DALLAS, Aug. 18 -- The strongest link yet between a chronic lung infection and heart disease has been found in a study of Alaska natives, researchers report in today's Circulation: Journal of the American Heart Association.
Other studies have reported finding the bacteria Chlamydia pneumoniae (C. pneumoniae) in atherosclerotic plaques -- the fatty deposits that build up in the walls of blood vessels and lead to heart attacks and strokes. However, the researchers say the new study is the first to show that the individuals were infected with the bacteria before heart disease was diagnosed.
Researchers studied samples of plaques obtained during autopsies of 60 Alaska natives, all of whom died from accidents. They also measured stored blood samples drawn seven months to 26 years earlier for disease screening programs. Adequate amounts of blood for testing were available for 56 of the individuals.
Scientists tested for the bacteria infection by measuring antibodies -- cells the body produces to defend against disease -- to C. pneumoniae.
The team identified the bacteria in coronary artery plaques from 22 (37 percent) of the Alaska natives who were studied. The organism was found in 39 percent of the early-stage plaques and in 35 percent of the more advanced deposits.
The study found that those who had severe infection were nearly 10 times more likely to have the bacteria identified in their blood vessels when they died than people with little or no evidence of earlier infection.
"The major finding of the report is the evidence of prior infection with Chlamydia pneumoniae. It provides strong evidence in linking this bacteria with atherosclerosis," says the study's lead author, Michael Davidson, M.D., M.P.H., a post-doctoral fellow at the Johns Hopkins University School of Hygiene and Public Health in Baltimore.