Factor analysis of symptoms among subjects with unexplained chronic fatigue - What can we learn about chronic fatigue syndrome? Journal of Psychosomatic Research, Volume 56, Issue 2 , February 2004, Pages 171-178 Rosane Nisenbaum [*] , Michele Reyes , Elizabeth R. Unger and William C. Reeves Viral Exhanthems and Herpesvirus Branch, Division of Viral and Rickettsial Diseases, National Centers for Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Road, Mail Stop A-15, Building 6, Room 116, Atlanta, GA 30333, USA [*] Corresponding author. Tel.: +1-404-6391561; fax: +1-404-6392779 E-Mail: mailto:ran7@cdc.gov Received 8 August 2002; accepted 3 February 2003. Available online 4 March 2004. Abstract 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. Author Keywords: Author Keywords: Case definition; CFS; Dichotomous factor analysis; Population-based survey; Symptoms; Unexplained fatigue Copyright © 2004 Elsevier Inc. All rights reserved.