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2 Epidemiology of Injuries: The Need for More Adequate Data Epidemiology is the fundamental science for studying the occurrence, causes, and prevention of disease. Injury epidemiology is a young scientific field with a theoretical basis within the wider framework of epidemiology ? 2 7 6 7 7 ~ 6 3 This new discipline has focused on the development of epidemiologic tools to identify problems, def ine their extent, and determine causative factors that are amenable to intervention. An equally important objective has been to develop evaluation methods to determine the effectiveness of counter meaSUreS. 2 7 7 ~ 2 0 7 Epidemiologic studies of injury should not exist in isolation, but must be able to draw ideas and methods from clinical, laboratory, and biomechanical research, just as these other forms of research need to draw from epidemiology. Furthermore, research methods applied to one segment of injury analysis may be relevant to others. For example, methods used for air-crash investigation have been applied to analysis of train crashes. Such exchange of ideas and methods is common in disease research, but unfortunately not in injury research. A prerequisite for the scientific study of injury is the acquisition of data on which to base priorities and research. Despite the obvious importance of injury as a public health problem, information to permit the study of the epidemiology of most injuries is not available.209 Although there are basic data on time, place, and person for some injur ies and deaths , even basic information is often lacking as to the numbers and characteristics of people injured and the factors that influence injury causation, especially in nonfatal events. Detailed information on the groups that are particularly sus- ceptible to injuries and their effects is not adequate. 25
26 :: -I.: Injuries from motor-vehicle crashes constitute the only exception to this limitation.: The incidence. prevalence, and effects of motor-vehicle injur ies, as well as measures to counter them, are moderately well understood, compared with the epidemiology of other injuries, although even here information about long-term effects is sparse. The acquisition of knowledge about motor-vehicle injuries is a direct result of the funding of research on injury epidemiology from two sources whose primary mandate is the study of automobile injuries--the National Highway Traffic Safety Administration and the Insurance Institute for Highway Safety. Little funding has been available for research into the epidemiology of other in jur ies; consequently, our knowledge of these other in jur ies is slight . HUMAN FACTORS IN INJURY CAUSATION Injuries, like diseases, do not occur at random. Some population groups are at increased risk of injury because of greater exposure to hazards, decreased ability to avoid hazards, or decreased resistance to injury, and some groups have a lower likelihood of complete recovery or survival once injured. Age differences between injured and uninjured persons are substantial injury rates are higher among persons under age 45, but the elderly and persons aged 15-24 have the highest injury fatality rates. Other demographic and social factors also influence the risk of in jury. The risk of fatal in jury is 2.5 times as great for males as for females; males are also at greater risk of nonfatal injury, although by a smaller factor. Fracture rates are higher in older women, because of the greater prevalence of osteoporosis or bone decalcification in thin group. The increased likelihood of fracture of the hip among the elderly is much greater for women than for men. Death rates for many injury categories vary by a factor of 10 or more among the states. Except for homicide and suicide, death rates are~highest in rural areas, perhaps because of differences in socioeconomic status, types of occupational and other exposures, and lower availability of prompt emergency care. Socioeconomic 'status can influence the likelihood of injury. For example, the incidences of homicide, assaultive injury, pedestrian fatality, and housefire
27 fatality are high among the poor. Although wealth can place people in high-risk categories for some injury causes, such as crashes of pr ivate planes and incidents associated with home pools, the burden of in jury rests disproportionately on Me poor. High-risk jobs, low- quality housing, older cars, and such hazardous products as space heaters tend to be concentrated among poorer people.~3 2~0 The death rate from unintentional injury as a whole is twice as high in low-income areas as in high-income areas. 14 The use and abuse of alcoholic beverages influence the likelihood of virtually all types of in jury, even among young teenagers. Almost half of fatally injured drivers and substantial proportions of adult passengers and pedestr fans k illed in motor-vehicle crashes--as well as in falls, drownings, fires, assaults , and suicides--have blood alcohol concentrations of 0.10 percent or higher . 2 0 6 In a study of emergency-room patients, alcohol was detected in 30 percent of the patients injured on the road, 22 percent in jured at home, 16 percent in jured on the job, and 56 percent injured in fights or assaults.