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On preventing all injuries: a response to Pless
  1. John Desmond Langley,
  2. Colin Cryer
  1. Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand
  1. Correspondence to Dr Colin Cryer, Injury Prevention Research Unit, Department of Preventive and Social Medicine, Dundedin School of Medicine, University of Otago, PO Box 56, Dunedin 9054, New Zealand; colincryer{at}

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Pless argues that the positions we put forward in our 2011 Commentary are ‘entirely wrong’ and challenges us to respond.1 ,2 We believe Pless has misunderstood parts of our Commentary and is wrong in respect to other parts, and so we have addressed the areas of disagreement that he raises. We have responded in detail as we believe the issues involved are fundamental to making significant progress in injury prevention. First though, we give a re-statement of the position taken by Molcho, Pickett, Rivara, Langley and Cryer in their respective Commentaries.1 ,3 ,4

We advocate acceptance of minor injury

The proposed position that minor injury (ie, injury that has no serious or long-term consequences) should be regarded as more acceptable than serious injury has been stated in the previous commentaries. For example, Molcho and Pickett3 wrote, Identification of some types of childhood injury as more acceptable than others has implications for prevention efforts. First, professionals in the fields of health promotion and injury prevention should obviously continue to aim to provide safe contextual environments for sports and recreational activities in order to minimise harms, while bearing in mind that some injuries are still likely to occur. Second, some injuries will be accepted and tolerated as part of the healthy development of child populations. (p. 148)

Also, Rivara4 wrote, I have long ignored injuries that do not make it to medical attention. Injuries requiring a band-aid and a mother's kiss are a part of growing up. (p. 149)

Our stated position was that1 the focus of injury prevention should be on important injury … defined as those injuries … which represent a high threat to life, high threat of disability, or high cost. (p. 73)

Intervene where the likelihood or frequency of serious injury is most significant

Pless summarises his first point made against our article, thus, My point is that unless Langley and Cryer can assure us that whenever someone trips they can guarantee only a scratched arm will result, we need to try and prevent all such injury sequences. (p. 285)

Such an assurance is not required. In reality, many ‘causes’ (let us call the set ‘A’) are associated with a chance of serious injury of, say, over 1 per million population per year. We argue that if a particular cause (‘B’) is associated with a chance of serious injury of 1 per billion per year, our efforts should go into intervening with respect to ‘A’ rather than ‘B’. The statement of Pless above suggests that he does not recognise this sort of priority setting. We do not agree with such a position. With limited resources, most people would focus their resources on ‘A’ rather than ‘B’.

As a profession, our record of preventing injuries is poor. (If it were good, we would see much lower rates of serious injury than we do.) We have had successes (eg, cycle and motorcycle helmets, seat belts, tractor roll over protection structure), but there still remains a large residual problem that we, as injury prevention professionals, need to address. We need to direct our effort at problems where we will have the most impact—that is, in preventing important injuries.

Coming to the example he cites, if a serious outcome is extremely unlikely for a particular set of circumstances of injury (eg, a child running and falling on the same level), our prevention activities should be prioritised away from these events and directed to those event types where the likelihood or frequency of serious injury outcomes is most significant.

We do not need to know whether a particular event will result in serious injury

Pless says, Because most bicycle mishaps do not result in a severe injury, Langley and Cryer would logically have to propose that only those likely to experience such an injury wear helmets (p. 285).

This is incorrect. We have never contended that one try to predict who will sustain a serious head injury and only intervene in those instances.

Clearly, only a small percentage of bicycle crashes result in serious outcomes. Although the percentage may be small, the size of the serious injury problem has been judged by many jurisdictions to warrant interventions such as cycle helmets. The only practical solution is to wear them all the time. Consequently, we have, and do, advocate that cycle helmets be worn by cyclists on all occasions. These will also prevent minor injuries among many riders, and this can also be considered in any cost–benefit analysis—but the purpose behind the promotion of this intervention is to primarily prevent serious injury.

