Two new studies — one in veterans and the other in retired football players — add to the mounting evidence linking head injuries to an increased the risk of dementia later in life.
Veterans who had been diagnosed with a brain injury, anything from a concussion to a severe head wound, were more than twice as likely to develop dementia compared to those with no injury to the brain, researchers reported today at the Alzheimer’s Association’ International Conference in Paris.
The results were even more striking in a study of retired football players: 35 percent of the former National Football League players had signs of dementia, which compares to a 13 percent Alzheimer’s rate in the general population.
For the veterans study, researchers reviewed the medical records of 281,540 military personnel age 55 and older who received care at Veterans Administration hospitals from 1997 to 2000 and who had at least one follow-up visit from 2001 to 2007. None of the veterans in the study were diagnosed with dementia at the beginning of the seven year study.
Almost 5,000 of the veterans had been diagnosed with a traumatic brain injury (TBI). Their risk of developing dementia by the end of the study was 15.3 percent. That’s compared to 6.8 percent of those with no TBI diagnosis.
The football player study is a follow-up of earlier research that included a survey of nearly 4,000 retired NFL players in 2001. In 2008, new surveys were sent to the 905 players who were over 50 years old.
Of those who responded to the second survey, 513 had wives who could complete a section of questions addressing the players’ memory and cognition. “We were surprised that 35 percent of [the players] appeared to have significant cognitive problems,” said the new study’s lead researcher, Dr. Christopher Randolph of Loyola University Medical Center in Chicago.
The study results were scary news for Ryan Lamke, 26, a medically retired Marine who lives in suburban Washington, D.C. Lamke suffered TBIs from multiple blast exposures when he served in Iraq in 2005.
“I’m diagnosed as a moderate [TBI], but it feels anything but mild,” said Lamke, who relies on electronic calendars and other gadgets to keep his life organized.
Now a university student, Lamke feels the results of his TBI keenly every time he goes to study. “I have to read for twice as long as my classmates,” he said. “I’ve not found a doctor so far who can give me a true understanding of what’s going to happen 20 or 30 years down the road.”
The two new studies add to rapidly accumulating evidence showing that head injuries, even concussions, can lead to severe consequences many years afterwards, said Dr. Gary Small, director of the University of California, Los Angeles, Longevity Center and author of the forthcoming book, “The Alzheimer’s Prevention Program.”
Some earlier research found a two-fold increased risk of Alzheimer’s associated with head injuries that caused a loss of consciousness lasting an hour or more, Small said. And that risk jumped to 10-fold when people also had a genetic mutation called APOE-e4.
A study that compared soccer players to swimmers found that soccer players performed less well on cognitive tests, Small added.
Scientists believe that each hit to the head, even concussions, causes stretching of the brain’s communication cables, known as axons. When the axons stretch, their inner structure is damaged. Studies have shown that damaged axons can spew out proteins that lead to plaques and tangles in the brain which are known to cause dementia and Alzheimer’s disease.
Studies conducted at the University of Pennsylvania in people who sustained moderate to severe TBIs found that an injury could spark the production of axon clogging proteins in some people. And those brain changes just intensified as the years went by.
That may explain all the deposits of stringy tau protein found in the autopsied brains of football players, Small said. His group has developed a scanner that will highlight tau deposits in living players. The group just scanned their first former NFL player. The hope is that we’ll be able to see what’s going on in these former players’ brains while they’re still alive,” Small said.
The new research in veterans should give us all pause, said Dr. Douglas Smith, a professor of neurosurgery and director of the Penn Center for Brain Injury and Repair.
We’ve all heard about Agent Orange,” he said. "That may pale in comparison to this. We don’t know how many soldiers have been exposed to blasts or what level of brain injury can trigger long term effects. We have to be concerned for years to come about the welfare of our soldiers. They may come home safely, but may not be home safe. This is the injury that keeps on taking.”
Msnbc.com wire services contributed to this report.
Linda Carroll is a health and science writer living in New Jersey. Her work has appeared in The New York Times, Newsday, Health magazine and SmartMoney. She is co-author of the forthcoming book "The Concussion Crisis: Anatomy of a Silent Epidemic."