Ultra-slow delta power in chronic fatigue syndrome.

The role of sleep in patients diagnosed with chronic fatigue syndrome is not fully understood. Studies of polysomnographic and quantitative sleep electroencephalographic (EEG) measures have provided contradictory results, with few consistent findings in patients with Chronic Fatigue Syndrome (CFS). For the most part, it appears that delta EEG activity may provide the best discrimination between patients and healthy controls. A closer examination of delta activity in the very slow end of the frequency band is still to be considered in assessing sleep in CFS. The present preliminary study compared absolute and relative spectral power in conventional EEG bands and ultra-slow delta (0.5-0.8Hz) between 10 young female patients with the CFS and healthy controls without psychopathology. In absolute measures, the ultra-slow delta power was lower in CFS, about one-fifth that of the control group. Other frequency bands did not differ between groups. Relative ultra-slow delta power was lower in patients than in controls. CFS is associated with lower ultra-slow (0.5-0.8Hz) delta power, underscoring the importance of looking beyond conventional EEG frequency bands. From a neurophysiological standpoint, lower ultra-slow wave power may indicate abnormalities in the oscillations in membrane potential or a failure in neural recruitment in those with CFS.