Measuring the public health impact of injuries.

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).