LONDON, Feb. 15 (Xinhua) -- Scientists in Britain warned Wednesday that professional footballers repeatedly heading the ball may suffer long-term brain damage.
Researchers from University College London (UCL) and Cardiff University examined the brains of five people who had been professional footballers and one who had been a committed amateur throughout his life.
Each had played football for an average of 26 years and all six went on to develop dementia in their 60s.
While performing autopsies, scientists found signs of brain injury, called chronic traumatic encephalopathy (CTE) in four cases.
The condition has been linked to memory loss, depression and dementia and has been seen in other contact sports.
Prof Huw Morris from UCL said in a media interview in London: "When we examined their brains at autopsy we saw the sorts of changes that are seen in ex-boxers, the changes that are often associated with repeated brain injury which are known as CTE.
"So really for the first time in a series of players we have shown that there is evidence that head injury has occurred earlier in their life which presumably has some impact on them developing dementia."
Dr David Reynolds from the charity Alzheimer's Research UK, said: "The causes of dementia are complex and it is likely that the condition is caused by a combination of age, lifestyle and genetic factors.
"Further research is needed to shed light on how lifestyle factors such as playing sport may alter dementia risk, and how this sits in the context of the well-established benefits of being physically active."
Reynolds said recreational footballers are unlikely to suffer long-term problems, adding that expert advice is that the benefit of exercise is likely to outweigh the risks.
The Football Association in London welcomed the study and said research was particularly needed to find out whether degenerative brain disease is more common in ex-footballers.
Dr Charlotte Cowie, of the FA, said: "The FA is determined to support this research and is also committed to ensuring that any research process is independent, robust and thorough, so that when the results emerge, everyone in the game can be confident in its findings."