Using hypothetical data to assess the effect of numerical format and context on the perception of coronary heart disease risk

Abstract

Purpose: To test the hypothesis that responses to coronary heart disease (CHD) risk estimates are heightened by use of ratio formats, peer group risk information, and long time frames.

Design: Cross-sectional, experimental, between-factors design.

Setting: Three regions in England.

Subjects: A total of 740 men and women ages 30 to 70 years.

Measures: Risk perception, "emotional" response, intention to change lifestyle.

Analysis: Logistic regression was used to investigate the impact of numerical format (ratio vs. percentage), peer group risk (personal vs. peer group), and time frame (10-year vs. 30-year) on risk perception. Analysis of variance was used to investigate the impact of these factors on emotional response and intention to change lifestyle questions.

Results: Higher perceived risk was observed when risk was presented as a ratio (p < .001) and when it was supplemented with peer group risk estimates (p = .006). Emotional responses to risk information were heightened when risk was presented as a ratio (p = .0004) and supplemented with peer group risk estimates (p = .002). Presentation with ratios also increased intention to make lifestyle changes (p = .047).

Conclusion: Perception of CHD risk information is affected by the presentation format. Where absolute risks may appear low, use of ratios and supplementation of personal risk estimates with peer group risk may increase risk perception.