New research has found that a serious head injury experienced at some point in your life may significantly increase your risk of developing dementia. According to the report, head injuries that cause lesions in the brain and require a person to stay in a hospital for three days or more can double a person’s dementia risk, but this risk is greatest when the head injury is sustained during midlife.

The study found that people who experience serious head injuries that require hospitalization are 90 percent more likely to develop non-Alzheimer’s dementia than those with with more mild head injuries that didn’t lead to brain lesions, New Scientist reported. Results of the study, which was based on 40,000 people who had sustained some type of head injury in their lifetime, found that 696 of the 19,936 people with severe head injuries went on to develop dementia. This was compared to only 326 of the 20,703 people with milder injuries going on to develop dementia. What’s more, dementia risk was highest in people who sustained severe, traumatic head injuries between the ages of 41 and 50.

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"It seems that the risk for developing dementia after TBI is the highest among middle-aged men. The more severe the TBI, the higher the risk for subsequent dementia, study co-author Rahul Raj explained in a recent statement on ScienceDaily. “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.”

While it’s not clear why this association exists, the team suggest that a head injury may be the catalyst for the brain process that eventually leads to dementia. The same study, however, did not find a link between head injuries and increased risk of ALS or Parkinson’s disease.

According to the Mayo Clinic, TBIs usually result from a blow to the head or the body, but can also be a result of something penetrating the skull. The injury can cause bruising, bleeding, and temporary dysfunction of brain cells. It is extremely serious and those who survive will often experience long-term handicaps from their injuries.

This is not the first time head injuries were noted for their danger. For example, about one in three individuals who experience a form of traumatic brain injury will die from it, and half of the survivors experience long-term disabilities from their injuries. The team hope their findings may inform better treatment for head injury patients.

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

Source: Raj R, Kaprio J, Korja M, et al. Risk of hospitalization with neurodegenerative disease after moderate-to-severe traumatic brain injury in the working-age population: A retrospective cohort study using the Finnish national health registries. PLOS Medicine . 2017

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