Explaining risks: turning numerical data into meaningful pictures

The risk communication literature has been useful in providing recommendations for how information about risk might be presented to patients.(1-3) It has also emphasised that risk communication is a two-way process, that people’s responses to risk rest on qualitative and quantitative aspects of a potential risk outcome, and that the way information is framed affects decisions. The fields of risk communication and informed decision making uphold the individual’s right to autonomous choice. They also recommend that people receive all relevant information to make informed decisions about their health. These guidelines are usually based on decisions about treatments where individual preferences are primary and decisions against the grain of current evidence are unlikely to affect the health of others (such as with cancer treatment or screening). Many treatment decisions carry no right or wrong answer because there is uncertainty regarding outcomes. The principle of autonomy underpins these guidelines.

However, there are situations where patient choices, which may be rational under the guidelines of autonomous decision making, can have significant repercussions for the wider community. Childhood immunisation against eradicable diseases provides an example. As diseases approach eradication or are well controlled, the risk posed by a vaccine could eventually be higher than for the disease it prevents.(4) Given both absolute and relative risk estimates, fully informed and rational individuals might rightly reject vaccination. If all individuals reacted in this way and ceased vaccinating, the population would be vulnerable to re-importation of a disease and outbreaks would ensue. In this context, the decision not to vaccinate a child may bear little consequence for them but when enough individuals choose this action, population or “herd” immunity is threatened and outbreaks occur. Hardin referred to this situation as the tragedy of the commons.(5) Over-fishing, industrial pollution of rivers, use of fossil fuels and unsustainable population growth also create a scenario where the aggregate costs of individual actions threaten populations and future generations.

Proponents of autonomous informed decision making shun persuasion. They rightly point out the problems when people are not fully informed about risks or feel pressured to make a decision. Although the concept of shared decision making acknowledges the role of the clinician, few writings in the patient decision literature confront situations where fully informed individuals make informed decisions that have deleterious effects on the wider community.(6-8)

In situations where informed autonomous individual choices put the community or future generations at risk, guidelines are needed for ways of upholding the ethical and legal imperative of valid consent while acknowledging the wider population effects of an individual’s decision. Further discussion on this difficult balance appears indicated.

References

1. Edwards A, Elwyn G, Mulley A. Explaining risks: turning numerical data into meaningful pictures. BMJ 2001;324:827-30.

2. National Research Council. Improving risk communication. Washington: National Academy of Sciences, 1989.

3. Bogardus ST, Holmboe E, Jekel JF. Perils, pitfalls and possibilities in talking about medical risk. JAMA 1999;281(11):1037.

4. Chen RT, Hibbs B. Vaccine safety: current and future challenges. Pediatric Annals 1998;27:445-55.

5. Hardin G. The tragedy of the commons. Science 1968;162:1243-8.

6. Gwyn R, Elwyn G. When is a shared decision not (quite) a shared decision? Negotiating preferences in a general practice encounter. Social Science and Medicine 1999;49:437-47.

7. Raffle AE. Information about screening - is it to achieve high uptake or to ensure informed choice? Health Expectations 2001;4:92-98.

8. Parker M. The ethics of evidence-based patient choice. Health Expectations 2001;4:87-91.