The link between head injuries and dementia has just grown stronger: A new study of 2.8 million people in Denmark, including those who had and had not experienced a traumatic brain injury (TBI) in their lifetime, found that those with at least one TBI had a 24 percent increased risk of dementia, on average. The average diagnosis age was 81.
TBIs occur whenever an external force causes physical damage to the brain, and they range from the mild and moderate to the severe. The dementia risk was slightly higher for severe TBIs. As expected, the number of TBIs is positively correlated with risk.
The NHS emphasize that this is about increased risk after receiving a TBI, however. The absolute risk of developing dementia throughout your lifetime is very small. Of this sample, only 5.1 percent of those that had a TBI developed dementia, compared to 4.5 percent of non-TBI people that also developed dementia.
Writing in The Lancet: Psychiatry, the team explain how they tracked the health of these people between 1999 and 2013, and marked off those who were diagnosed with dementia in that period. They adjusted for other health factors to try and rule out confounding variables that may have significantly contributed to the dementia diagnosis.
The researchers – from the University of Washington, Copenhagen University Hospital, and Aarhus University Hospital – also found that getting a TBI in your 30s is associated with a 37 percent increased risk, compared to a 2 percent increased risk for those in their 50s. A TBI in your 20s is associated with a 63 percent increased risk.
Professor Jonathan Schott, a neurologist at University College London (UCL) not involved in the study, said that this enormous sample size-based cohort study “provides perhaps the best evidence yet that traumatic brain injury is a risk factor for dementia.”