Exercise for stress and sleep Original paper

Exercise is known to improve sleep and reduce stress. Although a few studies have demonstrated this effect, a comprehensive evaluation of the results was needed.

This meta-analysis included 9 randomized controlled trials that involved 711 participants in total (ages 26–64; 90% women, 10% men) who completed exercise intervention programs.​​ Many of the participants had breast cancer.

The exercise interventions included aerobic (4 studies), mind-body (e.g., yoga; 4 studies), and dance (1 study) activities. Two studies had an extra breathing component. Exercise frequency and time varied, with participants completing interventions 2–5 times per week with durations of 20–90 minutes per session. Five of the 9 studies lasted 6 weeks, with a total range of 3–16 weeks among all included studies. The control groups used no exercise (4 studies), active control (3 studies), and usual care (2 studies).

Cortisol levels were measured as a biomarker for stress (6 studies used saliva and 3 used blood samples). Sleep quality was evaluated with subjective questionnaires in 8 studies (e.g., Pittsburgh Sleep Quality Index), and 2 studies included an extra objective measurement of sleep architecture (e.g., polysomnography, actigraphy).

Exercise improved cortisol levels and subjective sleep quality to a small degree when compared to the control, with moderate and low levels of certainty, respectively. The studies were considered to be moderately different from each other, likely because of differences in the health status of participants.

Analysis of cortisol from saliva may be more accurate than analysis of serum.^[1]