A single serious head injury can lead to brain damage decades later even if the patient apparently makes a complete recovery in the short term, researchers at Imperial College London have found.

Their study used a new positron emission tomography (PET) imaging technique to look at the biochemistry of 21 men and women who had suffered one traumatic brain injury (TBI) through an accident or assault between 18 and 35 years previously. They were compared with a demographically and educationally matched control group of 11 people with no history of such injury.

The results, published in Science Translational Medicine, showed that TBI victims were much more likely to have high levels of harmful tau protein in the brain than the control group or the general population. Scientists increasingly see a build-up of tau as a key indicator of developing neurodegeneration, which is likely to be followed by Alzheimer’s or another form of dementia. The TBI group, who were between 29 and 72 years old, also performed worse than the controls on memory and cognitive tests.