Sleep and chronic pain: challenges to the alpha-EEG sleep pattern as a pain specific sleep anomaly

The alpha-EEG sleep anomaly has been associated with chronic benign pain syndromes. Although controversial, the anomaly is believed by some to be an important biologic correlate of certain otherwise poorly explained painful conditions (e.g., fibromyalgia and chronic fatigue syndrome). To shed further light on this phenomenon, this study compared the sleep and psychological characteristics of chronic pain patients who exhibited the alpha-EEG sleep anomaly with pain-free psychiatric and medical patients who also were found to exhibit the alpha-EEG anomaly.

The alpha-EEG sleep was identified in the polysomnographic records of 5% of over 1000 consecutive sleep patients. Objective sleep parameters, daytime sleepiness and psychological characteristics (Minnesota Multiphasic Personality Inventory [MMPI] scores) of patients exhibiting this anomaly were examined.

The alpha-EEG anomaly was identified in only 5% of the total patient sample. Patients with the alpha-EEG anomaly could be further classified into three diagnostic subgroups: chronic pain, psychiatric and other medical/sleep disorders, The subgroups were compared on sleep parameters and psychological characteristics. Less than 40% of the patients exhibiting the alpha-EEG anomaly experienced chronic pain. Chronic pain patients evidenced disturbed sleep patterns and psychological characteristics that were for the most part similar to those observed in some pain-free medical and psychiatric patients. Only the medical subgroup exhibited objective daytime sleepiness. The alpha-EEG sleep disturbance was not accounted for by psychological characteristics.

These findings challenge the notion that alpha-EEG sleep is of direct etiological significance in producing the pain complaint among patients with chronic pain since the alpha-EEG sleep was not a sufficient condition for pain.