New research suggests the herpes simplex virus could increase the risk of Alzheimer's.

The finding could help researchers develop new treatments to help slow down, or even completely prevent, the degenerative disease, Umea University reported.

Alzheimer's disease is the most common condition of its types, and a number of studies have been pointing towards the idea that it is linked with infections such as the herpes virus; herpes is extremely common in many populations.

Once infected with herpes simplex the body is never flushed of the invader, but carries it forever. After it is contracted, herpes can be reactivated and cause mouth ulcers; the researchers  believe when the immune system is weakened later in life it can spread to the brain. This phenomenon could explain the mysterious link between herpes simplex and Alzheimer's.

The correlation between the two conditions has now been further confirmed through two large epidemiological studies.The first study looked at 3,432 participants who were followed for an average of 11.3 years. The conclusions suggested reactivated herpes infections came with a doubled risk of developing Alzheimer's compared with those who did not have the virus.

Another study looked at 360 people with Alzheimer's disease and an equal number of controls. These patients had donated samples to the Medical Biobank at Umeå University. The samples were taken at an average of 9.6 years before the initial diagnosis. This second study also confirmed an approximate doubled risk of developing Alzheimer's disease linked to the herpes simplex virus.

"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," said Hugo Lövheim, associate professor at the Department of Community Medicine and Rehabilitation, Geriatric Medicine, Umeå University, who is one of the researchers behind the study.  

The findings were published in a recent edition of the journal Alzheimer's & Dementia.