-1; Anima, Tokyo, Japan) was used. Patients were asked to sit on a bench with their hip and knee flexed at an angle of 90°. They performed isometric voluntary contraction of the quadriceps for a maximum of 5 seconds, thrice, for both legs. The average of the right and left maximal QIS divided by the dry weight (%DW) was used in the analysis. Sleep disturbances were measured using the Athens Insomnia Scale (AIS), a self-administered questionnaire consisting of eight questions, each scored from 0 to 3. The total scores range from 0 to 24, with higher scores indicative of worse sleep quality. Clinical characteristics, including age, sex, body mass index, HD vintage, comorbidity score, serum albumin, C-reactive protein, and the Mini-Mental State Examination, were investigated. Multiple linear regression analysis and multivariable-adjusted restricted cubic splines with four knots were used to examine the association between QIS and sleep disturbances. Results The median age was 68 (interquartile range: 59–76) years, and 62% of the patients were men. In multiple linear regression analysis, the AIS score was extracted as a significant factor related to QIS after adjusting for clinical characteristics (regression coefficient: -0.45, 95% confidence interval: -0.84 to -0.05, p = 0.028). In the multivariable-adjusted restricted cubic splines, a nonlinear relationship was found between QIS and the AIS score even after adjusting for clinical characteristics. In addition, it was shown that QIS decreased significantly as the AIS score increased up to 6, which is the cutoff value for discriminating sleep disturbances (Figure). Conclusion Higher AIS scores were independently associated with decreased QIS among patients on HD. Future studies should investigate the causality between QIS and sleep disturbance in patients undergoing HD.