There are a plethora of data available nationally40 and locally to define and research injury epidemiology. A number of these data sources have been used in the production of this chapter and are referenced; the vast majority of the data come from the CDC and NCIPC, specifically the WISQARS (Web-Based Injury Statistics Query and Reporting System) program.3 This database resource is web-based and interactive, allowing the user to determine the population or subpopulation of interest as well as the specific epidemiologic factors of interest. Although data on nonfatal injuries are not as comprehensive or robust as those on fatal injuries, significant improvement has occurred in recent years relating to the scope and quality of data collection. This has enhanced the understanding of the magnitude and significance of injury as a major public health problem.
Several of these databases provide information on several types of work-related injuries with a number of others focusing on injuries and injury deaths related to other unintentional and intentional injuries. Many are ongoing surveillance systems. This collective group of databases varies in scope and the extent to which they provide information on mechanism and intent, nature and severity, risk factors, health services use, costs, and health outcomes. Some are population based and some are not. Comprehensive data on fatalities are available from vital statistics data, although these data do not provide detailed information about the extent and nature of injury sustained.
Standardized data on nonfatal injuries treated in the ED, including those treated and released, transferred, or hospitalized are available from the National Electronic Injury Surveillance System—All Injury Program (NEISS-AIP).41 The NEISS-AIP is a collaborative effort between the National Center for Injury Prevention and Control (NCIPC) and the US Consumer Products Safety Commission (CPSC). This database acquires information on over half a million injury-related ED visits secondary to a consumer product to a nationally representative sample of 66 hospitals on an annual basis. Products include things such as bicycles, treadmills, cars, or ladders. The NEISS-AIP is the most comprehensive database on all nonfatal injuries presenting to hospitals with EDs that is currently available. These data, together with injury mortality data, can be accessed through WISQARS.3
Injuries that result in hospitalization can also be obtained from both the National Hospital Discharge Survey (NHDS) and the Healthcare Costs and Utilization Project (HCUP-3).42,43 Both sources can provide detailed information regarding the nature and severity of injuries, treatment, and discharge disposition, but they are limited in that codes for classifying the mechanism and intent of the injury are not routinely recorded. Although strategies exist for estimating distribution by mechanism and intent given incomplete data, the lack of uniform E-coding of hospital discharges as well as the exclusion of ED cases that are treated and released remains a significant impediment to the optimal use of these databases for studying the entire spectrum of injury epidemiology.
An additional confounder in the reliability and accuracy of these essentially administrative databases is the extent, prioritization, and accuracy of ICD coding. Also, it should be pointed out that these are only population based from the standpoint of the population of hospitalized patients. They do not capture all deaths and will not ever include patients with minor injuries not seeking treatment at hospitals.
More data on nonfatal injuries not resulting in hospital admission or death are available from the National Health Interview Survey (NHIS),44 and the National Ambulatory Care Survey (NAMCS).45 The NHIS relies on self-reports of injury events, whereas both the NAMCS and the NHIS rely on data abstracted from injury-related visits to hospital EDs, hospital outpatient departments, and/or physician offices. These databases do generally include E-codes.
In addition to these sources of comprehensive data across all types and severities of injury, several sources of national data exist that are specific to a particular mechanism or intent. Examples include the Fatal Accident Reporting System (FARS),46 the National Automotive Sampling System—General Estimates System,47 and the Crash Injury Research and Engineering Network (CIREN).48 Also worthy of note are the National Occupant Protection Use Survey (NOPUS), National Fire Incident Reporting System (NFIRS), the National Traumatic Occupational Fatality Surveillance System and the Survey of Occupational Injuries and Illness for Occupational Injuries, the National Crime Victimization Survey (NCVS) and the Uniform Crime Reporting System for Intentional Injuries (which excludes suicides and self-inflicted injuries),49 as well as the American Burn Association Burn Repository.50 These databases are particularly useful for monitoring injury rates specific to certain mechanisms and for identifying risk factors associated with their occurrence.
