Concussions drastically increase one's risk of developing Alzheimer's disease, new research shows.

Scans performed on wounded war veterans have revealed the clearest evidence to date that mild head injuries wear down the defenses of brain regions vulnerable to the disease.

Until now, doctors considered severe traumatic brain injury a key risk factor for developing neurodegenerative diseases such as late-onset Alzheimer's.

But this is the first study to prove even lower impact like concussion could have life-threatening consequences.

The findings come amid a surge in studies investigating the prevalence of concussions in the National Football League and high school sports.

A study has revealed the clearest evidence to date that mild head injuries like concussions wear down the defenses of Alzheimer's 'ground zero' brain regions

The new study, carried out at the Boston University School of Medicine (BUSM), involved 160 Iraq and Afghanistan war veterans, some who had suffered one or more concussions and some who had never had a concussion.

Using MRI imaging, the thickness of their cerebral cortex was measured in seven regions that are the first to show atrophy in Alzheimer's disease, as well as seven control regions.

'We found that having a concussion was associated with lower cortical thickness in brain regions that are the first to be affected in Alzheimer's disease,' explained lead author Dr Jasmeet Hayes, PhD, assistant professor of psychiatry at BUSM..

'Our results suggest that when combined with genetic factors, concussions may be associated with accelerated cortical thickness and memory decline in Alzheimer's disease relevant areas.'

Of particular note was that these brain abnormalities were found in a relatively young group, with the average age being 32 years old.

'These findings show promise for detecting the influence of concussion on neurodegeneration early in one's lifetime,' said Dr Hayes, who is also research psychologist at the National Center for PTSD, VA Boston Healthcare System.

'Thus it is important to document the occurrence and subsequent symptoms of a concussion, even if the person reports only having their 'bell rung' and is able to shake it off fairly quickly.

'Given that when combined with factors such as genetics, the concussion may produce negative long-term health consequences.'

The researchers hope that others can build upon these findings to find the precise concussion-related mechanisms that accelerate the onset of neurodegenerative diseases such as Alzheimer's disease, chronic traumatic encephalopathy, Parkinson's and others.

'Treatments may then one day be developed to target those mechanisms and delay the onset of neurodegenerative pathology,' she added.