Laypersons' understanding of relative risk reductions: Randomised cross-sectional study

BMC Medical Informatics and Decision Making, Jul 2008

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 quantitative information on the baseline risk of heart attack. The respondents had also been asked whether they were diagnosed with 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 quantitative information on baseline risk or not. Conclusion In this study, lay people's 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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Laypersons' understanding of relative risk reductions: Randomised cross-sectional study

BMC Medical Informatics and Decision Making Laypersons' understanding of relative risk reductions: Randomised cross-sectional study Lene Sorensen 1 2 Dorte Gyrd-Hansen 1 Ivar S Kristiansen 0 1 Jrgen Nexe 1 Jesper B Nielsen 1 0 Institute of Health Management and Health Economics, University of Oslo , Norway 1 Institute of Public Health, University of Southern Denmark , Odense , Denmark 2 Amgros I/S , Copenhagen , Denmark 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 quantitative information on the baseline risk of heart attack. The respondents had also been asked whether they were diagnosed with 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 quantitative information on baseline risk or not. Conclusion: In this study, lay people's 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. - Background Patient autonomy is a core element of medical ethics. Patient autonomy implies that patients and doctors share responsibility for medical decision to the extent patients wish to be included. For shared decision making to be meaningful, however, patients need to have an understanding of the effectiveness of medical interventions. This usually requires the use of the risk concept. Communicating risk information is therefore a fundamental and increasingly prominent part of medical practice. Effective risk communication can enhance knowledge, involvement in decisions about testing or treatment, autonomy and empowerment of patients [1]. However poor communication may possibly lead to anxiety or lack of confidence in health care professionals [2]. It is vital that we identify the available evidence about how risk communication should best be done. The effectiveness of an intervention for a chronic disease may be presented in terms of Relative Risk Reduction (RRR), Absolute Risk Reduction (ARR), Numbers Needed to Treat (NNT), or Odds Ratio (OR). These measures may subsequently be translated into increased (disease-free) life expectancy because the intervention postpones adverse events. The choice of effect measure has been discussed extensively in the scientific literature (e.g. by Gigerenzer et al [3] or Elmore et al [4]), but we still need more knowledge about how intervention effectiveness can be communicated to patients, doctors and health administrators. Decisions should, in line with expected utility theory [5], be based on the absolute risk reductions (or its reciprocal NNT) even though this principle in practice is frequently violated. However, there is evidence that lay-persons and professionals may have difficulties in understanding NNT [6-8]. Great effectiveness of a treatment corresponds with low value of NNT, and this may mislead patients if they associate great effectiveness with a large number. In contrast, for RRR a greater value means greater effectiveness. RRR, however, may be misleading because it usually is greater than ARR numerically, and may consequently "exaggerate" the treatment effect. Still, RRR is frequently presented in the medical literature, possibly because it is more stable across patient groups than ARR [9]. It is therefore conceivable that doctors on some occasions use RRR in their communication with patients. Even though decisions should not be based on RRR alone, we need to know to which extent patients can utilise information about RRR. We have searched the literature without finding any direct evidence of the extent to which lay people understand RRR. The size of baseline risk has been shown to influence acceptance of a hypothetical treatment [ (...truncated)


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Lene Sorensen, Dorte Gyrd-Hansen, Ivar S Kristiansen, Jørgen Nexøe, Jesper B Nielsen. Laypersons' understanding of relative risk reductions: Randomised cross-sectional study, BMC Medical Informatics and Decision Making, 2008, pp. 31, 8, DOI: 10.1186/1472-6947-8-31