The Effect of How Outcomes Are Framed on Decisions about Whether to Take Antihypertensive Medication: A Randomized Trial
et al. (2010) The Effect of How Outcomes Are Framed on Decisions about Whether to
Take Antihypertensive Medication: A Randomized Trial. PLoS ONE 5(3): e9469. doi:10.1371/journal.pone.0009469
The Effect of How Outcomes Are Framed on Decisions about Whether to Take Antihypertensive Medication: A Randomized Trial
Cheryl L. L. Carling 0
Doris Tove Kristoffersen 0
Andrew D. Oxman 0
Signe Flottorp 0
Atle Fretheim 0
Holger J. Schu nemann 0
Elie A. Akl 0
Jeph Herrin 0
Thomas D. MacKenzie 0
Victor M. Montori 0
Glyn Elwyn, Cardiff University, United Kingdom
0 1 Norwegian Knowledge Centre for the Health Services , Oslo , Norway , 2 Clinical Research and INFORMAtion Translation Unit, and Department of Epidemiology, Italian National Cancer Institute Regina Elena , Rome , Italy , 3 Department of Medicine, University at Buffalo, Buffalo, New York, United States of America, 4 Division of Cardiology, Yale University , New Haven , Connecticut, United States of America, 5 Department of Internal Medicine, Denver Health and Hospital Authority and University of Colorado Health Sciences Center , Denver , Colorado, United States of America, 6 Knowledge and Encounter Research Unit, Division of Endocrinology and Internal Medicine, Mayo Clinic College of Medicine , Rochester, Minnesota , United States of America
Background: 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. Methods and Findings: 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. Conclusions: 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. Trial Registration: International Standard Randomised Controlled Trial Number Register ISRCTN 33771631 PLoS ONE | www.plosone.org
Funding: This work was funded by the Norwegian Research Council (http://www.forskningsradet.no/en/Home+page/1177315753906). The funders had no role
in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
How information about treatment effects is presented affects
how it is understood and subsequent decisions . When
decisions are preference sensitive , i.e. where individual
preferences about the desirable and undesirable consequences
determine choice, it is important to provide patients with
information in a format that facilitates decisions that are consistent
with their values and preferences .The aim of the Health
Information Project: Presentation Online (HIPPO) was to improve
communication of information about the effects of health care
based on randomized trials of alternative ways of presenting this
evidence, in order to determine which presentations help people
make decisions that are consistent with their values.
Decision frame refers to the decision-makers
conceptualization of the decision problem and all its attributes, e.g. outcomes
and contingencies. This is partly dependent on the
decisionmakers 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 [3,10]. Information about health
effects can be framed either in terms of potential gains (advantages
or benefits), called positive framing, or in terms of potential losses
(disadvantages or harms), called negative framing. The valence
framing effect occurs when individuals choices vary depending
on whether outcome information is presented in a negative or a
positive light [11,12], as opposed to pure framing, which occurs
when outcomes and their probabilities are presented with different
wordings or formats that are objectively equivalent. . The
framing postulate of prospect theory suggests that people respond
differentially to messages depending on how these messages are
framed. Although the information presented is equivalent, the
willingness to incur risk in order to promote a desirable outcome
or avoid an undesirable outcome differs [14,15].
Hypertension is associated with increased risk for events that are
manifestations of serious cardiovascular disease (CVD), including
myocardial infarction and stroke . The focus of this trial was
on how framing of the benefits of taking antihypertensive
medication for people with hypertension affects their decisions
about whether or not to start taking medication. We chose this
decision because it is a common problem of broad interest and
many patients prefer not to take treatment for mild hypertension if
the advantages and disadvantages are explained . The
objective was to compare the impact of how the information
was framed on decisions about whether to take medication in
relation to the values of the participants. Values here refers to the
relative desirability of the possible consequences of a healthcare
intervention, including health outcomes (such as CVD and the side
effects of antihypertensive medication), the burden of treatment
(such as the inconvenience of taking antihypertensive medication
daily), and resource expenditures .
The main benefit of reducing high blood pressure is the
reduction of risk for serious cardio-vascular events such as stroke
and myocardial infarction , a preventive behaviour. According
to prospect theory , choosing a preventive behaviour would be
described as a risk-averse option, which people prefer when gains
are made salient. Therefore, one would expect a larger proportion
of people to choose to take antihypertensive medication if
information was positively rather than negatively framed.
However, empirical evidence does not consistently support this
We are not aware of any previous studies that have compared
the effects of positive and negative framing on the extent to which
peoples 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 .
