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What is an injury?
  1. J Langley1,
  2. R Brenner2
  1. 1Injury Prevention Research Unit, Dept of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
  2. 2Epidemiology Branch, Division of Epidemiology, Statistics, and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA
  1. Correspondence to:
 Professor John Langley
 Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand;

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A clear definition is needed

Paramount to the study of any disease is the clear definition of the subject of interest. The definition of injury is fraught with challenges and complexities. Importantly, injuries unlike most diseases must be defined simultaneously by the causative event and by the resulting pathology. For example, bruising can occur in the absence of a mechanical insult to the body (for example, in the case of sepsis or a bleeding disorder) and thus, taken alone, cannot be considered an injury. Similarly there are many events, such as car crashes, that result in no pathology, even if “victims” are bought to an emergency department for observation. Thus, the theoretical definition of injury must incorporate both cause and outcome. Equally challenging is the operational definition of injury, for example, which diagnoses, codes, or combination of codes from the International Classification of Diseases (ICD)1 define injury? In this paper we discuss shortcomings in existing theoretical and operational definitions of injury with a view to advancing injury prevention research and practice.


The theoretical definition of injury is problematic since there is no basic scientific distinction between disease and injury. In some cases the etiologic agents are identical, for example the result of the brief exposure to toxic gas is often called injury whereas eventual pulmonary effect of chronic exposures to low concentrations of the same gas may be called disease.2 Many of the public health orientated injury texts consider that the “energy definition” best describes the causes and pathologies of interest, namely “injury” refers to damage to the body produced by energy exchanges that have relatively sudden discernible effects.3 In contrast, “disease” tends to be used for pathologies such as cancer which manifest themselves over longer periods after first exposure to their causes. While this seems to …

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