Prevalence of Traumatic Brain Injury Among Trauma Patients in Ethiopia: Systematic Review and Meta-Analysis

Background: Traumatic brain injury (TBI) is a common cause of mortality and disability in young age populations, particularly in children and adolescents. The objective of this systematic review and metaanalysis was to assess the prevalence of TBI among trauma patients in Ethiopia. Methods: A three-stage search strategy was conducted on PubMed/Medline, Science Direct and African Journals Online, and a grey literature search was conducted on Google Scholar. Data were analyzed with R version 3.6.1. Results: The pooled prevalence of TBI in Ethiopia was 20% (95% confidence interval (CI), 11–32). Subgroup analysis revealed that road traffic accident was the commonest mechanism of injury in Ethiopia at 21% (95% IC, 15– 30), next was assault at 18% (95% CI, 5–48). Conclusion: This review shows a high prevalence of TBI among trauma patients in Ethiopia when compared with continental and global reports. Policymakers and stakeholders should work on regulatory laws on transportation; pre-hospital emergency medical care system is also in high demand. Protocol registration: CRD42020146643.


Introduction
Head injury is defined as any trauma to the head resulting from external mechanical force, such as rapid acceleration or deceleration, impact or penetration (1). The Centers for Disease Control and Prevention defines traumatic brain injury (TBI) as a disruption in the normal function of the brain that can be caused by a bump, blow, or jolt to the head, or a penetrating head injury (2). Head injury is a common cause of mortality and disability in the young age population, particularly in children and adolescents (1). Among all trauma-related injuries, head injury is considered the greatest contributor to death and disability globally (3). In addition, besides the impact on the individual, TBI can negatively affect families, communities, and the economy of the country through loss of productive age groups and treatment costs (4). It is estimated that in the USA about 5.3 million people are living with a TBI-related disability (5), and 7.7 million people in the European Union who have experienced TBI have disabilities (6). The World Health Organization (WHO) estimates that each year more than 10 million people in the world sustain TBI, resulting in death or severe disability (7).
The report on the Global burden of disease study shows there were 27.08 million new cases of TBI in 2016. The report also revealed that TBI caused 8.1 million years of life lived with disability. Sub-Saharan Africa had 2.9 million new cases of TBI, equivalent to 360 per 100,000 population. The report also showed that Ethiopia accounted for 659 (624-703) TBI cases per 100,000 population, roughly representing 10.8% of Sub-Saharan Africa and 28% of eastern Sub-Saharan Africa TBI cases (3). The incidence of TBI globally is rising, owing mainly to injuries associated with increases in population density and increased use of motor vehicles, particularly in middle-and low-income countries (8). Globally, road traffic accidents are responsible for more than 50 million injuries every year, with about 1.2 million ending in death (3,9,10). Indeed, many TBIs are the result of motor-related accidents, but the pattern of injury varies across regions: in high-income countries, individuals with TBI are generally motor vehicle occupants, whereas in middle-and low-income countries patients with TBI are often vulnerable road-traffic users such as pedestrians, cyclists, and motorcyclists. Increased motorization combined with inadequate traffic education and slow implementation of traffic safety regulations are the main causes of the increasing incidence of TBI in low-and middle-income countries (11). The prevalence of TBI among trauma patients in Ethiopia varied from town to town. A study conducted at Addis Ababa Emergency Center, Tikur Anbessa specialized hospital, showed that among 204 head injury patients enrolled in the study, 41% of injuries occurred from a road traffic accident and 21 patients died (10.3%) (12). Another study in Myungsun Christian Medical Center had a 24.9% prevalence of head injury among trauma patients visiting the adult emergency department (ED): road traffic accident was the leading cause of head injury (43.5%), next was fall accident 35.8% (13). A study done at Jimma University Teaching Hospital showed prevalence of head injury of 3.69% among patients admitted to adult ED, interpersonal violence accounted for 54.1% and road traffic accidents 31.1% (14). Another study in Tikur Anbessa specialized hospital shows a 1.9% mortality rate out of 9,956 patients who visited the ED; the most common cause of death was head injury (21.5%) (15). A study conducted at Ayder Referral Hospital shows the prevalence of head injury from a review of records of road traffic accident was 48.7% (16). Another study conducted at Dilla University referral hospital shows the prevalence of head injury was 32.1%, and road traffic accident was the main cause of head injury (17). A study at Gondar University referral hospital also showed a prevalence of 40.5% for head injury; of these 46.7% occurred due to interpersonal fight (18). A study in Ayder referral hospital showed prevalence of head injury was 56.3% and the most common causes were fall accident (41.9%), road traffic accident (24.9%), and interpersonal violence (24.8%) (19). In Ethiopia, a national prevalence of head injury is lacking, and health planners and policymakers use demographic health surveys. The current study aims to assess the national prevalence of TBI among trauma patients in Ethiopia.

