Objective To investigate whether a dose–response relationship existed between exercise and subjective sleep quality in postmenopausal women. This objective represents a post hoc assessment that was not previously considered.
Design Parallel-group randomised controlled trial.
Setting Clinical exercise physiology laboratory in Dallas, Texas.
Participants 437 sedentary overweight/obese postmenopausal women.
Intervention Participants were randomised to one of four treatments, each of 6 months of duration: a non-exercise control treatment (n=92) or one of three dosages of moderate-intensity exercise (50% of VO2peak), designed to meet 50% (n=151), 100% (n=99) or 150% (n=95) of the National Institutes of Health Consensus Development Panel physical activity recommendations. Exercise dosages were structured to elicit energy expenditures of 4, 8 or 12 kilocalories per kilogram of body weight per week (KKW), respectively. Analyses were intent to treat.
Primary outcome measures Continuous scores and odds of having significant sleep disturbance, as assessed by the Sleep Problems Index from the 6-item Medical Outcomes Study Sleep Scale. Outcome assessors were blinded to participant randomisation assignment.
Results Change in the Medical Outcomes Study Sleep Problems Index score at 6 months significantly differed by treatment group (control: −2.09 (95% CI −4.58 to 0.40), 4 KKW: −3.93 (−5.87 to −1.99), 8 KKW: −4.06 (−6.45 to −1.67), 12 KKW: −6.22 (−8.68 to −3.77); p=0.04), with a significant dose–response trend observed (p=0.02). Exercise training participants had lower odds of having significant sleep disturbance at postintervention compared with control (4 KKW: OR 0.37 (95% CI 0.19 to 0.73), 8 KKW: 0.36 (0.17 to 0.77), 12 KKW: 0.34 (0.16 to 0.72)). The magnitude of weight loss did not differ between treatment conditions. Improvements in sleep quality were not related to changes in body weight, resting parasympathetic control or cardiorespiratory fitness.
Conclusion Exercise training induced significant improvement in subjective sleep quality in postmenopausal women, with even a low dose of exercise resulting in greatly reduced odds of having significant sleep disturbance.
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To cite: Kline CE, Sui X, Hall MH, et al. Dose–response effects of exercise training on the subjective sleep quality of postmenopausal women: exploratory analyses of a randomised controlled trial. BMJ Open 2012;2:e001044. doi:10.1136/bmjopen-2012-001044
Contributors TSC and SNB designed and organised the study. TSC, CPE and SNB collected the data. CEK and XS performed the statistical analyses. CEK wrote the first draft of the manuscript. XS, MHH, SDY, CPE, SNB and TSC provided critical input at all stages and critically reviewed and contributed to the final draft. CEK and TSC are guarantors.
Funding This work was supported by grants HL66262 and HL082610 from the National Heart, Lung and Blood Institute of the National Institutes of Health, and the American Heart Association Texas Affiliate award 02651404. Life Fitness (Schiller Park, Illinois) provided exercise equipment for this study. The sponsors had no role in the study design, protocol development or in conducting the trial, data collection, data analysis or preparation of the manuscript.
Competing interests None.
Ethics approval This study was approved by Institutional Review Boards of the Cooper Institute (Dallas, Texas) and the Pennington Biomedical Research Center (Baton Rouge, Louisiana).
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The data set will be available from the corresponding author as part of an academic collaboration.
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