Background Chronic fatigue is a feature in a subset of women successfully treated for breast cancer. The clinical features of this group are not well characterised. This study examines differences in objective cognitive function, activity levels and sleep in disease-free women who do and do not meet the criteria for CRFS.

Methods Women between 3 months and 2 years after completion of any primary therapy were recruited from a nurse-led follow up clinic at a cancer centre. On the basis of a diagnostic semistructured interview they were classified as being cases of CRFS or non-fatigued controls. Participants underwent objective cognitive testing using a computerised battery and were asked to wear an activity monitor for a 1 week period. They also completed quality of life and fatigue questionnaires.

Results 114 women were recruited (69 controls and 45 cases of CRFS). There were significant differences between groups on fatigue, mood, sleep and quality of life scores. There were also significant differences in objective cognitive testing (tests of sustained attention, reaction time and verbal memory). There was an overall difference in daytime activity from actigraphy recordings. There were no differences on objective measures of sleep or in routine laboratory measures.

Conclusions Our study suggests that disease-free women with CRFS after successful treatment for breast cancer have a significantly lower subjective quality of life and mood. In addition, objective cognitive impairment in certain domains may play an important part in the subjective manifestation of these symptoms. There is also objective evidence on actigraphy of differing levels of activity. The subjective sleep disturbance and higher prevalence of insomnia do not correlate with objective measures.