Bidirectional relationship between sleep disturbances and pain in Japanese patients with chronic pain: findings from actigraphy and sleep diaries.

This study aimed to evaluate the bidirectional relationship between sleep and pain in Japanese patients with chronic pain through a prospective analysis of the impact of pain on sleep and the impact of sleep on pain the following day, based on both objective and subjective measures. Sleep and pain parameters were recorded every day for a 7-day period in 36 patients with chronic pain. Objective sleep data were collected using an actigraph, and total sleep time, sleep onset latency, total wake time after sleep onset, and sleep efficiency were determined. Subjective ratings of sleep and pain intensity were obtained using sleep diaries and a pain scale. A mixed-effects model was used for data analysis, and the bidirectional relationship between pain and sleep was examined in each direction. Sleep efficiency measured by actigraphy was significantly higher on days when pain before sleep was less intense (p < 0.05), but pain intensity did not affect subjective sleep satisfaction. Sleep efficiency did not affect pain after sleep the next day, but pain after sleep was significantly less intense on days when sleep satisfaction was high (p < 0.0001). The results of this study suggest that the relationship between pain and sleep is bidirectional, but objective sleep data and subjective ratings of sleep were inconsistent. Improvement of perceived sleep quality may be necessary in patients who do not notice any change in their sleep quality despite achieving better sleep efficiency through treatment.