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Searching for Syndromes by Factor Analysis of Symptoms

Robert W. Haley, MD; Thomas L. Kurt, MD, MPH; Jim Hom, PhD

JAMA. 1997;277(3):215-222.

Abstract
Objective.
—To search for syndromes in Persian Gulf War veterans.

Participants.
—Two hundred forty-nine (41%) of the 606 Gulf War veterans of the Twenty-fourth Reserve Naval Mobile Construction Battalion living in 5 southeastern states participated; 145 (58%) had retired from service, and the rest were still serving in the battalion.

Design.
—Particpants completed a standardized survey booklet measuring the anatomical distributions or characteristics of each symptom, a booklet measuring wartime exposures, and a standard psychological personality assessment inventory. Two-stage factor analysis was used to disentangle ambiguous symptoms and identify syndromes.

Main Outcome Measures.
—Factor analysis—derived syndromes.

Results.
—Of 249 participants, 175 (70%) reported having had serious health problems that most attributed to the war, and 74 (30%) reported no serious health problems. Principal factor analysis yielded 6 syndrome factors, explaining 71% of the variance. Dichotomized syndrome indicators identified the syndromes in 63 veterans (25%). Syndromes 1 ("impaired cognition," characterized by problems with attention, memory, and reasoning, as well as insomnia, depression, daytime sleepiness, and headaches), 2 ("confusion-ataxia," characterized by problems with thinking, disorientation, balance disturbances, vertigo, and impotence), and 3 ("arthro-myo-neuropathy," characterized by joint and muscle pains, muscle fatigue, difficulty lifting, and extremity paresthesias) represented strongly clustered symptoms; whereas, syndromes 4 ("phobia-apraxia"), 5 ("fever-adenopathy"), and 6 ("weakness-incontinence") involved weaker clustering and mostly overlapped syndromes 2 and 3. Veterans with syndrome 2 were 12.5 times (95% confidence interval, 3.5-44.8) more likely to be unemployed than those with no health problems. A psychological profile, found in 48.4% of those with the syndromes, differed from posttraumatic stress disorder, depression, somatoform disorder, and malingering.

Conclusion.
—These findings support the hypothesis that clusters of symptoms of many Gulf War veterans represent discrete factor analysis—derived syndromes that appear to reflect a spectrum of neurologic injury involving the central, peripheral, and autonomic nervous systems.

Author Affiliations
From the Epidemiology Division, Department of Internal Medicine (Drs Haley and Kurt), and the Department of Neurology (Dr Hom), University of Texas Southwestern Medical Center at Dallas, and The Neuropsychology Center, Dallas, Tex (Dr Hom).

Footnotes
Presented at the Intergovernmental Coordinating Board for the Gulf War Illness and to the staff of the Presidential Advisory Committee on Gulf War Veterans' Illnesses, Washington, DC, September 16,1995, and at a research conference on the Gulf War illness, Centers for Disease Control and Prevention, Atlanta, Ga, October 26, 1995.

Corresponding author: Robert W. Haley, MD, Epidemiology Division, Department of Internal Medicine, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd, Dallas, TX 75235-8874.

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