Around the world, about 16,000 people die every day as a result of injuries. For every death, many more people survive but suffer lifelong impairment. An injury is "a bodily lesion at the organic level resulting from acute exposure to energy (which can be mechanical, thermal, electrical, chemical, or radiant) interacting with the body in amounts or rates that exceed the threshold of physiological tolerance. In some cases (e.g., drowning, strangulation, or freezing), the injury results from an insufficiency of a vital element. The time between exposure and the appearance of injury needs to be short" (Krug 1999, p.2). It is the acuteness of exposure that distinguishes injury from disease. Long-term exposure to relatively low levels of a harmful agent may cause disease, but acute exposure to the higher levels of the same agent (e.g., lead) may cause injury.
Injuries can be unintentional or intentional. Most traffic injuries, fire-related injuries, falls, and drownings are classified as unintentional. On the other hand, homicides, suicides, war, and most poisonings are classified as intentional. Aside from the degree of intentionality, there are classifications of the purpose of the activity being undertaken (i.e., work-related, recreational), the nature of the injurious event (i.e., vehicle crash, fall, poisoning, drowning, fire), or the setting (i.e., home, workplace, road).
Basic Data on Injury Mortality
Accurate counts of the number of people who die as a result of injury are usually not available. Official mortality reports are often based on incomplete counts, biased sources, cursory or no investigation, or erroneous coding. This situation is common in developing countries and in remote areas of developed countries. Even in developed countries, many health information systems do not allow for easy identification of injury deaths. Among these poorly identified types of injury deaths are occupational fatalities, deaths resulting from the use or misuse of particular products, and falls where the cause of death may be coded as pneumonia occurring as a consequence of an earlier fall. Some types of injuries—child abuse, violence against women, and suicide—are likely to be underreported.
The World Health Organization has estimated that 5.8 million people worldwide died as a result of injuries in 1998, which corresponds to an injury mortality rate of 97.9 per 100,000 population. More than 90 percent of injury-related deaths occurred in low- and middle-income countries. The injury-related mortality rate in these countries was double the rate found in high-income countries.
Road-traffic injuries are the leading cause of injury mortality, resulting in over 1.1 million deaths per year worldwide and ranking tenth in the leading causes of death for both sexes in 1998 (see Table 1). Self-inflicted injuries result in about 950,000 deaths per year and were ranked as the eleventh-leading cause of death for both sexes in 1998. Other major causes of injury death in 1998 were interpersonal violence (more than 650,000 deaths), war injuries (more than 530,000 deaths), drowning (more than 400,000 deaths) and fires (more than 160,000 deaths).
The pattern of injury mortality differs between high-, medium-, and low-income countries. Road-traffic injuries rank tenth as the leading causes of death in each group of countries. However, self-inflicted injuries rank eleventh in the leading
|Estimated number of deaths worldwide resulting from fifteen leading causes in 1998|
|1||Ischaemic heart disease 3,658,699||Ischaemic heart disease 3,716,709||Ischaemic heart disease 7,375,408|
|2||Cerebrovascular disease 2,340,299||Cerebrovascular disease 2,765,827||Cerebrovascular disease 5,106,125|
|3||Acute lower respiratory infections 1,753,220||Acute lower respiratory infections 1,698,957||Acute lower respiratory infections 3,452,178|
|4||Chronic obstructive pulmonary disease 1,239,658||HIV/AIDS 1,121,421||HIV/AIDS 2,285,229|
|5||HIV/AIDS 1,163,808||Diarrhoeal disease 1,069,757||Chronic obstructive pulmonary disease 2,249,252|
|6||Diarrhoeal disease 1,149,275||Perinatal conditions 1,034,002||Diarrhoeal disease 2,219,032|
|7||Perinatal conditions 1,120,998||Chronic obstructive pulmonary disease 1,009,594||Perinatal conditions 2,155,000|
|8||Trachea/bronchus/ lung cancers 910,471||Tuberculosis 604,674||Tuberculosis 1,498,061|
|9||Tuberculosis 893,387||Malaria 537,882||Trachea/bronchus /lung cancers 1,244,407|
|10||Road-traffic injuries 854,939||Measles 431,630||Road traffic injuries 1,170,694|
|11||Interpersonal violence 582,486||Breast cancers 411,668||Malaria 1,110,293|
|12||Malaria 572,411||Self-inflicted injuries 382,541||Self-inflicted injuries 947,697|
|13||Self-inflicted injuries 565,156||Diabetes mellitus 343,021||Measles 887,671|
|14||Cirrhosis of the liver 533,724||Trachea/bronchus /lung cancers 333,436||Stomach cancers 822,069|
|15||Stomach cancers 517,821||Road traffic injuries 315,755||Cirrhosis of the liver 774,563|
|SOURC e: Violence and Injury Prevention, World Health Organization. Injury: A Leading Cause of the Global Burden of Disease, edited by E. Krug. Geneva: World Health Organization, 1999.|
causes of death in high-income countries but thirteenth in low- and middle-income countries. Inter-personal violence is not one of the fifteen leading causes of death in high-income countries, but it ranks fourteenth in the leading causes of death in low- and middle-income countries. Intentional injuries are generally more prevalent in areas (or among groups) where there is political or social instability.
