SummaryBackground and objectives The association between mortality and physical activity based on self-report questionnaire in hemodialysis patients has been reported previously. However, because self-report is a subjective assessment, evaluating true physical activity is difficult. This study investigated the prognostic significance of habitual physical activity on 7-year survival in a cohort of clinically stable and adequately dialyzed patients.Design, setting, participants, & measurements A total of 202 Japanese outpatients who were undergoing maintenance hemodialysis three times per week at the hemodialysis center of Sagami Junkanki Clinic (Japan) from October 2002 to February 2012 were followed for up to 7 years. Physical activity was evaluated using an accelerometer at study entry and is expressed as the amount of time a patient engaged in physical activity on nondialysis days. Cox proportional hazard regression was used to assess the contribution of habitual physical activity to all-cause mortality.Results The median patient age was 64 (25th, 75th percentiles, 57, 72) years, 52.0% of the patients were women, and the median time on hemodialysis was 40.0 (25th, 75th percentiles, 16.8, 119.3) months at baseline. During a median follow-up of 45 months, 34 patients died. On multivariable analysis, the hazard ratio for all-cause mortality per 10 min/d increase in physical activity was 0.78 (95% confidence interval, 0.66-0.92; P=0.002).Conclusions Engaging in habitual physical activity among outpatients undergoing maintenance hemodialysis was associated with decreased mortality risk.

Decreased lower extremity muscle strength was strongly associated with increased mortality risk in patients undergoing hemodialysis.

Maintenance of the walking ability is very important for smooth continuation of maintenance hemodialysis (HD). The aim of the present study was to clarify the physical activity level in daily living that HD patients should maintain to prevent deterioration of their walking ability. Outpatients undergoing maintenance HD, consisting of 65 males and 88 females with a mean age of 64 +/- 11 years, were recruited for the present study. Their physical activity level was recorded over a week with an accelerometer. The physical activity level in daily living was defined as the sum of the lengths of time for which the patients were engaged in physical activity of light or greater intensity during the day, and expressed as the average duration per day. The walking ability was assessed by the normal walking speed and maximum walking speed. Data were analyzed using the receiver operating characteristic (ROC) curve, and the cut-off point for the physical activity time was determined to predict deterioration of the walking ability. In the prediction of deterioration of the normal and maximum walking speeds, the areas under the ROC curve for the physical activity time were 0.78 (95% confidence interval, 0.69-0.87, P < 0.001) and 0.75 (95% confidence interval, 0.63-0.86, P < 0.001), respectively. Moreover, the ROC curve revealed that the cut-off point for the physical activity time to prevent deterioration of the normal and maximum walking speeds was 50 min/day. Thus, HD patients should engage in physical activity for at least 50 min/day to prevent deterioration of their walking ability.

After confirming the relationship between high-density lipoprotein cholesterol (HDL-C) levels and mortality in hemodialysis patients for study 1, we investigated the effect of physical activity on their HDL-C levels for study 2. In study 1, 266 hemodialysis patients were monitored prospectively for five years, and Cox proportional hazard regression confirmed the contribution of HDL-C to mortality. In study 2, 116 patients were recruited after excluding those with severe comorbidities or requiring assistance from another person to walk. Baseline characteristics, such as demographic factors, physical constitution, primary kidney disease, comorbid conditions, smoking habits, drug use, and laboratory parameters, were collected from patient hospital records. An accelerometer measured physical activity as the number of steps per day over five consecutive days, and multiple regression evaluated the association between physical activity and HDL-C levels. Seventy-seven patients died during the follow-up period. In study 1, we confirmed that HDL-C level was a significant predictor of mortality (P = 0.03). After adjusting for patient characteristics in study 2, physical activity was independently associated with HDL-C levels (adjusted R 2 = 0.255; P = 0.005). In conclusion, physical inactivity was strongly associated with decreased HDL-C levels in hemodialysis patients.