Less developed are the data systems that deal with violence-related injuries overall and firearm-related injuries in particular. Created in 2002, the NVDRS is a surveillance system that pulls together data on violent deaths in 32 states, including information about homicides, such as homicides perpetrated by an intimate partner (eg, boyfriend, girlfriend, wife, husband), child maltreatment (or child abuse) homicides, suicides, and deaths where individuals are killed by law enforcement in the line of duty.51,52 The system also collects data on unintentional firearm injury deaths and deaths of undetermined intent. Linking information about the “who, when, where, and how” from data on violent deaths provides insights about “why” they occurred. Frontline investigators, including homicide detectives, coroners, crime lab investigators and medical examiners, collect valuable information about violent deaths. But these data are often not combined in a systematic manner to provide a complete picture. NVDRS attempts to provide a more complete picture by collecting facts from four major sources about the same incident and pooling information into a usable, anonymous database. An incident can include one victim or multiple victims. The four major data sources are death certificates, coroner/medical examiner reports, law enforcement reports, and crime laboratories. The facts that are collected about violent deaths include circumstances related to suicide such as depression and major life stresses like relationship or financial problems, the relationship between the perpetrator and the victim—for example, if they know each other, other crimes, such as robbery, committed along with homicide, and multiple homicides, or homicide followed by suicide. As data are only provided from 32 states and are not nationally representative, and because of previously discussed issues with inaccurate data from some of the linked data sources, some estimates and conclusions that can be drawn from these data are limited. There has been some movement toward developing a data collection system similar to that developed for motor vehicle crashes, which would be an essential component to a nationwide effort at reducing the epidemic of violence currently being experienced in this country.
Of particular interest to trauma clinicians and clinical researchers are clinical databases. The most noteworthy of these is NTDB.27 This database is the largest aggregation of US trauma registry clinical data ever assembled. Since its inception, more than 6 million records have been amassed emanating from more than 900 trauma centers of various levels. Data completeness, accuracy, and validity, have been continuous concerns, which have been increasingly ameliorated over time. Recent implementation of mandatory submission of from trauma centers accredited by the American College of Surgeons Committee on Trauma has increased the utility of this important resource. As a partial solution to these issues, the American College of Surgeons Committee on Trauma, which administrates the NTDB, has instituted the National Sample Program that specifically seeks more highly controlled data from a nationally representative sample of 100 Level I and Level II trauma centers in the United States. The American College of Surgeons Trauma Quality Improvement Program (ACS TQIP®) collects data from over 300 trauma centers, ensures that they meet rigorous quality checks, and use them to provide feedback about each trauma center’s performance. The program uses risk-adjusted benchmarking to provide each trauma center with accurate national comparisons.53
Two additional phases of trauma care where data have been lacking are the prehospital phase and the post–acute care phase or rehabilitation. The National Emergency Medical Services Information System (NEMSIS)54 is the national repository that is being developed to store prehospital EMS data from every state in the nation. Since the 1970s, the need for EMS information systems and databases has been well established, and many statewide data systems have been created. However, these data- bases vary significantly in their ability to acquire patient and systems data and allow analysis at a local, state, and national level. Currently 37 states contribute to the NEMSIS database, which is being characterized as the National EMS Registry and utilizing the NEMSIS data dictionary. There is an increasing impetus due to initiatives from professional organizations and regulatory agencies to have prehospital run sheets and data systems be NEMSIS compliant, which will facilitate submission of consistent and valid data to the national database. Although a national database, it is a convenience sample and as a result does not give population-based estimates.
Information from the postacute phase of care is essential to long-term clinical and financial outcome studies. The Uniform Data System for Medical Rehabilitation (UDSMR)55 catalogs data from rehabilitation hospitals nationwide for use in evaluating the effectiveness and efficiency of their rehabilitation programs. It provides the most comprehensive data available on rehabilitation patients across many diagnostic categories, including injuries. The database includes information on demographics, type of injury, length of stay, primary payor, and postinjury rehabilitation circumstances such as employment status, living situation and Functional Independence Measure (FIM), which is the most widely accepted functional assessment measure in use by the rehabilitation community.
National data can be used for drawing attention to the magnitude of the injury problem, for monitoring the impact of federal legislation, and for examining variations in injury rates by region of the country and by rural versus urban/suburban environments. They can also be useful in aggregating sufficient numbers of cases of a particular type of injury to analyze causal patterns and clinical or other outcomes on an individual or systems basis.56 Often, however, these national data are not appropriate for developing and sustaining injury prevention programs at the state and local level. State and local data are more likely to reflect injury problems specific to the local area and therefore more useful in setting priorities and evaluating the impact of policies and programs in these more limited catchment areas. Additionally, local data are typically more persuasive than are national data in advocating to establish a policy or to achieve funding of injury control programs at the local level. Some of the previously described national databases do provide subsets of data at the state or even county level; however, many do not.
Availability, accuracy and completeness of local injury data varies substantially by state and county. Vital statistics and death certificate data are generally available for 100% of injury-related deaths. As previously discussed, however, these data are limited in the information they provide about the nature and circumstances of the injury, cause of death, and risk factors associated with the death. Medical examiner and coroner reports can be a useful adjunct to death certificate data, but once again, the completeness and quality of these data vary substantially from state to state. Autopsy rates are equally variable and are generally biased toward being performed in cases of suspected homicide.
