That Nagging Bronchitis Could Be Causing More Than a Cough
Feb. 26, 2001 -- As researchers learn more about the causes of heart disease -- bad genes, bad diet, or bad habits -- they can only explain about half of the cases seen each year, a frustrating fact that drives heart experts to look for other risk factors. In recent years, the focus has turned to infection -- usually gum infections -- as a possible risk factor, but now a major study from Austria suggests that any chronic infection may be a factor in heart attacks and stroke.
Stefan Kiechl, MD, says that individuals with infections like sinusitis, bronchitis, or even urinary tract infections are three times more likely to have a progression of atherosclerosis, the disease that leads to blocked arteries, than are people who are infection-free. The findings are reported in the current issue of Circulation: Journal of the American Heart Association.
Kiechl, a professor of neurology at Innsbruck University Clinic in Austria, and his colleagues used high-tech scanning equipment to check the carotid arteries of healthy volunteers at five-year intervals. The carotid arteries are the main blood supply to the brain, and the imaging equipment measured any changes or blockages that developed in the arteries. He says that when the 826 men and women were enrolled in 1990, 268 had some type of chronic infection.
One link between infection and atherosclerosis may be inflammation, Kiechl says. When an infection occurs, it triggers an inflammatory response by the body's immune system. Inflammatory response can be measured by a blood test that detects a substance called C-reactive protein, or CRP. In persons with chronic infections, CRP levels were about three times higher than in persons without infections, Kiechl says. Interestingly, this same inflammation marker is elevated in people who have heart attacks.
Infections also can release poisons called endotoxins, which attack the endothelium, the delicate inner lining of blood vessels.
Kiechl tells WebMD the link to bacterial infections included those infections caused by a number of different "bugs," including chlamydia and H. pylori -- the bug that causes most stomach ulcers.
He says, however, that he did not find a similar association for viral infections such as herpes zoster or hepatitis. But he says, "Our study does not refute the existence of an association between viral infections and atherosclerosis." Because only a small number of the study volunteers had those infections, he says, it was impossible to detect an association.