Older people carrying the virus had twice the risk of developing dementia over 15 years.
Carrying the herpes simplex virus doubles the risk of dementia in older people, research suggests.
The Swedish study, including 1000 participants aged 70, found those carrying anti-HSV IgG had 2.2 times the risk of being diagnosed with dementia over the following 15 years compared to those who had no HSV antibodies.
âAnti-HSV IgG was associated with a more than doubled dementia risk (fully adjusted hazard ratio = 2.26),â the researchers said in the Journal of Alzheimerâs Disease.
Invitation letters were sent to 2000 randomly selected Uppsala residents within two months of their 70th birthdays. The 1000 participants who took part in the study were assessed at ages 70, 75 and 80, and were followed through medical records at age 85.
At baseline, the Uppsala University researchers looked for serological evidence of past herpes infection (HSV IgG) as well as past cytomegalovirus infection (CMV IgG) and past infection with HSV1. They also checked for recent herpes infection (IgM).
Over the following 15 years, researchers followed up participants, noting any diagnosis of dementia or indications of cognitive impairment, as confirmed by a geriatrician.
After 15 years, 7% of participants had developed dementia from any cause, with 4% having the diagnosis of Alzheimerâs disease.
From the serological samples, it appeared 82% of participants had anti-HSV IgG, and data records showed 6% of that subgroup had received antiviral treatment for herpes at least five years before the end of follow-up.
It appeared, according to the researchers, that antiviral treatment did not affect the risk of developing dementia.
âThe potential effect of anti-herpesvirus treatment on the dementia risk needs to be studied in randomised controlled trials to circumvent issues inherent to observational studies,â they said.
First author and Uppsala University medical student Erika Vestin said the fact that all the participants in this study were the same age was a strength of the research, as dementia risk was different for different ages and this could confuse the results.
âMore and more evidence is emerging from studies that, like our findings, point to the herpes simplex virus as a risk factor for dementia,â she said in a statement.
