Editor,-Iain Duncan is mistaken in his assertion that the results of our study of patients with the chronic fatigue syndrome can be explained by daytime dozing. According to data from the diaries kept by the subjects in the study, the patients with the chronic fatigue syndrome slept for a mean of 11 minutes during the day and the healthy controls for 0 minutes. There was no association between either the time spent asleep or the time spent resting in bed during the day and the presence of any sleep disorder (or the time spent awake after the onset of sleep at night) in the patients with the chronic fatigue syndrome or the normal controls. Furthermore, in the few patients with the syndrome who wore their polysomnograph for the whole 24 hours there was no association between time spent asleep during the day and the time spent awake after the onset of sleep.
You can read the rest of this comment here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1678179/pdf/bmj00031-0056a.pdf
Source: Morriss R. Insomnia in the chronic fatigue syndrome. BMJ. 1993 Jul 24;307(6898):264. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1678179/