Around 70 percent of deaths from road-traffic crashes occur in developing countries. Developed countries report an annual road-crash mortality rate of about 2 deaths per 10,000 motor vehicles, compared to 20 to 70 deaths per 10,000 motor vehicles in developing countries. Some of the disparity in death rates is attributable to the differences in the traffic composition between developed and developing countries. Developing countries have high proportions of vulnerable road users such as pedestrians, bicyclists, and motorcyclists in the traffic stream. Trucks and buses also exist in greater proportions than in developed countries.
Transportation fatality rates differ substantially within and between modes. Overall, travel by air and rail results in fewer fatalities per billion passenger kilometers than travel by road. Within air travel, fatality rates are higher for general aviation than for scheduled passenger air services. About 90 percent of rail fatalities are occupants of road vehicles at railway crossings or railway employees involved in shunting and track maintenance. Within road transport, fatality rates are highest among motorcycle riders, pedestrians, and cyclists.
The number of deaths related to occupational injury is not well documented. It has been estimated that each year about 50,000 people die of occupational injuries in the Americas (North, Central, and South), and that about 100,000 people die of occupational injuries in India. In the developed world, many of the deaths from occupational injuries result from on- or off-road vehicles. In developing countries, most deaths occur in the workplace, resulting from factors such as old or poorly shielded machinery, toxic exposures, and minimal or nonexistent safety standards.
Trends in Injury Mortality
The trends in the numbers and rates of injury deaths differ among transport, occupational, and domestic injuries and between the developed and the developing countries. In developed countries, both the total number of fatalities and the fatality rates (as a function of distance traveled) have decreased for road traffic generally and for particular types of vehicles (e.g., passenger cars, large trucks, and so on) from the 1970s to the 1990s. The rate of railway-related fatalities has remained relatively stable. In the developing world, however, the number of vehicles is growing faster than the physical, legal, and institutional infrastructure needed to safely contain them, with the result that the number of fatalities is increasing.
The number of deaths due to falls is likely to increase in the Western world as the population ages. In developed countries at least, occupational deaths have been decreasing with increasing sophistication of equipment.
Factors Affecting the Risk of Injury Death
The risk of injury death is affected by individual factors such as alcohol consumption, propensity to take risks, and socioeconomic differences. Alcohol consumption increases the risk of involvement in motor vehicle crashes, whether as a driver or as a pedestrian. Alcohol consumption is also implicated in substantial numbers of railroad and aviation crashes, falls, drownings, fires, homicides and suicides. Prior psychological and social characteristics have been found to predict young drivers' crash involvement. Sensation seeking, impulsiveness, and risky lifestyles are associated with risk-taking and crash involvement.
Deaths from traffic injuries are often higher among children and adults from lower social positions and in more deprived socioeconomic areas. The mechanism underlying these findings may be increased exposure to risk (high traffic volumes, lack of safe areas for walking or recreation) or less education about risk avoidance. Injury mortality from other causes, such as occupational injury, also appears to be greater among persons of lower socioeconomic status.
Age and Gender Factors
Deaths related to injury commonly involve people under forty-five years of age, whereas noninjury deaths commonly involve people forty-five or older. Thus injury mortality leads to a greater number of years of potential life lost than many other causes of death (e.g., ischaemic heart disease). European data show that road traffic crashes lead to an average loss of 40 years of life expectancy, compared to 10.5 years for cancer and 9.7 years for cardiovascular illnesses.
The most common causes of injury mortality differ across age groups. For example, drowning is the leading cause of injury deaths among children under five years of age, ahead of war injuries and road traffic injuries. Road-traffic injuries are the leading cause of injury death for youths between the ages of five and fourteen, ahead of drowning, war injuries, fires, and interpersonal violence. Road-traffic injuries are the leading cause of injury death for individuals between fifteen and fortyfour, ahead of interpersonal violence, self-inflicted injuries, war injuries, drowning, and fires.
