By Amy Norton
MONDAY, March 25 (HealthDay News) -- Older adults who harbor certain infections, such as the herpes cold sore virus, may have poorer thinking and memory abilities than their peers, a new study suggests.
Researchers found that of more than 1,600 older adults, those with signs of chronic infection with herpes simplex and certain other viruses and bacteria scored lower on standard tests of mental skills.
But the findings, published in the March 26 issue of Neurology, do not prove the infections are to blame.
"They could just be bystanders," said lead researcher Dr. Mira Katan, a neurologist with Columbia University College of Physicians and Surgeons in New York City.
"We can't make any definite conclusions about causality," Katan said. "At this stage, you can just say there's an association."
Still, it's an "interesting" association that needs further study, she said.
Many people carry herpes simplex virus, or HSV. One form, HSV-1, usually causes cold sores around the mouth, while HSV-2 is the main cause of genital herpes. Once a person is infected with either form of HSV, the virus remains dormant in the body's nerve cells and can be reactivated repeatedly.
HSV can also move to any part of the body, including the brain, and for several decades, some researchers have speculated that chronic HSV infection might contribute to dementia -- possibly by causing persistent inflammation.
In the new study, Katan's team used blood samples from 1,625 older adults -- average age 69 -- to look for indicators of chronic infection with a few common pathogens: HSV and another virus in the herpes family called cytomegalovirus, which usually causes no symptoms; C. pneumoniae, a bacterium that causes respiratory infections; and H. pylori, a stomach-dwelling bacterium that can cause ulcers.
On average, the greater their "infection burden," the worse the older adults performed on a standard test of thinking and memory, the study found.
But the study hinted that exercise might play a protective role. The research team found that infection "burden" was related to mental impairment only among sedentary people -- and not those who said they got some exercise.