State and local data on trauma hospitalizations are generally available from two principal sources, either uniform hospital discharge data and hospital or system trauma registries. Hospital discharge data are predominantly administrative in nature, whereas trauma registry data are primarily clinical. Both types of databases have limitations, which have been alluded to previously. Trauma registries suffer from both selection bias and inconsistent inclusion criteria as well as highly variable data integrity. In both types of databases, ICD coding is not uniform. Administrative databases in general are not useful in attempting to analyze clinical issues despite available methods to estimate injury severity using ICD codes.57 Both hospital discharge databases and trauma registries do not include information on trauma deaths that occur at the scene, in transport, or in the ED nor do they routinely include patients treated and released.
Specifically, in comparison to hospital discharge data, trauma registries typically include more detailed information regarding the cause, nature, and severity of the injury. Some trauma registries will also include data on deaths occurring in the ED. Trauma registries, for the most part, may collect information only on “major trauma” patients. This leads to sample bias of a small subset of all injured patients in a population. It is important to reemphasize that caution should be exercised in using these databases for describing the epidemiology of trauma as neither is population based.
Uniform data on trauma patients treated and released from EDs, hospital clinics, and physicians’ offices are generally less accessible on a county or state level. Other data sources, often available at the state and local levels that can be useful in studying the epidemiology of injury, include routinely collected information from EMS, police, fire departments, poison control centers and child protective services, among others.
The utility of existing data at the state and local level can be significantly enhanced by linking data across multiple data sources. Single data sources are often limited in their content or scope of coverage, or both. Techniques have been developed and are continually being improved to facilitate linkage of these databases to avoid the high costs of gathering new data.58 Several states have now linked hospital discharge data, vital statistics, police crash reports, and prehospital run sheet data.
Local, state, and national data are extremely expensive to collect and even more expensive to ensure they are reliable and accurate. As a result, funding for registry or database initiatives is often hard to come by, and those resources supported by federal dollars are ever at risk for budget cuts. However, these data are incredibly important, forming the cornerstone for injury prevention, identifying areas in which additional research is needed, and pointing out where advocacy efforts are necessary.
In summary, injury imposes a heavy burden on society in terms of both mortality and morbidity along with its sizable economic burden on the health care system and society. Largely unrecognized is the fact that many fatal and nonfatal injuries are preventable using specific strategies guided by the analysis of injury epidemiology. Hence there is no societal level of tolerance, or perhaps intolerance, and fear of incidence as there is for HIV or West Nile virus and H1N1 influenza. Yet, these diseases contribute much less to the burden of public health disease than do injuries.
Risks of injury death vary by age and gender. The majority of injury deaths are unintentional, with elderly people at a particularly high risk of death from unintentional injuries. Considering intentional injuries, overall, suicide greatly exceeds homicides, but rates again vary by age, gender, and urban or rural residence. Mechanisms of injury death also vary be age. The risk of injury death on the job varies by occupation. From a global perspective, the United States compares less than favorably with other countries in terms of fatal injury, particularly those related to firearms (Figs. 2-4 and 2-5).
Comparison of the United States to other countries, fatal motor vehicle crashes.
Comparison of the United States to other countries, fatal injuries secondary to gun violence.
In total, injury deaths declined slightly during the 2002–2010 period with significant variation by mechanism of injury. All causes are declining with the exception of fall-related deaths, which are increasing significantly. Injury morbidity rates have demonstrated declining trends among all age groups except the elderly. Although certain assumptions or “profiling” may arise from the association of injury and certain mechanisms thereof, a number of confounding factors unrelated to racial origin have been outlined, which should dissuade broad generalizations that are unfounded. Alcohol and other drugs continue to be intimately associated with all types and mechanisms of injury.
In conclusion, although significant strides have been made in reducing the rate at which injury occurs, trauma remains a major public health issue. More efficient ways of treating injuries as they occur, or tertiary prevention, should and will continue to be the major thrust of clinical care providers and researchers. However, it is equally and perhaps more important that efforts to develop appropriate programs and policies that will prevent them from occurring also be prioritized. Education of policy makers and the public that this public health epidemic can and must be controlled is an essential component of this effort. Accurate, easily obtainable and understandable data is a key first step in this process.
Integrated efforts at primary, secondary, and tertiary prevention, along with public information and education programs, are the only effective means to effect injury control and reduce the burden of injury on individuals, the health care system and society at large.59 Understanding the importance of high-quality data as a building block for the study of injury science is important for all who participate in the care of the injured. Studying the epidemiology of injuries provides the opportunity for understanding how, when, and with whom to intervene.