Conceived and designed the experiments: CLLC. Performed the experiments: CLLC. Analyzed the data: CLLC. Wrote the paper: CLLC. Helped plan study: DTK ADO SF AF HJS EAA JH TDM VMM. Performed statistical analysis: DTK. Contributed to revisions: DTK ADO SF AF HJS EAA JH TDM VMM. Approved final version of manuscript: DTK ADO SF AF HJS EAA JH TDM VMM.
The authors have declared that no competing interests exist.
We conducted an Internet-based randomized trial comparing three valence framing presentations of the benefits of antihypertensive medication in preventing cardiovascular disease (CVD) for people with newly diagnosed hypertension to determine which framing presentation resulted in choices most consistent with participants' values.
In this second in a series of televised trials in cooperation with the Norwegian Broadcasting Company, adult volunteers rated the relative importance of the consequences of taking antihypertensive medication using visual analogue scales (VAS). Participants viewed information (or no information) to which they were randomized and decided whether or not to take medication. We compared positive framing over 10 years (the number escaping CVD per 1000); negative framing over 10 years (the number that will have CVD) and negative framing per year over 10 years of the effects of antihypertensive medication on the 10-year risk for CVD for a 40 year-old man with newly diagnosed hypertension without other risk factors. Finally, all participants were shown all presentations and detailed patient information about hypertension and were asked to decide again. We calculated a relative importance score (RIS) by subtracting the VAS-scores for the undesirable consequences of antihypertensive medication from the VAS-score for the benefit of CVD risk reduction. We used logistic regression to determine the association between participants' RIS and their choice. 1,528 participants completed the study. The statistically significant differences between the groups in the likelihood of choosing to take antihypertensive medication in relation to different values (RIS) increased as the RIS increased. Positively framed information lead to decisions most consistent with those made by everyone for the second, more fully informed decision. There was a statistically significant decrease in deciding to take antihypertensives on the second decision, both within groups and overall.
For decisions about taking antihypertensive medication for people with a relatively low baseline risk of CVD (70 per 1000 over 10 years), both positive and negative framing resulted in significantly more people deciding to take medication compared to what participants decided after being shown all three of the presentations.
International Standard Randomised Controlled Trial Number Register
How information about treatment effects is presented affects how it is understood and subsequent decisions
“Decision frame” refers to the decision-maker's conceptualization of the decision problem and all its attributes, e.g. outcomes and contingencies. This is partly dependent on the decision-maker's personal characteristics and partly on the way the problem is formulated. Framing studies can manipulate logically equivalent information or give more or less the same information though not logically equivalent
Hypertension is associated with increased risk for events that are manifestations of serious cardiovascular disease (CVD), including myocardial infarction and stroke
The main benefit of reducing high blood pressure is the reduction of risk for serious cardio-vascular events such as stroke and myocardial infarction
We are not aware of any previous studies that have compared the effects of positive and negative framing on the extent to which people's decisions are consistent with their values. Thus, we designed this study to assess the extent to which positive and negative framing affect choices about whether to take medication for hypertension. Although it has been shown that how information is presented can influence patients' decisions, it is not clear how best to inform patients in this situation
This study was approved by the Norwegian Data Protection Agency, the Norwegian Medical Ethics Board and the Health Sciences Institutional Review Board (HSIRB) of the University at Buffalo.
The CONSORT checklist and the protocol for this study are available as supporting information; see
The study was an Internet-based randomized trial in which participants were randomized to one of three ways of framing information about the effects of antihypertensive medication on the 10-year risk of cardiovascular disease (CVD) or to no information (
We evaluated the following three ways of framing the information: 1. positively framed information showing gain over 10 years (positive framing for 10 years); 2. negatively framed information showing loss over 10 years (negative framing for 10 years), and 3. negatively framed information showing loss per year over 10 years (negative framing per year) (
We planned two main comparisons in advance: 1. positively versus negatively framed information over 10 years, and 2. negatively framed information per year versus negatively framed information over 10 years.
Information about the study was broadcast on Puls, a popular nationally televised weekly health program with approximately 700,000 viewers (total population of Norway = 4.5 million). On the program, we presented documentation regarding the use of antihypertensive medication in Norway and invited viewers to go to our website to participate in the study. A reminder was broadcast on the program after a few weeks.
The website was in Norwegian. Upon logging on participants were presented with information about the study and asked to give informed consent by clicking on an arrow in order to proceed and participate in the study. The participants viewed a brief scenario in which each was asked to imagine that he or she was a 40 year-old man who does not smoke, is active and has a healthy diet. The doctor tells him that he has high blood pressure and therefore has an increased risk of cardiovascular disease, particularly stroke and heart attack. Explanations were available for terms such as high blood pressure and stroke using hypertext links.
