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Traumatic brain injury increases dementia risk

Rahul Raj

Sustaining a moderate-to-severe traumatic brain injury is associated with an increased risk for dementia in the future, according to a study published in PLoS Medicine. 

“Traumatic brain injury (TBI) is a globally increasing health care problem, affecting persons of all ages,” Rahul Raj, MD, PhD, from the University of Helsinki in Finland, and colleagues wrote. “Following the early phases of TBI, patients face a significant risk of long-term disability and neurological morbidity. Previous epidemiological studies have found an association between history of TBI and risk for future neurodegenerative disease (NDD) (a concept including dementia, Parkinson’s disease, and amyotrophic lateral sclerosis), but the results have been conflicting and few studies have focused on the working-age population.”

Raj and colleagues conducted a comprehensive nationwide study in Finland to investigate the risk of NDD after moderate-to-severe TBI in adults aged between 18 and 65 years. They used the Finnish Care Register to identify patients who were hospitalized between 1987 and 2014 for TBI without a diagnosis of NDD at baseline. The risk for hospitalization with NDD was compared between individuals who were hospitalized with moderate-to-severe TBI (n = 19,936) vs. those with mild TBI (n = 20,703). Moderate-to-severe TBI was defined as having intracranial lesions, while mild TBI was defined as lacking intracranial lesions. The researchers recorded follow-up NDD diagnoses, including dementia, Parkinson’s disease and amyotrophic lateral sclerosis from one year after the TBI occurred and continuing until the end of 2014. They adjusted for age, sex, education and socioeconomic group using a Cox proportional hazards model.

“In Finland, we have tax-funded free health care for everybody and extremely high-quality nationwide health care registries, which makes Finland an optimal location to conduct studies like this,” Raj told Healio Internal Medicine.

Among individuals with moderate-to-severe TBI, 3.5% developed NDD, compared with 1.6% of individuals with mild TBI. Adjusted analysis indicated an association between moderate-to-severe TBI and an increased risk for NDD (HR = 1.8; 95% CI, 1.6-2.1). The risk was highest among individuals whose injury occurred in middle age (HR = 2.7 for age 41-50 years; HR = 2 for 51-60 years). Moderate-to-severe TBI increased the risk for dementia (HR = 1.9, 95% CI, 1.6-2.2), but not Parkinson’s disease or amyotrophic lateral sclerosis.

“Our results suggest that in working-aged persons, moderate-to-severe TBI increases the risk for developing NDD later in life... The effect of covariates, such as comorbidities, lifestyle factors and genetic factors, should be accounted for in future etiological studies, as well as studies to improve diagnostics and prevention of dementia after TBI,” Raj and colleagues concluded.

The researchers noted that the study contained several limitations including the fact that the database only included hospital patients and the potential for misdiagnosis of TBI, miscoding and unmeasured confounders.

“TBI itself might not be the reason for dementia but rather a triggering factor for already genetically susceptible individuals,” Raj said in an interview. “Yet, the study highlights the need for aggressive treatment of dementia risk factors after sustaining a brain injury.”

“For clinicians seeing persons with a history of TBI, it is important to minimize other risk factors for dementia, such as high BP, high levels of cholesterol, diabetes, tobacco smoking and alcohol consumption,” he said. – by Alaina Tedesco

Disclosure: Raj reports receiving personal research grants from Svenska Kulturfonden among several other institutions. Please see full study for complete list of relevant financial disclosures.