Preventive Medicine 53 (2011) 250–252
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Preventive Medicine
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / y p m e d
Why the prevention paradox is a paradox, and why we should solve it:
A philosophical view
Stephen John
Hughes Hall Centre for Biomedical Science in Society, Hughes Hall, University of Cambridge, Mortimer Road, Cambridge, CB1 2EW, UK
a r t i c l e
i n f o
Available online 30 July 2011
Keywords:
Ethics
Risk
Geoffrey Rose
Prevention paradox
a b s t r a c t
This paper provides some philosophical comments on Rose's prevention paradox, suggesting why that
paradox seems so difficult, and why policy-makers should care about solving it. The assumptions underlying
the paradox section sets out two ways of understanding the notion of “benefit” in public health programmes,
and shows how the prevention paradox arises from combining both understandings. Thinking through the
paradox section argues that if we find the second understanding of benefit appealing, then we should rethink
how we typically assess preventive public health measures. The implications section shows how these
theoretical arguments imply that public health practitioners should care about solving the prevention
paradox, rather than simply denying the legitimacy of one of the two views from which it arises.
© 2011 Elsevier Inc. All rights reserved.
In his classic The Strategy of Preventive Medicine, Geoffrey Rose
outlines the “prevention paradox” (Rose, 2008). The problem arises
from a “fundamental axiom of preventive medicine”, that “a large
number of people exposed to a small risk [of some disease] may
generate many more cases [of that disease] than a small number
exposed to a high risk” (Rose, 2008, 59). This implies that “population
strategies” which focus on reducing the risk of those already at low or
moderate risk will often be more effective than strategies which focus
on “high risk” individuals at improving population health. Hence the
apparent paradox that to have the greatest possible impact on
population health, “some way must be found to reduce the risk of
large numbers of people who, more often than not, will not benefit
from the change” (Rose, 2008, 60).
This paper aims to establish which assumptions make the
prevention paradox a paradox and why we should accept them,
such that we should care about solving it. The assumptions underlying
the paradox section sets out two ways of understanding “benefit” in
public health programmes, and shows how the prevention paradox
arises from combining both understandings. Thinking through the
paradox section argues that if we find the second understanding
appealing, then we should rethink how we assess preventive public
health measures. The implications section shows how these
theoretical arguments imply that public health practitioners should
care about solving the prevention paradox, particularly if they appeal
to “solidarity” concerns to motivate individuals.
E-mail address: sdj22@cam.ac.uk.
0091-7435/$ – see front matter © 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.ypmed.2011.07.006
The assumptions underlying the paradox
That targeting interventions at the (few) members of high-risk
groups will often be less effective a way of improving population health
outcomes than targeting the (many) members of moderate- or low-risk
groups is certainly important. However, it is not a paradox, but a slightly
counter-intuitive fact which policy-makers can easily forget. Rose seems
to think that what is paradoxical about his results is the implication that
the most effective public health strategies have little benefit for the vast
majority of those they affect (Rose, 2008, 47). However, there are two
different ways of understanding how preventive public health programmes benefit individuals, which, arguably, Rose fails to distinguish.
This section shows how it is only when we employ both senses
simultaneously that we fully understand Rose's problem.
Sometimes, Rose writes as if those targeted by public health
campaigns benefit only if they do not die as a result. On this “actual
outcome” understanding of benefit, the prevention paradox consists in
two, inter-related phenomena. First, most people targeted by preventive
measures will not benefit from those measures, but only suffer any
related inconvenience (although when implementing the policy we will
be unable to predict who). Second, often, the more effective a strategy at
reducing overall mortality amongst those targeted by the intervention,
the greater will be the ratio of not-at-all-benefitted to benefitted
individuals. These are both important phenomena, related to debates
about distributive justice. Furthermore, they clearly seem relevant to a
key topic of Rose's book: how best to motivate individuals to comply with
preventive strategies, given the low chance that they themselves will
benefit (Rose, 2008, Chap. 4). However, on the actual outcomes
understanding of public health policy, the situation Rose describes does
not seem any more paradoxical than the fact that most people who enter
a lottery will lose and only a very few gain.
S. John / Preventive Medicine 53 (2011) 250–252
At other points, however, Rose formulates the prevention paradox in
a different manner, adopting what I call an “ex-ante” understanding of
the benefit of public health programmes, which assesses “benefits” in
terms of changes in individuals' levels of risk of harm. Sometimes, rather
than say that most people will not benefit from population strategies, he
instead says that they will each benefit but only “negligibly” (Rose, 2008,
59), presumably by having their individual risk of harm reduced. On this
interpretation, everyone who is targeted by a public health intervention
does gain something from that programme, a very slight reduction in
the risk that she will suffer harm (John, 2009).