Although natural frequencies may be better understood and
preferred , natural frequencies can be presented either
positively (the frequency of CVD not occurring) or negatively
(the frequency of CVD occurring). Frequencies can also be
presented over different timeframes (the frequency of CVD per
year or the frequency of CVD for 10 years). There is high quality
evidence of the effects of antihypertensive medication on CVD
, but not for how to present this evidence to patients. Because
it is a preference sensitive decision that is affected by patients
values, one would expect some degree of correlation between how
important the desirable and undesirable consequences of taking
antihypertensive medication are to them and the likelihood that
they would decide to take medication. In other words, one would
expect that people for whom the benefits of taking
antihypertensive medication were more important and the downsides less
important would be more likely, on average, to decide to take
medication than people for whom the benefits were less important
and the downsides were more important.
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
The CONSORT checklist and the protocol for this study
are available as supporting information; see Checklist S1 and
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 (Figure 1 Consort flow-diagram). The estimate of
CVD risk without antihypertensive medication was based on
Framingham data  for a 40 year-old man with blood pressure
of 160/95 without other risk factors. Because a 40 year-old man
would have a low risk for stroke, we estimated the benefit over 10
years based on a 20% relative risk reduction in CVD . We
selected this scenario because it was within the lower range of risk
levels for which antihypertensive medication is commonly
recommended  and we assumed that decisions whether to
take antihypertensive medication are more preference sensitive
when the risk of CVD is relatively low.
Interventions and Comparisons
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) (Figure 2). We included
the third group to determine whether a shorter time frame with
correspondingly fewer events would affect participants decisions.
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,
copayments for the medication, and going to the doctor 12 times
per year) using horizontal 100-point visual analogue scales (VAS)
(Figure 3). The lower and upper anchors of the VAS were labelled
Not important and Very important.
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
(Figure 4), based on random allocation. When the participants
logged-on to the study, the system randomised them, using block
randomisation with a sequence of 100 blocks of four that was
generated on http://www.randomization.com. After viewing the
presentation to which they were allocated or receiving no
information, participants were asked to indicate whether they
would or would not take antihypertensive medication with two
response options: yes or no (Figure 4). We then asked their sex, age
and years of education using drop-down response options.
Afterwards, all participants were shown additional information
about hypertension and its treatment (Figure 5), shown all three
presentations in a block-randomized sequence, and asked to
reconsider their original decision and indicate anew if they would
take antihypertensive medication.
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.
Analysis and Sample Size
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
Figure 3. Visual analogue scales (VAS) used to elicit participants preferences. 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.
decision to take medication (yes or no) as the dependent variable,
and the RIS and allocated presentation as predictors. The
following model was used:
logitD ~ b0 z b1gGg z b2S z b3gGg
where D is the decision to take medication or not, G is the
presentation group, S is the RIS value and G*S is the interaction
between the presentation and the RIS value. To make inferences
about the response within each group and for the comparisons of
groups we used dummy variable coding with reference
parameterization for the presentation groups, i.e. directly estimating the
difference in the effect between the presentation group and the
reference group, i.e. negative framing for 10 years. Wald tests were
used for the p-values and confidence intervals from the logistic
regression and chi-square tests were used to compare frequencies.
Based on the results of previous studies [20,23,24], we estimated
we would need about 350 participants per group to achieve 80%
power at a significance level of 0.025 after applying a Bonferroni
correction for the two main comparisons (a = 0.05/2); i.e. for the
comparison of the slope of the linear predictors for the group of
positively versus the group of negatively framed information over
10 years and for the group of negatively framed information per
year versus the group of negatively framed information over 10
years. It cannot be assumed that the presentation group with the
steepest slope resulted in choices that were most consistent with
participants values. We therefore also planned comparisons of the
difference in log odds at 1st and 3rd quartiles and the median
values of RIS.
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 (Figure 1). We broke the
randomisation code when there were 1,601 complete records. We
excluded records from respondents who stated they were not
participating in the study for the first time (n = 57) or were under 18
years old (n = 16). We included the remaining 1,528 records in the
analysis. The participants were evenly distributed across the four
comparison groups and the groups were similar with respect to age,
Figure 4. Presentation of advantages and disadvantages of antihypertensive medication and decision elicitation. 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.
sex, education and VAS scores (Table 1). Fifty-three percent were
women, compared to 51% in the Norwegian population .
Compared to the general population, there were more people 50
59 years old (29% versus 17%)  and a higher proportion of
participants with university level education (59% versus 23%) .