~97 Contrary to popular perception, alcohol can reduce the human tolerance to impact and increase the risk of perma- nent paralysis and other serious injuries. This reduced tolerance is receiving only scant attention and study. Understanding this might provide clues to methods of preventing in jury. In both highway and nonhighway event';, the more severe ache event, the higher the percentage in which alcohol plays a role. Alcoholic-beverage use is involved, for example, in about 10 percent of property-damage crashes, about 20 percent of crashes with a serious injury to an occupant, about 50 percent of all fatal crashes, and about 60 percent of all single-vehicle fatal crashes .2 ~ 2 0 4 Other chemicals and drugs have not been shown to play a causal role in a substantial proportion of injuries, but some evidence suggests that abuse of amphetamines, marijuana, or other drugs can seriously impair driving performance, and individual cases of drug contributions to crashes have been documented.92 208 Use of multiple drugs, especially the combination of an alcoholic bev- erage with one or more other drugs, can create additional problems. Laboratory studies indicate that many drugs in co~ranon use--such as benzodiazepines, barbiturates, and phenothiazines--have a harmful additive or synergistic
28 effect when used in combination with alcoholic bev- erages.' 2 2 o ~ 2 ~ 9 Identifying particular groups of people likely to drive under the influence of drugs is especially important for effective preventive efforts; unfortunately, data for such identification are very limited. Numerous studies have attempted to correlate per- sonality traits and other behavioral factors with injuries; their results have been of limited practical use in predicting who will be injured. The bulk of the evidence suggests that the behavioral factors studied are very transient.~63 Constant monitoring of those behavioral factors in the population would be necessary for identifying persons at acute r isk . Such monitor ing is not feasible or acceptable in this country. PRODUCT, WHICLE, ~ TROLL FACTORS IN INKY CAUSATION Much more attention has been paid to identifying the role of people in initiating injury events than to identifying the role of products, vehicles, and other environmental factors. Only minimal information is available on the often subtle interaction of human and environmental factors in event initiation, because the necessary epidemiologic studies have never been done. Specific environmental contributions have occasionally been identified, BS in motor-vehicle or ho~-pr~uct investigations leading to either voluntary or compulsory product recalls. More often, excessive injury experience is found to be associated with an environmental factor whose exact role cannot be proved. For example, Utah uses a dense material to build itch roads, with resulting low coefficients of friction, and has more wet-weather crashes in which poor road friction is often a factor-- than do surrounding states, which use a less dense material. Specific design features have been associated with high error rates not seen with other designs. The arrangement of knobs on some stoves, for exile, makes it much easier for people to turn on the wrong burner and burn themselves or start a fire than it is with other knob arrangement. In World War lI, We reverse positioning of controls for landing gear and flaps resulted in more than 500 plane crasher.' More in known about characteristics of specific environmental and vehicle design and construction features as determinants of the severity of injury,
2g because of the attention, especially dur ing the last 15 years, to features of motor vehicles and the road environ- ment that produce or prevent in jury . Some studies have been particularly successful because they have involved multidisciplinary approaches based on epidemiology, clinical medicine, pathology, and biomechanics. The knowledge gained has led to important interventions, such as improved door locks and windshield glass, energy- absorbing steer ing columns, removal of roadside obstacles, and development of breakaway signs and lam hosts 3 9 S ~ ~ 2 2 ~ 6 6 ~ 7 ~ But important as - cts repin largely unknown, and we still need information about product features that contribute to injury and death in fires, falls, and recreational and other injuries. EATS OF ~ INJURY S==IL~CE SYSTEM Injuries have definable and correctable causes. Local, state, and federal authorities can make decisions about how to prevent injuries when they understand the elements of effective preventive measures and know who is at high risk, what types of injuries are sustained, the severity of their consequences, and when, where, and under what circumstances injuries occur. By comparing such information over time and among different popula- tions, they can observe changing patterns of injuries and identify and implement strategies of intervention. When specific interventions are carried out, the same informa- tion can be used to evaluate their effectiveness. Development of effective intervention strategies requires an adequate national surveillance system for monitoring injuries, their causes, and their short-term and long-term consequences. Continued monitoring of the most severe injuries and of ~ representative sample of less revere injuries is an essential component of efforts to implement and evaluate the effectiveness of measures to reduce injuries. Table 2-1 lists some typical data needs for effective injury surveillance. The data listed would not all be developed in a single surveillance system, but rather would emerge in a coordinated program involving several systems ~ some continuous and others periodic, some simple but geographically broad and others more complex but limited to a few representative com- munities. Such a mix of systems can yield necessary information on which to base and evaluate safety programs at lower cost and with greater feasibility than a single complex and continuous surveillance system.
