Sleep intensity in fibromyalgia (FM): focus on the microstructure of the sleep process

Alpha electroencephalography (EEG) predominance has been described
during sleep in patients suffering from the fibromyalgia
syndrome (FMS). However, EEG power density in the lower
frequency bands probably better reflects the restorative
functions of sleep. This study was conducted to describe the
energy in all frequency bands in the sleep EEG. Ambulatory
sleep recordings were performed on 12 women with FMS and 14
control women. Epochs were classified according to standard
criteria. Moreover, all 2-s segments (n = 287,355) of the EEG
in non-rapid-eye-movement (NREM) 2-4 sleep were subjected to
frequency analysis using autoregressive 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 higher
frequency bands [two-way analysis of variance (ANOVA), alpha:
P = 0.043; sigma: P = 0.004] at the expense of the lower
frequencies (ANOVA, 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
low-frequency range might reflect a disorder in homoeostatic
and circadian mechanisms during sleep and may contribute to
daytime symptoms in patients with fibromyalgia.

Drewes AM, Nielsen KD, Taagholt SJ, Bjerregard K, Svendsen L, Gade J

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