Middle-aged adults who experience a moderate to severe traumatic brain injury may be at significantly greater risk of developing dementia in later life, a new study suggests.

a brain wrapped in a bandageShare on Pinterest
Researchers have linked moderate to severe TBI with greater risk of dementia.

Traumatic brain injury (TBI) is defined as a blow, bump, or jolt to the head that causes damage to the brain.

Symptoms of TBI may include headache, blurry vision, fatigue, and thinking problems, such as difficulty concentrating or remembering new information. In severe cases, TBI may lead to long-term deficits in cognitive and motor functions.

According to the Centers for Disease Control and Prevention (CDC), in 2013, TBI played a role in more than 2.5 million emergency department visits and 282,000 hospitalizations in the United States.

What is more, around 5.3 million people in the U.S. are living with a disability as a result of TBI.

Previous research has suggested a link between a history of TBI and increased risk of neurodegenerative diseases, including dementia, Parkinson's disease, and amyotrophic lateral sclerosis (ALS).

Study co-author Dr. Rahul Raj, of the University of Helsinki in Finland, and colleagues sought to investigate this association further.

The researchers recently published their findings in the journal PLOS Medicine.

Middle-aged men at greatest risk

The study included the data of 40,639 Finnish adults aged between 18 and 65 years, all of whom had been hospitalized for either a mild or moderate to severe TBI between 1986 and 2014.

Using the Finnish Care Register for Health Care, the researchers pinpointed which participants had been hospitalized for dementia, Parkinson's disease, or ALS after their TBI.

The data revealed that 3.5 percent of subjects who had a moderate to severe TBI went on to receive a dementia diagnosis, compared with 1.6 percent of subjects who had a mild TBI.

When the team accounted for numerous confounding factors - including age, sex, education, and socioeconomic status - the researchers found that participants who experienced a moderate to severe TBI were 90 percent more likely to be diagnosed with dementia than those who had a mild TBI.

Dementia risk was highest for adults whose moderate to severe TBI occurred between the ages of 41 and 50, the team reports, and middle-aged men were more likely to develop the neurodegenerative disease than middle-aged women.

"It seems that the risk for developing dementia after TBI is the highest among middle-aged men," notes Dr. Raj.

"The more severe the TBI, the higher the risk for subsequent dementia. While previous studies have identified good education and high socioeconomic status as protective factors against dementia, we did not discover a similar effect among TBI survivors."

Dr. Rahul Raj

The researchers found no link between TBI and increased risk of Parkinson's or ALS.

TBI patients need long-term monitoring

Dementia has become one of the biggest health burdens of our time, affecting more than 47 million people worldwide. By 2030, this number is expected to rise to 75 million.

Dr. Raj and colleagues believe that their findings indicate that TBI sparks a process that leads to dementia later in life, but further studies are needed to pinpoint the exact mechanisms behind this process.

In the meantime, the team hopes that the study helps to encourage longer-term monitoring of adults who have a TBI, in both clinical and research settings.

"It is a tragedy when an adult of working age develops dementia after recovering from a brain injury, not just for the patient and their families, but it also negatively impacts the whole society," says Dr. Raj.

"In the future, it will be increasingly important to prevent TBIs and to develop rehabilitation and long-term monitoring for TBI patients."

Learn how medication for post-traumatic stress disorder may raise the risk of dementia.