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More on diet and population health

Posted by Ted Schrecker
Ted Schrecker
Ted Schrecker is a clinical scientist at the Élisabeth Bruyère Research Institut
User is currently offline
on Tuesday, 08 January 2013
in CHNET-Works!

A recent posting featured two important research syntheses on overweight and obesity. Another, especially useful for non-specialist audiences, appeared as a special report on “The big picture” in the December 15 issue of The Economist.

Commendably, the report does not sugar-coat the difficult politics of reducing overweight and obesity. It notes, for example, that “while lots of people remain fat, the associated ailments represent big business for the drug companies.”  It is candid about the role of companies like soft-drink manufacturers and fast-food chains in contributing to the epidemic of overweight, and the conflicts of interest that can arise in partnerships like one between Nestlé and the International Diabetes Federation, or the “Responsibility Deal” between food and alcohol companies and Britain’s Department of Health. (In negotiations about the action plan that emerged from the UN Summit on non-communicable diseases in September 2011, Canada was among the countries pressing for removal of text that mentioned such conflicts.) And it presents a succinct overview of efforts to deal with overweight and obesity through taxation and regulation. So far, those efforts have met with modest success, although that may be a consequence of modest ambition rather than of limitations intrinsic to the available policy instruments.

Unfortunately, the report is not open-access, although non-subscribers will be able to read part of it online. Unfortunately as well, the report pays insufficient attention to connections between the built environment and overweight, or to the cost of a healthy diet. Nevertheless, it is a refreshing signal that approaches going beyond the usual health promotion nostrums are moving into the policy mainstream.

Shortly before the Economist report appeared, Britain’s Department of Environment, Food and Rural Affairs released its annual Family Food Survey for the year 2011. Among the survey’s disturbing findings: fruit and vegetable purchases were 10 percent lower in 2011 than in 2007, with an even larger decline among the bottom fifth of Britain’s income distribution. Households in the lowest tenth of the income distribution were spending 17 percent more on food in 2011 than in 2007. A report in The Guardian quoted the director of the consumer protection organization Which? as saying: “One in six people say rising food prices are making it difficult to eat healthily,” and the preceding month a report in the same newspaper warned of a “nutrition recession” - this in a country where benefit caps planned for 2013 will cut the incomes of many people in full-time jobs as well as those who cannot find work. 

Closer to home, Ottawa's deparment of public health released the lastest issue of an annual calculation showing that if you are living on social assistance and paying market rents in the city, it is arithmetically impossible - as it is much of the rest of the province- to pay for the diet recommended by Ontario's Public Health Standards. In the capital of a weathly G7 country, 48,000 people a month turn to food banks. Against the background of ongoing concern about health care spending and areport recommending an immediate increase in Ontario social assistance rates to " the lower rate category, single adults receiving Ontario Works, as a down payment on adequacy while the system undergoes transformation," it may be worth asking`just how does making healthiy diets unaffordable contribute to a healthier population and lower health system costs down the road?

Our big fat complicated population health problem: Perspectives from both sides of the Atlantic

Posted by Ted Schrecker
Ted Schrecker
Ted Schrecker is a clinical scientist at the Élisabeth Bruyère Research Institut
User is currently offline
on Friday, 30 November 2012
in CHNET-Works!

 Overweight and obesity contribute directly to a variety of adverse health outcomes, as pointed out in a recent Lancet series.  At least in high-income countries, these conditions exhibit a pronounced socioeconomic gradient, and therefore present both a challenge and an opportunity.  A challenge, because of the complex etiology of overweight and obesity; an opportunity, because of the tremendous improvements in health that can be anticipated from any population-wide shift toward healthy weights.

