Players had an increased risk of Alzheimer's disease and other types of dementia. An exception was goalkeepers, who rarely need to head the ball according to new research.

A study of male footballers in Sweden, over many years, found they were one and a half times more likely to develop dementia than the general population.

Nearly 9% developed the condition compared with 6% of other people - but goalkeepers who rarely need to head the ball.were not at higher risk, the research suggests.

Heading the ball repeatedly has been linked to brain injury, yet there are many causes of dementia according to 
Researchers from the Karolinska Institutet in Sweden.

Peter Ueda of Sweden's Karolinska Institutet, who led the research, said it shows elite male players is at "serious risk" of developing degenerative brain disorders.

"One hypothesis is that the repetitive striking of the ball with the head is the reason players are at greater risk, and seeing the difference between goalkeepers and outfield players supports this theory," Ueda said.

Gill Livingston, professor in psychiatry of older people at the University College London, said the "high-quality paper" added to "convincing evidence" that  footballers whose heads come in contact with the ball were at a higher risk of dementia.

"We need to act to protect people's heads and brains and keep playing sport," said Livingston, who was not involved in the research.

The study found no increased risk of motor neuron diseases such as ALS among the footballers and an even slightly lower risk for Parkinson's disease.

Ueda cautioned that the observational study was not able to show that playing football directly caused dementia, and its findings could not be extended to female, amateur, or youth football players.

"There are more and more voices calling for the sport to introduce more measures to protect brain health and our study may help when making decisions to limit risks," added Ueda.

Last year a study led by the University of Glasgow found former rugby players were 15 times more likely to develop motor neurone disease than the general population.

A 2017 Boston University study found all but one of 111 deceased former National Football League players, who donated their brains for research, had evidence of Chronic Traumatic Encephalopathy (CTE).

CTE develops after multiple head injuries and can lead to behavioral changes and long-term dementia.

The NFL now has a concussion protocol in place for games.

It says the protocol is reviewed yearly to ensure that players receive care that reflects the most up-to-date medical consensus on the identification, diagnosis, and treatment of concussions.