More Evidence Links Heart Disease With Infection

04:47 p.m Aug 17, 1998 Eastern

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - Researchers said Monday they have found the strongest evidence yet linking some cases of heart disease with a bacterial infection.

They have shown for the first time that people who developed the fatty blockages that mark heart disease had a bacterial infection first.

``The major finding of the report is the evidence of prior infection with Chlamydia pneumoniae,'' Dr. Michael Davidson at Johns Hopkins University in Baltimore said.

This does not mean yet that heart disease can be treated with antibiotics, Davidson stressed.

``A lot of people would love to think that's going to be the answer,'' he said in a telephone interview.

``I think in part that's because a lot of us love to eat as we wish and adopt the lifestyle that is most comfortable for us. But we have got some very, very well-established risk factors.''

These include smoking, a lack of exercise and a diet rich in saturated animal fats.

The study was published in the journal Circulation, which is put out by the American Heart Association.

Many studies have linked heart disease with infections by bacteria or viruses.

Several teams have found chlamydia bacteria in the hardened plaques blocking the arteries, as well as Helicobacter pylori, bacteria now known to cause stomach ulcers, and a virus known as cytomegalovirus.

Last year British researchers found that men who had antibodies to chlamydia, indicating that they had been infected at some point, were four times more likely to suffer second heart attacks. Antibiotics lowered the risk. More studies are going on now to see if this proves true in larger groups.

But Davidson said the link is still tenuous. Bacteria could just be innocent bystanders in heart disease, or could be just one small part of a very complex interaction.

Davidson, who worked with researchers at Louisiana State University and the University of Washington, set out to see if people first infected with chlamydia later developed signs of heart disease.

``We were able to look back in time and ask the question did infection precede the onset of disease,'' he said.

They looked at fatty plaques taken from the arteries of 60 Alaskan natives who were killed in accidents. They also looked at blood samples taken from 56 of them in the past.

Most of the men and women had at least some fatty plaques in their arteries, and 37 percent of these had chlamydia bacteria in the plaques.

Those who had evidence of a severe chlamydia infection in their past blood samples were 10 times as likely to have the bacteria in their plaques when they died as people who had had a mild infection or none at all.

Chlamydia pneumoniae is a very common infection, causing up to 10 percent of all cases of pneumonia and symptoms ranging from cough to bronchitis. It is related to, but not the same thing as, a common sexually transmitted disease.

Gum infections have been linked to heart disease as well.

One theory is that bacteria from the infection -- whether it is a gum infection or a chlamydial infection -- cause chronic inflammation of the blood vessel lining. This would make it easier for fatty plaques to build up there.

Davidson found the chlamydia bacteria were associated with macrophage foam cells, which are abnormal immune system cells linked with the deposit of fatty plaques in the arteries.

It is not clear whether the chlamydia attract the macrophages to the arteries, or whether the macrophages may, for some unknown reason, carry the chlamydia there. ``It is possible they could bring the organism to the region,'' Davidson said.

Last week, researchers said they had found chlamydia in the brains of 17 out of 19 victims of Alzheimer's disease. Alzheimer's, which starts with confusion and dementia and progresses to death, is also marked by ``plaques'' in the brain and inflammation.

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