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A research team co-led by Simon Fraser University (SFU) Psychology Professor Allen Thornton has found that socially and economically vulnerable persons suffer from unprecedently high rates of traumatic brain injury (TBI), compared to other populations.

Thornton is an Investigator with the B.C. Mental Health and Substance Use Services Research Institute and heads SFU’s Human Neuropsychology Laboratory, which trains clinical scientists. The team at the lab investigates neuropsychological models of brain function with an interest in what factors alter cognitive and emotional functioning. 

Thornton and colleagues have been investigating TBI in vulnerably housed, marginalized persons. To spearhead their recent TBI work, the team published a meta-analysis in Lancet Public Health that estimated lifetime TBI occurrence of over 50 per cent in homeless and vulnerably housed samples.

Their subsequent prospective work, entitled Traumatic brain injury in precariously housed persons: Incidence and risks, clarified the gravity of the situation. The study reported in Lancet’s EClinicalMedicine, prospectively followed 326 precariously housed persons residing in Vancouver’s Downtown Eastside (DTES) for one year with monthly assessments.

This was the most in-depth longitudinal investigation of TBI in such a sample. An alarming annual TBI incidence proportion of 31 per cent was observed. Past TBI histories were associated with increased odds for new TBI. Poorer social and occupational role functioning conveyed higher odds as well.

For the study, Thornton supervised the first author and SFU Psychology PhD alumnus Tiffany O’Connor, who is now a clinical neuropsychologist at Hamilton Health Sciences. The work was conducted in collaboration with UBC psychiatry professors William Panenka and William Honer, SFU psychology professor Wendy Loken Thornton, and statistics and actuarial science professor X. Joan Hu.

We spoke with Professor Thornton about his research.

Your studies have found rates of TBI in vulnerably housed persons that appear to be magnitudes higher than that observed in the general population and in athlete samples. Why is this type of injury so common? 

Persons living in unstable, impoverished housing endure compromised safety, victimization, isolation, stigma, and barriers to accessing essential services. These conditions put individuals at risk for substance use as well as for TBI. Complex cycles emerge, with worsening health and declining functioning for which TBI appears to be part. The patterns may well be recursive and bidirectional. For instance, we found that both poorer role functioning and past TBI histories increased the odds for new TBIs, potentially portending a common route to progressively acquired disability entailing neurocognitive loss and neurodegeneration.

What made you want to study TBI prevalence in this population in particular?

Although TBI has been of research interest for decades, investigations have primarily studied relatively healthy premorbid brains from persons living relatively privileged lives. However, compared to other identifiable groups, such as athletes, who have received considerable attention in the TBI literature, the neurologically vulnerable persons we are now investigating may suffer the costliest consequences from TBI. This is a pressing matter with implications for underserviced persons who suffer a myriad of challenges. Since TBIs can be prevented, we have opportunities to potentially mitigate disability.

Based on your research as a neuroscientist, does suffering a concussion or TBI result in other long-term health challenges?

Multiple repetitive TBIs, even mild TBIs (i.e., concussions), can cause decline in neurocognition and other aspects of daily and emotional functioning. But some persons who are marginalized may be particularly vulnerable to such decline, which is arguably the most important concern. In persons on the DTES we have reported very high rates of cerebrovascular disease with associated neurocognitive impairment in articles published in The Journal of the American Heart Association and the journal Stroke. Cerebrovascular disease alone contributes to neurodegeneration and persons suffering from such are apt to be particularly vulnerable to the negative impacts of TBI. We intend to investigate these relationships further. 

What are your recommendations for those in precarious housing on the DTES? For health care and service providers?

The most urgent implication of the work is in educating stakeholders, including our participants, about the gravity of TBIs within this context. Stakeholders often anticipate a high TBI incidence, but not the remarkable magnitude we observed with rigorous methods.  People also fail to recognize the potential neuropsychological implications. The concept of brain reserve applies here. For people with reduced reserve due to existing cerebrovascular disorders and/or past brain injuries, TBIs are likely to have an inordinate impact and might be central to acquired disability.

This research was funded by: Canadian Institutes of Health Research, Natural Sciences and Engineering Research Council of Canada, William and Ada Isabelle Steel Research Fund, Simon Fraser University Vice-President Research Undergraduate Student Research Award and Simon Fraser University's Psychology Department Research Grant.

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