Post hoc ergo propter hoc

In our commentary, we suggested the desirability of focusing on serious injury in our injury control efforts. In so doing, Pless says, In essence, their whole argument is based on the astonishing and presumptuous assumption that the outcome of an injury event can be accurately predicted in all instances. … I contend that short of passing a soothsayer course with flying colours, this is not possible. (p. 285)

He misunderstands the point we make about focusing on important injury. Injury prevention professionals work backwards from the outcome, to the cause, and then to the prevention solution all the time. Like any good epidemiologist and public health professional, we

  1. define an important outcome of interest;

  2. investigate what factors are causally related to the outcome;

  3. investigate ways of intervening in respect of the factors identified;

  4. evaluate those interventions.

Going back to the cycle helmet example: why are we interested in cycle helmets? The answer is because they reduce the risk of serious head injury following a crash. In respect of the sequence above, we have (A) an important outcome of interest, which is serious head injury, (B) a proximal cause—that is, cycling, (C) a means of injury control, namely cycle helmets, and (D) evidence to support their effectiveness.5 We use the serious injury outcome to guide our interest in cycling and cycle helmets. We then advocate cycle helmets for the whole population of cyclists. There was no soothsaying involved.

A population approach to prevention

Pless states, They are, in effect, suggesting a high risk, targeted approach to prevention. (p. 285)

That is not what we are suggesting; rather it is that priorities for prevention should be based on a consideration of important injury. As the bicycle helmet example illustrates, it does not follow that the prevention initiative should be ‘targeted’ (eg, only those cycling among moving vehicles).

He goes on to state that he is proposing a population strategy in his aim to prevent all injury. He cites Geoffrey Rose's position in support of his own (ie, prevention of all injury) and gives the example of salt and hypertension. On the contrary, Rose's position and the salt and hypertension example are more in line with our own position. For the salt and hypertension example, Pless states, he [Rose] viewed it as more realistic and more effective to try to reduce salt intake in the entire population than to do so only for those who were hypertensive or likely to become so. (p. 285)

Health professionals are interested in hypertension as it can result in, among other things, stroke and myocardial infarction. The aim of salt reduction is to reduce the likelihood of hypertension and hence the risk of serious circulatory diseases. We argue, therefore, that Rose's interest in salt reduction started with serious health outcomes and moved back through the causal pathway to salt.

So similar to this model, we start with serious head injury, identify cycling as a proximal cause and wearing cycle helmet as an intervention for all cyclists—an all population approach.

The ‘prevent all injury’ paradigm is counterproductive

Pless asks us to elaborate on why we feel the paradigm is counterproductive. We give three reasons.

The first reason was identified by Molcho and Pickett3 and was what prompted their paper. It warrants repeating here: Physical activity specialists often argue that injury is an inevitable side effect of a healthy, active lifestyle. Hence, some injuries should be accepted. Injury control professionals typically offer the perspective that childhood injuries by definition are inherently bad, irrespective of their origins. Such positions seem to be opposed to one another, and occasionally pit one side of our profession against the other. We have recently been asking ourselves if there [is] room for compromise in this debate. (p. 147)

Our second reason is that prevention resources are limited and we must try and use them to give the greatest return. Pless’ logic would have us spending significant resources in preventing rare events that 99.99% of the time results in minor injury. This would undoubtedly be at the cost of events that are at higher risk of having severe outcomes.

A third reason relates to our concern that the ‘prevent all injury view’ (ie, that we must aim to prevent all injury, no matter how minor the risk or consequences) brings injury prevention into disrepute by the wider public. An example of this occurred recently in New Zealand with the Auckland City Council declaring that the tradition of throwing lollies (ie, sweets/candy) and squirting water at the crowd has been banned from Christmas parades due to health and safety concerns.6 No evidence of previous injury was produced in support of this ban. Many members of the public claimed this was ‘political correctness gone mad’.

Closing remarks

There are approximately 7 billion people in the world. Most of them would experience an injury each week. The overwhelming majority of these injuries would be superficial (eg, a ripped fingernail, a paper cut) and others would be so minor as to go unnoticed. It clearly makes no sense to try and prevent 7 billion injuries per week. As we have argued, and many agencies implicitly agree by their prevention actions, we need to focus on those events that produce significant numbers of important injuries, whether importance is measured by mortality, threat to life, (threat of) disability or cost.

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We wish to thank Hank Weiss and Shanthi Ameratunga for reviewing earlier versions of this paper.



  • Contributors Both authors contributed to all aspects of the preparation of this commentary.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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