title: Chronic Chlamydia pneumoniae infection as a risk factor for coronary heart disease in the Helsinki Heart Study.
abstract: OBJECTIVE
  To investigate in the prospective Helsinki Heart Study, whether chronic Chlamydia pneumoniae infection, indicated by elevated antibody titers against the pathogen, chlamydial lipopolysaccharide-containing immune complexes, or both, is a risk factor for coronary heart disease.
  
  
  METHODS
  The Helsinki Heart Study was a randomized, double-blind, 5-year clinical trial to test the efficacy of gemfibrozil in reducing the risk for coronary heart disease. Participants were randomized to receive either gemfibrozil (2046 patients) or placebo (2035 patients). Fatal and nonfatal myocardial infarction and sudden cardiac death were the main study end points. Serum samples were collected at 3-month intervals from all patients.
  
  
  METHODS
  One hundred forty cardiac events occurred during the follow-up period. Serum samples from 103 case patients obtained 3 to 6 months before a cardiac end point were matched with those from controls for time point, locality, and treatment. Samples were tested for markers of chronic chlamydial infection.
  
  
  METHODS
  Immunoglobulin A (IgA) and G (IgG) antibodies to C. pneumoniae were measured using the microimmunofluorescence method. Lipopolysaccharide-containing immune complexes were measured using two antigen-specific enzyme immunoassays, the lipopolysaccharide-capture and immunoglobulin M (IgM)-capture methods.
  
  
  RESULTS
  Using a conditional logistic regression model, odds ratios for the development of coronary heart disease were 2.7 (95% CI, 1.1 to 6.5) for elevated IgA titers, 2.1 (CI, 1.1 to 3.9) for the presence of immune complexes, and 2.9 (CI, 1.5 to 5.4) for the presence of both factors. If we adjusted for other coronary heart disease risk factors such as age, hypertension, and smoking, the corresponding values would be 2.3 (CI, 0.9 to 6.2), 1.8 (CI, 0.9 to 3.6), and 2.6 (CI, 1.3 to 5.2), respectively.
  
  
  CONCLUSIONS
  The results suggest that chronic C. pneumoniae infection may be a significant risk factor for the development of coronary heart disease.
authors.affiliation: University of Helsinki, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Saikku
authors.forename: M
authors.initials: M
authors.lastname: Leinonen
authors.forename: L
authors.initials: L
authors.lastname: Tenkanen
authors.forename: E
authors.initials: E
authors.lastname: Linnanmäki
authors.forename: M R
authors.initials: MR
authors.lastname: Ekman
authors.forename: V
authors.initials: V
authors.lastname: Manninen
authors.forename: M
authors.initials: M
authors.lastname: Mänttäri
authors.forename: M H
authors.initials: MH
authors.lastname: Frick
authors.forename: J K
authors.initials: JK
authors.lastname: Huttunen
mesh_terms: D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood; D000936:Antigen-Antibody Complex / Q000097:blood / Q000737:chemistry; D002690:Chlamydia Infections / Q000150:complications* / Q000276:immunology; D016993:Chlamydophila pneumoniae / Q000276:immunology; D002908:Chronic Disease; D003327:Coronary Disease / Q000276:immunology / Q000382:microbiology*; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D008070:Lipopolysaccharides / Q000097:blood / Q000276:immunology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D011446:Prospective Studies; D012307:Risk Factors
chemical_list: D000907:Antibodies, Bacterial; D000936:Antigen-Antibody Complex; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D008070:Lipopolysaccharides