Common virus 'almost doubles' risk of dementia - but treatment could slash odds

A COMMON MEDICINE USED BY MILLIONS COULD SLASH THE RISK OF ALZHEIMER'S AS A NEW STUDY STRENGTHENS THE LINK BETWEEN THE COLD SORE VIRUS AND DEMENTIA 13:29, 21 May 2025 The virus that

causes cold sores has been linked to a higher risk of developing Alzheimer's disease, according to new research. Herpes simplex virus type 1, also known as HSV-1, is a common virus that

is found in over 64 per cent of people under the age of 50, the World Health Organisation (WHO) says. Previous research has found that the so-called cold sore virus can lie dormant in human

cells for a lifetime before 're-awakening' and triggering dementia symptoms. The virus has also shown to cause changes in the brain similar to those seen in dementia patients.

Now, a large study suggests that treating cold sores with anti-viral medicines could help slash the risk of Alzheimer’s disease. Scientists looked at medical records from over 300,000 people

in the US aged 50 and over, splitting them into two groups: those who had been diagnosed with Alzheimer’s disease, and those who had not. The researchers then looked at whether those with a

history of HSV-1 infection were more likely to go on to develop Alzheimer’s. Article continues below They found that a total of 1,507 (0.44 per cent) people diagnosed with Alzheimer's

disease had a history of HSV-1 infection, compared with 823 (0.22 per cent) without a diagnosis. The study concluded that people who had suffered the herpes virus had an 80 per cent

increased risk of Alzheimer’s, even when other factors like genetics were taken into account. However, those with HSV-1 who used anti-virals, such as the drug aciclovir, to treat the virus

were 17 per cent less likely to develop the disease compared with those who did not. The authors wrote in the study: "Findings from this large…study implicate HSV-1 in the development

of Alzheimer’s disease and highlight anti-herpetic therapies as potentially protective for Alzheimer’s and related dementia." Exactly how HSV-1 and other viruses might fuel the risk of

dementia is not yet clear. Prof Tara Spires-Jones, Director of the Centre for Discovery Brain Sciences at the University of Edinburgh, who was not involved in the study, said: "Why

viral infections may increase risk of dementia is not fully understood, but the most likely explanation is that infections increase inflammation in the body and contribute to age-related

brain inflammation. "More research is needed to understand the best way to protect our brains from Alzheimer’s disease as we age, including a better understanding of links between viral

infection and Alzheimer’s risk." However, Dr Richard Oakley, Director of Research and Innovation at Alzheimer’s Society, stresses that the study 'doesn't prove' that

cold sores cause Alzheimer’s disease, or that antivirals prevent it. Dr Oakley added: "The data came from insurance records, often based on self-reported symptoms which may miss or

misclassify infections, and didn’t track how often people had cold sores or how consistently they took medication. “Much more research is needed to explore exactly how viruses might be

involved and before we can draw firm conclusions. It is critical we explore every avenue to understand the complex causes of the diseases which cause dementia – infections are a growing area

of interest. “If you are worried about a cold sore or your general health, be sure to seek the appropriate help from a health professional.” Similarly, Dr Sheona Scales, Director of

Research at Alzheimer’s Research UK, says there is not yet enough evidence to add viral infections to the list of 14 established risk factors for dementia. The 14 risk factors are: Article

continues below The study was published in the journal _BMJ Open_.