About twice as many males as females die as a result of injury. This statistic may reflect both greater exposure (greater involvement in potentially injurious activities) and greater risk-taking by males. Road-traffic injury is the leading injury cause of death in males, but self-inflicted injury is the leading injury cause of death in females.
Intentional and Unintentional Injuries
Injuries are commonly categorized as intentional or unintentional. This categorization is satisfactory most of the time, but some injury events may be difficult to place into one category or the other. For example, some single-vehicle road crashes can be identified as suicides (e.g., if a note is left), but others may be unidentified suicides. Some poisonings may be clearly intentional or unintentional, but others may be difficult to classify.
How to Decrease the Risk of Injury Deaths
In the first half of the twentieth century, the main approach to decreasing injury and injury deaths addressed the shortcomings of the victims: bad drivers, lazy workers, and unaware children or parents. The emphasis was on educational measures such as posters and pamphlets and on training courses and materials.
It is now recognized that injuries, including fatal injuries, usually involve a complex series of events that include environmental factors and the interaction of human performance and the task to be performed. Intervention at any point in the causal chain can prevent the injury or reduce its severity. Prevention of injury is relatively more important than treatment because many deaths from injury occur so quickly or because the damage is so severe that death is unlikely to be prevented by treatment.
Injury prevention has become a sophisticated science with clearly defined steps of problem identification, countermeasure development, implementation, and evaluation. Evaluation is needed to assess whether interventions have worked or not and to provide support for further implementation. The physician William Haddon Jr., who became the first director of the U.S. National Highway Safety Administration, developed a list of ten general strategies designed to prevent injury:
- Prevent the creation of the hazard (e.g., stop producing particularly hazardous substances).
- Reduce the amount of the hazard (e.g., package toxic drugs in smaller, safer amounts).
- Prevent the release of a hazard that already exists (e.g., make bathtubs less slippery).
- Modify the rate or spatial distribution of the hazard (e.g., require automobile air bags).
- Separate, in time or space, the hazard from that which is to be protected (e.g., use sidewalks to separate pedestrians from automobiles).
- Separate the hazard from that which is to be protected by a material barrier (e.g., insulate electrical cords).
- Modify relevant basic qualities of the hazard (e.g., require a maximum distance between cot-slats to prevent children from being strangled).
- Make what is to be protected more resistant to damage from the hazard (e.g., improve the person's physical condition by appropriate nutrition and exercise programs).
- Begin to counter the damage already done by the hazard (e.g., provide emergency medical care).
- Stabilize, repair, and rehabilitate the object of the damage (e.g., provide acute care and rehabilitation facilities).
Most of these general strategies apply to the prevention of both unintentional and intentional injury.
The specific interventions that have been identified as most effective in reducing deaths resulting from road crashes, include improvements in the ability of vehicles to protect occupants in a crash (both vehicle structure and safety devices such as seat belts and air bags), improvements to roads and roadsides to prevent crashes or reduce their severity, laws and enforcement to reduce drunk driving, and graduated licensing laws to allow young drivers to gain experience under less risky conditions. The specific interventions to reduce deaths relating to other injury causes have been less well documented. The interventions that have proved effective include child-resistant closures for toxic materials, lifeguards, isolation fencing for swimming pools, fire-resistant nightwear for children, smoke detectors, bars on high residential windows, firearm restrictions, and technological improvements in workplace equipment (including farm machinery).
One of the most important issues in the prevention of injury deaths (and injury in general) has been the need to ensure implementation of effective interventions. There are many interventions that have not been adopted or have been adopted only partially and whose potential has therefore not been realized. Some examples from road safety include seat belts, bicycle helmets, and measures to prevent drunk driving.
The transfer of particular interventions across cultures has been uneven. Many engineering measures to improve road safety were developed decades ago in advanced industrial countries. The social, political, economic, and cultural contexts in which they were developed differ significantly from those of motorizing countries. The different contexts are likely to be reflected in different patterns and motivations of road-user behavior. Therefore the engineering measures may not be as effective or may even be counterproductive when applied in motorizing countries.
Injury is a leading cause of death to people under the age of forty-five. Road-traffic injuries are the most common type of injury death. Self-inflicted injury is a more common type of injury death among females than road-traffic injuries. While there is a downward trend in road traffic deaths in the developed world, these deaths are likely to continue to increase in the developing world. Some effective measures to prevent injury deaths have been developed but have not always been fully implemented. Measures that have proved effective in one culture are not always easily transferable to another culture. Evaluation of the effectiveness of measures to reduce injury mortality is crucial.
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NARELLE L. HAWORTH