Two recent syntheses of research findings offer useful insights, and also a few (intentional and unintentional) warnings, about how best to address overweight and obesity. A report by a committee of the US Institute of Medicine got the diagnosis absolutely right, from a health equity perspective: “If a community has no safe places to walk or play, lacks food outlets offering affordable healthy foods, and is bombarded by advertisements for unhealthy foods and beverages, its residents will have less opportunity to engage in physical activity and eating behaviors that that allow them to achieve and maintain a healthy weight.” Unfortunately this valuable analysis was not, in the end, used to arrive at system-level recommendations appropriate to the scale of the problem. The committee described its approach in terms of “large-scale transformative approaches,” but in its proposed responses it drifted back into behavioural nostrums like “mak[ing] physical activity and integral and routine part of life” and “mak[ing] schools a national focal point for obesity prevention” – an example of the phenomenon Jennie Popay and colleagues have described as “lifestyle drift.” 


Some environments are far more supportive of maintaining healthy weights than others.


A recent literature review on policy interventions to tackle the obesogenic environment produced by the Scottish Collaboration for Public Health Research and Policy, a research unit headed by expat Canadian John Frank, is more effective at avoiding what I have come to think of as the lifestyle trap. Focused on the situation of working-age adults, the review is organized using a framework called ANGELO (Analysis Grid for Environments Linked to Obesity): a simple four-by-two matrix in which four aspects of the environment – physical, economic, political or legislative, and sociocultural – are each analyzed at two levels, micro (the household or community) and macro (the region, province or nation). The authors make a point that has broad applicability in other population health contexts: “[M]any strategies aimed at obesity prevention may not be expected to have a direct impact on BMI, but rather on pathways that will alter the context in which eating, physical activity and weight control occur. Any restriction on the concept of a successful outcome … is therefore likely to overlook many possible intervention measures that could contribute to obesity prevention.”


 The authors of the review are candid about the difficulties facing large-scale interventions that are expensive or challenge vested interests, yet do not shrink from asking tough questions about the need for these, noting (for example) that the transport mode split in urban areas is 84% by car versus 9 percent walking in the United States, while it’s 36% by car versus 39% walking in Sweden. “Suffice it to say, it has been a concerted combination of infrastructure provision, integrated transport planning and disincentives for private cars which has helped to bring about the higher active travel rates,” which include a much larger role for cycling as well. And they argue that because of the relatively high price elasticity of soft drink taxation, it should be considered as a promising intervention along with price reductions of healthy foods like fruit and vegetables. (As an aside on a related point, I once heard a leading aboriginal health researcher wonder why Ontario can ensure that a bottle of whisky costs the same in the province’s far north as in downtown Toronto, but can’t or won’t do this for a carton of milk or a bag of apples.)


A further step in the Scottish review was to create another matrix classifying potential interventions on two criteria: certainty of effectiveness and potential population impact. Here a sugared beverage tax scored high on both criteria, as did healthy eating advocacy campaigns backed with supportive regulation, although curiously none of the policies that have been adopted to increase the costs of car travel scored similarly high, despite the authors’ extensive documentation of the role of public policy and their warning about defining successful outcomes too narrowly. But this is a minor disagreement with an important research synthesis on a complex problem that also provides a methodological template for reviews in other areas. It should be read by everyone concerned with social determinants of health, even if not specifically with overweight. Health policy analysis has joined other, more familiar high quality products for which Scotland is justifiably known far beyond its borders.  

 Blog-overweight 2

 Not the only quality product of Scotland.




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Acting on social determinants of health: how much do we need to know?

Posted by Ted Schrecker
Ted Schrecker
Ted Schrecker is a clinical scientist at the Élisabeth Bruyère Research Institut
User is currently offline
on Friday, 09 March 2012
in CHNET-Works!

Many readers will remember the sequence of events in which former football star O.J. Simpson was acquitted of the murder of his estranged wife and a friend in a criminal trial, yet found liable for damages in a civil suit brought by the family of one of the victims. Leaving aside the sociological roots of the not-guilty verdict in the United States' tragic history of racial antagonisms, in analytical terms the discrepancy can be explained with reference to the higher standard of proof in a criminal trial (proof beyond a reasonable doubt) than in a civil proceeding where a claim for damages can be sustained on a preponderance of the evidence or, in some common law jurisdictions, on the balance of probabilities.

