Viral Infections Linked to Dementia
Infection With Common Viruses May Increase Dementia Risk
Aug. 14, 2003 -- Certain viral infections may increase the
likelihood of mental decline and dementia, especially among older adults with
A new study shows that elderly people with evidence of
infection with three common viruses -- viruses that cause cold sores, genital
herpes, and a mono-like illness -- were more than twice as likely to suffer
Researchers say the study adds new evidence to the theory that
inflammation, which is part of the body's natural response to infection, plays
an important role in the development of several health problems, such as heart
disease, stroke, and dementia.
Viruses May Trigger Dementia
"Inflammation has been implicated in dementia, and viral
infections could be a triggering factor," says researcher Timo E.
Strandberg, MD, PhD, of the University of Helsinki in Finland, in a news
release. "Our findings should be tested in other studies, but if these
viruses are involved, there are existing therapies such as vaccination and
antiviral drugs that could be used to prevent or treat dementia."
In the study, which appears in Stroke: Journal of the
American Heart Association, researchers tested 383 elderly men and women
with heart disease for the antibodies that are produced in response to
infection with three common viruses: herpes simplex 1 (HSV1), herpes simplex
type 2 (HSV2) and cytomegalovirus (CMV), and followed them for 12 months.
HSV1 causes cold sores, and HSV2 causes genital herpes. CMV is
a virus that infects between 50% to 85% of American adults by age 40, but it
causes few symptoms and no long-term health problems in most people.
The mental function of the participants was also assessed at
the beginning and end of the study.
After testing for the viruses multiple times, researchers found
that up to 60% of the participants tested positive for one or more or the
viruses. And the more viral exposure, the higher the risk of dementia.
Those who had evidence of infection with all three viruses were
2.5 times more likely to have mental impairment than those with antibodies for
less than three of the viruses.
Dementia was found in about 5% of people who were infected with
one or none of the viruses, but those numbers grew dramatically with additional
infections. Sixteen percent of those infected with two viruses had dementia and
27% of those exposed to all three had dementia.
The researchers also looked at whether infection with two
common bacteria was related to dementia risk but found no association between
bacterial infections and mental decline.
Because all of the participants also had heart disease,
researchers say further studies should examine whether similar results are
found in otherwise healthy individuals.