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Week of 12 February 1999

Vol. II, No. 23

Feature Article

BUSM findings suggest antibiotics may reduce risk of heart attack

By Eric McHenry

Researchers at the BU School of Medicine have helped expose what might prove to be a chink in the armor of heart disease, the nation's number one killer.

In a study published February 3 and covered extensively in the national news media, Hershel Jick, MED associate professor of medicine, and colleagues at the Boston Collaborative Drug Surveillance Program revealed that people who had taken certain antibiotics were considerably less likely to have suffered heart attacks than people who had not. Their findings strengthen the associative link, and suggest a causal link, between Chlamydia pneumoniae, a common bacterium related to the germ that causes the sexually transmitted disease chlamydia, and heart disease.

Using a computerized database containing information on more than three million patients of British general practitioners, the team examined the medical records of 3,315 first-time heart attack victims and 13,139 healthy control subjects. They determined that those who had taken tetracyclines or quinolones -- antibiotics believed to attack the chlamydia bacterium -- in the three years prior to the indexing date had a lower incidence of heart attack by 30 and 55 percent, respectively. Several drugs not known to combat the bacterium, including penicillins, appeared to have no such association with reduced risk.

Although the study, which appeared in the Journal of the American Medical Association, is the first to identify antibiotics as a possible preventive of acute myocardial infarction (AMI), the researchers are stressing that it is far too early to begin prescribing the drugs for such a purpose.

"It's a tiny step in that direction," Jick says. "This is very indirect evidence, and there are a lot of things we would like to know about the subjects of this study that we just don't know."

Although the researchers reduced mitigating factors by limiting their survey population, according to the JAMA report, to people "free of clinical conditions potentially related to an increased risk of developing AMI" such as hypertension and cardiac arrhythmias, they had no way of determining in which of their subjects the bacteria were present.

"Our approach is unique because we have this data resource," Jick says, "but otherwise it's not a wildly satisfying study from our point of view because we're not sure what infections these people had and so forth."

While tentative, the report's conclusions are likely to spur further investigation into the role bacterial infections might play in the promotion of AMI. If the presence of Chlamydia pneumoniae in coronary arteries can be shown to cause damage to blood vessels, Jick says, the case for using antibiotics to preempt heart attacks will be bolstered.

"If these organisms in fact get into the heart, attack the wall, and create inflammation," he says, "that would be the most direct sort of evidence that there's something to this."

Although cautious when assessing the study, Jick is unreserved in his praise for the General Practice Research Database, which BCDSP scientists helped develop and to which they retain exclusive access. The product of a unified shift in the British medical community from paper to digital records, it holds 10 years worth of data from about 1,000 physicians.

"There's just nothing anywhere close to this in the world, nor is there likely to be in the foreseeable future," he says.

BCDSP research teams have published more than 70 papers using records from the database. According to Jick, it is an especially useful resource for studies such as this recent one.

"The best way to demonstrate the effect of an isolated factor such as the use of an antibiotic," he explains, "is to look at people who are otherwise healthy. This database gave us an opportunity to identify over 3,000 people who had a first AMI and no accompanying risk factors."

While it's too early to gauge the long-term impact of the antibiotics study, Jick has a history of laying groundwork for important medical developments. A quarter-century ago he was one of the first to suggest that using aspirin might reduce heart attack risk.

"This is very early stuff," he says of the antibiotics report, "just as the aspirin study was when we published it in '74. That was sort of off-the-wall at the time. It's only been in the last 10 years or so that conclusive evidence has come in."