Sleep in depressed and nondepressed participants with chronic low back pain: electroencephalographic and behaviour...

To study the nature of sleep disturbance in depressed and nondepressed patients with chronic low back pain (CLBP).

A controlled, consecutive 4-night polysomnographic study.

Participants were screened (psychologic, psychiatric, and physical) to determine their study group, and 21 participants (CLBP: 4 depressed, 6 nondepressed and 11 controls) were studied.

On all nights, standard polysomnographic sleep measures as well as midline occipital and frontal electroencephalography and respiration were recorded on a Grass Model 7 polygraph. Pain, sleep quality, and depression were also measured. Participants with CLBP reported significant levels of pain and sleep disturbance as compared to controls, but all groups had equivalent amounts of sleep and comparable sleep architecture. The electroencephalographic power spectral analyses revealed significant differences, with controls having more sigma across sites, more low beta activity occipitally and frontally than nondepressed patients with CLBP, and more occipital sigma and less high beta activity than depressed participants. Between pain subgroups, the depressed participants showed more occipital delta, more occipital and central alpha, and more high beta activity across all sites than did the nondepressed participants.

Lower sigma power in participants with CLBP suggests less-effective sensorimotor gating that may contribute to poor sleep quality. Pain subgroup differences underscore the need to consider the influence of depression in the evaluation of sleep in clinical populations. This study controlled for many factors other than pain that may contribute to the sleep complaints in this population. Consequently, the absence of signs of major sleep disturbance must not be interpreted as evidence of a lack of a true sleep problem in CLBP but more likely reflects control of these factors as well as the difficulty in measuring sleep quality.