Cognitive Task Performance and Subjective Cognitive Symptoms in Individuals With Chronic Fatigue Syndrome or Fibromyalgia: A Cross-Sectional Analysis of the Lifelines Cohort Study.

OBJECTIVE

This study examined cognitive task performance and self-reported cognitive functioning in individuals with chronic fatigue syndrome (CFS) and fibromyalgia (FM) in a population-based sample and investigated the role of mood and anxiety disorders as well as severity of the physical symptoms.

METHODS

This study was performed in 79,966 participants (mean [standard deviation] age = 52.9 [12.6] years, 59.2% women) from the Lifelines general population. Symptoms consistent with the diagnostic criteria for CFS and FM were assessed using questionnaires. Two comparison groups were used: participants with self-reported medical disorders with well-defined pathophysiology (i.e., multiple sclerosis and rheumatic arthritis) and controls without these diseases. Objective task performance was based on the computerized CogState cognitive battery and subjective cognitive symptoms using the concentration subscale of the Checklist Individual Strength.

RESULTS

Cognitive task performance was poorer in individuals with CFS versus controls without disease and controls with a medical disorder, although the severity of cognitive dysfunction was mild. Participants meeting the criteria for CFS ( n = 2461) or FM ( n = 4295) reported more subjective cognitive symptoms compared with controls without a medical disorder ( d = 1.53, 95% confidence interval [CI] = 1.49-1.57 for CFS; d = 1.25, 95% CI = 1.22-1.29 for FM) and participants with a medical disease ( d = 0.62, 95% CI = 0.46-0.79 for CFS; d = 0.75, 95% CI = 0.70-0.80 for FM). These differences remained essentially the same when excluding participants with comorbid mood or anxiety disorders or adjusting for physical symptom severity.

CONCLUSIONS

Subjective cognitive symptoms and, to a lesser extent, suboptimal cognitive task performance are more prevalent in individuals with CFS or FM compared with controls without these conditions.