Effect of zero-time exercise on physically inactive adults with insomnia disorder: A randomized controlled trial

Background: Whether simple lifestyle-integrated exercise training can improve insomnia remains unclear. In this study, we examined whether zero-time exercise, a simple exercise incorporated into daily routines without extra time, can improve sleep in physically inactive adults with insomnia. Methods: This was a single-blinded, parallel-group, randomized controlled trial. A total of 140 physically inactive adults (mean [SD] age, 46.7 [14.0] years; 115 [82.1 %] women; mean [SD] insomnia duration, 4.9 [6.7] years) with insomnia disorders were randomly allocated (1:1) to the zero-time exercise intervention group or the sleep hygiene education control group. They received two 2-h zero-time exercise training sessions or sleep hygiene education lessons within 2 weeks and two phone call reminders per week for 8 weeks to follow their respective programs. The outcomes were assessed at 8, 16, and 24 weeks. The primary outcome was the Insomnia Severity Index score at week 24. Results: The intervention group showed a significantly greater decrease in the Insomnia Severity Index scores than those in the control group at weeks 16 (− 1.59 points, 95 % CI -3.09 to − 0.08; P = 0.039) and 24 (− 2.59 points, 95 % CI -4.17 to − 1.01; P = 0.001); however, the difference at week 8 was not significant (− 1.23 points, 95 % CI -2.54 to 0.07; P = 0.065). No serious adverse events were observed. Conclusions: Zero-time exercise effectively reduces insomnia severity in physically inactive adults and can be easily incorporated into daily routines to improve insomnia symptoms and daytime impairment. Trial registration: ClinicalTrials.gov, NCT04227587 (Registration date: January 13, 2020; The first participant was recruited on September 1, 2020). Word count: 240.