Ethnic differences in traumatic brain injury

Ethnic differences in different aspects of traumatic brain injury (TBI) are under reported, with over 70% of research studies omitting ethnicity information on their reports [1].

As a result, identifying whether certain ethnicities are more at risk of sustaining a TBI than others can become difficult without this information, as does exploring potential direct or indirect discrimination in access to healthcare, social support, or health research.

What is ethnicity?

To understand the scope of research on ethnicity, we must look closely at the definition of ethnicity adopted in different studies. The Office for National Statistics states that “there is no consensus on what constitutes an ethnic group and membership is something that is self-defined and subjectively meaningful to the person concerned”[2]. In addition, ethnicity and race are two separate concepts.

Race refers to physical characteristics and ethnicity refers to subjective, self-reported characteristics such as culture, customs, and religion [3]. However, the two concepts are often combined into a single category by researchers [4].

This brings lack of clarity to the field and makes understanding the research surrounding brain injury and ethnicity more difficult. Nevertheless, there is a small number of studies that investigated the potential interaction between ethnicity and the prevalence and outcomes of TBI.

Ethnic differences in the prevalence of brain injury

Prevalence is the term used in health research to describe the proportion of a population who is affected by a health condition at a specific time. When searching for research exploring the relationship between ethnicity and the prevalence of TBI we identified six studies which investigated this and all found a difference in prevalence of brain injury between ethnicities, but they differed in the direction of their findings. Furthermore, most of the studies we identified were focused on Traumatic Brain Injury (TBI) and very few investigated brain injuries caused by other mechanisms such as for example Stroke, Encephalitis, or brain tumours, which may reveal a potential gap in the literature. Because of this, we chose to focus primarily on TBI for this article.

One retrospective study by Brenner and colleagues [1] used the United States Census Bureau to create an expected outcome and then compared it to data from the Pennsylvania Trauma System Foundation. In 2010, these authors reported in their study that Black participants had a higher prevalence of TBI compared to the expected outcome, and that Asian, and White participants had lower TBI prevalence than expected. In 2016, this trend repeated, but with White participants having an expected prevalence of TBI.

Cohen-Manheim and colleagues [5] found a higher rate of TBI in the Arab population in Israel in their 2020 study into motorcycle crashes. They suggested that this may have been linked to the likelihood of wearing a helmet, which was seven times less likely among the Arab population compared to the Jewish population in their study. The reason for this difference in helmet use was not explored in the study, but such insights may provide an understanding of different possible approaches to risk reduction, including for example the role of social deprivation, or socio-economic factors. In addition, the study only looked at TBI resulting from motorcycle crashes, and therefore these findings may not apply to other causes of TBI.

Other studies such as Kisser and colleagues [6] found that, amongst young people in the USA, White participants from a low socioeconomic status (SES) were at the highest risk of TBI. However, among older individuals, it was African Americans from low SES who were at the highest risk. These researchers and others have pointed out that low SES is linked to higher risk of TBI regardless of race, which is something that needs further investigation, since it is a common finding in many countries for ethnic minorities to be of lower SES. It should also be noted that Kisser and colleagues used the term “race”, not ethnicity, but this was self-reported potentially making this factor closer to ethnicity.

Outcomes

As well as prevalence, there is evidence indicating inequality between ethnicities in outcomes after TBI. Ethnic minorities have been found to be at a higher risk of death after TBI [7] and differences were also found on other functional outcomes such as dealing with chronic pain [8].

Furthermore, differences have also been found in the way that rehabilitation and treatment are delivered after a TBI, with some studies suggesting that ethnic minorities are less likely to be discharged to inpatient rehabilitation [9] or, when discharged into this setting, to be discharged slower [10].

The reasons for these differences are likely numerous and may involve multiple individual factors, including age and socio-economic differences, which in turn have been found to be linked with experiences of institutional discrimination resulting in health inequalities.

It is also important to note that many of these studies were conducted in the USA, where the system of access to health care is very different from the UK NHS.

What groups have been most studied?

Many of the studies we have identified reported data about Black, White, and Asian participants, although there is research including indigenous populations such as those in the USA [11], Australia, and New Zealand [12]. Some studies have made the distinction between race and ethnicity and collected these data separately.

Brenner and colleagues’ study collected information about race as well as whether people identified as being Hispanic or non-Hispanic, while Miller and colleagues’ study [13] included Hispanic, non-Hispanic white, non-Hispanic black and non-Hispanic other as their studies’ race / ethnicity categories.

However, the way information about race and ethnicity is collected varies depending on the country where studies originate from, and on the demographic diversity of their populations. For example, many of the studies conducted in the USA have looked at differences between White, Black, Asian, and Hispanic communities, but the study in Israel by Cohen-Mannheim and colleagues focused on differences between Arab and Jewish populations.

In the UK, the Office for National Statistics recommends the use of 18 ethnic groups, which can be sub-divided in five main categories, in social surveys, but these are not universal and even differ slightly depending on whether data are collected in England, Scotland, Wales, or Northern Ireland. This may be for the best as using universal measures for ethnicity could be impractical due to international demographic differences.

We were unable to find any UK studies that investigated TBI, therefore future research on the prevalence and outcomes of TBI in the UK should include data on ethnicity to evaluate to what extent ethnicity is linked to health inequalities and ensure that any data investigated is representative of all groups in the population.

Conclusion

The current research literature reports some differences between ethnicities on the prevalence and outcomes of TBI, but our understanding of where these differences stem from is still limited. However, some studies have indicated the presence of health inequalities.

It is therefore important to capture ethnicity data in future research, for gaining a better understanding of the factors underpinning these health inequalities and learn how these may be prevented or counteracted.