Common Infection May Increase Risk of Heart Attack in Seniors
"Certainly the interest and all the work that's been going on in inflammation raises the interest in infections as well," David S. Siskovick, professor of medicine and epidemiology at the University of Washington, tells WebMD. "Whether our observation or other observations related to infection account for the inflammation associations or vice versa is unknown, but it does potentially fit."
In their study, Siskovick and colleagues looked at data on antibody levels in the blood of more than 600 participants aged 65 years or older. The study group included 213 people who had died from a heart attack. The remaining participants in the study were included for comparison purposes. The researchers looked for antibodies to the herpes simplex virus type 1, Chlamydia pneumoniae, and another common infectious agent, cytomegalovirus.
They found that among these older subjects, people who had evidence in the blood of antibodies to the herpes virus were twice as likely as others to have had a heart attack and to have died from heart disease. In contrast, exposure to cytomegalovirus apparently did not increase a person's risk for heart attack, and only those with very high blood levels of antibodies to Chlamydia pneumoniae were at increased risk for heart problems, although the reasons why are unclear.
One expert, though, cautions that antibody levels may not be the most reliable means for determining associations between infection and heart disease. "Antibody [levels] are not very specific in telling who has just been exposed, who is currently infected, or who was chronically infected," says Ignatius W, Fong, MD, professor of medicine at the University of Toronto and head of the division of infectious diseases at St. Michael's Hospital, also in Toronto.
"What you get is a mishmash of patients you look at who may have a combination of previous exposure but are not persistently infected, some who are persistently or chronically infected -- which we think are the ones that will have it in the circulating blood cells and are more at risk for having atherosclerosis -- and the antibody [tests] cannot differentiate them; you can get an overlap and conflicting data from various studies," Fong says.