Deciphering the temporal link between pain and sleep in a heterogeneous chronic pain patient sample: a multilevel daily process study.

OBJECTIVES: Because insomnia is a common comorbidity of chronic pain, scientific and clinical interest in the relationship of pain and sleep has surged in recent years. Although experimental studies suggest a sleep-interfering property of pain and a pain-enhancing effect of sleep deprivation/fragmentation, the temporal association between pain and sleep as experienced by patients is less understood. The current study was conducted to examine the influence of presleep pain on subsequent sleep and sleep on pain reports the next day, taking into consideration other related psychophysiologic variables such as mood and arousal. DESIGN: A daily process study, involving participants to monitor their pain, sleep, mood, and presleep arousal for 1 wk. Multilevel modeling was used to analyze the data. SETTING: In the patients' natural living and sleeping environment. PATIENTS: One hundred nineteen patients (73.9% female, mean age = 46 years) with chronic pain and concomitant insomnia. MEASUREMENT: An electronic diary was used to record patients' self-reported sleep quality/efficiency and ratings of pain, mood, and arousal at different times of the day; actigraphy was also used to provide estimates of sleep efficiency. RESULTS: Results indicated that presleep pain was not a reliable predictor of subsequent sleep. Instead, sleep was better predicted by presleep cognitive arousal. Although sleep quality was a consistent predictor of pain the next day, the pain-relieving effect of sleep was only evident during the first half of the day. CONCLUSIONS: These findings challenge the often-assumed reciprocal relationship between pain and sleep and call for a diversification in thinking of the daily interaction of these 2 processes.