title: Exercise effects on night-to-night fluctuations in self-rated sleep among older adults with sleep complaints.
abstract: 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 55 years 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, 6 months and 12 months. 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 6 months no differences in IIV were observed by group. At 12 months, 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 12 months. 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.
authors.affiliation: Stanford Prevention Research Center, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305-5411, USA. mbuman@stanford.edu
authors.forename: Matthew P
authors.initials: MP
authors.lastname: Buman
authors.forename: Eric B
authors.initials: EB
authors.lastname: Hekler
authors.forename: Donald L
authors.initials: DL
authors.lastname: Bliwise
authors.forename: Abby C
authors.initials: AC
authors.lastname: King
mesh_terms: D015444:Exercise / Q000502:physiology; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012890:Sleep / Q000502:physiology; D012893:Sleep Wake Disorders / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome