The virus causing your cold sore may put you at risk for something more insidious: Lower cognitive abilities.
In a study of 1,625 people, researchers at Columbia University measured specific antibodies to common infectious agents in each person's blood, and using this information, created an "infectious burden index." Participants higher on the infectious burden index were more likely to have worse cognition, or cognitive abilities.
The study, published Monday in the journal Neurology, further suggests a link between cognitive decline and herpesviridae viral infections in particular, which previous studies have also linked to Alzheimer's disease and risk of stroke, an accompanying editorial notes. Herpesviridae is a family of viruses including HSV-1 or herpes simplex virus-1, which causes cold sores and can cause genital herpes, and HSV-2, which commonly causes genital herpes.
For the study, researchers tracked participants for eight years, giving them tests to measure cognition each year, but found no link between decline in abilities and viral infections over that period. The associated decline occurred before the study even began; the participants infectious burden index score did not make that person more or less likely to experience cognitive decline over the course of the study.
Only physical activity significantly reduced the association between infectious burden and cognitive decline, researchers found.
A study starting with younger participants - this study's average was 69 years old - and over a longer period may reveal more about how the decline progresses over time, says Dr. Mira Katan, the lead study author.
"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 in a statement.
"For example, exercise and childhood vaccinations against viruses could decrease the risk for memory problems later in life."
"This is a fascinating area which certainly deserves a treatment trial," says Dr. Timo Strandberg, author of the editorial, from the Department of Medicine, geriatric clinic, at the University of Helsinki (Finland) and University Hospital in Helsinki. "We are currently planning one... just remember what a paradigm change there was in ulcer disease in the 1980s. Of course this could have great potential if proved to be right. Nevertheless, old age AD (Alzheimer's disease) is a multifactorial geriatric syndrome (in my opinion), so several factors are contributing at the individual level."
However, said Dr. William Schaffner, chairman of the preventive medicine department at Vanderbilt University's School of Medicine, "They cannot impute causal associations, these are just interesting phenomenon."
"My concerns are, who are these people who are drawn into these studies? Because they're not a representative population," says Schaffner, who was not involved in the research. "They of course have had a dropout rate, so I'm just very cautious about what we can conclude from this association."
But Schaffner says he finds the study "intriguing and provocative" He says, "The more we pick at this and find infectious disease antecedents for chronic illness, the more provocative it is, because it opens up more doors for prevention.".