A team at the U.S. National Institute on Ageing (NIA) and Duke University in North Carolina has been studying correlations between head injuries in US Army veterans and their later development of Alzheimers.

“We found that head injury in early adult life was associated with increased risk of Alzheimer’s disease and dementia in late life, and that this risk increased with the severity of the injury,” However they also cautioned that the study does not show that injuries directly cause Alzheimer’s.

The exact mechanics of any link will be the focus of continued research, but in eventually fatal head injuries pathologists found traces of amyloid – the building block of the “plaques” that cause Alzheimers – forming within a few days or weeks of the head injury. There is specualtion that amyloid and other chemicals working to heal the brain can sometimes kill off apparrently healthy cells.

Obviously the 50 year gap betweeen some of the injuries (traced through Army medical records) and the appearance of Alzheimers means a whole host of other factors could be involved but the correlation – double disease risk in mild head injuries, quadruple risk with severe injuries – is significant enough to provide another reason to keep that helmet on whenever you ride.