Data from the 2014 North Carolina Behavioral Risk Factor Surveillance System (BRFSS), an annual representative telephone survey of non-institutionalised adults 18 years and older regarding their health-related conditions and risk behaviours, were used.²⁵ Trained survey administrators identified respondents using random-digit-dialling methods, conducting surveys via landline and cell phone interviews. The BRFSS employs a complex sampling design adjusting respondent data to known proportions of age, race, ethnicity and sex within the state. The overall response rate was 37.5%; calculated using standards set by the American Association of Public Opinion Research Response Rate formula.²⁶²⁷ All respondents completed the core BRFSS items. In 2014, North Carolina employed two survey versions that included optional and state-added modules. ABI and ACE modules were state-added questions in 2014, the most recent survey year with both modules of interest. Therefore, the cross-sectional study sample comprised 3454 participants who completed questionnaire Version 1, which included both ABI and ACEs modules.

Descriptive statistics and prevalence estimates for ACEs, ABI and TBI were individually calculated. Weighted frequencies of demographic characteristics among participants who reported an ABI and those who did not report an ABI were examined; percentages and 95% CI are reported. Four sets of multivariable logistic regression models were used to first determine the relationship between ACEs and ABI, and second, to determine the relationship between ACEs and TBI. In the first set of regression models, self-reported ABI was the outcome variable, and cumulative ACE score was the predictor of interest after controlling for gender, age, race/ethnicity and self-reported employment. The second models were similar, except with TBI as the outcome variable controlling for gender, age, race/ethnicity and self-reported income. In the third set of models, multivariable logistic regression assessed the bivariate associations between each of the eight ACE types and cumulative ACE score with ABI as the outcome variable, controlling for the same sociodemographic variables. The final set of models were similarly constructed, except with TBI as the outcome. All models were specified using the appropriate survey weights to account for the complex sampling design used by the BRFSS. Adjusted ORs with 95% CIs are reported. Analyses were conducted using SAS, V.9.4.²⁸

Among the 3454 adult respondents, 201 individuals reported an ABI and 107 (52%) individuals reported a TBI that limited their activities for more than a week. Approximately 25.37% were caused by a motor vehicle crash, and 22.53% were caused by a health problem (table 1). The weighted distribution among the sample who reported experiencing an ABI was mostly male (57.22%), 45 years or older (62.39%), white (77.00%) and had an income less than US$25 000 (55.93%). Around 50.90% of respondents reporting an ABI had at least some college education, and 38.28% were employed. Demographic characteristics by ABI status are provided in table 2.

This study examined the relationship between ACEs and ABI that limited a respondent’s activities for more than a week. Data from the 2014 North Carolina BRFSS revealed that ACEs were prevalent, and many ACEs were significantly associated with ABI and TBI. Over half of respondents reporting an ABI stated it was caused by a health problem (ie, tumour, stroke) or a motor vehicle crash, followed by falls, sports-related event and other/ multiple causes. Our findings are similar to other statistics using TBI-related emergency department visits that report an elevated risk of TBI among men, persons age 75 and older and TBIs caused by a fall or motor vehicle crash.²¹

Compared with respondents with zero ACEs, the odds of reporting ABI by individuals with three or more ACEs increased by 255%, while individuals with four or more ACEs had an odds increase by 351%. In addition, associations between TBI and ACE score showed similar effects; compared with respondents with zero ACEs, the odds of reporting a TBI by individuals with three or more ACEs increased by 416%, while individuals with four or more ACEs had an odds increase by 339%. Although these results are novel in relation to ABI/TBI within a general population, these findings align with previous studies in female children, adults with severe mental illness and adult homeless population linking ACEs to risk for brain injury.^29–31 Data on individual ACEs and their association with ABI and TBI were provided. Findings revealed that five out of the eight ACEs examined were significantly associated with ABI, while four out of the eight ACEs (ie, sexual abuse, physical abuse, household mental illness and an incarcerated household member) were significantly associated with TBI. ACEs that were significantly associated with ABI, but not TBI, had a similar effect size (emotional abuse: AOR=1.64 for ABI, AOR=1.80 for TBI; household substance abuse : AOR=1.86 for ABI, AOR=1.74 for TBI). However, the 95% CI around TBI for all associations are wider due to a higher incidence of ABIs than TBIs that may account for non-significance for these individual ACEs, despite similar effect sizes.

