Injury is a leading cause of death, disability and health care costs worldwide. The Global Burden of Disease Study, which creates a unique framework by which to assess national trends in all-cause and cause-specific mortality and morbidity, has shed light on the burden of injury relative to the denominator of all morbidity and mortality.¹ This research and other prominent publications have been instrumental in moving injury to a level of recognition commensurate with its level of disease burden. Injury has begun to gain recognition as a prominent public health issue as thought leaders, researchers, and clinicians are vigorously studying the issues within a framework by which prevention efforts, trauma systems, and advocacy strategies can be developed and maintained.

Approximately 5.8 million people die globally from injury-related causes. As a consequence of inadequate surveillance in many parts of the world, that number is likely to be much higher. Injury is responsible for more deaths worldwide than HIV, tuberculosis and malaria combined. The impact is projected to increase over time relative to other leading causes of death (Table 3-1).² Greater than 90% of injury deaths occur in low and middle income countries, and, within individual countries, vulnerable populations tend to be of lower socioeconomic status. This further hampers the progress of already struggling communities.

In several ways the burden and demographics of injury in the United States provide an example of the patterns seen worldwide; that is, injury is most prevalent in communities of lower socioeconomic status, rates of injury are higher in men than women, and young people are disproportionately affected by injury. According to the Centers of Disease Control and Prevention, unintentional injury remained the leading cause of death in the United States from age 1 to 44 years in 2013. Unintentional injury, suicide, and homicide are the first, second and third leading causes of death in the age group 15–34 years, respectively. Homicide remains the leading cause of death in the United States in African-Americans 15–34 years old and second in Hispanics of the same age. Unintentional injury is the third leading cause of death of all Americans with motor vehicle crashes and falls, particularly in the elderly, having a significant impact.³

Death is the tip of the iceberg in understanding the impact of injury.² In order to understand its magnitude, it is important to look at disability, along with the age at which a person is killed or injured. Calculations of disability adjusted life years (DALY), or the sum of years of life lost due to premature death and the years of productive life lost due to disability, are performed using a standard disability weight for each particular type of injury such as amputation, paralysis, post-traumatic stress disorder, etc.⁴ Although the DALY calculation has been criticized in its global applicability, it highlights the impact of injury on the younger portion of the population who are either very early in their lives or in the middle of their years of economic productivity which imposes a tremendous societal cost.

To round out the picture of the impact of injury, cost should be taken into consideration. Direct health care costs can be calculated and modeled. Indirect costs, including the psychological impact, loss of productivity affecting entire families, and societal costs of injury are more difficult to calculate, but we have a growing understanding of their magnitude. Road traffic injuries alone cost most countries 1–2% of their gross national product.^5,6 A study in Ghana found that 25% of households affected by injury had a decline in their food consumption.⁷ The recent release of the Lancet Commission on Global Surgery included a discussion on catastrophic expenditure from surgical disease, defined as out of pocket payment for treatment services exceeding 10% of annual household income. This is a critical issue in surgical care, and injury is a leading part of that. In the United States, hospitalization alone for injury exceeded $80 billion in direct costs and $150 billion in lost wages in 2010.⁸

A chapter focused on Injury Prevention cannot properly be discussed without first understanding injury’s influence on health and wealth. Understanding the global, national, and local impact of injury by mechanism and demographics is a critical start to launching into a strategy of targeted injury prevention appropriate for a particular location and population. A detailed investigation into these components along with understanding risk factors and protective factors not only allows us to understand the target population for prevention efforts, but can also be the cornerstone of creating a strategic plan for appropriate measures in education, engineering, and enforcement. In addition, understanding the public health impact of injury allows targeted advocacy for legislation and financial resources necessary to initiate many prevention plans. Understanding the direct and indirect costs of injury creates opportunities to conduct studies in cost-effectiveness, a compelling tool when advocating for prevention measures in an environment of limited resources.

The importance of injury prevention efforts is pointed out by trauma mortality patterns. One-third to one-half of trauma deaths still occur in the field before any possibility of treatment even by the most advanced trauma treatment system.^9,10 Such deaths can only be decreased by prevention efforts. In terms of severely injured persons who survive long enough to be treated by prehospital personnel, very few “preventable deaths” occur in a modern trauma system with a well-run emergency medical system and designated trauma centers. Even among those who survive to reach the hospital, a significant portion of in-hospital deaths are directly related to injuries to the brain and occur despite optimal use of currently available therapy. In one study, out of 753 consecutive deaths, over 50% were deemed possibly preventable only by prevention efforts, with only 13% due to pulmonary embolus, multiorgan failure, and sepsis.¹¹ Hence, injury prevention is critical to further significantly reduce the toll of death caused by trauma. Moreover, prevention efforts can also decrease the severity of injuries and thus the likelihood of disability that arises after trauma.

