Patterns of daytime physical activity in patients with chronic fatigue syndrome.

Objectives: To classify patients with chronic fatigue syndrome (CFS) by pattern of physical activity and determine the clinical associations of each type.
Methods: 579 out of 641 participants with CFS from the PACE (Pacing, graded Activity, Cognitive behavioural therapy: a randomised Evaluation) trial wore an Actiwatch (accelerometer) for between 3 and 7 days before any trial treatments, which provided a measure of physical activity. Participants' activity was categorised into one of four patterns (pervasively inactive, pervasively active, boom and bust, or indeterminate) primarily using a priori definitions of activity. Clinical associations were sought with each group using an exploratory logistic regression with the indeterminate activity group being the reference group.
Results: 124 (21%) of the participants were classified as pervasively inactive, 65 (11%) as pervasively active, 172 (30%) showed a 'boom and bust' pattern of activity, and 218 (38%) had an indeterminate pattern. Pervasively inactive patients were more physically disabled, those in the pervasively active group were more anxious, and those in the boom and bust group had more sleep disturbance.
Conclusion: We were able to classify patients with CFS into groups by their daytime activity pattern. The different patterns of activity were associated with important clinical variables, suggesting that they might be helpful in determining prognosis and targeting treatments. These associations need replication.
Competing Interests: Declaration of Competing Interest PDW is a member of the Independent Medical Experts Group, which advises the UK Ministry of Defence regarding its Armed Forces Compensation Scheme, as well as providing consultancy advice to a re-insurance company. MS has received royalties from several publishers of academic books, TC is the author of Coping with chronic fatigue, published by Sheldon Press, and is a co-author of Overcoming Chronic Fatigue, published by Constable and Robinson. The other authors declare no conflict of interest.
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