Spa therapy improves sleep quality: evidence from questionnaire and actigraphy

Background Sleep-wake rhythm is highly correlated with core body temperature, and bathing in the hot spring can effectively manipulate core body temperature to improve sleep quality. However, there is still a lack of experimental research on the influencing factors of utilizing hot spring facilities to positively affect sleep. Methods In this study, we aimed to explore the factors improving sleep quality via hot spring bathing in terms of both subjective (self-rating scales) and objective (actigraphy) measures, 33 insomniacs were recruited and randomly divided into the afternoon (AG) and evening bathing groups (EG). Results The results showed that after the intervention, subjective sleep quality was improved significantly in both groups, and the evening bathing group had a better performance. In contrast, neither group had a significant change in objective sleep measures. Moreover, we found that hot spring spa therapy is particularly effective in reducing pre-sleep thoughts inventory and shortening sleep onset latency, and it is more applicable to people with difficulty falling asleep. Conclusion This study identified the timing and individual's behaviour traits as the important factors, and these formed practical guidance for sleep improvement by spa therapy.