Could that cold sore increase your risk of memory problems?

The study found that people who have had higher levels of infection in their blood (measured by antibody levels), meaning they had been exposed over the years to various pathogens such as the herpes simplex type 1 virus that causes cold sores, were more likely to have cognitive problems than people with lower levels of infection in the blood.

"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 author Mira Katan, MD, with the Northern Manhattan Study at Columbia University Medical Center in New York and a member of the American Academy of Neurology. The study was performed in collaboration with the Miller School of Medicine at the University of Miami in Miami, FL.

For the study, researchers tested thinking and memory in 1,625 people with an average age of 69 from northern Manhattan in New York. Participants gave blood samples that were tested for five common low grade infections: three viruses (herpes simplex type 1 (oral) and type 2 (genital), and cytomegalovirus), chlamydia pneumoniae (a common respiratory infection) and Helicobacter pylori (a bacteria found in the stomach).

The results showed that the people who had higher levels of infection had a 25 percent increase in the risk of a low score on a common test of cognition called the Mini-Mental State Examination.

The memory and thinking skills were tested every year for an average of eight years. But infection was not associated with changes in memory and thinking abilities over time.

"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," said Katan. "For example, exercise and childhood vaccinations against viruses could decrease the risk for memory problems later in life."

The study was supported by the National Institutes of Neurological Disorders and Stroke (NINDS), the Swiss National Science Foundation and the Leducq Foundation.