Protocol and registration
The systematic review and meta-analysis was conducted based on the Preferred Reporting Items for Systematic and Meta-analysis (PRISMA) protocols. This systematic review and meta-analysis was registered in Prospero international prospective register of systematic reviews (PROSPERO identifier CRD42020146643)

Eligibility criteria
Types of studies All cross-sectional studies reporting the prevalence of traumatic brain injury among trauma patients in Ethiopia, without any date and language restrictions, were incorporated.

Types of participants
Participants were all trauma cases having a head and/or neck injury.

Outcomes of interest
The primary outcome of interest was the prevalence of TBI among trauma patients in Ethiopia. Risk factors for TBI among trauma patients in different regions of the country were secondary outcomes.

Context
The review incorporates studies conducted in Ethiopia.

Inclusion criteria
The review included all cross-sectional studies to assess the magnitude of TBI, and other cross-sectional studies conducted on pattern and outcomes of trauma that report TBI as a secondary outcome. Exclusion criteria Studies that didn't report TBI, randomized controlled trials, cohort and case-control studies, systemic reviews, and case reports and series were excluded.

Search strategy
The search strategy intended to explore all available published and unpublished studies on traumatic brain injury among trauma patients in Ethiopia without date and language restrictions. A three-step search strategy was employed in this review. An initial search on PubMed/Medline, Science Direct and African Journals Online was carried out, followed by an analysis of the text words contained in the Title/Abstract and indexed terms. A second search combined free text words and indexed terms with Boolean operators. The third search used reference lists of all identified reports and articles for additional studies. Finally, an additional and grey literature search was conducted on Google Scholar up to 10 pages. Supplementary material 1 shows the search strategy conducted in PubMed.

Data extraction
Data from each study were extracted with a customized format by two independent authors. Disagreements between the two independent authors were resolved by the other two authors. The extracted data include author names, date of publication, sample size, prevalence of head injury among trauma patients, mean age of participants, and risk factors for the trauma. Finally, data were imported for analysis in R version 3.6.1.

Data analysis
Data analysis was carried out in R version 3.6.1 with meta and metafor packages. The pooled prevalence of TBI was determined with a random effect model as there was substantial heterogeneity. The heterogeneity among the included studies was checked with forest plot, χ2 test, I2 test, and the p-values. Substantial heterogeneity among the included studies was investigated with subgroup analysis. Publication bias was checked with a funnel plot and the objective diagnostic test was conducted with Egger's correlation, Begg's regression tests, and trim and fill method. In addition, moderator analysis was carried out to identify the independent predictors of TBI among trauma patients. The results were presented based on the Preferred Reporting Items for Systemic Reviews and Meta-Analysis (PRISMA) (31).

Description of included studies
A total of 198 articles were identified from different databases, as described in the methodology section with the PRISMA flow diagram (Figure 1). Twenty-one articles were selected for evaluation after successive screening. Twelve articles with 14,017 participants reporting the prevalence of head injury as a primary outcome were included and the characteristics of each included study were described (Table 1) (3), two in Amhara and one in Tigray regional states. However, no study reported the magnitude of TBI in Somalia, Afar, Gambella, Benshangul Gumuz, and Dire Dawa City administrations. The five included studies assessed the prevalence and outcomes of TBI; the remaining seven studies were on pattern and outcomes of trauma and they reported TBI. Most included studies reported the prevalence of TBI alone and the rest reported the prevalence of head and neck injury. Two of the included studies used total admission to calculate prevalence and 10 of the included studies used the total trauma cases as a source of population. Seven studies identified road traffic accident as the main mechanism of TBI, followed by assault; five studies reported assault as the main mechanism of injury, next was road traffic accident.