This chapter provides the historic and scientific framework by which prevention efforts are implemented today. Although the list is not comprehensive, topics that cover both unintentional and intentional injury and site strategies that represent best practices and some newer promising practices in the United States are discussed. Many of these practices have evaluation and cost-effectiveness built in from program inception and stand as examples of the scientific principles presented in the chapter. Finally, the global implications of injury are reviewed. This includes injury as it affects low and middle-income countries and developing strategies in surveillance, prevention and injury control necessary to make a difference amongst populations at greatest risk.

History of Injury Prevention

Historically, injuries were seen as “accidents” that could not be predicted, and, therefore, could not be prevented. This limited perspective resulted in an unaggressive approach to injury prevention of restricted scope that had little effect.^12,13 Over the last 100 years, several visionary individuals had successive insights that established the public health basis for injury prevention. These frameworks resulted in a rational approach that now guides effective injury prevention.

In 1916, a volunteer pilot in the Canadian Royal Flying Corps named Hugh DeHaven was on his final training flight when his plane collided with another and fell 500 ft to the ground.¹⁴ The gunner of the plane died, but DeHaven survived with significant injuries, spending the rest of his military service as a clerk who was involved in the collection of bodies during World War I.¹⁴ He began to notice different injury patterns and began to theorize that the design of the plane’s interior may affect or even prevent the injuries sustained by its passenger. These observations led to the earliest developments of modern injury prevention. By applying engineering principles to injury events, DeHaven created the biomechanical foundation for injury that ultimately led to the development of automotive safety belts.^15,16

The epidemiologist John E. Gordon built on DeHaven’s foundation with another novel perspective by pointing out that injuries can be evaluated using the standard epidemiologic framework of host, agent, and environment (Table 3-2). Just like any other condition affecting human health, Gordon explained that injuries were not random, but occurred with recognizable patterns across time and populations.¹⁷ This conceptual evolution was a paradigm shift—from single-cause explanations of injury that inadequately described the injury event and, therefore, limited prevention opportunities to a multifactorial understanding of the components of injury. This would allow injuries to be studied from several perspectives and opportunities for prevention identified.¹⁸

The fundamental work done by DeHaven and Gordon applying public health principles to injury set the stage for the most notable of the early pioneers of injury prevention, William Haddon, the first director of the National Highway Traffic Safety Administration (NHTSA). Haddon is most well known for his expansion of Gordon’s epidemiologic framework for injury prevention, by incorporating a temporal element to the host-agent-environment schema, which ultimately became known as Haddon’s Matrix (Table 3-3).¹⁹ The pre-event phase allows us to examine the factors surrounding host, agent, and environment that influence the likelihood that an event capable of producing an injury will occur (such as a car crash). An example of a host factor in the pre-injury phase would be alcohol impairment, agent factors could include brakes or maintenance, while an environmental factor could be road condition. During the event phase, there are factors influencing the probability that the event (ie, car crash) will result in an injury, and if so, to what extent. A host factor during the event could be seatbelt use, an agent factor might be crush resistance of the car, and an environmental factor could be the presence or absence of dividers that would keep the car from ricocheting into ongoing traffic. In the post-event phase, these three components (host, agent, and environment) can be evaluated for factors that influence the ultimate consequences of injury.

This conceptual framework was further leveraged by Haddon to develop 10 strategies that formed the foundation of most current injury prevention and control efforts (Table 3-4).¹⁹ The underlying concept to most of these strategies is based on the work pioneered by DeHaven; that is, separating the injury-producing “energy” from the host.^18,19 Haddon’s work marks the most pronounced shift in the transition from a simplistic, single-cause, individual-level perspective of injury events to complex, multifactorial, societal-level causation. Haddon’s approach also integrated multidisciplinary involvement into injury prevention, including clinicians, epidemiologists, engineers, law enforcement agencies, policy experts, educators, and mental health experts.