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 = 20.09, p = 0.0001) (Figure 6).
There were statistically significant differences (p,0.001) in the
proportion of participants who chose to take medication across the
four groups (Table 2). The largest proportion was in the
noinformation group (80.3%) followed by the group shown
negatively framed information for 10 years (66.4%) and negatively
framed information per year (62.8%). The group that viewed
positively framed information had the smallest proportion of
participants who chose to take medication (55.9%). Overall,
46.9% chose to take medication after viewing all additional
information and all three presentations compared to 66.6% that
opted for medication on the first decision.
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 (Table 2).
Decisions in Relation to Values
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 (Figure 7). The likelihood of
deciding to take antihypertensive medication increased as RIS
scores increased, as expected. The likelihood of deciding to take
medication was greatest in the no information group across RIS
values (Table 3 and Figure 7). Among the three presentation
groups it was greatest in the group shown negatively framed
information for 10 years and least in the group shown positively
framed information. The interaction between RIS and
presentation group was not statistically significant (p = 0.2) in the logistic
regression model. Therefore the null hypothesis of equal slope of
the linear predictors was not rejected. Thus, we report only the
ORs for the two pair-wise comparisons that we specified a priori
(Table 4). The likelihood for deciding to take antihypertensives
with positive framing for 10 years versus the likelihood with
negative framing for 10 years resulted in a statistically significant
odds ratio of 0.63 (p,0.004) while the comparison of these
likelihoods between negative framing per year and negative
framing for 10 years was not significant.
Because the interaction term was not statistically significant and the
differences in slopes (Figure 7) might be due to chance, we removed
the interaction term, thus using a model that assumes the slopes are
the same. We compared the odds of a positive decision to take
antihypertensives on the first decision for each group to the odds of a
positive second decision for the pooled estimate for the other three
presentation groups (Table 5). All four groups were significantly more
likely to decide to take medication on the first decision.
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 (p,0.0001 and p = 0.009), suggesting that the
respondents were more likely to change their mind with increasing values
of RIS. The interaction was not significant (p = 0.8), i.e there was
no significant difference between the slope of the linear predictors
of the decision switch versus RIS.
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.
N = 1,528
n = 365
n = 369
n = 393
n = 401
Table 1. Participant characteristics.
Values (on 100-point visual analogue scale)
*For the Norwegian population, the proportion of women and each age group is based on the population over 17 in 2004 . The proportion of people with different
levels of education is based on the highest completed education for people over 16 years old .
What Was Already Known and What This Study Adds
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 [2,3].
Edwards and colleagues found six studies that investigated loss
versus gain framing on uptake of screening (i.e., describing the
risks or disadvantages of not being screened versus describing the
benefits or advantages of being screened) . Uptake of screening
was more likely with loss framing compared to gain framing (OR
1.18, 95% CI 1.01 to 1.38 for 4 studies). This is consistent with
the prediction that loss-framed messages would be most effective,
because of the assumption that detection behaviours are
perceived as risky in the short term because of their ability to
detect disease . Moxey and colleagues found that framing
effects varied with the type of scenario, patient characteristics,
scenario manipulations, and study quality . Surgery was more
likely to be preferred with positive framing (survival) than
negative framing (mortality) (RR 1.51, 95% CI 1.39 to 1.64 for
5 comparisons from 4 studies). Ten studies examined gain versus
loss framing for health behaviours, of which three provided data
on the proportion undertaking the desired health behaviour.
Respondents were more likely to perform the desired behaviour
when information was framed as gains compared to loss (RR
1.22, 95%CI 1.04 to 1.43), consistent with what the prospect
theory would predict. Overall no significant framing effect was
evident for immunization (5 studies). Eleven studies examined
positive versus negative framing for medication treatment
decisions, but only one study with inconclusive results provided
data on the proportion choosing medical treatment. Those with
little interest in behaviour at baseline were more likely to be
influenced by framing, particularly information framed as gains.
Framing effects were less in studies with a lower risk of bias and
ones that examined actual decisions.
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 [e.g. 27, 28] and
that the effect of positive compared to negative framing varies with
the probability of success [e.g. 29]. Finally, prospect theory was
developed to explain decisions where there is one risky choice and
one sure thing [10,30] and it may not apply here.
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 , but they did not.
