Dose-response effects of exercise training on the subjective sleep quality of postmenopausal women: exploratory analyses of a randomised controlled trial.

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 VO(2peak)), 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.

TRIAL REGISTRATION NUMBER

clinicaltrials.gov identifier: NCT00011193.