Relation between sleep quality and daily physical activity in hemodialysis outpatients

The purpose of this study was to examine the correlations among objective sleep variables, sleep-wake cycle parameters, and daily physical activity in hemodialysis patients and controls. Twenty-four hemodialysis patients (HD group) were compared with a control group consisting of 24 healthy participants matched for age, height, and weight. Sleep variables (total sleep time [TST], sleep efficiency [SE], sleep latency [SL], and waking after sleep onset [WASO]), sleep-wake cycle parameters (the sleep-wake cycle period and the peak of sleep-wake cycle variance), and daily physical activity (steps per day) for each participant were assessed by objective methods for two weeks. While there was no difference in TST between the two groups, the HD group showed a significantly increased SL (HD: 0:29±0:20 vs control: 0:16±0:13, p < 0.05) and WASO (HD: 2:21±1:00 vs control: 1:35±0:41, p<0.05) and decreased SE (HD: 67.1±13.6% vs control: 77.5±9.7%, p<0.01) compared to the control group. There was no significant difference in sleep-wake cycle period between the HD and control groups. However, the peak of sleep-wake cycle variance in the HD group (0.050±0.028) was significantly lower (t = 2.49, p<0.05) than in the control group (0.068±0.019). The number of daily steps taken in the HD group (4,774± 2,845 steps) was also significantly lower than in the control group (8,696± 3,047). The peak of sleep-wake cycle variance was significantly correlated with SE (r = 0.532, p<0.01), SL (r = -0.501, p<0.01), and WASO (r = -0.436, p<0.01), whereas the number of steps showed a weak correlation only with WASO (r = -0.308, p<0.05) among the objective sleep parameters. Our results suggest that sleep quality in HD patients may be more effectively improved by maintaining the regular 24-hour sleep-wake cycle rather than by increasing the amount of daily physical activity, indicating that intervention such as measures to prevent napping during hemodialysis sessions may prove effective in improving the quality of sleep in HD patients.