Epidemiology of Traumatic Brain Injury
Original Editor - Anna Ziemer
Reviewing epidemiological data facilitates the development of preventive strategies by identifying the main causes for traumatic brain injury, the factors contributing to severity, the most prevalent age groups and other demographics of the risk groups.
Understanding both the incidence and severity, in conjunction with identification of the mechanism of injury, allow us to design appropriate health care services from subacute and emergency medicine to neurorehabilitation and so determine the training needs of the healthcare workforce. It also allows us to estimate future socioeconomic needs to minimise the burden on wider society and governments.
It has been estimated that traumatic brain injury affects over 54 to 60 million people annually leading to either hospitalisation or mortality. Of all types of injury, those to the brain are among the most likely to result in death or permanent disability. 
According to the Global Burden of Disease Study 2016  there were 27.08 million new cases of traumatic brain injury, with age-standardised incidence rates of 369 per 100,000 population, per year. (An age-standardised rate (ASR) is a summary measure of the rate that a population would have if it had a standard age structure).
|2016 Counts||2016 Age-Standardised
Rates (per 100000)
|Percentage Change in
Rates, 1990 - 2016
|2016 Counts||2016 Age-Standardised
Rates (per 100000)
|Percentage Change in
1990 - 2016
(24,302091 to 30,298710)
(331 to 412)
(1·8 to 5·5)
(53,400547 to 57,626214)
(731 to 788)
(7·7 to 9·2)
The primary causes of traumatic brain injury vary by age, socioeconomic factors, and geographic region, so any planned interventions must take into account this variability. The low and medium-income countries (LMICs) experience nearly three times more cases of traumatic brain injury proportionally than high-income countries (HICs), with Southeast Asian and Western Pacific regions experiencing the greatest overall burden. 
Age related traumatic brain injury differences demonstrate three main age groups with the highest prevalence:
- Early childhood with falls being main cause
- Late adolescence / early adulthood with road traffic accidents (RTAs) being main cause
- Elderly with falls being the main cause.
Childhood injuries are most likely in poorest countries with WHO claiming 98% occurrence in LMIC and 5 times greater frequency than in industrialised nations.  In the last 20 years there is an increased incidence of falls amongst the elderly. Gender differences also show a global trend with males being more prevalent with rates from 1.5:1 to 2.5:1 across the world, apart from the 8th and 9th decade of life.
In recent research, falls have been identified as the main cause of traumatic brain injury (attributable traumas increased from 43% to 54% between 2003 and 2012), followed by road traffic accidents (attributable traumas dropped from 39% in 2003 to 24% in 2012) , violence, sport related injuries and work-related injuries.
The dominant cause of traumatic brain injury can vary depending on the countries’ income, geographical region and political circumstances, i.e.conflict areas. The proportion of traumatic brain injury resulting from road traffic collisions is greatest in Africa and Southeast Asia (both 56%) and lowest in North America (25%), while South America, the Caribbean and Sub Saharan Africa represent the highest world incidence of traumatic brain injury related to violence.
There is some discrepancy with rural and urban traumatic brain injury incidence, respectively being 9.7 and 6.3 per 100,000 population following China based studies, and 172.1 and 97.8 per 100,000 following USA based studies. 
Brain injury is the leading cause of death and disability worldwide, with traumatic brain injury being the leading cause of seizure disorders. However, in recent years we have observed a decrease in mortality post traumatic brain injury.
The Case Fatality Rate (CFR) is determined by severity of traumatic brain injury and age and is as follows:
- General CFR ranges from 0.9 to 7.6 per 100 traumatic brain injury patients
- CFR of severe traumatic brain injury ranges from 29 to 55 per 100 traumatic brain injury patients
- Average mortality is 10.53 per 100,000 population per year, with 68% of the individuals dying before reaching hospital.
There is a close link between traumatic brain injury and alcohol consumption. In the UK the incidence of head injury in acutely intoxicated patients is estimated to be as high as 65%. In Asia, a substantial amount of night time RTAs in Asia are alcohol related (10-30% depending on the country).  Alcohol intoxication also imposes serious diagnostic difficulties post traumatic brain injury.
It is estimated that 80% of individuals living with traumatic brain injury related impairment live in LMIC, but at the same time in those regions, only 2% of these have access to rehabilitation services so support their quality of life. Higher-income countries have been successfully decreasing the numbers of both overall traumatic brain injury and traumatic brain injury-related impairments following implementation of preventive measures, more rigorous safety measures, legislative changes, educating the general population, improved emergency and neuro-trauma services, and the implementation of evidence-based guidelines in treating survivors of traumatic brain injury.
Annually two million Americans are treated and released from hospital emergency departments as a result of traumatic brain injury. An estimated 56,000 individuals die as a result of a traumatic brain injury, whilst 80,000 individuals are estimated to be discharged from the hospital with some traumatic brain injury-related impairment and need assistance with activities of daily living. An estimated 5.3 million Americans are living today with impairment related to traumatic brain injury costing the country more than $56 billion per year considering care cost and loss of earnings.
