Learning Objectives
- Understand the global impact of injuries and their relative importance as a cause of morbidity and mortality worldwide
- Know the most common categories of intentional and nonintentional injuries, and their relative importance in the global burden of disease
- Identify recommended focus areas for future research in injury prevention
Introduction
Injury is a leading cause of mortality worldwide, resulting in more than 5 million deaths annually.1 Global mortality due to injury exceeds that of HIV/AIDS, tuberculosis, and malaria combined.2 Deaths due to injury represent only the tip of the injury iceberg, however. For every person who dies from an injury, several thousand injured persons survive with permanent disability. Additional adverse consequences spill over to affect multiple individuals within the family and community of each injured person.
In 2004, injuries accounted for approximately 10% of the world’s deaths and over 12% of the global burden of disease.3 The relative importance of injuries within the global burden of disease is expected to rise even further, with injury becoming the third leading cause of death and disability by 2020.4
In the past, the term accident was used to describe various categories of unintentional injuries, including those associated with road traffic collisions, falls, burns, and other causes. This traditional view implies that the events leading to injury are random, unavoidable, and unpredictable. Public health officials now recognize that injuries are preventable nonrandom events. After years of historical neglect, injury prevention has become a major area of emphasis within the public health arena. In 2000, the World Health Organization (WHO) established a Department for Injuries and Violence Prevention to promote global initiatives in injury prevention and control. The phenomenon of injury has now been taken out of the realm of chance “accident” and placed squarely within the framework of scientific study, where research is being conducted to design effective injury control interventions.
Using the accepted conventions of the WHO,5 injuries can be divided into two broad categories: intentional injuries and unintentional injuries. Intentional injuries are subdivided into self-inflicted injuries (i.e., suicide attempt or completion), interpersonal violence (i.e., homicide or intentional injury to others), and war-related violence. Unintentional injuries are further subdivided into road traffic injuries, poisoning, falls, fires, and drowning. Most public health experts and organizations, including the WHO, use this classification scheme in discussions of global injury surveillance and prevention.
Mortality due to injuries is a very important indicator of the magnitude of the problem. However, nonfatal outcomes with associated disability and other adverse sequelae must also be considered to fully appreciate the impact of injuries on global health. The disability-adjusted life year (DALY) is an epidemiologic indicator that has been developed to quantify the combined impact of disability and premature death due to illness or injury. One DALY is defined as 1 lost year of healthy life, either due to disability or premature death (see Chapter 2).
Although injuries are a leading cause of morbidity and mortality worldwide, the nature and scope of the problem varies considerably by region, age, sex, and socioeconomic status. For example:
- More than 90% of the world’s deaths due to injuries occur in low-income and middle-income countries.2
- Injury mortality among men is almost twice that among women worldwide.2
- Males in Africa have the highest injury mortality rates, and women in the Americas have the lowest injury mortality rates worldwide.
- Young people between the ages of 15 and 44 years (the most economically productive segment of society) account for almost 50% of global injury mortality.6
The relative importance of different types of injuries also varies significantly based on geographic and demographic variables.
- Men have almost three times higher mortality rates from road traffic injuries and interpersonal violence than do women.6
- Children ages 0 to 14 years account for more than 50% of DALYs lost due to burn injuries and more than 50% of global mortality due to drowning.6
- Road traffic injuries are the leading cause of injury-related mortality in most regions except for Europe, where self-inflicted injuries predominate, and in the low- and middle-income countries of the Americas, where interpersonal violence is the most common cause of injury-related death.5
More research is needed to clarify the reasons for these disparities and develop strategies to reduce them.
The global economic burden of injuries is enormous. For example, the annual cost of road traffic injuries alone is estimated at US$518 billion worldwide.7 In low-income countries, the cost of caring for road traffic injuries is estimated to exceed the amount of development assistance these countries receive. At the individual and family level, medical costs associated with injuries can have a devastating effect on personal finances. This is especially true in low- and middle-income countries, where most injured persons are poor and scarce resources that are needed for other basic necessities must be diverted to pay for medical care. In addition, because injuries disproportionately affect young healthy adults who are in their peak earning years, the loss of earning power due to injury-related death or disability further compounds the economic burden.
Unintentional Injuries
Approximately two-thirds of injuries worldwide are unintentional injuries, with road traffic injuries comprising the largest category.