If we allow that the second, ex-ante interpretation of benefits is
plausible, but also find the “actual outcome” understanding of benefit
appealing, then population strategies can seem truly paradoxical.
Imagine that we adopt a population strategy which reduces the risk of
death of members of a low risk group slightly, thereby benefiting them a
little (in the ex-ante sense), but that this programme also imposes a small
hardship on each group member (say, remembering to take a pill every
day). Imagine that, ex-ante, each member of the targeted population
would rationally prefer not to take the pill and not to suffer the risk of
death. Ex-ante, each individual seems to lose more than she gains from
the policy. However, at the same time, we might know, from the
(expected) “actual outcomes” perspective that at least some people will
benefit from the policy, because they would otherwise have died. The
very same policy both harms everyone and, yet, benefits some of them!
Thinking through the paradox
It is unclear whether Rose uses the term “prevention paradox” to
describe the motivational and distributive justice problems which arise
if we assume the “actual outcomes” understanding of the benefits of
public health policy, or to describe the genuinely paradoxical situation
which arises if we assume both the actual outcomes and ex-ante
perspectives. This is not to criticise Rose, as the distinctions drawn above
are both unfamiliar and not central to his own work. This section,
however, suggests an important implication of the arguments above: if
the ex-ante perspective is at least sometimes a legitimate way to think
about policy, then the moral theory which normally structures
discussion of public health policy, consequentialism, should be
supplemented by an alternative, “contractualist” approach.
One important approach to political philosophy is “consequentialism”: the view that we should choose actions on the basis of a
function of their expected welfare consequences (Sinnot-Armstrong,
2006). There are well-known problems with using consequentialism
for thinking about all public health policy; for example, consequentialist reasoning would seem to recommend that we should kill
healthy people to harvest their organs for the sake of saving the lives
of others! (Sinnot-Armstrong, 2006). Therefore, it is often claimed
that consequentialist reasoning must be limited by consideration of
rights. However, much writing on public health policy assumes that as
long as rights violations are not at stake we should choose between
policies on the basis of their expected consequences. As such, debates
typically turn around two axes: first, whether some policy will violate
individuals' rights; second, which consequences matter, such as
whether we should assess consequences using QALYs or DALYs, and
whether we should value equality of outcome (Nord, 1999).
The broadly consequentialist approach to thinking about public
health policy clearly relates to the “actual outcomes” understanding of
public health benefit. On that approach, the prevention paradox is not,
truly, a paradox, but simply the problematic fact that many people
must all suffer a tiny deprivation for the sake of some other people
enjoying a major benefit. For a consequentialist deciding whether we
should go ahead with a population strategy which does not violate
rights, then the question is simply whether aggregate small losses for
a few outweigh aggregate great gains for a few. It seems plausible that,
often, they do, such that consequentialists will, typically, be in favour
of non-rights-violating population strategies. However, consequen-
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tialist reasoning seems to miss out an important potential feature of
policy choices, highlighted by the ex-ante understanding of benefit:
that each individual might seem to be burdened more than she gains
from a policy. In effect, consequentialist reasoning seems to overlook
the possibility that individuals might, reasonably, want to take risks
with their health. This seems a valid consideration in formulating
policy goals, even if the policy would not actually violate anyone's
rights.
These comments suggest we need an alternative, or at least a
supplement, to consequentialism. Such an alternative is offered by the
approach to moral and political theorising called “contractualism”. To
simplify, contractualists claim that policies are right if and only if noone affected by those policies could “reasonably reject” those policies.
Individuals can reasonably reject policies if they can offer some
complaint against that policy and propose an alternative, such that
no-one else has a stronger complaint against her proposal than she
has against the original (Scanlon, 1998, 153). In Rahul Kumar's crisper
formulation: “a valid principle is one that is most acceptable to the
person for whom it is least acceptable” (Kumar, 2003, 33). Central to
contractualism is a focus on the standpoints and complaints of each
individual, particularly those who are most burdened by a policy, and
an associated refusal to “aggregate” costs and benefits to individuals.
Of course, no-one thinks that we can actually ask every individual
whether they object to a particular policy; rather, contractualism
provides a framework for thinking through issues by asking how
people might object to policies.
The contractualist can provide an alternative account of the
prevention paradox. She can assess whether we should adopt the
population strategy by asking what objections members of the
population could make against such a policy from the ex-ante
perspective. From this perspective, each member of the population
would, I have stipulated, prefer to suffer the tiny risk and not suffer
inconvenience, rather than vice versa. Therefore, the contractualist can
argue that, even if it does not violate anyone's rights to do so, the
population strategy is “reasonably rejectable” in favour of the status quo.
