Brain injuries are bad no matter what age they occur, but a new study is suggesting that getting a mild concussion after the age of 65 increases an individual's risk of getting dementia.

According to lead author Dr. Raquel Gardner, clinical research fellow at the San Francisco Veterans Affairs Medical Center, the results of the study were surprising because it suggested that older brains may be particularly vulnerable to injuries regardless of the severity.

Another way of looking at it is that younger brains may just be more resilient when it comes to mild traumatic brain injuries or may take a longer time in showing dementia symptoms.

Gardner explained that most patients and doctors understand that falls are dangerous, and this study points out that preventing falls may also be an effective way of deterring dementia. It did not, however, show how exactly brain injuries can develop dementia.

Earlier studies have proven that traumatic injuries to the brain early in life increases risks of dementia developing, but establishing whether or not late-life injuries pose the same risks has been more difficult.

Researchers tracked close to 52,000 emergency room visits between 2005 and 2011 in California. All subjects suffered various types of traumatic injuries in 2005 or 2006 and were aged over 55.

Less than six percent of non-brain injuries developed dementia, while over eight percent of those with mild to moderate traumatic brain injuries did. These results were for patients 55 years old and above. By the time they reach at least 65 years old, even mild injury to the brain already increases dementia risk.

"If a person falls and gets a traumatic brain injury, then they may be 26 percent more likely to get dementia than if they had fallen and broken their arm or leg," said Gardner. As for those who suffered more than one traumatic injury to the brain, dementia risk more than doubles.

The study does have a few limitations, though. For starters, it didn't factor in family history, other head injuries and prior illnesses. It also didn't identify the type of dementia that a patient developed.

"Does traumatic brain injury just remove a chunk of brain function and then cause a person to show earlier signs of the dementia that they were going to get anyway regardless of the injury? Does traumatic brain injury actually cause or accelerate degeneration of the brain?" Gardner asked. These issues will require further research.

The study was published in the journal JAMA Neurology.

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