It is important for healthcare providers to consider the relationship between early adversity and the risk of experiencing ABI or TBI. Although many causes of TBI are due to accidental events such as falls and health-related problems, additional causes are due to risk behaviours, motor vehicle crashes and violence. Studies suggest that maltreated children can experience reduced executive functioning and demonstrate hypervigilant responses to perceived threats.¹⁹ Altered brain architecture in response to toxic stress explains in part the associations between ACEs and impulse control, emotional regulation and other cognitive challenges which may contribute to an increased risk of certain causes of TBI (ie, mother vehicle crashes, intentional self-harm).^17–19 Early adversity in childhood increases engagement in substance use⁸ that may increase the risk for TBI as a significant proportion of those that sustain a TBI (25%) test positive for alcohol or illicit drugs.⁸³² Additionally, multiple studies have identified a strong link between early adversity and later victimisation¹²¹³ that may result in an injury such as a TBI. As such, comprehensive TBI prevention could include efforts to reduce exposure to early adversity, a known risk factor for these precursors to TBI.

While this analysis has focused on the relationship between ACEs and brain injury, the experience of a brain injury in childhood could be conceptualised as an additional, unmeasured ACE. Beyond the potential psychological trauma due to the circumstances of experiencing a brain injury, a brain injury in childhood can significantly alter the developmental trajectory of a child, particularly when it occurs during critical periods of brain development.³³ Often the effects of a brain injury are not immediately apparent and manifest at a later age when a new developmental challenge is impacted by a previously unknown deficit.³⁴ Beyond the potential for lifelong disability, brain injuries have been shown to affect key cognitive (eg, self-regulation, executive function), academic (eg, lower grades and educational attainment) and social-behavioural (social information processing, social adjustment) skills that can lead to difficulties in adulthood.³⁴ These difficulties can range from subtle to significant, depending on the severity of the brain injury, and can include underemployment, legal problems and incarceration.³⁵ While there is a robust literature on the short-term and intermediate-term health impacts of childhood TBI, there is a need for more longitudinal research establishing that brain injury experienced in childhood is associated with longer-term adult morbidity and mortality.³⁵

This study has several limitations. First, a clear definition of ABI or TBI was not stated before respondents were given the module, relying on an individual’s awareness about the full range of signs and symptoms indicative of a brain injury. For example, many individuals believe a loss of consciousness (occuring in less than 25% of brain injuries) needs to happen to have a brain injury.³⁶ Studies have found that providing a definition that lists all symptoms of ABI or concussion increases estimates significantly,³⁶ therefore, ABI among the sample could be an underestimate. Second, the ABI questions may be biassed toward more severe brain injuries due to: (1) asking about lifetime ABIs which could increase the likelihood of forgetting less severe brain injuries and (2) inclusion of the phrase “that limited their activities for more than a week,” as this likely led respondents to exclude many mild ABIs they experienced. Third, some respondents who reported an ABI did not report a cause, therefore whether it was a TBI could not be determined. Consequently, some number of TBIs were not classified as such in the TBI-specific analyses. Fourth, due to the nature of telephone surveys, the results may underestimate the level of health risk in the population due to excluding individuals who do not have access to telephones. Fifth, declining response rates among telephone surveys should be noted, as non-response bias may affect estimates. Finally, the study did not assess when ACEs or ABI occurred; therefore, some respondents may have experienced an ABI before experiencing early adversity or may have experienced the ABI as a result of early adversity (ie, physical abuse). Due to the retrospective and cross-sectional nature of the data, temporality and causality cannot be established. However, previous studies have established the general validity of self-reported childhood adversity.³⁷ Furthermore, ACEs measured on the BRFSS do not encompass the entire spectrum of early adversities that a child may experience nor do the items measure critical dimensions of exposure (ie, age of onset or severity), which can significantly moderate the impact of ACEs on health and well-being.³⁸

This paper highlights the link between ACEs and ABI, including TBI. Prevention of early adversity may help in reducing the incidence of ABIs and TBIs, preventing future unintentional injuries. Assuring the conditions that prevent early adversities, like ACEs, from occurring in the first place, comprehensive approaches that promote protective factors and minimise risk factors are critical. Strategies that change social norms, provide quality childcare and education, improve economic conditions for families and intervene to lessen harm and prevent future risk can help children to achieve their optimal health.³⁹ To improve outcomes for those who have experienced adversity, healthcare providers who are informed about ACEs and equipped with treatment options and resources could reduce the number of children and adults that need treatment and care further downstream. By assuring that all children have access to safe, stable, nurturing relationships and environments,⁴⁰ healthcare providers and communities can prevent ACEs and alleviate the impact of ACEs on health and well-being, including injury and health outcomes.