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Chlamydia Infection Associated With AMI Risk

Reuters Health Information 2005. © 2005 Reuters Ltd. By Will Boggs, MD

NEW YORK (Reuters Health) Apr 14 - Infection with Chlamydia pneumoniae within the past 1 to 5 years is associated with an increased risk of acute myocardial infarction (MI), according to a report in the April 15th issue of Clinical Infectious Diseases.

"There have been many seroepidemiological studies exploring this association," Dr. M. Arcari from University of Wisconsin Medical School, Madison, told Reuters Health. "Some report positive results, others report negative results. Attention has not been given to the timing of the exposure measurement of infection, which was explored in this study."

Dr. Arcari and colleagues investigated the relationship between C. pneumoniae antibody titers and coronary heart disease in 300 individually matched case-control pairs of active-duty military men between 30 and 50 years old.

After adjustment for demographic and cardiovascular risk factors, a high titer to C. pneumoniae IgA was associated with a 78% higher risk of acute MI; and a high titer to C. pneumoniae IgG was associated with a 74% increased risk of acute MI, compared with very low or negative titers, the authors report.

The highest risk for acute MI (2.11-fold higher) was seen among individuals with a high titer to C. pneumoniae IgA 1 to 5 years before the onset of acute MI, the report indicates.

There was no significant relationship between the time of a high titer to C. pneumoniae IgG and the increased risk of acute MI, the researchers note.

The relative risk of acute MI was higher among older (40-50 years old) individuals than among younger (30-39.9 years old) individuals.

"These data suggest that a recent or chronic active C. pneumoniae infection before a first MI might be related to coronary heart disease," the authors conclude.

"It probably makes sense to diagnose and treat C. pneumoniae infections -- especially in patients with cardiovascular risk factors," Dr. Arcari said. "Possibly patients with underlying CVD risk factors who have febrile respiratory disease should be screened for C. pneumoniae. The catch with this recommendation is that many labs -- perhaps most -- don't do C. pneumoniae screening or diagnosis."

"The fact that 30-50-year-old men with myocardial infarction had significantly more high-titer C. pneumoniae antibody, despite the fact that the control subjects all had some atherosclerosis and a high prevalence of antibody, suggests that the association between C. pneumoniae and coronary heart disease in the study...is stronger than the numbers would indicate," Dr. J. Grayston from University of Washington, Seattle, wrote in a related editorial.

"This leads to the presumption that those with myocardial infarction had more-severe atherosclerosis and that higher-titer C. pneumoniae antibody is associated with more-severe atherosclerosis," Dr. Grayston added.

Clin Infect Dis 2005;40:1123-1132.