People who have been hospitalized for a major traumatic brain injury (TBI) may have a higher risk of developing dementia when compared to people who do not have a TBI, according to a new study. Major TBI was defined as having bleeding in the brain and a hospital stay of three or more days. Researchers did not find an increased risk for people who had minor TBI, which was defined as a concussion with no more than a one-day hospital stay.