We then asked participants to indicate the relative importance of three consequences of hypertension and its treatment: avoiding CVD (stroke and heart attack), the side effects of antihypertensive medication (which were listed), and the inconvenience associated with taking antihypertensive medication (taking pills every day, co-payments for the medication, and going to the doctor 1–2 times per year) using horizontal 100-point visual analogue scales (VAS) (
Translation of value elicitation instrument, which was presented in Norwegian. Pop-up descriptions of stroke and heart attack were provided if participants clicked on the hypertext links.
Participants then viewed one of the three presentations of the advantages of antihypertensive medication and a standard presentation of the disadvantages or received no information (
Translation of the information, which was presented in Norwegian. Participants randomised to “no information” were not shown any information about the advantages or disadvantages of taking antihypertensive medication.
Translation of the information, which was presented in Norwegian.
Responses from participants who stated that they were at least 18 years-old and that they were filling in the questionnaire for the first time were included in the analysis. Participants' responses to the questions on our website were directly saved into a database where the data were stored anonymously. Confidentiality of data was ensured by not collecting any information that would make it possible to identify the participants. Voluntary contact information that some participants supplied in order to be informed of future studies was stored in a separate database; thus it was not possible to couple contact information and study data. Participants were informed on the consent screen that they could leave the study at any time, and they were given the option of choosing to have any data that they might have entered deleted.
For each participant, we calculated a Relative Importance Score (RIS), by subtracting the sum of her VAS-scores for the relative importance of avoiding the downsides of antihypertensive medication (side effects and inconvenience) from her VAS-score for the relative importance of avoiding cardiovascular disease. We expected that higher RIS would be correlated with an increased likelihood of deciding to take medication.
We used logistic regression to compare the effects of the different presentations on the decision to take medication, with the decision to take medication (yes or no) as the dependent variable, and the RIS and allocated presentation as predictors. The following model was used:
Based on the results of previous studies
We also considered which group made decisions that were the most consistent with the “more fully informed” second decision, made by the participants after they had seen all three presentations and been provided more detailed information. This was done by comparing the linear predictor for each group for the first decision with the linear predictor (pooled estimate) across the other three groups for the second decision, using the model above without the interaction term. We used a logistic regression model to explore whether the respondents changed their decision from ‘Taking medication’ to ‘Not taking medication’ versus ‘Did not change decision’ depending on the RIS, presentation group, and their interaction.
There were 4,609 log-ons to the study website between November 2004 and May 2005 (
Positive framing for 10 years | Negative framing for 10 years | Negative framing per year | No information | Total | Norwegian population |
||
% | % | % | % | % | % | ||
52.9 | 52.3 | 52.9 | 54.6 | 53.2 | 51.0 | ||
18–29 | 14.8 | 14.4 | 11.7 | 13.5 | 13.5 | 19.4 | |
30–39 | 15.3 | 17.9 | 18.1 | 15.5 | 16.7 | 20.0 | |
40–49 | 18.6 | 17.6 | 20.1 | 21.2 | 19.4 | 18.3 | |
50–59 | 31.0 | 27.1 | 29.0 | 29.7 | 29.2 | 17.0 | |
60–69 | 15.3 | 17.9 | 16.5 | 16.0 | 16.4 | 10.7 | |
70–79 | 4.9 | 4.6 | 4.3 | 4.0 | 4.5 | 8.6 | |
over 80 | 0.0 | 0.5 | 0.3 | 0.2 | 0.3 | 6.0 | |
Elementary | 6.6 | 10.0 | 8.9 | 5.7 | 7.8 | 31.0 | |
High school | 34.5 | 31.7 | 34.1 | 33.7 | 33.5 | 42.7 | |
University | 58.9 | 58.3 | 57.0 | 60.6 | 58.7 | 23.3 | |
mean (SD) | mean (SD) | mean (SD) | mean (SD) | mean (SD) | |||
CVD | 93.2 (12.5) | 93.7 (12.2) | 94.4 (12.6) | 92.6 (12.4) | 93.5 (12.4) | ||
Side effects | 75.0 (25.0) | 73.1 (25.8) | 74.8 (26.2) | 74.6 (25.8) | 74.4 (25.7) | ||
inconvenience | 45.1 (36.8) | 45.6 (36.8) | 46.2 (37.2) | 43.7 (35.9) | 45.2 (36.6) | ||
RIS | −26.9 (51.9) | −25.0 (52.9) | −26.6 (51.3) | −25.7 (50.8) | −26.1 (51.7) |
*For the Norwegian population, the proportion of women and each age group is based on the population over 17 in 2004
The importance of avoiding CVD and the side-effects of medication did not vary with age. The importance of avoiding the inconveniences of medication was negatively correlated with age (Spearman r = −0.09,
Visual analogue scores (VAS) for the relative importance of avoiding cardiovascular disease, side effects, and the inconvenience of taking antihypertensive medication with lower and upper anchors of “Not important” and “Very important”.