Assessment of methodological quality
Articles identified for retrieval were assessed for methodological quality by two independent authors, using a standardized critical appraisal tool adapted from the Joanna Briggs Institute, before inclusion in the review (20) ( Table 2). Disagreements between the authors appraising the articles were resolved through discussion with the other two authors. Articles with average scores greater than 50% were included for data extraction.

Meta-analysis
Twelve studies reporting TBI were included for metaanalysis: five studies were on the prevalence of TBI, and seven were on patterns of trauma but were included in the meta-analysis because of the reported prevalence of TBI. The pooled prevalence of TBI in Ethiopia was 20% (95% CI, 11-32 studies, 12,915 participants) (Figure 2). Subgroup analysis by region showed prevalence of TBI was highest in Tigray state, 49% (95% CI, 43-54, 1 study, 322 participants), next was Oromia state 20% (95% CI, 3-66, 3 studies, 4972 participants); the lowest were in Amhara state 15% (95% CI, 3-53, 2 studies, 4413 participants), next were Addis Ababa and Sothern Nations Nationalities People's Region (Figure 3). Subgroup analysis by mechanism of injury revealed road traffic accident was the highest mechanism of injury in Ethiopia at 21% (95% CI, 15-30, 7 studies, 3530 participants), next was assault at 18% (95% CI, 5-48, 5 studies, 9,385 participants) (Figure 4). The funnel plot for evaluating publication bias did not show asymmetric funnel plot ( Figure 5). Also, the rank correlation and Egger's regression test did not show a significant difference for small study effect (p-value >0.05). Moderator analysis failed to identify the effects of study quality, mean age of participants, year of publication and sample size on effect estimate of TBI among trauma patients, p>0.05.

Discussion
The pooled prevalence of TBI in Ethiopia was 20% (95% CI, 11-32). The finding of this review is in line with a systemic review conducted in the Sub-Saharan African region. The similarity may be explained by relatively similar socio-economic status, mode of transportation, and infrastructure within these regions (30). The global report on traumatic brain injury revealed that TBI prevalence was very low in the USA, China, Norway, and Finland (3) than in this systemic review. The possible explanation for this discrepancy might be due to road safety protocols, better infrastructure, and community awareness towards possible risk factors for injury including violence, driving speed, substance abuse and use of safety belts (3). This systemic review revealed that personal violence/assault was the second most common cause of TBI in Ethiopia.  Personal violence was the least mentioned cause of TBI, as shown in other systemic reviews conducted in the Sub-Saharan region and globally (3,28,30). This discrepancy might be due to the current tribalism and instability in the Ethiopian context. The systemic review revealed that road traffic accident was the most common cause of TBI, which corroborates another systemic review conducted in the Sub-Saharan region (30). The similarity may be explained by the similar mode of transportation, socioeconomic status, transportation and principles of road safety (30). The subgroup analysis showed a higher prevalence of TBI in Tigray regional state than in other regional states. This discrepancy might be due to few studies carried out, only one study on the prevalence of TBI in this region, study setting and small sample size.    Limitation of the study The review incorporated a few studies assessing the prevalence of TBI among trauma patients. Besides, the number of studies was small in some regions and other regions had no studies at all assessing the prevalence of TBI. As a result, the review had substantial heterogeneity. The methodological qualities of the included studies were high to moderate, as shown with the methodological assessment tool. However, the overall quality of evidence was low because there was an inconsistency effect estimate within studies, and also because it is a meta-analysis of cross-sectional studies (low levels of evidence).

Conclusion
The review revealed that the prevalence of TBI among trauma patients in Ethiopia is high when it is compared with continental and global reports. Road traffic accident and assault were the most common causes of TBI in Ethiopia. To reduce the prevalence of TBI in Ethiopia, policymakers and stakeholders should work on awareness-creation strategies on road safety, regulatory laws on transportation, mode of transport, types of vehicles, driving license, and pre-hospital emergency medical care system that is highly in demand. More evidence with a large sample size on the prevalence of TBI and associated factors from each region is still needed.