Healthy Skepticism Library item: 14010

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Publication type: Journal Article

Sorensen L, Gyrd-Hansen D, Kristiansen IS, Nexoe J, Nielsen JB.
Laypersons' understanding of relative risk reductions: a randomised cross-sectional study.
BMC Med Inform Decis Mak 2008 Jul 17; 8:(1):31
http://www.biomedcentral.com/1472-6947/8/31

Abstract:

BACKGROUND: Despite increasing recognition of the importance of involving patients in decisions on preventive healthcare interventions, little is known about how well patients understand and utilise information provided on the relative benefits from these interventions. The aim of this study was to explore whether lay people can discriminate between preventive interventions when effectiveness is presented in terms of relative risk reduction (RRR), and whether such discrimination is influenced by presentation of baseline risk.

METHODS: The study was a randomised cross-sectional interview survey of a representative sample (n=1,519) of lay people with mean age 59 (range 40-98) years in Denmark. In addition to demographic information, respondents were asked to consider a hypothetical drug treatment to prevent heart attack. Its effectiveness was randomly presented as RRR of 10, 20, 30, 40, 50 or 60 percent, and half of the respondents were presented with the baseline risk of heart attack. The respondents were also asked whether they were suffering from hypercholesterolemia or had experienced a heart attack.

RESULTS: In total, 873 (58 ) of the respondents consented to the hypothetical treatment. While 49 accepted the treatment when RRR=10%, the acceptance rate was 58-60% for RRR>10. There was no significant difference in acceptance rates across respondents irrespective of whether they had been presented with information on baseline risk or not.

CONCLUSION: In this study, lay peoples decisions about therapy were only slightly influenced by the magnitude of the effect when it was presented in terms of RRR. The results may indicate that lay people have difficulties in discriminating between levels of effectiveness when they are presented in terms of RRR.

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