Research ‘most compelling evidence ever' of viral trigger for Alzheimer's

US-based scientists analysed post-mortem brain tissue as part of the study.

Alzheimer’s disease has been linked with the presence of high levels of herpes viruses in the brain.

A new study found those with the neurological disorder had twice the levels of two strains of herpes, HHV-6A and HHV-7, than those without the condition.

The research, published in journal Neuron, offers “the most compelling evidence ever” pointing to a possible viral trigger for Alzheimer’s, the authors said.

Experts stressed it was not clear if the viruses caused dementia or were caused by it.

The study, using evidence from post-mortem brain tissue, was carried out by researchers from Mount Sinai Health System in New York in the US.

Lead author Dr Joel Dudley said: “If it becomes evident that specific viral species directly contribute to an individual’s risk of developing Alzheimer’s or their rate of progression once diagnosed, then this would offer a new conceptual framework for understanding the emergence and evolution of Alzheimer’s at individual, as well as population, levels.”

Sam Gandy, professor of neurology and psychiatry, and co-author of the study, said: “This is the most compelling evidence ever presented that points to a viral contribution to the cause or progression of Alzheimer’s.”

Studies have previously suggested that viruses might be linked with Alzheimer’s but the new research suggests a relationship between viruses and the activity of genes associated with the disease.

Dr James Pickett, head of research at Alzheimer’s Society, said: “The relationship between viruses and Alzheimer’s disease has been an area of interest for researchers for a while, but it is still unclear if higher levels of viruses cause dementia or are caused by it.”

Dr David Reynolds, chief scientific officer at Alzheimer’s Research UK, said the viruses highlighted in the study were not the same as those that caused cold sores.

Instead they were much more common forms which most people carried, usually without any problems.

He added: “While the findings indicate a link between the activity of these viruses and Alzheimer’s, they don’t tell us whether they contribute to the development of the disease, help the brain to cope with the disease, or just occur alongside Alzheimer’s processes without having an impact on the health of the brain.”

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