Exercise effects on night-to-night fluctuations in self-rated sleep among older adults with sleep complaints

Sleep interventions have rarely explored reductions in night-to-night fluctuations [i.e. intra-individual variability (IIV)] in sleep, despite the negative impacts of such fluctuations on affective states and cognitive and physical symptoms. In a community-based randomized controlled trial we evaluated whether physical exercise reduced IIV in self-rated sleep outcomes among middle-aged and older adults with sleep complaints. Under-active adults 55years and older (n=66, 67% women) with mild to moderate sleep complaints were randomized to 12 months of a moderate-intensity endurance exercise (n=36) or a health education control group (n=30). Daily sleep logs, Pittsburgh Sleep Quality Index (PSQI) and in-home polysomnographic sleep recordings (PSG) were collected at baseline, 6months and 12months. Sleep log-derived means and IIV were computed for sleep-onset latency (SOL), time in bed, feeling rested in the morning, number of nighttime awakenings, and wake after final awakening (WAFA). Using intent-to-treat methods, at 6months no differences in IIV were observed by group. At 12months, SOL-based IIV was reduced in the exercise group compared with the control (difference=23.11, 95% CI: 3.04-47.18, P=0.025, Cohen's d=0.57). This change occurred without mean-level or IIV changes in sleep-wake schedules. For all sleep variables, except SOL and WAFA, IIV changes and mean-level changes in each variable were negatively correlated (r=-0.312 to -0.691, P<0.05). Sleep log-derived IIV changes were modestly correlated with mean-level PSQI and PSG-based changes at 12months. Twelve months of moderate-intensity exercise reduced night-to-night fluctuations in self-rated time to fall asleep, and this relationship was independent of mean-level time to fall asleep.