30 TABLE 2-1 Examples of Data Needs for Injury Surveillance Category Data Needs Time Place Person Types of in jur ies Causation Circumstances Date and time of in jury event State, county, city; indoor, outdoor, road, etc. Demographic character istics of in jured and unin jured persons: age, sex, r ace, SES, phys ical character istics, occupation, place of res idence Types and sever ities of in jur ies Agents caus ing in j ury; other mediating factors (such as vectors and vehicles) Host factors (alcohol, underlying diseases, debility), intention (suicide, homicide, accident), environmental conditions ( Human-environment mismatch.), vector-vehicle factors (mater ial failure , misuse, etc. ), nonmedical emergency activities Medical care Resuscitation, EMS, ER, hospitaliza tion, rehabilitation, long-term care Health outcome Death, amputation, permanent disability, disability days, costs, causes of morbidity and mortality EXISTING INJURY SURVEILLANCE SYSTEMS AND THEIR LIMITATIONS Information on injuries and injury-related events must be obtained from various sources and through different means. For example, information on severe injuries may be available only from hospital records, but information on vehicle crashes typically originates in police reports. Moreover many reportable and even serious crashes are not
31 reported to the police. A surveillance system aimed at injury prevention therefore requires a combination of methods for both gather ing and integrating information from a variety of sources. It also requires the interest and ability to carry out a collaborative endeavor among the several groups that may be collecting or analyzing the data. Today, no national system can provide comprebensive information about injuries and disabilities. Surveil- lance systems have been important in control ling and studying other serious health problems, especially infectious disease and cancer. They involve collection of data at local, state, and federal levels by such organizations as the Centers for Disease Control, the National Cancer Institute, and the separate state cancer r egistr ies . Most of the data sources currently available for the study of injury have serious inadequacies. National mortality statistics on injuries are collected by the National Center for Health Statistics (NCHS ) and are based on the International Class if ication of Diseases (ICD) codes. ~ 9 9 These codes divide fatal in juries, according to the apparent intent of the persons involved, into three categories--unintentional, homicide, and suicide. They specify injury types and also classify the events and circumstances related to the injuries. The current codes are seriously limited; for example, there is no way to identify work- or recreation-related deaths. In addition, it is not possible to determine from NCHS files the location or time of an injury; with respect to location, only the residence of the deceased and the place and date of death are specified. Another problem related to the NCRS mortality data is the delay (typically about 3 years) in their availability. . More detailed, and Are useful, mortality data are collected on all motor-vehicle crash deaths by the National Highway Traffic Safety Administration (MENSA). The Fatal Accident Reporting System (FARS ) is a com- puteriied data base that describes fatal crashes since 1975 on the basis of information collected by agencies in each state government under contract to NETSA.~27 The sources include police accident reports, state vehicle registration files, state driver licensing files, state highway department files, vital statistics, death cer- tificates, and coroner or medical examiner reports. The FARS information, which contains 90 data elements for each fatal crash, has proved invaluable to researchers
32 concerned with reducing motor-vehicle crash deaths and Injuries ~ ~ ' Recently, MESA began another ma jor data collection program: the National Accident Sampling System (NASS), which is designed to produce a nationally representative sample of all tow-away motor-vehicle crashes. ~ .~ The NASS uses specially trained crash investigation teas at 50 sites across the country to collect data. Each team is responsible for collecting detailed information about the people, vehicles, and environment involved in a sandpile of motor-vehicle crashes. The resulting data are much more detailed than those available from police reports. They include specific hospital and other information on the injuries involved, as well as on the deformation of vehicles--information that should be invaluable in relating vehicle crash forces to the injuries sustained. The NASS teams investigate about 10,000 crashes a year. Routinely collected data on nonfatal in jur ies are seriously limited. As part of the National Health Interview Survey, NCHS collects information on ire juries, but the samples are small, details are few, and the data have only slight utility for epidemiologic research. The Consumer Product Safety Commission (CPSC) collects data only on injuries and fatalities associated with most consumer products (excluding automobiles and work-related equipment not used in the home). Through the National Electronic Injury Surveillance System, CPSC collects data on in jury circumstances and the products involved from sample of 73 hospitals.