Most studies indicate that males are far more likely to incur a traumatic brain injury than females. The highest rate of traumatic brain injury occurs between the ages of 15 - 24 years, with persons under the age of 5 or over the age of 75 also at a significantly higher risk. Between 20 - 30% of older people who fall, suffer moderate to severe injuries including bruising, hip fractures, or head trauma.
Veterans are a vastly growing population of traumatic brain injury survivors in the United States, with 350,000 troops identified with traumatic brain injury by the Department of Defence between 2000 and 2017 as a result of the global war on terror (GWOT).  The nature of current combat has seen an increased incidence of blast related traumatic brain injury, with an estimated 15% of all actively serving troops in Iraq and Afghanistan sustaining a traumatic brain injury, recognising that this number may be underestimated due to reporting and data collection limitations. Improved armor and emergency medicine protocols have allowed greater rates of survival. The full extent of traumatic brain injury-related burden is not fully acknowledged due to the longitudinal nature of the problem with cumulative injury effect, the overlap of symptoms with PTSD, with peak socioeconomic problems occurring up to 30 - 40 years post conflict.
In the European Union, brain injury accounts for 1.5 million hospital admissions per year and 57,000 deaths. The incidence is at 287 per 100,000 with fatality of 15 per 100 000, with some countries, like the UK, reporting significantly higher incidence at 453 per 100 000 of which 10.9% are considered moderate to severe. The difference in the incidence is related to the data collection methodology, not factual difference of incidence.  The most prevalent group include male urban residents and children, with the most common cause being RTIs, peaked at late afternoon and early evening. 
The leading causes of traumatic brain injury vary by age: falls are the leading cause of traumatic brain injury among persons aged 65 years and older; transportation is the leading cause of traumatic brain injury among persons under the age of 65 years. Motor vehicle crashes including motorcycles, bicycles, and pedestrians account for 50% of all traumatic brain injury. According to Peeters at al  epidemiological analysis, Scandinavian countries report more falls related traumatic brain injury. Estimates suggest that sports related brain injury accounts for close to 300,000 injuries each year, with winter sports such as skiing and ice-skating accounting for close to 20,000 brain injuries
Latin America and Caribbean
The epidemiology of traumatic brain injury in Latin America and the Caribbean is dictated heavily by socioeconomic status with RTIs and violence being the main causes, with violence related traumatic brain injury being a principal cause of TBIs-related deaths. The incidence is much higher and approximately 360 per 100 000 of the population per year. The most at risk are male (83%) and the age group of higher incidence is of young adults.
The transition we are witnessing amongst Low and Middle-Income Countries create new and multiple risks of traumatic brain injury including increased motorisation and urbanisation, along with increasing number of non-communicable diseases. Therefore, the trend of increasing number of traumatic brain injury and resultant disability is observed similarly to High -income Countries.  Along with insufficient health care and poor preventive strategies the socioeconomic burden of traumatic brain injury has been increasing.
According to GBD 2016  the incidence of RTIs, falls and violence-related traumatic brain injury has been increasing sharply with India, China and Other Asian countries having the greatest incidence. Compared to other world regions, Asia has a different distribution of contributing causes with falls contributing to 77% of all traumatic brain injury and only 3% of traumatic brain injury resulting from the war. However, caution needs to be applied to the data due to inefficient data collection mechanisms and definition and assessment protocols discrepancies.
Asian males from LMIC are more prevalent to sustain traumatic brain injury due to greater exposure to risk factors. According to Raja , in Lahore Region 75% traumatic brain injury related admissions are of male patients. Similar gender differences have been observed in Singapore and China, with 75% casualties with severe traumatic brain injury being male.
In relation to the age, Asian data demonstrates similar pattern to other regions with children under 11 being at greater risks of traumatic brain injury, with over 50% injuries in 4-6 years old being related to falls, with a greater prevalence in boys.
Traumatic brain injury is a leading cause of mortality, morbidity and socioeconomic loss in India. India has been experiencing a much higher incidence of fall related traumatic brain injury with fractured skull and intracranial long-term injuries in comparison to other countries, with the incidence rate amongst Indian males of 50.3 per 100 000 population, in comparison with the global average of 13. 3 per 100 000.
According to Pauvanachandra and Hyder , in India approximately one million individuals requires rehabilitation as a result of traumatic brain injury consequences at any given time. In China, traumatic brain injury is a leading traumatic injury cause and 5th leading cause of death in younger adults. RTAs account for 61% of traumatic brain injury with one-third of those motorcyclists, 31% pedestrians and only 14% of car users.
Middle Eastern and other Asian Regions do not have consistent data collection process, but some local studies are emerging e.g. in Yemen traumatic brain injury prevalence rate at the level of 210 per 100 000 population, with domestic violence and falls being the leading causes, followed closely by RTAs.
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