Measuring the Public Health Impact of Injuries

Abstract

In its groundbreaking 1985 report, Injury in America: A Continuing Public Health Problem, the Institute of Medicine’s Committee on Trauma Research stated that “injury is caused by acute exposure to energy, such as heat, electricity, or the kinetic energy of a crash, fall, or bullet. It may also be caused by the sudden absence of essentials, such as heat or oxygen, as in the case of drowning. Injury may be either unintentional (accidental) or deliberate (assaultive or suicidal)” (1, pp. 3–4). The extent, severity, and impact of injury are largely determined by the amount of this energy concentrated outside the band of human tolerance. Records on the impact of injuries date back to biblical times, when we are told about the massive drowning that occurred when “the waters returned and covered the chariots and the horsemen and all the hosts of the Pharaoh that had followed [the Israelis] into the sea; not so much as one of them remained” (Exodus 14:28). Although the specific mechanisms by which injuries happen may have changed over time, the collective impact on society of all fractures, sprains, cuts, contusions, and the many other forms of injury has been felt since the beginning of history. Measuring this impact and its characteristics has been critical to our efforts to identify priorities for programs and policies aimed at reducing injuries and their consequences. In contrast to other reviews, which present scales to measure the impact of injuries at the individual level (2), in this paper we focus on metrics used to quantify the burden of illness and injuries to populations. We present the evolution of these metrics and discuss their application to injury. We start with those that quantify the burden related to fatal injuries. We then cover metrics that expand the measurement to nonfatal injuries. Lastly, we discuss metrics that integrate fatal and nonfatal consequences. For each metric, we summarize its characteristics, advantages, and disadvantages. When possible, we also present what knowledge each has contributed to our understanding of the “burden” of injuries. Table 1 lists all of the metrics reviewed, together with the principal reference describing their development. Table 2 summarizes the extent to which the metrics cover fatal and/or nonfatal consequences, whether they apply to subpopulations, and whether there are population norms for them (at least in the United States). Counts of the absolute numbers of injury deaths and their relation to other causes of death have been one of the primary means of quantifying the burden of injuries. They remain an important metric for establishing injuries as an important public health problem. The first published leading cause-of-death report in the United States showed unintentional injuries as the fourth cause of death over all ages, suicide as the 12th, and homicides as the 18th for the year 1949 (3). In 2000, the latest year for which similar statistics are available, the 97,900 fatal unintentional injuries constituted the fifth leading cause of death, after diseases of the heart, malignant neoplasms, cerebrovascular disease, and chronic lower respiratory diseases (4) (table 3). Suicides (n = 29,350) have increased in rank from 12 to 11 and homicides (n = 16,765) from 18 to 14 (5). Taken together, all injuries (unintentional and intentional) constitute the fourth leading cause of death over all ages. Further breakdowns of the leading causes of death by age and gender provide interesting additional information on the burden of injuries. For example, among children and young adults aged 1–34 years, unintentional injuries, homicide, and suicide constitute the first, second, and third leading causes of death, respectively. More lives of persons aged 1–34 years are lost to injury than to all other causes of death (table 3). For of all ages, unintentional injuries are the fourth leading cause of death, the and homicides the among of all ages, unintentional injuries are the leading cause of death and suicide the homicides not rank in the leading causes of (5). injuries, the leading mechanisms of death are related to and for and of all injury deaths in 2000, or one of all injury deaths when for an additional of injury deaths and for the of injury deaths by by age and gender a of those is the of this measure the impact of injury as a leading cause of death among children and young we from at absolute of deaths to years of lost in information about age at death with years of to of the of showed that the leading cause of lost years of in after diseases of the of have been on whether one age years, age years, or or other of an age which is to is to be such as years of years or burden of of the of the to be a metric for quantifying the burden of injury in of lives 1 the leading causes of in the United States in are the leading to age years, for of all injuries for 18 and constitute the leading to followed by malignant suicide and health of all (5). of the burden of i