Factor analysis of symptoms among subjects with unexplained chronic fatigue: what can we learn about chronic fatigue syndrome?

J Psychosom Res. 2004 Feb;56(2):171-8. doi: 10.1016/S0022-3999(03)00039-4.


Objective: Chronic fatigue syndrome (CFS) case definitions agree that fatigue must be unexplained, debilitating and present for at least 6 months, but they differ over accompanying symptoms. Our objective was to compare the 1994 CFS case-defining symptoms with those identified by factor analysis.

Methods: We surveyed the Wichita population and measured the occurrence of 21 symptoms in 1391 chronically fatigued subjects who did not report fatigue-associated medical or psychiatric conditions. We used factor analyses to identify symptom dimensions of fatigue and cluster analysis to assign subjects to subgroups.

Results: Forty-three subjects had CFS. We confirmed three factors: musculoskeletal, infection and cognition-mood-sleep, essentially defined by CFS symptoms. Although factor scores were higher among CFS subjects, CFS and non-CFS distributions overlapped substantially. Three clusters also showed overlap between CFS and non-CFS subjects.

Conclusion: CFS symptomatology is a multidimensional phenomenon overlapping with other unexplained fatiguing syndromes and this must be considered in CFS research.

MeSH terms

  • Cluster Analysis
  • Factor Analysis, Statistical
  • Fatigue Syndrome, Chronic / diagnosis*
  • Female
  • Humans
  • Male
  • Middle Aged
  • Population Surveillance
  • Severity of Illness Index
  • Surveys and Questionnaires*