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EEG spectral indices and sleep fragmentation

CORRELATING EEG SPECTRAL INDICES AND SLEEP FRAGMENTATION IN CHILDREN WITH OSAS.

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Scott Coussens BSc(1,2), Dr David Parsons PhD(2), Dr David Saint PhD(1), Dr Yvonne Pamula PhD(2), Dr D. Kennedy MD(2), Dr D. Abbot PhD(1), Matthew Berryman Beng(1), Helen Newman BSc(2).
(1) Adelaide University, Department of Physiology, Australia, (2) Women's & Children's Hospital, Pulmonary Medicine. North Adelaide, Australia.

Children with Obstructive Sleep Apnoea Syndrome (OSAS) have disrupted sleep and show reduced cognitive, attention and social task performance.

Recent studies have shown a strong correlation between autonomic nervous system (ANS) activation and the theta band (3-7Hz) of the EEG power spectra. The link between ANS activity and memory formation in the hippocampus and between ANS activity and sleep disturbance suggests that this measure may be used as an indirect indicator of sleep fragmentation.

We have begun to explore the link between ANS activity, other sleep regulatory processes and sleep fragmentation events through the analysis of correlated EEG spectral bands. Preliminary findings indicate that these correlates may be a useful measure of sleep fragmentation and potentially form the basis of a generally applicable Index of Sleep Fragmentation (SFI) . A paired samples t-test (p=0.05, n=28) was used to compare short epochs of sleep from six subjects that included fragmentary events (stage 4 hyponoeas) to epochs that were unfragmented. Two frequency bands (0.5 -2.5 Hz and 3 -7 Hz) of the power spectrum showed significantly reduced relative power measures (p<0.05, p<0.02 respectively).

We continue to explore this alternative approach to accounting for the cognitive deficits observed in children with OSAS, by focussing on the importance of disruption to neural processes while sleeping rather than to damage caused by the observed variable blood-oxygen levels.

Key words: EEG, sleep fragmentation, Autonomic, OSAS.

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