The virus that causes common cold sores may be behind cognitive problems and memory loss later in life.
New research published in Neurology on March 25, found people who had higher levels of the herpes simplex type 1 virus circulating in their blood were more likely to have cognitive deficits than those who had lower levels of the virus in their blood.
"While this association needs to be further studied, the results could lead to ways to identify people at risk of cognitive impairment and eventually lower that risk," study author Dr. Mira Katan, a neurologist with the Northern Manhattan Study at Columbia University Medical Center in New York City, said in a statement.
Cold sores are caused by one of two types of herpes simplex virus. The other typically affects the genital area. People with the herpes simplex 1 virus may not show any symptoms, but some develop painful cold sores that are often unsightly can last a week or more. There is no cure for the virus.
Researchers conducted tests that measured memory, thinking and processing abilities in 1,625 people who were on average 69 years old and lived in northern Manhattan in New York. Tests were given annually for eight years on average. Participants were also given blood tests that looked for five common infections the researchers considered low-grade: herpes simplex type 1, herpes simplex type 2, cytomegalovirus (a virus that can cause serious illness in people with weakened immune systems), chlamydia pneumoniae (which can cause the common respiratory infection pneumonia) and Helicobacter pylori (a bacteria found in the stomach that can cause ulcers).
"We found the link was greater among women, those with lower levels of education and Medicaid or no health insurance, and most prominently, in people who do not exercise," said Katan.
People who had higher levels of the infections were 25 percent more likely to have a lower cognitive score than those with the lowest levels. The study only showed an association, not cause and effect. Infection was not associated with any changes in memory or thinking abilities over the course of the eight-year testing period, the researchers also found.
Katan said the findings suggest exercise and childhood vaccinations against viruses could reduce risk for memory problems later in life.
linked the herpes virus that causes cold sores to increased risk for Alzheimer's disease. Researchers tagged viral particles with fluorescent proteins and watched them under a microscope, only to find the particles damaged nerve cells in ways that may lead to Alzheimer's.
Dr. Timo Strandberg, a cognitive disease researcher at the University of Helsinki in Finland, and Allison Aiello, an associate professor of epidemiology at the University of Michigan, wrote an editorial accompanying to the new study that called for more research to look at the interactions between disease pathogens and damage to the brain.
One& expert cautioned while the study was intriguing, not much can be made from it at this stage.
"My concerns are, who are these people who are drawn into these studies? Because they're not a representative population," Dr. William Schaffner, an infectious disease expert who chairs the preventive medicine department at Vanderbilt University in Nashville, told CNN. He was not involved in the study. "I'm just very cautious about what we can conclude from this association."