Abstract
ObjectivesTo explore cognitive performance in chronic fatigue syndrome (CFS) examining two cohorts. To establish findings associated with CFS and those related to co-morbid depression or autonomic dysfunction.MethodsIdentification and recruitment of participants was identical in both phases, all CFS patients fulfilled Fukuda criteria. In Phase 1 (n = 48) we explored cognitive function in a heterogeneous cohort of CFS patients, investigating links with depressive symptoms (HADS). In phase 2 (n = 51 CFS & n = 20 controls) participants with co-morbid major depression were excluded (SCID). Furthermore, we investigated relationships between cognitive performance and heart rate variability (HRV).ResultsCognitive performance in unselected CFS patients is in average range on most measures. However, 0–23% of the CFS sample fell below the 5th percentile. Negative correlations occurred between depressive symptoms (HAD-S) with Digit-Symbol-Coding (r = -.507, p = .006) and TMT-A (r = -.382, p = .049). In CFS without depression, impairments of cognitive performance remained with significant differences in indices of psychomotor speed (TMT-A: p = 0.027; digit-symbol substitution: p = 0.004; digit-symbol copy: p = 0.007; scanning: p = .034) Stroop test suggested differences due to processing speed rather than inhibition.Both cohorts confirmed relationships between cognitive performance and HRV (digit-symbol copy (r = .330, p = .018), digit-symbol substitution (r = .313, p = .025), colour-naming trials Stroop task (r = .279, p = .050).ConclusionCognitive difficulties in CFS may not be as broad as suggested and may be restricted to slowing in basic processing speed. While depressive symptoms can be associated with impairments, co-morbidity with major depression is not itself responsible for reductions in cognitive performance. Impaired autonomic control of heart-rate associates with reductions in basic processing speed.
Highlights
Chronic fatigue syndrome (CFS) is a chronic debilitating condition that affects at least 0.2– 0.4% of the UK population and is life changing [1,2]
Negative correlations occurred between depressive symptoms (HAD-S) with Digit-Symbol-Coding (r = -.507, p = .006) and Trail Making Test (TMT)-A (r = -.382, p = .049)
In CFS without depression, impairments of cognitive performance remained with significant differences in indices of psychomotor speed (TMT-A: p = 0.027; digit-symbol substitution: p = 0.004; digit-symbol copy: p = 0.007; scanning: p = .034) Stroop test suggested differences due to processing speed rather than inhibition
Summary
Chronic fatigue syndrome (CFS) is a chronic debilitating condition that affects at least 0.2– 0.4% of the UK population and is life changing [1,2] Despite this there are currently no diagnostic tools beyond symptom recognition and no curative treatments [2]. Almost 90% of those with CFS describe cognitive abnormalities, including poor concentration, memory loss, an inability to take in information, and a general reduction in cognitive ability [3,4,5,6,7,8] These studies have identified a number of cognitive deficits, they are often of small magnitude and involve multiple domains, so no consistent profile has been identified across studies. Previous evidence regarding the role of depressive symptoms in the cognitive deficits of CFS has been mixed, with some [8, 15] but not all [16, 17] studies showing a relationship
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