In this comprehensive 22-year retrospective analysis of mortality data derived from the CDC WONDER database, notable findings have been discerned, carrying substantial implications for public health policy. Initially, the overall AAMR remained relatively stable from 1999 to 2007 (APC: 0.3, 95% CI: -0.2 to 2.1), followed by a slight non-significant decline from 2007 to 2010 (APC: -1.6, 95% CI: -2.4 to 2.1), and a subsequent significant upward trend from 2010 to 2020 (APC: 1.3, 95% CI: 0.2 to 2.1). This temporal pattern exhibited remarkable consistency across both adult male and female cohorts. Furthermore, a demographic analysis revealed that individuals belonging to the American Indian or Alaska Native racial group and the 85 years and older age cohort exhibited the highest TBI-related AAMRs in comparison to their respective counterparts. Additionally, pronounced regional disparities emerged, with the Southern region displaying the highest TBI-related AAMR, trailed by other regions. Furthermore, nonmetropolitan areas consistently exhibited elevated mortality rates when juxtaposed with their metropolitan counterparts.
Our investigation revealed a total of 1,026,185 TBI-related fatalities over a 22-year period. In comparison to findings from various geographical regions, a study conducted in Seychelles, East Africa, over 30 years (1989–2018), reported a considerably lower count of 327 TBI-related deaths [15]. In the People’s Republic of China, two separate studies covering eight years (2006–2013) and four years (2014–2018) reported 93,793 and 16,169 TBI-related deaths, respectively [16–17]. Additionally, a comprehensive study across 25 European countries in 2012 reported 33,415 TBI-related deaths [24]. Notably, our inquiry also underscores that the US exhibits the highest AAMR of 24.6 concerning TBI when juxtaposed against the aforementioned geographical regions, which ranges from 3-21 [15,16,17,–24]. The U.S. has a higher TBI mortality rate than China and European countries combined at any point in time, which is concerning given that these regions have a larger population. This variation among different economies can be attributed to several contributing factors, including disparities in healthcare infrastructure, socioeconomic differences, distinct safety regulations, variations in transportation systems, culturally influenced practices, discrepancies in preventive strategies, and differing degrees of urbanization [25], but mainly in US it is due to firearm injuries [26,27,28], whereas these are much less frequent in China or Europe [29–30]. Additionally, upon analyzing trends, it has been observed that the AAMR related to TBI continues to rise in subsequent years in the US [3, 4, 11, 31, 32]. In contrast, two separate studies from China [16–17] have shown a gradual decrease in the AAMR for TBI over the years. The higher mortality rates among adults in the US, compared to China, can be attributed to various factors including differences in growth and aging dynamics, an increase in motor vehicle accidents, assault and firearm-related injuries, falls, intentional self-harm, participation in sports and recreational activities, substance abuse, and limitations in timely access to healthcare services [1, 32–33].
Additionally, our investigation underscores a significant gender-based disparity in AAMRs, with males consistently exhibiting considerably higher AAMRs throughout the entire study period. This gender-based distinction aligns with findings reported in analogous studies conducted in other countries [15,16,17, 24]. However, a salient divergence emerges in the temporal trajectory of their AAMRs within our study. Specifically, our analysis reveals a discernible pattern wherein males displayed a declining AAMR trend until 2012, after which a marked and rapid increase occurred. In contrast, females exhibited a similar decreasing trend in AAMRs until 2011, followed by a slight increase in subsequent years, which is in agreement with two separate studies conducted in China [16–17]. In contrast, a study conducted by Abio et al., reported a significant decline in AAMR for men and a slight increase in AAMR for women [15]. The observed difference in our study can be attributed to male biological factors and a predilection for riskier behaviors, resulting in an elevated incidence of road traffic accidents and a higher propensity for involvement in instances of violence and assaults, among the western population compared to eastern parts of the world [34,35,36]. Moreover, the increase in TBI rates from 2011/2012 onward in our study may be influenced by factors such as changes in societal behaviors, including increased substance abuse, higher participation in high-risk activities (e.g., extreme sports), or a greater prevalence of motor vehicle accidents linked to distractions such as mobile phone usage. Additionally, improvements in data collection and reporting practices during this period may have contributed to the observed increase in documented TBI cases.
Moreover, our investigation reveals that the highest AAMRs were notably observed among older adults, specifically those aged 85 years and above, and individuals in the age range of 75–84 years, which aligns with studies conducted in China, and in older adults of the USA [16, 17, 37]. Conversely, research conducted in Seychelles presents a contrasting scenario, where TBI-related deaths are more strongly associated with younger adults compared to their older counterparts [15]. This discrepancy underscores the importance of considering regional and demographic variations in the impact of TBI in terms of age groups, emphasizing that the relationship between TBI and mortality is not universally consistent across different populations and age groups. The factors that collectively contribute to a higher burden of TBI-related mortality in the US among the elder population, include falls, road traffic accidents, health conditions like osteoporosis, elder abuse and generally having a larger aging population are more prominent shared risk factors [1, 11].
Our study identifies significant disparities in AAMRs related to TBIs among different racial groups in the US. Specifically, American Indian or Alaska Native patients have the highest TBI-related AAMRs, followed by White and Black or African American individuals [38–39]. Possibly, these disparities can be hypothesized to stem from various factors, which include socioeconomic disparities, cultural factors, higher rates of alcohol and substance use, variations in healthcare access and quality, and higher rates of violence [39,40,41,42,43]. Addressing these disparities through culturally tailored, multidisciplinary interventions may offer a pathway to mitigate racial disparities in TBI-related mortality among adults [44].
In addition, our study uncovers significant geographic disparities in TBI-related mortality among adults, with the South region of the US experiencing the highest burden. These disparities result from factors such as limited healthcare access and infrastructure, which lead to delayed or inadequate TBI treatment in some areas. Furthermore, the Southern region has exhibited a significantly higher incidence of homicide and suicide cases, approximately 40%, nearly double that of other regions [45]. These elevated rates have played a pivotal role in contributing to the heightened TBI-related mortality rates observed in the South region. Moreover, our findings also show that non-metropolitan areas have a higher TBI-related mortality burden among adults compared to metropolitan areas [45–46]. This is mainly due to limited healthcare access, socioeconomic disparities, and a higher incidence of high-risk activities, exacerbated by the reliance on personal vehicles in nonmetropolitan regions with limited public transportation options [45,46,47,48,49].
Study limitations
Several limitations should be noted. Firstly, reliance on ICD codes and death certificates introduces the risk of misrepresentation or omission of traumatic brain injuries (TBI) as a cause of death. The study lacks access to detailed clinical data, including TBI severity, comorbidities, and specific treatments administered, limiting the investigation into factors contributing to TBI mortality. Additionally, the study covers data from 1999 to 2020 but does not account for potential alterations in TBI diagnosis and reporting standards during this period, potentially affecting the accuracy of observed mortality rates and trends. While the study stratifies data by census regions and urbanization groups, it does not explore more localized geographic variations. Lastly, socioeconomic determinants of health, which can impact healthcare access, are not included in the study.
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