Quantification of Alpha-EEG Activity During Sleep in Fibromyalgia:

Abstract

Objectives: Based on visual ratings of the electroencephalography [EEG], the alpha EEG sleep anomaly has been described in subjects suffering from the fibromyalgia syndrome [FMS]. The aim of this study was to quantify the alpha EEG in patients with FMS compared to normal subjects using ambulatory recordings. Methods: Twelve women with FMS and 14 age-matched controls completed 2 nights of ambulatory polysomnography recordings. The epochs from the second night were classified blindly and manually according to the standard criteria. Moreoever, all 2s segments [N = 287,355] of the EEG [F1-A2 derivation] were subjected to frequency analysis using autoregressive modelling. The power in the alpha band relative to the total power was calculated in all epochs. Results: Fibromyalgics spent more time in stage wake [p35.0 veersus 17.1 minutes] and non-rapid eye movement [NREM] stage 1 [15.9 versus 9.5 minutes] and had a lower sleep efficiency index [87.6% versus 92.3%]. The latency to NREM stages were longer in FMS> The frequency analysis demonstrated more energy in the alpha band in NREM2-4 in FMS, even after epochs with hyperventilation, movements, etc., had been omitted. The increased power in the alpha band was also seen when sleep cycles were analysed separately. Moreover, the alpha EEG showed more variance in fibromyalgics. Conclusion: The study, using a reproducible mathematical model, confirmed the findings of more alpha EEG in FMS, compared to controls, even when ambulatory recordings were used, mimicking the normal conditions of sleep. The greater variability of the alpha power in fibromyalgics suggests a greater fluctuation of the cortical arousal activity during sleep. The EEG abnormalities reflected in the general architecture of FMS sleep may represent a genuine arousal mechanism contributing to their daytime complaints.

KEYWORDS:

• Fibromyalgia
• ambulatory
• polysomnography
• sleep. electroencephalograpy
• spectral analysis