A SINGLE head injury may be enough to trigger dementia, according to a ground-breaking study by Scots researchers.

Scientists in Scotland and America found large numbers of proteins in the brains of some of those hurt, which are typical of those seen in people with Alzheimer’s disease.

Brain tissue from 39 people who had recovered from a brain injury and 47 people who had never had a brain injury were examined after their deaths. All of the people were from the west of Scotland.

Scientists found the large number of proteins, which they referred to as “abnormalities”, in a third of those who had a head injury.

The research was carried out by a team at the Southern General Hospital in Glasgow and the University of Pennsylvania in Philadelphia.

Dr William Stewart, who led the team in Glasgow and is co-author of the study, said: “We were really quite astonished to find up to a third had extensive pathology.”

More than 150,000 people in the UK suffer a head injury every year and the study suggests a brain injury can spark a process in which the brain is damaged in other ways.

Almost one-quarter of people over 80 develop Alzheimer’s and one in 20 of those over 65 develop the illness.

Dr Stewart said: “The abnormalities we saw in the brain are normally seen in people with dementia or very old people, but we are seeing this in people in their 20s, 30s, 40s. The proteins are typical of those you might find in Alzheimer’s disease.

“We have found a potential link between head injury and dementia. This is the first study of its kind.

“We know a higher proportion of people with a head injury have a higher risk of dementia.

“But we don’t know whether the ones we looked at have dementia, they had never been diagnosed with dementia, but it creeps up and we are looking at that now.

“The abnormality was really quite extensive,” he added.

A team of four worked on the project for two years, and the head injuries were as a result of falls, road crashes and assaults.

The 39 post-mortem brains used in the study came from people who had survived between one and 47 years after their head injury.

In 2009 Canadian researchers revealed people concussed in their youth show signs of mental and physical problems more than 30 years later. The study found athletes with a history of concussion in sports such as rugby had worse physical and mental test scores.

Experts said minor head injury recovery could be slow, but this was the first hint of a longer-lasting effect.

In the same year footballers were advised by the Scottish Professional Footballers’ Association to register head injuries following concern they could be leading to problems in later life.

The call came as the families of former Celtic players Billy McPhail and Jock Weir prepared to go to court to claim for alleged damages caused by heading the ball. Both Mr McPhail and Mr Weir died in 2003 and their families blamed the men’s dementia on contact with heavy leather footballs during their careers.

Dr Stewart, a consultant neuropathologist, said: “Part of the challenge in dementia is that a lot of the work we do is with people who already have it.

“What we don’t understand is how they get to that stage and what sets off the process in their brain. What we might be able to do is study patients after a head injury and work out what’s happening inside their heads.”

Dr Stewart said the scientists were trying to work out on a wider scale what is happening.

“The diagnostic archive we used is unique internationally,” he added.

The research is published on the website of the journal Brain Pathology.