Editors' ChoiceTraumatic Brain Injury

Exploring the Link Between Traumatic Brain Injury and Dementia

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Science Translational Medicine  05 Nov 2014:
Vol. 6, Issue 261, pp. 261ec191
DOI: 10.1126/scitranslmed.aaa1532

The literature contains conflicting evidence about the effect of traumatic brain injury (TBI) on the risk of subsequent dementia. Gardner et al. now report the results of a carefully designed experiment that avoids a previous experimental problem: Patients with TBI also have characteristics that increase their risk for dementia. To get around this confounder, the authors compared patients with TBI to a particularly appropriate control group: patients with trauma but not TBI (nonbrain trauma). Patients (55 years and older) were included if they had a diagnosis of TBI or nonbrain trauma during an emergency department or inpatient visit in 2005 or 2006. The authors hypothesized that the risk for a dementia diagnosis in a subsequent visit would increase with age and TBI severity, after controlling for confounders.

Approximately 30% of the 164,661 trauma patients had TBI. A total of 10,971 (6.7%) patients were diagnosed with dementia during the follow-up period. They found that TBI was in fact associated with a dementia diagnosis, with a hazard ratio of 1.26 (95% confidence interval 1.21 to 1.31). (Moderate to severe TBI was associated with increased risk of dementia across all ages, while mild TBI was associated with increased risk only in patients aged 65 to 74 years.)

Although this study used a retrospective design and an administrative database with limited clinical data, these results are the most suggestive to date that experiencing TBI predisposes at least some people to dementia.

R. C. Gardner et al., Dementia risk after traumatic brain injury vs nonbrain trauma: The role of age and severity. JAMA Neurol. 10.1001/jamaneurol.2014.2668 (2014). [Full Text]

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