SLEEP INTENSITY IN FIBROMYALGIA - FOCUS ON THE MICROSTRUCTURE OF THE SLEEP PROCESS

Alpha electroencephalography (EEG) predominance has been described dur ing sleep in patients suffering from the fibromyalgia syndrome (FMS). However, EEG power density in the lower frequency bands probably bette r reflects the restorative functions of sleep. This study was conducte d to describe the energy in all frequency bands in the sleep EEG. Ambu latory sleep recordings were performed on 12 women with FMS and 14 con trol women. Epochs were classified according to standard criteria. Mor eover, all 2-s segments (n = 287 355) of the EEG in non-rapid-eye-move ment (NREM) 2-4 sleep were subjected to frequency analysis using autor egressive modelling. Frequency bands were: delta (0.5-3.5 Hz), theta ( 3.5-8 Hz), alpha (8-12 Hz), sigma (12-14.5 Hz) and beta (14.5-25 Hz). In patients with FMS, there was a predominance of EEG power in the hig her frequency bands [two-way analysis of variance (ANOVA), alpha: P = 0.043; sigma: P = 0.004] at the expense of the lower frequencies (ANOV A, delta: P = 0.005; theta: P = 0.008). The same trends were obtained for the individual sleep cycles. The calculations of total delta power in the time domain showed an exponentially declining curve in healthy subjects, but a flatter decline in FMS. The decreased power in the lo w-frequency range might reflect a disorder in homoeostatic and circadi an mechanisms during sleep and may contribute to daytime symptoms in p atients with fibromyalgia.