Chronic Infection and the Risk for Heart Disease

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The summary below is from the full report titled "Baseline IgG Antibody Titers to Chlamydia pneumoniae, Helicobacter pylori, Herpes Simplex Virus, and Cytomegalovirus and the Risk for Cardiovascular Disease in Women." It is in the 19 October 1999 issue of Annals of Internal Medicine (volume 131, pages 573-577). The authors are P.M. Ridker, C.H. Hennekens, J.E. Buring, R. Kundsin, and J. Shih.

What is the problem and what is known about it so far?

Some studies suggest that people with chronic infection are more likely to have common types of cardiovascular disease (coronary heart disease and strokes) than people without chronic infection. However, these studies have not been able to sort out whether chronic infection occurred before or after the disease developed. Some of the bacteria and viruses ("germs") that researchers have found in people with coronary disease include Chlamydia pneumoniae, Helicobacter pylori, herpes simplex virus, and cytomegalovirus.

Why did the researchers do this particular study?

The researchers wanted to find out if people who were exposed to any of these bacteria or viruses in the past were more likely than people without this exposure to get cardiovascular disease in the future.

Who was studied?

The researchers studied women who were in the Women's Health Study. This study collected a lot of health information from healthy women, through surveys and reviews of medical records, over a number of years. All of the women in this study were health professionals. This study focused on 122 women who developed heart attacks or strokes during the years of the study and 244 women who did not develop these problems.

How was the study done?

All of the women gave blood samples at the beginning of the study. The researchers tested these samples to look for antibodies to four kinds of bacteria and viruses. Antibodies are substances that develop in the blood to help fight infection. If a person has antibodies to a certain bacteria or virus in their blood, this means they had an infection with that germ some time in the past. The researchers compared whether the women who had heart attacks or strokes were more likely than those that did not to have antibodies suggesting past infections.

What did the researchers find?

Women with blood tests that suggested they had not had past infections were just as likely to develop heart disease or strokes as women whose blood tests suggested they did have previous infections.

What were the limitations of the study?

The study could not rule out very small increases in heart attacks or strokes. Also, the researchers looked at only four types of bacteria or viruses.

What are the implications of the study?

Treating infections is not likely to be a good way to prevent heart attacks and strokes. Of course, there may be other reasons to treat these infections.