title: A case-control study to assess possible triggers and cofactors in chronic fatigue syndrome.
abstract: OBJECTIVE
  To assess possible triggers and cofactors for chronic fatigue syndrome (CFS) and to compare levels of selected cytokines between cases and an appropriately matched control group.
  
  
  METHODS
  We conducted a case-control study of 47 cases of CFS obtained through a regional CFS research program maintained at a tertiary care medical center. One age-, gender-, and neighborhood-matched control was identified for each case through systematic community telephone sampling. Standardized questionnaires were administered to cases and controls. Sera were assayed for transforming growth factor-beta (TGF-beta), interleukin-1 beta, interleukin-6, tumor necrosis factor-alpha, and antibody to Borrelia burgdorferi and Babesia microti.
  
  
  RESULTS
  Cases were more likely to have exercised regularly before illness onset than controls (67% versus 40%; matched odds ratio (MOR) = 3.4; 95% CI = 1.2 to 11.8; P = 0.02). Female cases were more likely to be nulliparous prior to onset of CFS than controls (51% versus 31%; MOR = 8.0; 95% CI = 1.03 to 170; P = 0.05). History of other major factors, including silicone-gel breast implants (one female case and one female control), pre-morbid history of depression (15% of cases, 11% of controls) and history of allergies (66% of cases, 51% of controls) were similar for cases and controls. However, cases were more likely to have a diagnosis of depression subsequent to their diagnosis of CFS compared to a similar time frame for controls (MOR = undefined; 95% CI lower bound = 2.5; P < 0.001). Positive antibody titers to B burgdorferi (one case and one control) and B microti (zero cases and two controls) were also similar.
  
  
  CONCLUSIONS
  Further investigation into the role of prior routine exercise as a cofactor for CFS is warranted. This study supports the concurrence of CFS and depression, although pre-morbid history of depression was similar for both groups.
authors.affiliation: Minnesota Department of Health, Minneapolis, 55440-9441, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: MacDonald
authors.forename: M T
authors.initials: MT
authors.lastname: Osterholm
authors.forename: K H
authors.initials: KH
authors.lastname: LeDell
authors.forename: K E
authors.initials: KE
authors.lastname: White
authors.forename: C H
authors.initials: CH
authors.lastname: Schenck
authors.forename: C C
authors.initials: CC
authors.lastname: Chao
authors.forename: D H
authors.initials: DH
authors.lastname: Persing
authors.forename: R C
authors.initials: RC
authors.lastname: Johnson
authors.forename: J M
authors.initials: JM
authors.lastname: Barker
authors.forename: P K
authors.initials: PK
authors.lastname: Peterson
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis; D000913:Antibodies, Protozoan / Q000032:analysis; D001403:Babesia / Q000276:immunology; D015748:Borrelia burgdorferi Group / Q000276:immunology; D016022:Case-Control Studies; D003627:Data Interpretation, Statistical; D003863:Depression / Q000150:complications; D015673:Fatigue Syndrome, Chronic / Q000097:blood / Q000209:etiology*; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000150:complications; D007375:Interleukin-1 / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D010298:Parity; D005082:Physical Exertion; D012307:Risk Factors; D011795:Surveys and Questionnaires; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000097:blood; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis
chemical_list: D000907:Antibodies, Bacterial; D000913:Antibodies, Protozoan; D007375:Interleukin-1; D015850:Interleukin-6; D016212:Transforming Growth Factor beta; D014409:Tumor Necrosis Factor-alpha