Principles of Injury Prevention

Most interventions can be thought of as either being active or passive on the part of the person being protected. Active interventions involve a behavior change and require people to perform an act such as putting on a helmet, fastening a seatbelt, or using a trigger lock for a handgun. Passive interventions require no action on the part of those being protected and are built into the design of the agent or the environment, such as airbags or separation of vehicle routes and pedestrian walkways. Passive interventions are generally considered more reliable than active ones^19,20; however, many interventions that are considered passive still inherently carry an active component, even if it is at the societal or political level, such as passing legislation to require certain safety features in automobiles. The number of times an active intervention needs to be performed to be effective is also a consideration in terms of efficacy. For example, a seatbelt must be used each time to be effective, while a vaccine usually only requires active participation for a limited time interval for it to have long-term effectiveness.

Another framework often applied to injury prevention strategies is that of the following “three E’s”: (1) enforcement and legislation, (2) education and behavior change, and (3) engineering and environmental modifications. Initially, education was the main area of focus for injury prevention. If applied uncritically without a strong framework and thorough evaluation, behavior change through educational interventions in isolation can be difficult to achieve. A comprehensive report has suggested that the most effective interventions are engineering/environment, followed by enforcement, and lastly by education.²¹ Educational interventions are usually most effective when complemented with modalities from the other “E’s”; that is, the most effective injury strategies typically have components of all three. An example is the child safety seat, an engineering solution for injury prevention, which was only successfully implemented through successful education campaigns and careful law enforcement.²¹

Other factors that must be considered when choosing and implementing injury control strategies are fidelity versus adaptability. Fidelity refers to the measure to which a program is implemented as intended. Fidelity has been found to influence the measured effectiveness of an outcome.²² While fidelity to the program’s intended implementation is critical to achieving desirable outcomes, contexts may differ widely in a number of ways, ranging from socioeconomic characteristics of the population served to cultural nuances that may influence implementation of the program. Adaptability is the ability of a program to be modified so that it is applicable in a specific context. An effective injury control program needs to strike an appropriate balance between fidelity to established, evidence-based methodology, while being adaptable enough to maintain relevance to the specific population being served. Often, the fidelity and adaptability of a specific program will influence its prioritization among potential injury control interventions.

Prioritization of targets in injury control for intervention depends on multiple factors.¹⁸ The frequency and severity of a type of injury are fundamental to whether investments should be made to prevent or improve treatments for that injury; that is, having a solid base of evidence for the epidemiology of injury is key to prioritization. Certain injuries may occur frequently, but if the consequences of that injury in terms of severity are minimal, there may be a more important target for injury prevention or control. The cost of injuries in terms of direct health care costs and indirect societal and economic effects must also be considered. Effective arguments for implementing an injury control program can be made if savings in terms of averted injury-associated costs are demonstrated. Awareness of the importance of cost-effectiveness analyses and their potential as a tool for advocacy is steadily increasing.^23,24,25 Understanding of the resources available to fund and sustain the intervention is of primary consideration, as well, and will clearly influence the intervention chosen. Finally, less easily quantifiable but equally important are the acceptability and feasibility (including political) of a program in the community.¹⁸ When several strategies for injury control are available and found to be acceptable as potential interventions, prioritizing them may be difficult. Obviously, the most effective strategy proposed should be prioritized; however, often, a mixed strategy is most effective and should be used, if resources allow.²⁶ When choosing between primarily active versus primarily passive interventions, the passive intervention is usually favored as the more reliable approach.^19,20 Finally, sustainability of a potential program is essential if it is to provide long-term effect, so assessing the ability of a program to become ultimately accepted and sustained may play into the decision as to whether or not to adopt it. An “institutionalized” program is one that achieves ongoing support and commitment from the agency, organization, or community in which it is based.¹²

Certain common characteristics run through many successful injury prevention programs. These include a multidisciplinary approach and community involvement and should involve ongoing evaluation of both the process and outcome of the program. Depending on the targeted injury type, a program might involve contributions from the following: health care professionals, public health practitioners, epidemiologists, psychologists, manufacturers, traffic safety and law enforcement officials, experts in biomechanics, educators, and individuals associated with the media, advertising, and public relations as previously noted. Health care professionals might include those in primary care, such as pediatricians, and those involved in acute trauma care. Finally, individual members of the public might be involved.^20,27

Injury Control: From Surveillance to Dissemination

The public health approach can be applied to injury prevention and control as it is applied to any problem at the population level. This approach is comprised of the components described below¹⁸:

1. 
   

   Surveillance

   
   
2. 
   

   Risk factor identification

   
   
3. 
   

   Ascertaining natural history

   
   
4. 
   

   Intervention

   
   
5. 
   

   Evaluation

   
   
6. 
   

   Dissemination

The components of a comprehensive injury prevention program are demonstrated in Box 3-1.