Physical Activity And Sleep Patterns Following Physical And Cognitive Challenge In Patients With Chronic Fatigue Syndrome.

Abstract

Chronic fatigue syndrome (CFS) is a disorder characterised by profound fatigue which is not relieved by rest and can be exacerbated by physical or cognitive activity. Patients generally report poor sleep and being less physically active than pre-illness; little is known how this is affected by exertion. PURPOSE: To characterise sleep and physical activity patterns in patients with CFS during the post-exertional exacerbation of fatigue following physical and cognitive challenge. METHODS: Two studies were conducted: a physically-demanding challenge (moderate-intensity aerobic exercise; EXER), and a cognitively-demanding challenge (simulated driving; COG). Each study included a well-characterised sample of patients with CFS (EXER: N=10; COG: N=11) and healthy matched control participants (EXER: N=12; COG: N=11). In each study, self-reported ratings of fatigue and symptoms were obtained at baseline and at time-points in the first 24 hours post-challenge. A triaxial accelerometer was worn for a 24 hour baseline period and the first 24 hours following each challenge. RESULTS: Patients with CFS reported substantial fatigue, functional impairment and poor sleep at baseline in each study (all p<0.02). Patients displayed comparable performance to control participants during each challenge, but reported higher perceived exertion (p<0.02). Each challenge induced an immediate exacerbation of fatigue in patients (p<0.02), which was maintained 24 hours following. Patients displayed longer night-time sleep (overall mean CFS: 8.9±1.1 hrs/night, controls: 7.5±1.2 hrs/night, p<0.001) and more time spent lying down during waking hours (overall mean CFS: 29±15%, controls: 14±10%, p<0.001). Patients’ sleep duration and activity patterns were not affected by either challenge, excepting a trend towards less movement (p=0.06) and more lying down (p=0.07) following the exercise challenge. Patient’s fatigue at baseline correlated with a more severe reduction in movement during waking hours following the challenges (r=-.58, p=0.006). CONCLUSION: Patients with CFS displayed low levels of daytime physical activity and excessive night-time sleep at baseline. Despite the exacerbation of fatigue by both exercise and cognitive challenge, patients’ physical activity patterns were not significantly affected. Individual differences in post-exertional change in physical function were linked to baseline levels of fatigue.