Estimating the global incidence of traumatic brain injury

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OBJECTIVE

Traumatic brain injury (TBI)—the “silent epidemic”—contributes to worldwide death and disability more than any other traumatic insult. Yet, TBI incidence and distribution across regions and socioeconomic divides remain unknown. In an effort to promote advocacy, understanding, and targeted intervention, the authors sought to quantify the case burden of TBI across World Health Organization (WHO) regions and World Bank (WB) income groups.

METHODS

Open-source epidemiological data on road traffic injuries (RTIs) were used to model the incidence of TBI using literature-derived ratios. First, a systematic review on the proportion of RTIs resulting in TBI was conducted, and a meta-analysis of study-derived proportions was performed. Next, a separate systematic review identified primary source studies describing mechanisms of injury contributing to TBI, and an additional meta-analysis yielded a proportion of TBI that is secondary to the mechanism of RTI. Then, the incidence of RTI as published by the Global Burden of Disease Study 2015 was applied to these two ratios to generate the incidence and estimated case volume of TBI for each WHO region and WB income group.

RESULTS

Relevant articles and registries were identified via systematic review; study quality was higher in the high-income countries (HICs) than in the low- and middle-income countries (LMICs). Sixty-nine million (95% CI 64–74 million) individuals worldwide are estimated to sustain a TBI each year. The proportion of TBIs resulting from road traffic collisions was greatest in Africa and Southeast Asia (both 56%) and lowest in North America (25%). The incidence of RTI was similar in Southeast Asia (1.5% of the population per year) and Europe (1.2%). The overall incidence of TBI per 100,000 people was greatest in North America (1299 cases, 95% CI 650–1947) and Europe (1012 cases, 95% CI 911–1113) and least in Africa (801 cases, 95% CI 732–871) and the Eastern Mediterranean (897 cases, 95% CI 771–1023). The LMICs experience nearly 3 times more cases of TBI proportionally than HICs.

CONCLUSIONS

Sixty-nine million (95% CI 64–74 million) individuals are estimated to suffer TBI from all causes each year, with the Southeast Asian and Western Pacific regions experiencing the greatest overall burden of disease. Head injury following road traffic collision is more common in LMICs, and the proportion of TBIs secondary to road traffic collision is likewise greatest in these countries. Meanwhile, the estimated incidence of TBI is highest in regions with higher-quality data, specifically in North America and Europe.

ABBREVIATIONS AFR = African Region; AMR-L = Region of the Americas–Latin America; AMR-US/Can = Region of the Americas–United States and Canada; EMR = Eastern Mediterranean Region; EUR = European Region; GBD = Global Burden of Disease; GBD 2015 = GBD Study 2015; HI = head injury; HIC = high-income country; IHME = Institute for Health Metrics and Evaluation; LIC = low-income country; LMICs = low- and middle-income countries; MIC = middle-income country; MOI = mechanism of injury; P(RTI) = probability that a member of the population will sustain an RTI annually; P(RTI|TBI) = probability that TBI is secondary to RTI; P(TBI|RTI) = probability that an RTI will lead to a TBI; PRISMA = Preferred Reporting Items for Systematic Reviews and Meta-Analyses; RTI = road traffic injury; RTITOTAL = total number of RTIs in a country annually; RTI∩TBI = intersection of RTITOTAL and TBITOTAL; SEAR = Southeast Asian Region; TBI = traumatic brain injury; TBITOTAL = total number of TBI cases in a region annually; WB = World Bank; WHO = World Health Organization; WPR = Western Pacific region; ∩ = intersection of 2 events; | = conditional on 1 event.

Downloadable materials

  • Supplemental Calculation and Tables (PDF 557 KB)

Article Information

Correspondence Michael C. Dewan: Vanderbilt University Medical Center, Nashville, TN. michael.dewan@vanderbilt.edu.

INCLUDE WHEN CITING Published online April 27, 2018; DOI: 10.3171/2017.10.JNS17352.

Disclosures Dr. Shrime has received support from the GE Foundation and the Steven C. and Carmella Kletjian Foundation for non–study-related clinical or research effort.

© AANS, except where prohibited by US copyright law.

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Figures

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    Methodology flow diagram. P(RTI) = probability that a member of the population will sustain an RTI annually; P(RTI|TBI) = probability that a TBI is secondary to an RTI; P(TBI|RTI) = probability that an RTI will lead to TBI; RTITOTAL = total cases of RTI, with or without TBI; RTI∩TBI = intersection of RTIs and TBIs, thus representing either the number of RTIs that lead to TBI or the number of TBIs secondary to RTIs; TBITOTAL = total cases of TBI, whether the mechanism is an RTI or a non-RTI. Figure is available in color online only.

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    PRISMA diagram for P(TBI|RTI): quantifying the proportion of RTIs that include TBI.

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    PRISMA diagram for MOIs: quantifying the proportion of TBIs secondary to RTIs [P(RTI|TBI)].

  • View in gallery

    Map showing incidence of TBI (cases per 100,000 people) by WHO region (left). Bar graph (upper right) indicating the estimated volume of TBI annually across WHO regions. Map (lower right) showing incidence of TBI (cases per 100,000 people) secondary to traffic collisions by WHO region. Regarding maps, reproduced with permission from OpenStreetMap Contributors, CC BY-SA 2.0 (http://www.openstreetmap.org/copyright). Figure is available in color online only.

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