Chlamydia pneumoniae IgG titres and coronary heart disease: prospective study and meta-analysis.
OBJECTIVE
To examine the association between coronary heart disease and serum markers of chronic Chlamydia pneumoniae infection.


METHODS
"Nested" case-control analysis in a prospective cohort study and an updated meta-analysis of previous relevant studies.


METHODS
General practices in 18 towns in Britain.


METHODS
Of the 5661 men aged 40-59 who provided blood samples during 1978-80, 496 men who died from coronary heart disease or had non-fatal myocardial infarction and 989 men who had not developed coronary heart disease by 1996 were included.


METHODS
IgG serum antibodies to C pneumoniae in baseline samples; details of fatal and non-fatal coronary heart disease from medical records and death certificates.


RESULTS
200 (40%) of the 496 men with coronary heart disease were in the top third of C pneumoniae titres compared with 329 (33%) of the 989 controls. The corresponding odds ratio for coronary heart disease was 1.66 (95% confidence interval 1.25 to 2.21), which fell to 1.22 (0.82 to 1.82) after adjustment for smoking and indicators of socioeconomic status. No strong associations were observed between C pneumoniae IgG titres and blood lipid concentrations, blood pressure, or plasma homocysteine concentration. In aggregate, the present study and 14 other prospective studies of C pneumoniae IgG titres included 3169 cases, yielding a combined odds ratio of 1. 15 (0.97 to 1.36), with no significant heterogeneity among the separate studies (chi(2)=10.5, df=14; P>0.1).


CONCLUSIONS
This study, together with a meta-analysis of previous prospective studies, reliably excludes the existence of any strong association between C pneumoniae IgG titres and incident coronary heart disease. Further studies are required, however, to confirm or refute any modest association that may exist, particularly at younger ages.
Danesh
J
J
Clinical Trial Service Unit and Epidemiological Studies Unit, University of Oxford, Oxford OX2 6HE.
Whincup
P
P
Walker
M
M
Lennon
L
L
Thomson
A
A
Appleby
P
P
Wong
Y
Y
Bernardes-Silva
M
M
Ward
M
M
D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood*; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D002690:Chlamydia Infections / Q000150:complications* / Q000276:immunology; D016993:Chlamydophila pneumoniae / Q000276:immunology; D003327:Coronary Disease / Q000276:immunology / Q000382:microbiology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic
D000907:Antibodies, Bacterial; D015415:Biomarkers; D007074:Immunoglobulin G