(Of course, this claim assumes that each member of the population
values the risk-reduction less than avoiding inconvenience: this will not
always hold true. However, at least when it does, contractualism can
explain why population strategies seem problematic. Furthermore,
contractualism can explain why cases where there is disagreement over
which risks are tolerable are morally complicated. Consequentialist
reasoning, by contrast, can make such concerns seem mysterious.)
Furthermore, as well as explaining why some population strategies may seem paradoxical, the contractualist can also explain why
“high risk” strategies sometimes seem preferable to “population
strategies”, even though the former will, foreseeably, produce less
overall benefit than the latter. When we think about the choice
between population and high-risk strategies, each member of the
high-risk group has a stronger complaint against adopting the
population strategy than each member of the moderate risk group
has against the high-risk strategy, because the gain for each high risk
individual from the high-risk strategy is greater than is the gain of
each moderate risk individual from the population strategy. (Of
course population strategies will, often, benefit high-risk individuals,
as I shall discuss below. My comments here are intended to illuminate
what we might say when the gain members of the “high-risk” group
will make from a “population strategy” are lower than those they
would make from a high-risk strategy, in the hope of clarifying more
complex real-life cases).
In short, if we are faced with a strict choice between a population and
a high-risk strategy in some prevention paradox cases, then our policy
recommendations will be very different depending on whether we are
consequentialists or contractualists. Consequentialists will tend to
prefer population strategies, whereas contractualists will tend to prefer
high-risk strategies. Therefore, recognising why the prevention paradox
seems paradoxical—because we confuse two senses of benefit—also
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S. John / Preventive Medicine 53 (2011) 250–252
suggests a broader problem, because the different senses of benefit
relate to different moral theories with different normative implications
for practice.
Implications
If we think that the ex-ante perspective on public health policies is
sometimes legitimate, and interpret this claim in contractualist terms,
then we can explain two puzzling facts: first, why (some) population
strategies seem paradoxical; second, why high-risk strategies may
seem preferable to population strategies. However, it might seem that
there is an easy solution to the prevention paradox: we should simply
reject the ex-ante perspective and the associated contractualist moral
framework. This temptation may be particularly strong for public
health professionals, familiar with the expected outcome consequentialist perspective. This section suggests two reasons why public
health policy-makers should not try to dodge the paradox, but should,
instead, recognise that the ex-ante perspective is valid, such that there
is a genuine problem to resolve.
One reason is purely strategic: when assessing public attitudes
towards public health programmes, such concerns need not reflect a
poor understanding of the facts behind such programmes or a selfish,
immoral lack of concern for population outcomes. Rather, public
attitudes might be shaped by a (largely) inchoate moral theory
framed in ex-ante terms. Recognising this fact may facilitate
communication between policy-makers and publics.
A second, more positive reason for public health practitioners to be
aware of ex-ante contractualism relates to Rose's concerns about
motivation. Rose suggests that population policies will not only produce
the greatest population benefit, but will also often benefit those in
“high-risk” groups greatly (Rose, 2008, Chap. 6). For example, reducing
the salt consumption of very many individuals at low risk of
cardiovascular disease might not only benefit (some proportion of)
that population, but also reduce the risk of those at high-risk, because as
mean salt consumption decreases, the entire risk distribution will shift
downwards.
Rose often stresses that it will be hard to motivate most people to
accept the minor privations associated with population policies.
However, he appeals to the considerations just adduced as one way in
which to resolve this problem: we should make people aware that
there are “solidarity” based reasons to alter their behaviour, because,
even such changes will foreseeably benefit those at the tail of the risk
distribution (Rose, 2008, Chap. 6). This hope seems both plausible and
appealing. However, it implicitly assumes that those who are at high
risk are, in some sense, more needy than those at low risk, such that
the decent thing for low risk people to do is to help their fellow high
risk citizens. Such implicit assumptions require us to be able to
articulate to members of the low and moderate risk groups that highrisk people have a stronger complaint against not implementing the
population policy than the low/moderate risk individuals have against
implementing that policy. That is to say, even if we value population
strategies on consequentialist grounds, at least when contractualist
reasons point in the same direction, we may have reason to formulate
public discourse in the latter terminology.
If policy-makers are willing to use Rose's attractive “solidarity”
strategy in attempting to motivate others to follow population policies,
then they face a problem: how to resolve the apparent paradox which
arises when we combine the actual outcomes and ex-ante understandings of the benefits of public health policy. Even if policy-makers refuse
to appeal to solidarity, it seems they should still be aware that ex-ante
considerations shape how others might think about public health policy.
This paper has not shown how to resolve the prevention paradox, but it
has argued that we cannot hope to dodge that problem, but, rather,
should accept the premises from which it emerges.
Conflict of interest
I have no conflicts of interest.
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