Effect of physical exercise intervention on daily sleep quality in women with breast cancer and severe psychological distress: a series of N-of-1 trials

ObjectiveA good quality of sleep is essential within the context of breast cancer. Nonetheless, poor sleep quality is highly prevalent in breast cancer patients, particularly in women with psychological distress. Physical activity is recommended to improve sleep quality in the context of breast cancer. However, no previous physical activity intervention has been specifically tested to improve the sleep quality for women with breast cancer and psychological distress. Thus, the aim of this preliminary study was to examine the effects of a 12-week remote supervised physical activity intervention on daily self-reported sleep quality among women with breast cancer and severe psychological distress, at the individual level. MethodA series of N-of-1 trials with an A-B-A’ design was carried out with ecological momentary assessments. Phase A and A’ (2-week) represented pre- and post-intervention measures and phase B (12-week) represented the intervention phase. For the entire 16-week, participants received a daily prompt to report their sleep quality. The insomnia severity index was filled pre- and post-first phase A and end of phase B. Sixteen participants completed the treatment. ResultsA significant improvement of sleep quality was observed in 9 participants with moderate to large effects. However, the intervention was detrimental for the sleep quality in 2 patients. Paradoxically, the self-reported sleep disorder remained elevated at the end of intervention. ConclusionThis is the first study to show that physical activity is potentially effective in women with breast cancer and severe psychological distress. The findings justify extension to a randomized controlled trial.