New results could change the face of Alzheimer's treatment; the herpes simplex virus is found to play a vital role in the condition, and antiherpetic medication is shown to have a dramatic effect on dementia risk.
The postmortem analyses of brain tissue found that people who lived with this dementia type also had more herpesviruses 6 and 7 than people without Alzheimer's.
Now, a scientific commentary suggests that the study that MNT covered is not the only one to pinpoint a link between herpes and dementia.
In fact, three more studies have strengthened this link, and the commentary — recently published in the Journal of Alzheimer's Disease – takes a look at all three.
Ruth Itzhaki, who is a professor of neuroscience and experimental psychology at the University of Manchester in the United Kingdom, alongside Richard Lathe, who is a professor in the Division of Infection and Pathway Medicine at the University of Edinburgh, also in the U.K., authored the commentary.
'Remarkable magnitude of antiviral effect'
The studies referenced in the commentary are two articles (Tsai et al., 2017, and Chen et al., 2018) that suggest that acute herpes zoster infection puts people at a higher risk of dementia, and one article that shows that aggressive treatment with antiherpetic medication drastically lowers dementia risk.
The latter study — deemed "most important" by Profs. Itzhaki and Lathe — examined 8,362 people aged 50 and above who received a diagnosis of herpes simplex virus (HSV) infection, as well as a control group of 25,086 age-matched healthy people.
The two groups were followed for almost a decade, between 2001 and 2010. In the herpes group, the risk of dementia was over 2.5 times higher than in the control group.
Significantly, the study also revealed that aggressive antiviral treatment reduced the relative risk of dementia by 10 times.
Prof. Lathe comments on these new findings, saying, "Not only is the magnitude of the antiviral effect remarkable, but also the fact that — despite the relatively brief duration and the timing of treatment — in most patients severely affected by HSV1 it appeared to prevent the long-term damage in [the] brain that results in Alzheimer's."
"This article and two others [...] provide the first population evidence for a causal link between herpes virus infection and Alzheimer's disease, a hugely important finding."
Prof. Ruth Itzhaki
"I believe we are the first to realize the implications of these striking data on this devastating condition which principally affects the elderly," Prof. Itzhaki adds.
"But," she says, "we believe that these safe and easily available antivirals may have a strong part to play in combating the disease in these patients." She also suggests that in the future, it may be possible to prevent the disease "by vaccination against the virus in infancy."
"Successful treatment by a specific drug, or successful vaccination against the putative microbe, are the only ways to prove that a microbe is the cause of a non-infectious human disease," says Prof. Itzhaki.