Abstract
BackgroundCognitive difficulties and autonomic dysfunction have been reported separately in patients with chronic fatigue syndrome (CFS). A role for heart rate variability (HRV) in cognitive flexibility has been demonstrated in healthy individuals, but this relationship has not as yet been examined in CFS. The objective of this study was to examine the relationship between HRV and cognitive performance in patients with CFS.MethodsParticipants were 30 patients with CFS and 40 healthy controls; the groups were matched for age, sex, education, body mass index, and hours of moderate exercise/week. Questionnaires were used to obtain relevant medical and demographic information, and assess current symptoms and functional impairment. Electrocardiograms, perceived fatigue/effort and performance data were recorded during cognitive tasks. Between–group differences in autonomic reactivity and associations with cognitive performance were analysed.ResultsPatients with CFS showed no deficits in performance accuracy, but were significantly slower than healthy controls. CFS was further characterized by low and unresponsive HRV; greater heart rate (HR) reactivity and prolonged HR-recovery after cognitive challenge. Fatigue levels, perceived effort and distress did not affect cognitive performance. HRV was consistently associated with performance indices and significantly predicted variance in cognitive outcomes.ConclusionsThese findings reveal for the first time an association between reduced cardiac vagal tone and cognitive impairment in CFS and confirm previous reports of diminished vagal activity.
Highlights
Chronic fatigue syndrome (CFS) is a debilitating disorder characterised by medically-unexplained, disabling fatigue and constitutional and neuropsychiatric symptoms of at least 6 months duration [1]
There was a trend towards higher body mass index (BMI) in the control participants [chronic fatigue syndrome (CFS): M = 23.8, standard deviation (SD) = 3.7 vs Controls: M = 25.4, SD = 3.0, t(68) = 1.83, p = 0.06]
This study found a significant reduction in cognitive performance speed in patients with CFS compared with healthy controls
Summary
Chronic fatigue syndrome (CFS) is a debilitating disorder characterised by medically-unexplained, disabling fatigue and constitutional and neuropsychiatric symptoms of at least 6 months duration [1]. Formal evaluation of cognitive impairment in CFS has revealed subtle deficits across a number of domains, which are best explained in terms of a generalised impairment in concentration, attention, or information processing speed. Such impairment would broadly affect performance in general, and account for the most consistently reported deficits in working memory and slowed response speed [3,4,5]. The cognitive deficits associated with CFS bear similarities to those reported in patients with major depressive disorder [5,6,7]. Cognitive difficulties and autonomic dysfunction have been reported separately in patients with chronic fatigue syndrome (CFS).
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