Study: Cold sores linked to memory loss

The virus that causes cold sores, including other viral or bacterial infections, may be linked to memory loss, according to the results of a study published in the March 26 issue of Neurology. Indeed, if further studies establish such a link, it could potentially be used to help prevent strokes or Alzheimer’s disease.

The study involved a group of 1,625 people from a neighborhood in New York City, some of whom had been exposed to various pathogens like the herpes simplex type 1 virus, which causes cold sores. As a result, not only did those exposed to pathogens have higher levels of infection in the blood, but researchers found they were also more likely to have cognitive problems than those with lower levels of infection in the 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," said Dr. Mira Katan, author of the study. "For example, exercise and childhood vaccinations against viruses could decrease the risk for memory problems later in life,” she said.

The study was conducted at the Northern Manhattan Study at Columbia University Medical Center in New York, in collaboration with the Miller School of Medicine at the University of Miami. Dr. Katin said results from the study also found a greater link between infections and memory loss among women, those who were less educated – and, most prominently, among non-exercisers.

For the study, researchers tested the thinking and memory of the participants who were 69 years old on average – and lived in one neighborhood located in northern Manhattan. Each of the participants provided blood samples that were tested for five common, low-grade infections, which included three viral infections: 1) oral herpes simplex type 1; 2) genital herpes simplex type 2; and 3) cytomegalovirus – and two common bacterial infections: 1) chlamydia pneumonia, a respiratory infection; and 2) Helicobacter pylori, a stomach infection.

The results found that those who had higher levels of infection, also had a 25 percent increase in their risk of having a low score on a common cognitive test: the Mini-Mental State Examination.

The researchers then followed up with the participants, testing their memory and thinking skills each year over a period of eight years on average. As a result, they found that – over time – infection was not linked with changes in memory and thinking.

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

The March 26 issue of Neurology included an editorial about the study by Dr. Timo Strandberg and Dr. Allison Aiello, who agreed that there is still much work to be done, but they agree further study is worthwhile.

“Undoubtedly, demonstrating that old-age cognitive diseases, including AD, are slowly progressing diseases of viral etiology would revolutionize the dementia research field and be Nobel Prize-worthy,” they wrote. “However, great challenges remain. Such a study is nevertheless worth doing and the editorialists hope that the study… will stimulate this endeavor.”

SOURCE: Neurology, March 26, 2013 (vol. 80 no. 13 1209-1215). Abstract