A lack of physical fitness - not mood disorders such as depression or anxiety, may raise the risk of suffering from Chronic Fatigue Syndrome (CFS) 6 months after a bout of infectious mononucleosis, researchers report.

The study of 250 patients with mononucleosis or upper respiratory tract infections also found that patients who initially had enlarged lymph nodes in their neck and were on bed rest were at increased risk of CFS 2 months after being diagnosed with mononucleosis.

The findings, which are published in the December 8th issue of The Lancet, provide insight into why a minority of people with certain infections develop CFS.

An estimated 9% to 42% of individuals who contract infections such as mononucleosis and upper respiratory tract infections will be diagnosed with CFS, a syndrome marked by a range of symptoms including fatigue, headache, sleep problems, muscle pain and difficulty concentrating, the report notes.

The cause is unknown, and there is no laboratory test that can diagnose the illness.

The results also dispute earlier findings that life events and mood disorders trigger CFS after infectious mononucleosis, according to Dr. Peter D. White from St. Bartholomew's Hospital in London, UK, and colleagues.

"Neither of these factors are important in causing a virally triggered fatigue syndrome of less than 7 months duration," White told Reuters Health in an interview. Rather, "deconditioning is probably a causal factor leading to CFS after a virus."

Previous studies have shown that patients who take part in a gradual exercise program can reduce fatigue and disability, and slowly improve their exercise capacity.

White stressed that the results of the study should be confirmed, and he recommended that future studies investigate the link between patients' perceptions about their illness and how they cope with the disease, and which immune factors cause fatigue after the onset of an infection.

Mononucleosis is caused by infection with the Epstein-Barr virus and is typically accompanied by fatigue, fever, swollen throat, and enlarged lymph nodes. The virus is spread through saliva by kissing or sharing eating utensils.

SOURCE: The Lancet 2001;358:1946-1954.

The Study:

Predictions and associations of fatigue syndromes and mood disorders that occur after infectious mononucleosis

Authors: Peter D. White, Janice M. Thomas, Hillar O. Kangro, William D. A. Bruce-Jones, John Amess, Dorothy H. Crawford, Shirlyn A. Grover, Anthony W. Clare

Author Affiliations: Departments of Psychological Medicine (P D White MD, W D A Bruce-Jones MPhil, Prof A W Clare MD), Computer Sciences (J M Thomas MSc), Virology (H O Kangro PhD), and Haematology (J Amess MB), St Bartholomew's and the Royal London School of Medicine and Dentistry, London; Department of Virology, St George's Hospital Medical School, London (S A Grover); and Department of Medical Microbiology, University of Edinburgh, Edinburgh, UK (Prof D H Crawford DSc)

Correspondence to: Dr Peter D White, Department of Psychological Medicine, St Bartholomew's and the Royal London School of Medicine and Dentistry, St Bartholomew's Hospital, London EC1A 7BE, UK (e-mail:P.D.White@qmul.ac.uk)

Summary

Background: Certain infections can trigger chronic fatigue syndromes (CFS) in a minority of people infected, but the reason is unknown. We describe some factors that predict or are associated with prolonged fatigue after infectious mononucleosis and contrast these factors with those that predicted mood disorders after the same infection.

Methods: We prospectively studied a cohort of 250 primary-care patients with infectious mononucleosis or ordinary upper-respiratory-tract infections until 6 months after clinical onset. We sought predictors of both acute and chronic fatigue syndromes and mood disorders from clinical, laboratory, and psychosocial measures.

Findings: An empirically defined fatigue syndrome 6 months after onset, which excluded comorbid psychiatric disorders, was most reliably predicted by a positive Monospot test at onset (odds ratio 2·1 [95% CI 1·4-3·3]) and lower physical fitness (0·35 [0·15-0·8]). Cervical lymphadenopathy and initial bed rest were associated with, or predicted, a fatigue syndrome up to 2 months after onset. By contrast, mood disorders were predicted by a premorbid psychiatric history (2·3 [1·4-3·9]), an emotional personality score (1·21 [1·11-1·35]), and social adversity (1·7 [1·0-2·9]). Definitions of CFS that included comorbid mood disorders were predicted by a mixture of those factors that predicted either the empirically defined fatigue syndrome or mood disorders.

Interpretation: The predictors of a prolonged fatigue syndrome after an infection differ with both definition and time, depending particularly on the presence or absence of comorbid mood disorders. The particular infection and its consequent immune reaction may have an early role, but physical deconditioning may also be important. By contrast, mood disorders are predicted by factors that predict mood disorders in general.

Source: The Lancet 2001; 358: 1946-54