Sleep in older chronic pain patients: a comparative polysomnographic study.

OBJECTIVES: The relationship between chronic pain and sleep disturbances is not yet fully understood, despite much evidence linking them. Polysomnography is the gold standard for assessing sleep architecture, and in this naturalistic study, we wanted to compare both macrostructure and microstructure sleep variables in older chronic pain patients with healthy older persons using polysomnography.
METHODS: Sleep variables investigated in this study include sleep onset latency, total sleep time, wake time after sleep onset, sleep efficiency, sleep latencies to different sleep stages, number of awakenings, time spent in each sleep stage, and arousal index, as well as apnea-hypopnea index and periodic leg movement index. In addition, the power spectrum of the α and δ frequency bands was analyzed.
RESULTS: The chronic pain group spent significantly longer time in bed and had poorer sleep than the control group in terms of sleep onset latency, sleep latency to N2, sleep efficiency, wake time after sleep onset, and number of awakenings. However, sleep duration and time spent in each sleep stage did not differ between the 2 groups. The composition of power spectrum frequencies revealed that older people with chronic pain have lower intensity in the δ frequencies (0.5 to 1.99 Hz and 2 to 4 Hz) throughout the whole night, especially in the first 6 hours. The findings are in accordance with the idea that the quality of sleep while in chronic pain is particularly characterized by difficulties with the wake-sleep transition and a lower intensity of the deep restorative sleep throughout the night.