Dementia may begin in the womb when spelling mistakes in DNA store up problems for the future, a study by Cambridge University suggests.
Researchers already knew that inherited mutations in some specific genes make people far more likely to develop neurodegenerative diseases like Alzheimer’s and Parkinson’s.
But a new study suggests that those same genes can go haywire even when people do not inherit risky variants from their parents.
In tissue samples of the brains of 54 people, 40 of whom had varying forms of dementia, scientists discovered that half had spontaneous flaws in their DNA, which may have contributed to their illness.
The scientists believe the genetic defects occurred before the people were even born, while they were embryos growing in the womb. And they fear that the same mutations may be carried by a huge number of the population, which is why dementia is so prevalent.
“These spelling errors arise in our DNA as cells divide, and could explain why so many people develop diseases such as dementia when the individual has no family history,” said lead author Professor Patrick Chinnery
“These mutations likely form when our brain develops before birth – in other words, they are sat there waiting to cause problems when we are older.”
“Our discovery may also explain why no two cases of Alzheimer’s or Parkinson’s are the same. Errors in the DNA in different patterns of brain cells may manifest as subtly different symptoms.”
Around 850,000 people suffer from dementia in Britain, which is largely caused when sticky clumps of amyloid plaques form in the brain, preventing neurons from communicating.
Although one in 20 patients who develop neurodegenerative disease have a family history where genetic variants inherited from their parents raise their risk, the cause of why most people get the diseases has remained unknown.
Drug trials are already underway for inherited dementia, and the new study suggests that medication which works in those cases may also work for the majority of sufferers.
“The question is: how relevant are these treatments going to be for the ‘common-or-garden’ variety without a family history?,” added Dr Chinnery.
Our data suggests the same genetic mechanisms could be responsible in non-inherited forms of these diseases, so these patients may benefit from the treatments being developed for the rare genetic forms.”
The research was welcomed by charities who said that it could help unravel the role the genes play in developing dementia.
Dr James Pickett, Head of Research at the Alzheimer’s Society, said: “The small errors that can occur as brains develop are often harmless, but can sometimes lead to conditions such as cancer or dementia.
“It’s interesting to see that many of the mutations in this study were found in the area of the brain that Alzheimer’s starts in.
“There will be around 1 million people with dementia by 2021. Our researchers are working hard to learn more about the inherited and non-inherited genes that could cause dementia, so that we can understand more to help find new treatments.”
Dr David Reynolds, Chief Scientific Officer at Alzheimer’s Research UK, said: “Our genetic makeup can have a huge impact on our health and errors in this DNA code can occur in embryonic development as well as throughout our lives.
“In recent decades, genetic clues have been vital for uncovering new areas of biology to explore in the search for new treatments for diseases like Alzheimer’s.
“This study provides a valuable platform for further research to continue to unravel the complex role our genes play in the development of the diseases that cause dementia.”
The research was published in the journal Nature Communications.