~° Occupational injuries were recently included. CPSC also collects death certificates involving injury, but reporting is incomplete and state confidentiality laws limit the amount and type of information about products associated with those deaths. To understand the characteristics of products that are involved in injury, researchers must have detailed information on the products. With the notable exception of motor vehicles, however, most injury reporting systems do not record brands or models of involved products. The Occupational Safety and Health Administration (OSRA) reporting forms do not include the type, manufac- turer, or model of industr ial machines involved in worker injuries. When information that might identify a manufac- turer is part of the CPSC files, it must be expurgated before the file can be made available to anyone outside that agency, including those seeking information under
33 the Freedom of Information Act, unless the manufacturer gives permission to divulge the information. Thus, the only national data on injury and death related to most products cannot be used to identify the hazardous characteristics that may be peculiar to, or most common among, specific brands or modern. This lack of brand or even gener ic information on products associ- ated with injuries is clearly a major barrier to the prevention of injuries. In contrast, the presence of motor-vehicle identification information in police and national data f iles , available to private researchers, has resulted in substantial specification of the charac- teristics of vehicles that are associated with excessive crashes either alone or in combination with various driver characteristics. Recalls of vehicles with modifiable hazards and changes in designs of new vehicles have resulted from this free flow of information. EPIDEMIOLOGIC USES OF INJURY DATA Surveillance systems can enable identification of important shifts in patterns of injury or injury complica- tions; e.g., some occur suddenly or locally and others occur more slowly or over wider geographic areas. If a system for identifying the immediate cause of death from injury had been available, it would hare been apparent much sooner after World War I] that the immediate cause of death shifted from abock that resulted from blood loss to kidney failure, then to respiratory failure, and then to delayed infection caused by usually harmless organisms that overwhelm immune mechanisms and cause multiple organ failure. What each surgeon was identifying as an appar- entry unique problem involving his patients was in each of the above modes of death, after considerable delay, found to be a national trend affecting thousands of patients. In contrast, the National Electronic Injury Surveil- lance System (NEISS), a modest surveillance system developed by CPSC to identify new injury pattern., permitted early identification of a true epidemic of skateboard injuries and resulted in many local programs to deal quickly with this; new phenomenon. It also helped to identify quickly a shift away from skateboards to skates and thus led to avoidance of safety legislation that had been predicated on continued growth in the popularity of skateboards. Surveillance systems should
' . ! 34 be able to identify and respond to new and potentially threatening patterns, such as the occurrence of death and injury resulting from apparent outbreaks of suicide attempts among students attending specific high schools. To understand whether a particular product, behavior, or other factor is hazardous, epidemiologists consider it essential to know not only about the frequency of its involvement in injuries, but also whether that frequency is greater than its frequency in nonin jury situations. This sort of exposure information is not collected by the NASS, the NEISS, or OSHA and is collected - only rarely by most other data collection systems. A number of states have computerized files of police crash reports that are available for research purposes. These files contain little information on injuries. Typically, motor vehicle-related in jur ies are divided into only four categories--one for death and three to cover the entire spectrum of nonfatal injuries. Moreover, police data tend to underestimate--sometimes substan- tially--the numbers of injuries that occur.