Heading a football just 20 times could be enough to have a detrimental effect on brain function, according to a new study. 

Research led by Liverpool Hope University took a group of test subjects and analysed cognitive function, including memory and mental ability. before and immediately after they headed a football twenty times. 

The results, published this week in the journal Science and Medicine in Football, showed how ‘working memory’ declined by as much as 20 per cent.

Worryingly, the vast majority of test subjects also displayed signs of concussion. 

Jake Ashton, a Postgraduate research student at Hope, said: “Our results are both surprising and concerning.

READ MORE: Sir Geoff Hurst joins call for ban on children heading footballs amid dementia risk concern 

“We investigated the immediate effect heading a football has on cognitive function. 

“Participants performed a series of cognitive function tests before and after a bout of 20 headers. 

“They also performed a pitch-side screening for concussion, which showed that 80 per cent of the participants showed potential signs of concussion. 

“With the cognitive tests, there was a significant reduction in verbal and spatial working memory.”

The study itself involved a group of 30 recreational male soccer players aged between 18 and 21 years old. 

They were split into three groups - that undertook 20 consecutive headers with either a  soft (8.8 psi) ball, hard ball (16.2 psi), or no ball at all. 

Overall, when ‘Saccadic eye speed’ was measured - ie, how quickly you can locate and identify visual targets - function decreased by around 10 per cent. 

Spatial span - the recall of objects in space within a particular sequence - reduced by an average of 15 per cent. 

READ MORE: Dementia experts hail 'exciting' study breakthrough in Alzheimer's Disease 

Meanwhile ‘digit span’ - the recall of certain numbers within a particular sequence - tailed-off by 20 per cent in the group heading the hard football. 

There are also ramifications when it comes to concussion.

The ‘Saccadic eye speed test’ is adopted by many experts in North American sports as an indicator of concussion. 

The time needed to complete the test increased by three seconds when compared to baseline, it’s considered a possible concussion and athletes are removed from competition. 

As part of the research, participants indicated a four second gain following headers, while also being more error prone.  

Jake adds: “Ten of the participants headed balls with a PSI of around 8, while the other 10 headed balls with a PSI of around 16 - pressures at either end of FA guidelines. 

“The group with the higher-pressure ball showed greater declines in working memory than the other group. 

“And overall both groups showed significant reductions in verbal and spacial working memory. 

“Our research doesn’t look at the repercussions of heading a football over a number of years. 

“While more research is needed, there may also be a need to put measures in place to limit heading during football training sessions, in all ages. 

“It may also be advantageous to use sponge balls during children’s training sessions, so they can practice the technique without having the repercussions of heading a heavier ball.

READ MORE: Scientist urges caution in 'cold shock' outdoor swimming dementia 'cure' hopes

“The impacts of using a harder ball should also not be ignored.”

Jake also suggests that referees at grassroots levels measure the ball pressure before match kick offs. 

There is growing concern about the links between dementia and football to be further investigated following the recent dementia diagnosis of World Cup winner Sir Bobby Charlton. Celtic legend Billy McNeill is among the Scots players who have succummed to the disease.

The initial move to limit heading in training came following a separate report, published in October last year by the University of Glasgow, which found links between former professional footballers and brain disease. 

The study suggested players could be three and a half times more likely to die of dementia. 

At the time Dr Willie Stewart, the consultant neuropathologist who led the University of Glasgow study, said: “A lot more research is needed to understand the factors contributing to increased risk of neurodegenerative disease in footballers. 

“Meanwhile it is sensible to act to reduce exposure to the only recognised risk factor so far."