Amateur boxers are exposing themselves to twice the risk of dementia, scientists warned yesterday.
They called for punches to the head to be banned to cut the toll of brain injuries.
The study by Cardiff University was based on the health records of 1,123 men in nearby Caerphilly.
Of the 73 who had boxed seriously, a third showed signs of dementia between the ages of 75 and 89.
Compared with non-fighters, this made them twice as likely to experience some level of cognitive impairment, and three times as likely to have signs of Alzheimer's.
Amateur boxers are exposing themselves to twice the risk of dementia, scientists warned as they called for punches to the head to be banned to cut the toll of brain injuries (stock image)
Two years ago, a major study found that footballers are three times more likely to die from dementia.
Several high profile players from England's 1966 World Cup winning squad, including Nobby Stiles and Sir Bobby Charlton, developed the disease.
And new guidelines were introduced in England this year to limit the use of headers in football training, with children under 12 have also been banned from heading the ball.
Yesterday's research into boxing looked at 1,123 men in Caerphilly, who were followed for 35 years - 73 of whom had boxed 'seriously' when they were younger.
The study said the onset of dementia was five years earlier in the men who had boxed, compared to those who did not take up the sport as youngsters.
A 20019 study found footballers are three times more likely to die from dementia. Players from England's 1966 squad, including Sir Bobby Charlton (pictured in 2014), developed the disease
Lead author Professor Peter Elwood said: 'Professional boxing is known to cause chronic traumatic brain injury - but there has been little to no long-term research on this issue in amateur boxing.
'Our study therefore provides some of the best available evidence suggesting that amateur boxing is associated with clinically measurable long-term brain injury, manifested as earlier onset Alzheimer's-like impairment.
'Over the years the introduction of increasingly tight controls in the amateur sport, with shorter bouts and mandatory headgear, means that the chances of serious brain injury are much reduced - but there is still a true long-term impact of boxing.
'Banning blows to the head would seem to be an acceptable preventive measure, as this need not reduce the competitive aspect of the sport but would preserve its undoubted considerable physical and social benefits.
'Millions of people are affected by dementia and the links between this devastating disease and certain types of contact sport are only now starting to come to light.
'Further research in this area is vital so that we can bring in simple measures now to protect the health of generations to come.'