There were statistically significant differences (p<0.001) in the proportion of participants who chose to take medication across the four groups (
Decision | Positive framing for 10 years | Negative framing for 10 years | Negative framing per year | No information | Total | |
Responses | ||||||
% ( |
% ( |
% ( |
% ( |
% ( |
||
Would take medication | 55.9 (204) | 66.4 (245) | 62.8 (247) | 80.3 (322) | 66.6 (1018) | <0.001 |
Would take medication | 39.7 (145) | 45.8 (169) | 48.9 (192) | 52.6 (211) | 46.9 (717) | 0.004 |
From “take” to “not take” | 35.8 (73) | 36.7 (90) | 26.3 (65) | 38.5 (124) | 34.6 (352) | 0.016 |
From “not take” to “take” | 8.7 (14) | 11.3 (14) | 6.8 (10) | 16.5 (13) | 10.0 (51) | 0.122 |
Total changes | 23.8 (87) | 28.2 (104) | 19.1 (75) | 34.2 (137) | 26.4 (403) |
Among those who changed their decision, participants in all four groups were significantly more likely to change from taking to not taking than from not taking to taking medication (p<0.001 for all four groups). Among all those who first answered that they would take medication, 34.6% changed their decision from taking medication to not taking medication. Among those that first answered negatively, only 10.0% changed their decision. There were statistically significant differences in the proportions that switched their decision from taking to not taking medication across the four groups (p<0.001). The largest proportion changed their decision in the no information group (38.5%) and the smallest proportion (26.3%) changed their decision in the group shown negatively framed information per year (
There was a clear association between participants' RIS and the decisions they made in all four groups and across groups for the second, more fully informed decision (
Relative importance score (RIS) values indicate the relative importance to participants of the desirable and undesirable consequences of taking antihypertensive medication. As anticipated, the likelihood of participants deciding to take medicine is greater when the relative importance of the desirable consequences (less risk of CVD) is greater and the relative importance of the downsides of taking medication is less.
Presentation | 1st quartile | Median | 3rd quartile | |||
RIS = −70 | RIS = −22 | RIS = 8 | ||||
Odds (95% CI) | Predicted % (95% CI) | Odds (95% CI) | Predicted % (95% CI) | Odds (95% CI) | Predicted % (95% CI) | |
0.86 (0.66–1.13) | 46.3 (39.7–53.0) | 1.35 (1.09–1.67) | 57.4 (52.0–62.5) | 1.78 (1.37–2.33) | 64.1 (57.7–69.9) | |
1.19 (0.91–1.57) | 54.3 (47.5–61.0) | 2.21 (1.75–2.80) | 68.9 (63.6–73.7) | 3.27 (2.42–4.44) | 76.6 (70.8–81.6) | |
1.10 (0.85–1.43) | 52.5 (45.9–58.9) | 1.85 (1.49–2.30) | 65.0 (59.8–69.7) | 2.57 (1.94–3.40) | 72.0 (66.0, –77.3) | |
2.39 (1.80–3.18) | 70.5 (64.3–76.1) | 5.35 (3.95–7.24) | 84.3 (79.8–87.9) | 8.89 (5.84–13.55) | 89.9 (85.4–93.1) | |
0.66 (0.58–0.76 | 39.7 (36.5–43.0) | 0.91 (0.82–1.00) | 47.5 (45.0–50.1) | 1.11 (0.98–1.25) | 52.5 (49.5–55.5) |
RIS = Relative importance score.
Predicted % = proportion deciding to take antihypertensive medication based on logistic regression.
Presentation | Odds Ratio (98.3% CI) |
|
Positive framing for 10 years versus Negative framing for 10 years | 0.63 (0.46–0.86) | <0.004 |
Negative framing per year versus Negative framing for 10 years | 0.86 (0.63–1.17) | 0.343 |
Adjusted overall CI level = 0.95.
Because the interaction term was not statistically significant and the differences in slopes (
Presentation | Odds ratio (95% CI) | p-value |
Positive framing for 10 years | 1.33 (1.05–1.70) | 0.02 |
Negative framing for 10 years | 2.25 (1.75–2.89) | <0.0001 |
Negative framing per year | 2.02 (1.58–2.57) | <0.0001 |
No information | 5.29 (4.01–6.99) | <0.0001 |
As only 10% changed their decision from ‘Not taking medication’ to ‘Taking medication’, we used the logistic regression model of whether the respondents changed their decision from ‘Taking medication’ to ‘Not taking medication’ versus ‘Did not change decision’ depending on the RIS, presentation group, and the interaction. Presentation group and RIS were significant variables (
In general, as participants' RIS values increased in a direction that would favour taking antihypertensive medication, they were more likely to decide to take medication, regardless of what information they were provided. While the relative importance of CVD and side effects of medication were constant across age groups, the relative importance of the inconvenience of taking medication decreased in relation to the age of the participants.
