Effects of Zero-time Exercise on inactive adults with insomnia disorder: a pilot randomized controlled trial

Objective: To evaluate the feasibility and clinical effects of a lifestyle-integrated exercise, namely zero-time exercise (ZTEx), on improving insomnia in inactive adults with insomnia disorder. Methods: In this pilot randomized controlled trial, 37 physically inactive adults (mean age: 49.9 years; SD: 13.6 91.9% female) fulfilling the diagnostic criteria of insomnia disorder recruited from the community were randomly assigned to ZTEx training or sleep hygiene education (SHE) groups. Subjects in the ZTEx group (n = 18) attended two 2-hour training lessons to learn ZTEx which they then practiced daily for eight weeks. Subjects in the SHE group (n = 19) attended two lessons of the same schedule and duration. The primary outcome measure was the Insomnia Severity Index (ISI). Results: The ZTEx group had lower ISI scores than the SHE group, with a large between-group effect size of 0.93–1.10 at weeks two, four, six, and eight, but the difference became non-significant at week eight, suggesting a loss of efficacy two months after the training. For secondary outcomes, no significant between-group differences were found in sleep parameters by sleep diary or objective actigraphy. The adherence to the ZTEx training course was satisfactory, with 83% of the group completing two sessions and 78% continuing to practice ZTEx for five days or more per week during the eight-week intervention period. Conclusion: The simple and brief ZTEx training showed high acceptability and exercise compliance and the first evidence of efficacy in reducing insomnia severity in inactive adults with insomnia disorder. Confirmatory trials with longer follow-up are justified. Trial registration number: ClinicalTrials.gov, #NCT03155750