Mild concussion, which can be caused from heading a football, could raise the odds of dying by the age of 40, scientists found

A single blow to the head in childhood could have devastating consequences years later, scientists have warned.

Even a mild concussion could raise the odds of poor school grades, mental illness and death by the age of 40.

Doctors need to be aware it is not just severe brain injuries which can cause lasting problems, Oxford University researchers say.

And they said their findings could lead to changes in the design of playgrounds, as well as tighter rules for sports in which collisions occur – including the heading of the ball in football.

The study focussed on traumatic brain injuries (TBIs) - knocks to the head bad enough to cause dizziness or wooziness.

It is thought around one in ten Britons suffers such a blow when young.

The researchers analysed data on more than a million Swedes from when they were born between 1973 and 1985 up to the age of 41.

Some 9.1 per cent suffered a TBI before their 25th birthday. Some of the blows were so severe the patients spent months in intensive care but most were mild concussions.

Despite this, the long-term consequences were severe.

Compared with people who had not experienced a head injury, those who suffered a TBI when young were 76 per cent more likely to have qualified for disability payments, meaning they could not work.

They were also 58 per cent more likely to have left school without any qualifications.

Also, they were almost twice as likely to have been admitted to hospital for a psychiatric problem and 72 per more likely to have died before the age of 41.

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Doctors need to be aware it is not just severe brain injuries which can cause lasting problems, Oxford University researchers say

Multiple brain injuries significantly increased the risks and a TBI in the late teens and early 20s was riskier than when younger.

Lead researcher Dr Amir Sariasian said all of those studied had gone to hospital and many other cases of mild brain injury may have gone unreported.

WHAT ARE THE SIGNS YOUR CHILD IS CONCUSSED? According to the Centers for Diseases Control, a parent should call 911 or take the child to the emergency department if a child has one or more of these signs: One pupil larger than the other

Drowsiness or inability to wake up

A headache that gets worse and does not go away

Slurred speech, weakness, numbness or decreased coordination

Repeated vomiting or nausea, convulsions, or seizures (shaking or twitching)

Unusual behavior, increased confusion, restlessness or agitation

Loss of consciousness (passed out / knocked out) Advertisement

He said: ‘This means we have essentially under-estimated our effects.

‘The differences between the unexposed and exposed groups is likely larger than we have found here.

‘To summarise, we found even a single mild traumatic brain injury will predict poor adult functioning.

‘The risk will increase with severity and recurrence and older age at first injury.’

Writing in the journal PLOS Medicine, Dr Sariasian it is important to put the risks in context and remember most people who suffer a TBI won’t experience long-term problems.

For instance, while a head injury increases the odds of premature death, just 1.6 per cent of those with a TBI die by 40.

In an accompanying commentary piece, Sheharyar Raza, a Canadian neuroscientist, said 'the solution is prevention'.

He added: ‘The solution is not to trivialise concussions; neither is it to pursue a risk-free lifestyle because excess sedentary activity can also contribute to poor functioning in adulthood.'

Peter Jenkins, a neurologist at St George’s Hospital, said: ‘In healthcare at the moment, we don’t necessarily recognise these persistent problems.'

Those who had suffered a head injury when they were young were 58 per cent more likely to have left school without any qualifications

He continued: 'We don’t necessarily have the resources available to help deal with those problems and that’s something we need to be aware of.’

Professor Huw Williams, of the Exeter University, said it does not mean we should ban children from playing contact sports.

He added: 'Care is needed, especially in managing a child's return to play, so that they don't get injured again when they are still suffering from an injury, and managing their return to school.

‘We also need to make sure the rules are followed - more than 20 per cent of concussion injuries in rugby appear to happen during foul play.’

Peter McCabe, chief executive of brain injury charity Headway, said: ‘This research is a clear warning signal the physical and psychosocial implications of brain injury can last a lifetime.