Abstract:
Chronic pain is a major health problem both in New Zealand and worldwide. Sleep disturbance is common amongst chronic pain sufferers. The relationship between pain and sleep has become a major area for exploration in the literature with a myriad of experimental, cross-sectional, and prospective studies conducted. Recently, depression and depressed mood have begun to emerge as major contributors to this relationship. Repetitive thought processes (e.g., rumination, or pre-sleep cognitive arousal) have also been highlighted as a factor which may be present in chronic pain, insomnia, and depression. This study examines the day-to-day inter-relationships between pain, sleep, and depressed mood in a heterogeneous group of chronic pain patients. The design utilised a micro-longitudinal approach using repeated daily diary measures of pain, sleep, depressed mood, and pre-sleep cognitive arousal with concurrent actigraphic monitoring of sleep. The discrepancy between subjective and objective accounts of sleep was also a key area for investigation in this study. The data were analysed at the between-persons and within-persons levels. This allows conclusions to be drawn about what is common to this population on average and to examine the relative importance of temporal fluctuations between the variables. While reciprocal relationships between pain and sleep, pain and mood, and sleep and mood were suggested at baseline and between-persons data they were not in within-persons analyses. The results offered support for an emerging theory that suggests that pain may not be the primary reason for insomnia in chronic pain patients. Importantly, pre-sleep cognitive arousal was implicated as a link between the variables. It appears that this thought process may serve to perpetuate a vicious cycle between pain, sleep, depression, and depressed mood.
