Head injuries including mild concussion significantly raise the risk of developing dementia, a major study has found. Picture: AP

Head injuries including mild concussion significantly raise the risk of developing dementia, a major study has found.

Brain injuries – typically caused by a fall, car accident or assault – increase the chances of Alzheimer’s and other forms of dementia by 24 %.

The severity of the injury and the younger a person is further increase the risk of a dementia diagnosis in later life, as does the more knocks someone has – suggesting that athletes such as boxers could be at particular risk.

But even those who had suffered only one mild concussion had a 17 % higher risk of developing the condition.

However, the US and Danish researchers, writing in the journal The Lancet Psychiatry, stressed that although the relative risk of dementia rises after a traumatic brain injury, ‘the absolute risk increase is low’.

The scientists tracked almost three million people in Denmark over 36 years between 1977 and 2013.

They found more people with dementia (5.3 %) than without the disease (4.7 %) had a history of traumatic brain injury.