Risk of Dementia After Hospitalization Due to Traumatic Brain Injury A Longitudinal Population-Based Study

Background and Objectives Traumatic brain injury (TBI) is considered a potential modifiable dementia risk factor. We aimed to determine whether TBI actually increases the risk of dementia when adjusting for other relevant dementia risk factors. Methods This was a national prospective longitudinal cohort study that included random and representative population samples from different parts of Finland of patients 25 through 64 years of age from 1992 to 2012. Major TBI was defined as a diagnosis of traumatic intracranial hemorrhage and hospital length of stay (LOS) >= 3 days and minor TBI was defined as a diagnosis of concussion and hospital LOS <= 1 day. Dementia was defined as any first hospital contact with a diagnosis of dementia, first use of an antidementia drug, or dementia as an underlying or contributing cause of death. Follow-up was until death or end of 2017. Results Of 31,909 participants, 288 were hospitalized due to a major TBI and 406 were hospitalized due to a minor TBI. There was a total of 976 incident dementia cases during a median follow-up of 15.8 years. After adjusting for age and sex, hospitalization due to major TBI (hazard ratio [HR] 1.51, 95% CI 1.03-2.22), but not minor TBI, increased the risk of dementia. After additional adjustment for educational status, smoking status, alcohol consumption, physical activity, and hypertension, the association between major TBI and dementia weakened (HR 1.30, 95% CI 0.86-1.97). The risk factors most strongly attenuating the association between major TBI and dementia were alcohol consumption and physical activity. Discussion There was an association between hospitalized major TBI and incident dementia. The association was diluted after adjusting for confounders, especially alcohol consumption and physical activity. Hospitalization due to minor TBI was not associated with an increased risk of dementia. Classification of Evidence This study provides Class I evidence that major TBI is associated with incident dementia.