Volume 35 Issue 09 - Sep 2005
Psychological Medicine (2005), 35: 1317-1326
doi:10.1017/S0033291705005052
Published Online 31 May 2005


Original Articles

The epidemiology of chronic fatigue in the Swedish Twin Registry

BIRGITTA EVENGÅRD a1, ANDREAS JACKS a1, NANCY L. PEDERSEN a2a3 and PATRICK
F. SULLIVAN a4c1
a1 Department of Laboratory Medicine, Karolinska Institutet at Karolinska
University Hospital Huddinge, Stockholm, Sweden
a2 Department of Medical Epidemiology and Biostatistics, Karolinska
Institutet, Stockholm, Sweden
a3 Department of Psychology, University of Southern California, CA, USA
a4 Departments of Genetics, Psychiatry & Epidemiology, University of North
Carolina at Chapel Hill, NC, USA

Abstract

Background. Chronic fatigue syndrome (CFS) remains an idiopathic and
controversial entity.

Method. We screened 31405 individual members of the Swedish Twin Registry
(aged 42-64 years) for the symptoms of fatiguing illness via a telephone
questionnaire. We refined self-reported symptoms via data from several
national registries and from physician review of all available medical
records in order to approximate closely the dominant case definition of CFS.

Findings. The 6-month prevalence of CFS-like illness was 2·36% (95% CI
2·19-2·53) and was markedly higher in women than men, odds ratio 3.92 (95%
CI 3·24-4·72) with no significant association with age or years of
education. There was a highly significant association with occupation that
disappeared after accounting for gender.

Interpretation. CFS-like illness may be more common that previously
acknowledged. There is a marked increase in risk by gender. Previous reports
that CFS is more prevalent in individuals in certain occupational categories
were not confirmed and may have been due to confounding by gender.



Correspondence:
c1 FRANZCP, Department of Genetics, CB #7264, 4109D Neurosciences Research
Building, University of North Carolina, Chapel Hill, NC, 27599-7264, USA.
(Email: pfsulliv@med.unc.edu)