Researchers in Sweden have found a link between Alzheimer's disease and cold sores, which can double the risk.

The researchers at Umea University discovered that the herpes simplex virus, the cause of cold sores, weakens the immune system allowing it to reach different parts of the brain, which could lead to dementia, according to Delhi Daily News.

This link may lead to medicines that can decrease the advancement of or inhibit the disease altogether, the researchers hope.

"Whether treatment of herpes infection with antiviral drugs may slow the Alzheimer's progression is not known, but is certainly worth investigating in clinical studies," said Hugo Lovheim, an associate professor in the department of community medicine and rehabilitation at Umea University in Sweden and lead researcher of the study.

At least 90 percent of adults carry the virus, but only a quarter of them will experience the frequent outbreaks of cold sores, the Daily Mail reported. It is a virus that the body carries forever after the first infection.

The virus can be spread by contact with saliva, such as through sharing drinks.

The research was conducted with two large studies before the results were published.

The first study involved 3,432 participants over a period of 11.3 years, resulting in the discovery that having certain antibodies to a herpes infection doubles the risk of Alzheimer's. The second study used samples from 360 people whose Alzheimer's was detected 9.6 years earlier than when they were diagnosed, Delhi Daily News reported.

The way the virus affects the brain over time involves a buildup of plaque, the Daily Mail reported. The plaques are formed in the brain and results in the death of brain cells, often breaking down the connection between the cells.

This causes a loss in the ability to think, which is a symptom of Alzheimer's.

Researchers hope to be treating patients for Alzheimer's within a few years as a result of this breakthrough.