~s Despite these limitations, police data on crashes are valuable, especially when relatively great sample size is more important than detailed injury data. A variety of specialized data sources for specific ir,jury t "es, such as burns, are available, but all have serious limitations for epidemiologic research. Trauma center registries, for example, are not population-based and cannot relate their selected cases to less seriously injured or noninjured populations. Indeed, for nonfatal injuries, there is no alternative to specially focused and often expensive data collection projects. Little is known about the less severe injuries that cause most of the visits to physicians and restriction of normal activities. The long-term consequences of what may appear to be minor injury are essentially unknown. For example, the long-term effects of brain injuries that initially are considered minor are unknown, although data from recent studies of boxers suggest that even apparently minor head injury can have serious long-term seque}ae.~ ask Many types of injuries produce a wide range of chronic disabilities, but the long-term impact of injuries in the United States is unknown. For many other health problems, such as cancers and cardiovascular diseases, long-term longitudinal studies have prc~ided valuable epidemiologic data on which to base intervention strategies. There is
35 every reason to believe that similar studies of injuries would yield similarly valuable information. High-quality epidemiologic data are essential for the planning, development, and evaluation of efforts to prevent injuries. Despite this essential intertwining of epidemiology and prevention, many preventive activities have not been based on epidemiology; nor have they been evaluated epidemiolog ically. For example, the huge federal effort supporting high-school driver education as a means of reducing injuries was not evaluated before such education was greatly increased. More than 10 years later, research showed that dr iver-education programs actually increased injuries by encouraging teenagers to drive earlier and that such education did not reduce the crash involvement of those trained. 6 3 Valuable resources were wasted, because the interventions chosen were not based on adequate data or sound epidemiology. However, even with limited resources for research into injury control, considerable advances in the state of knowledge have been made in specific cases, through sound research based on adequate data and epidemiologic principles. Many more such advances involving a wide range of injuries are possible. For almost any generally homogeneous set of injuries that has been studied, it has been possible to identify factors that greatly increased risk and factors that could be changed. For example, when children's fatal falls in New York City were studied in adequate detail, researchers found that such fatalities resulted mainly from falls from windows in multistory buildings. Fatal falls of children were reduced ';ub';tantially by an inter- vention program that combined distribution of window cover ings, education regarding the problem, and required use of the coverings by landlords. Drowning is an example of a phenomenon on which more ref. ined epidemiologic knowledge than is now available is needed, if better prevention strategies are to be devel- oped. To prevent drowning, information in needed about the bodies of water involved, the activities of the drowned persons and others in their company at the time of the drownings, and the environmental conditions. If most children who drowned wandered alone into unfenced, unattended swimming pools, the appropriate intervention strategy would be different from that if most children who drowned did so because they played in streams or ponds. Unfortunately, where data are available at all ,
36 this kind of specification of circumstances is usually not included. Injur ies and injury-related deaths can be greatly reduced in the next several decades. The reductions will require substantial programs of national surveillance, epidemiologic analysis, and evaluation. Ma jor research questions that could be addressed with proper epidemio- logic data are discussed in the next chapter. RECOMMENDATIONS 1. The United States requires effective injury sur- veillance systems for gather ing and integrating informa- tion from a variety of sources on which to base the planning and evaluation of control efforts. This would include long-term longitudinal studies of in juries and the co' lection of more refined data on specific types and causes of injuries and exposures to injurious environments. 2. A national capacity should be developed for the quick identification and control of outbreaks of specific Incur yes. 3. A consistent and accurate system for coding the causes of injuries needs to be used by hospitals. 4. Research is needed to determine the short- and long-term costs of injuries.