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
(Table 2). They might, in fact, argue that none of the presentations
were satisfactory, since all of them resulted in smaller proportions
of participants deciding to take antihypertensive medication
compared to the no information group. We assumed that the
additional information and the cognitive processing required in
order to understand it would foster a more systematic use of the
information, thereby minimizing the heuristics and biases that
might interfere with people making a decision according to their
preferences, so that the second, more fully informed decision
Would take medication
Would take medication
Change from first to second decision
From take to not take
From not take to take
No information Total
n = 365
n = 369
n = 393
n = 401
N = 1528
would best reflect decisions consistent with the participants values.
Although the decisions in the positively framed information group
appeared to differ least from the second decision that was made
after viewing all three presentations, there was a significantly
higher likelihood to decide to take medication on the first decision
in all groups (Table 5). Thus none of the three presentations is
clearly best in terms of helping participants to make decisions
that were most likely consistent with their preferences.
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 (p = 0.004) differences in the proportion of
people deciding to take medication on the second decision after all
four groups had been shown all three presentations. These findings
could be explained by a reluctance of people to change their
decision after first making a choice. It is uncertain why participants
shown negatively framed information per year would be less likely
to change their decision than participants in the other groups. It is
possible that the impression of a small difference made by that
presentation (7 versus 56) elicited a greater feeling of certainty,
referred to as the certainty effect , than the other
presentations (70 versus 56, and 930 versus 944) (Figure 2). This
would be consistent with prospect theory .
Applicability of the Findings and Implications
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 (Table 1). It is uncertain that the
findings are applicable to populations with less education [2,23].
The study attracted more men than our previous study using the
same recruitment strategy (47% versus 31%), which focused on
antibiotic treatment of sore throat, and more participants over 40
years old (70% versus 40%) . Nonetheless, most of the
participants were women and only 36% were between 30 and 49
years old. Fifty-four percent of those who started the study did not
complete it (Figure 1). We do not have demographic information
for those people, although it is likely that many chose not to
complete the study because they did not find the scenario relevant.
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 . It is uncertain to what extent
their responses to the hypothetical scenario we used, where they
were asked to pretend that they were a 40 year-old man, reflect what
they would actually decide [13,33,34]. Context affects the way
information is understood and processed , so that it is likely that
decisions made under hypothetical conditions might differ from real
decisions. Nonetheless, responses made under hypothetical
conditions may predict real-life behaviour .
Although these results have limited relevance to personal
communication with an active interaction between a physician
and a patient , we believe the results are likely to be relevant for
electronic and printed patient information and generally
applicable to people who are uncertain about whether to take
antihypertensive medication for two reasons. Firstly, 55% of
participants who were not shown any information for their first
decision changed their minds for the second decision, after they
were given information, and 45% of all of the participants changed
their mind from the first to the second, more fully informed
decision (Table 2). This suggests that participants were uncertain
and that the information that was provided influenced their
decision. Most of those in the no information group who
changed their mind (91%) changed from a decision to take
antihypertensive medication to a decision not to take it. This
suggests that most participants (80%) started out assuming that the
desirable consequences of taking antihypertensive medication
outweighed the undesirable consequences, and many of those
participants (39%) changed their mind. This is in contrast with our
earlier study where most participants (77%) started out assuming
that the desirable consequences of taking antibiotics for sore throat
did not outweigh the undesirable consequences.
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 (Figure 7). Thus, for people
with a relatively low risk of CVD, as was used in our scenario (7%
Figure 7. Likelihood of deciding to take medication in relation to RIS. 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.
over 10 years), this appears to be a preference-sensitive decision
[4,35] and the hypothetical decisions taken in this study are
consistent with what we would expect. These findings support the
recommendation that the absolute risk of cardiovascular disease
should be used as the basis for discussing with a patient whether
drug treatment should be initiated .
In this study, negatively framed information appears to have
resulted in decisions that were least consistent with decisions that
Negative framing per year 1.10 (0.851.43)
Second decision (all)
RIS = 270
RIS = 222
RIS = 8
RIS = Relative importance score.
Predicted % = proportion deciding to take antihypertensive medication based on logistic regression.
Table 4. Comparisons of the presentation groups.
Odds Ratio (98.3% CI)a p-Value
Positive framing for 10 years versus 0.63 (0.460.86)
Negative framing for 10 years
Negative framing per year
versus Negative framing for 10 years
aAdjusted overall CI level = 0.95.
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
[20,37], although presenting both positive and negative frames
may lead to information overload . For clinicians, the results
suggest that it may be important to take the time to present the
benefits of antihypertensive medication in several different ways.
Odds ratio (95% CI)
Positive framing for 10 years
Negative framing for 10 years
Negative framing per year
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
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
OdgaardJensen for statistical advice.
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.
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