The coroner who attended the inquest of the first road traffic death in 1896 was reported to have said, “This must never happen again.”8 More than a century later, road traffic accidents have become the leading cause of injury-related death and disability worldwide. Approximately a quarter of all injury deaths are due to road traffic injuries. Over 90% of these deaths occur in low-and middle-income countries. Each year, road traffic crashes kill more than 1.2 million people and injure or disable up to 50 million people. Young people between the ages of 5 and 44 years and vulnerable road users (pedestrians, cyclists, and passengers on public transport) are at the highest risk.9
In recent decades, road traffic death rates have decreased significantly in high-income countries but have increased dramatically in low- and middle-income countries. There is considerable variation among different countries within the same region and economic classification, however. For example, from 1975 to 1998 in North America, the road traffic fatality rate decreased by 27% in the United States but by 63% in Canada. During the same period, road traffic fatality rates in Asia increased by 44% in Malaysia but by 243% in China. By 2020, road traffic fatalities are projected to increase by 83% in low- and middle-income countries, and to decrease by 27% in high-income countries. This will result in a predicted 67% overall increase in global road traffic deaths. Thus road traffic injuries are expected to become the sixth leading cause of death worldwide and the third largest contributor to the global burden of disease (DALYs lost) by 2020.10
Many factors contribute to the high number of road traffic injuries and deaths in the developing world, including:
- Large numbers of vulnerable road users, such as pedestrians and cyclists, who must share the road with larger vehicles
- Poorly equipped and maintained motor vehicles, which often lack basic safety features such as seatbelts
- Poorly designed and maintained roads with inadequate lighting
- Inadequate establishment and enforcement of traffic safety laws
- Lack of access to quality prehospital and hospital care for injured persons.
The WHO has identified the following five key areas for effective interventions that can reduce the burden of road traffic injuries worldwide: speed, alcohol, seatbelts, helmets, and visibility.11
Speed is a contributing factor in approximately 30% of road traffic fatalities. For every 1 km/hour increase in speed, there is a 3% increased risk of a crash resulting in injury and a 5% increased risk of a fatal crash. Effective interventions include setting and enforcing speed limits, improved road design, and utilization of traffic-calming measures such as speed bumps and traffic circles. For example, placement of speed bumps on an accident-prone stretch of highway in Ghana resulted in a 35% reduction in the number of crashes, a 76% reduction in serious injuries, and a 55% reduction in road traffic fatalities at that location.11
Blood alcohol concentrations greater than 0.04 g/dL significantly increase the risk of road traffic crashes. An alcohol-impaired driver has a 17-fold increased risk of being involved in a fatal crash than an unimpaired driver.12 For any alcohol level, the risk of crash fatality increases with decreasing driver age and experience. Suggested interventions include setting and strictly enforcing blood alcohol concentration limits in drivers, mass media educational campaigns, and utilization of random breath testing. For example, since 1993 in Australia, widespread random breath testing has been credited with an estimated 40% reduction in alcohol-related deaths.11
The use of seatbelts has saved more lives than any other road safety intervention. Seatbelts reduce the risk of fatal or serious injury in a crash by an estimated 40% to 65%. In addition, proper use of child restraints can reduce toddler deaths by 54% and infant deaths by 71%. Suggested interventions include establishment and enforcement of mandatory seatbelt and child restraint use, mass media educational programs, use of audible seatbelt reminders, and child restraint loan programs. For example, a well-publicized police enforcement campaign in the Republic of Korea resulted in an increase in seatbelt use from 23% in 2000 to 98% in 2001, accompanied by a 5.9% decrease in road traffic fatalities.11
Head injuries are a major cause of death and disability among users of motorized two-wheel vehicles (mopeds and motorcycles). Nonhelmeted riders have a three-fold increased risk of head injury in a crash when compared with helmeted riders. The proper use of helmets has been shown to reduce the risk of serious or fatal head injury by up to 45%. Suggested interventions include establishment and enforcement of mandatory helmet laws, targeted educational campaigns, and development of safe inexpensive helmets that are comfortable in tropical climates. For example, enforcement of the helmet law in Thailand resulted in a five-fold increase in helmet use, accompanied by a 41% decrease in head injuries and a 20% decrease in deaths.11
The abilities to see and be seen are fundamental requirements for the safety of all road users. Poor visibility of pedestrians and motor vehicles significantly increases the risk of road traffic injuries. In addition to being relatively unprotected in a crash, pedestrians and cyclists are harder to see than larger vehicles and are therefore more vulnerable to injury. Inadequate street lighting and insufficient use of reflective equipment and vehicle lights also contribute to poor visibility. Proposed interventions include improved street lighting, increased use of reflective clothing and equipment for pedestrians and cyclists, and requiring use of daytime running lights for motorized vehicles. Crash rates are 10% to 15% lower for vehicles using daytime running lights than for those that do not.11
