The association of fatigue and pain with cognitive test performance in patients with myalgic encephalomyelitis/chronic fatigue syndrome.

OBJECTIVES

Patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) typically perform worse on cognitive tasks compared to controls. The present study explored the independent associations of fatigue and pain symptoms with cognitive performance in a large sample of patients who met CDC criteria of CFS (n = 1375), of whom most also met NICE/ IOM criteria (n = 1072). Moreover, we tested the hypothesis that these associations become stronger with older age and longer symptom duration.

METHODS

Questionnaires and diaries were employed assessing fatigue and pain severity, together with the impact of health problems on daily life (using the SF-36 'Physical Functioning' and 'Bodily Pain' subscales). Cognitive outcomes consisted of speeded performance measures, namely the Symbol Digit Test, motor speed, simple and choice reaction time (RT), and response inhibition. Categorical regression with lasso penalization was employed to identify relevant correlates of cognitive performance.

RESULTS

Fatigue severity remained as only correlate of response inhibition. For the other cognitive outcomes, fatigue severity consistently emerged together with contributions of pain severity, bodily pain and/or physical functioning. Restricting these analyses to those patients meeting NICE/IOM criteria revealed overall similar results. Age, not symptom duration, moderated several relationships, showing more pronounced associations between cognitive performance and pain severity, physical functioning, and bodily pain with older age.

CONCLUSIONS

This study highlights that a multidimensional nature of symptoms, including fatigue and pain severity, and the impact on daily-life functioning, relate to lower cognitive performance in patients with ME/CFS. Studies are needed to identify the direction and potential causality of these associations.