Herpes Simplex Virus Tied To Alzheimer’s Risk

A novel study on the association between herpes simplex virus and Alzheimer’s disease, entitled “Herpes simplex infection and the risk of Alzheimer’s disease-A nested case-control study,” was recently published in the journal Alzheimer’s & Dementia by Prof. Hugo Lövheim, from the Department of Community Medicine and Rehabilitation, Geriatric Medicine, Umeå University, Umeå, Sweden, and colleagues.

This new study demonstrates that the herpes simplex virus type 1 infection appears to increase the probability of developing Alzheimer’s disease, the most common neurodegenerative disease. Herpes simplex virus type 1 has a high prevalence in humans. After the first infection, the virus remains in a dormant state in the body permanently, and can be reactivated when the infected person’s immune system is weakened, causing the common mouth ulcer.

The research team performed two large epidemiological studies where they confirmed the association between herpes simplex virus type 1 and the development of Alzheimer’s disease. The first study was based on data from the Betula project, a study on aging, memory and dementia that has been ongoing for 20 years, where the main goal is to understand how memory functions change during adult life. In this epidemiological study, Dr. Hugo Lövheim and colleagues analyzed 3,432 participants that were followed for 11.3 years and concluded that a reactivated herpes infection increases two times the risk of developing Alzheimer’s disease.

In another study, the research team analyzed samples from 360 people with Alzheimer’s disease, donated to the Medical Biobank at Umeå University, and matched the samples with subjects that did not develop the disease. The samples were collected for an average 9.6 years before diagnosis. The researchers concluded that a subject infected with the herpes virus has two times more the probability of developing Alzheimer’s disease than an uninfected subject.

The research team stated that the hypothesis that associates the herpes virus infection with Alzheimer’s disease is based on the fact that older subjects who have more fragile immune systems state and this is an opportunity for the virus to reach other parts of the organism, mainly the brain. And thus this can be the trigger that leads to the development of Alzheimer’s disease.

“Our results clearly show that there is a link between infections of herpes simplex virus and the risk of developing Alzheimer’s disease. This also means that we have new opportunities to develop treatment forms to stop the disease,” said Prof. Hugo Lövheim, in the Umeå University press release.

The research team said that the hypothesis that associated the herpes virus with Alzheimer’s disease is based on the fact that in older subjects the immune system is more fragile, creating an opportunity for the virus to reach other parts of the organism, mainly the brain. Thus, this can be the trigger of the processes that lead to the development of Alzheimer’s disease.

“Something which makes this hypothesis very interesting is that now herpes infection can in principle be treated with antiviral agents. Therefore within a few years we hope to be able to start studies in which we will also try treating patients to prevent the development of Alzheimer’s disease,” says Hugo Lövheim.