Sleep-Wake Behavior in Chronic Fatigue Syndrome Rahman K; Burton A; Galbraith S; Lloyd A; Vollmer-Conna U. SLEEP 2011;34(5):671-678. http://www.journalsleep.org/ViewAbstract.aspx?pid=28135 I believe these were basically baseline results for patients enrolled in an Australian CBT/GET programme. It is interesting to note that they found no differences in sleep hygiene, nor activity patterns between patients and exercise level matched controls (eg sedentary controls). Polysomnography was not used however. There were no statistically significant differences in diurnal salivary cortisol levels, nor scores on the Perceived Stress Questionnaire. (I have previously argued that differences in salivary cortisol response reflected lower stress/activity levels in patients compared to controls) Apparently both afternoon and previous day activity predicted evening fatigue levels. The only novel finding was that patients had significantly lower heart rate variation while sleeping. While sleeping, the sympathetic aspect of the ANS takes over, so any potential dysfunctions there could cause this result. However the potential reason provided for the reduced HRV in the paper was highly speculative. One of the cited studies mentions that reduced HRV is even associated with immune system dysfunction, but that was not mentioned in this study.