The majority of the participants (66.6%) chose to take medication in all four groups for the first decision, with statistically significant differences across the groups (from 60% in the group shown positively framed information to 80% in the group shown no information). Only 47% of participants chose to take medication for the second decision, after being more fully informed. The decrease in the proportion of participants choosing to take medication from the first to the second, more fully informed decision for the group shown no information for the first decision suggests that the participants may have assumed that the benefits of antihypertensive medication were greater than they are for a 40 year-old man without other risk factors.
Two systematic reviews of the effects of different ways of presenting information to patients included a total of 16 studies investigating the effects of positive and negative framing
Our results do not support the prediction of prospect theory that positive framing promotes risk aversive behaviours, such as uptake of preventive behaviours, compared to negative framing for preventive behaviours. In fact, the results support the opposite conclusion. The group shown positively framed information was least likely to decide to take antihypertensive medication. A possible explanation for this is that when risks are small and they are presented as natural frequencies, differences in the number of people with an event (between small numbers) are perceived as larger than differences between the people without an event (between large numbers), even though these differences are the same.
Another explanation is that the participants perceived the prospect of suffering the downsides of taking antihypertensive medication as more risky to their well-being than the risk of suffering from CVD. Other studies have also found that positive framing promotes uptake of preventive behaviours when the undesirable effects are small or not mentioned
Nonetheless, the higher odds across all levels of RIS of those shown negatively framed information deciding to take antihypertensive medication compared to those shown positively framed information illustrates a valence framing effect due to violation of the principle of invariance, i.e. people should make the same choices given equivalent descriptions and values
Public health advocates might argue that the negatively framed information was “best” since it resulted in the highest proportion of participants deciding to take antihypertensive medication (
Similar proportions of people changed from a decision to take medication to not taking medication in the positively and negatively framed groups over 10 years (36% and 37%), whereas a smaller proportion changed in the group shown negatively framed information per year over 10 years (26%). There were still statistically significant (
The participants were recruited through a popular nationally televised weekly health program and needed to have access to the Internet. TV-recruitment and the randomisation process worked well, generating four comparable groups. There were more than twice as many respondents with university education compared to the Norwegian population (
In this study we chose not to collect additional information about the participants in order not to burden them with questions that were not necessary for the primary analyses, with the hope that this would increase the proportion of people who would complete the study after starting it. Thus, although participants were likely attracted to the study, at least in part, because of a personal interest in antihypertensive treatment, we do not know how salient the scenario was for the participants
Although these results have limited relevance to personal communication with an active interaction between a physician and a patient
Secondly, we found that the likelihood of participants deciding to take antihypertensive medication was greater when the relative importance of the desirable consequences (less risk of CVD) was greater and the relative importance of the downsides of taking antihypertensive medication were less (
In this study, negatively framed information appears to have resulted in decisions that were least consistent with decisions that were made by all of the participants after they were more fully informed and had seen all three presentations, but participants shown all three presentations were significantly more likely to have decided to take medication on the first decision. The implication of this is that those preparing and using electronic or printed patient information or decision aids for preference sensitive decisions for people at low risk should be cautious about presenting only negatively framed information. It may be best to present information framed both positively and negatively to help people to reach decisions that are consistent with their own values
Our findings suggest that presenting either positive or negative framing alone may result in decisions that are inconsistent with patients' values. Some patients appear more likely to decide to take antihypertensives when their preference is to not. These findings apply to people with a relatively low 10-year risk of CVD and may apply to other low risk situations. In such situations, presenting treatment effects using both gains and losses may help to improve the extent to which patients make choices that are consistent with their values and preferences.
The extent to which these results can be applied to other decisions is not clear. They are most likely to be relevant for Internet-based and printed patient information, and for people at low risk considering interventions that have modest effects and relatively important down sides. Although they are less likely to be relevant in the context of personal communication between doctors and patients, they suggest that it is likely to be important to explore how individual patients perceive and balance reasons for and against taking antihypertensive medication
CONSORT Checklist.
(0.19 MB DOC)
Trial Protocol.
(0.07 MB DOC)
We would like to express our deep appreciation to Jan Arve Dyrnes, Gro Alice Hamre and Sandra Haga for programming the web pages that were used for this study and providing technical support and to Jan Odgaard-Jensen for statistical advice.