The idea of a standard of proof is critical to understanding the question posed in the title of this posting. A classic article published in 1978 by economist Talbot Page (1) used this concept to analyze public policies toward "environmental risks" like toxic chemicals, which share such characteristics as incomplete knowledge of the mechanism of action, long latency periods between exposure and illness, and irreversibility. He pointed out that most forms of scientific inquiry are organized around minimizing Type I errors – that is, 'false positives' or incorrect rejections of the null hypothesis. Page used the analogy of the standard of proof in criminal trials, and went on to argue that minimizing Type I errors may be a thoroughly inappropriate principle when applied to use of scientific evidence in public policy, because it fails to take into account uncertainty and consequences. Stated another way, "a risk/benefit assessment," albeit often an implicit one, "is part of every public policy action which is based upon the interpretation of the results of a scientific investigation." (2)

Evidence-picture-1Waiting for "evidence of dead bodies" may be inappropriate when responding to health threats from environmental hazards.
Photo by biofriendly, reproduced under a Creative Commons licence.

This point has often been lost sight of in controversies about controlling toxic exposures in the environment and the workplace, with industry resisting regulation by demanding stronger – usually epidemiological – evidence and trying to cast the issue as one of scientific uncertainty: demanding what another economist has described as a "tobacco industry standard of proof." (3) Page correctly pointed out that: "In its extreme, the approach of limiting false positives requires positive evidence of 'dead bodies' before acting." This is, in fact, the standard of proof that has often been applied to research on the health effects of environmental hazards. A further point of importance is that the conventional threshold of statistical significance – 95 percent – may require extremely large and unmanageable sample sizes when the prevalence of a particular adverse outcome is only moderately elevated over background levels. (4) As Page pointed out, "there is literally no information content in a negative finding unless there is an analysis of ... the probability of a false negative." (1)

Choosing a standard of proof for purposes of public health policy therefore is unavoidably an ethical decision, having to do – as yet another author pointed out at around the same time – with the relative acceptability of being wrong in different kinds of ways (5) while we wait for evidence that may or may not be obtainable. Interestingly, a workshop on conceptual and methodological issues in public health science held at the University of Cambridge in 2010 revisited these questions, suggesting that understanding of them in the relevant research communities remains incomplete, even as they remain topical with respect to such issues as environmental causes of breast cancer .

The question of how much evidence is needed for action on social determinants of health underscores the value-laden nature of choices about the appropriate standard of proof. At least two issues are critical.

First, what kinds of research findings are relevant? Clinical epidemiology now widely accepts a hierarchy of evidence with the randomized controlled trial (RCT) at the top; presumably, this is what two authors writing on global health governance had in mind when they claimed that "[f]ew global health interventions are evidence-based, and interventions to improve population health among the poor are often untested ..." To some of us, this assertion is nothing short of bizarre, and neglects the fact that many interventions outside clinical settings cannot be assessed using RCTs, for reasons of ethics, logistics, or both. Colleagues and I pointed out a decade ago, in the context of research on preventing mental illness, that "choosing certain research strategies and standards of proof means the big questions ... probably will not be studied in ways that demonstrate the effectiveness of larger-scale, contextual interventions, and even the small questions will be asked in ways that seriously circumscribe the set of possible answers."

A methodologically pluralist approach, organized around what a former colleague calls a "portfolio of evidence," will yield more meaningful and policy-relevant answers. Unbeknownst to us, Michael Marmot had made a similar point the previous year in a general discussion of evidence for influences on population health: "The further upstream we go in our search for causes ... the less applicable is the randomized controlled trial. .... We must therefore rely on observational evidence and judgment in formulating policies to reduce inequalities in health. In this process, the best should not be the enemy of the good. While we should not formulate policies in the absence of evidence to support them, we must not be paralyzed into inaction while we wait for the evidence to be absolutely unimpeachable." (6) He continues to make this point.

Food-bank-can-use-help395,000 Ontarians received help from food banks in March, 2011.
Image courtesy Ontario Association of Food Banks.

Second, is it necessary to wait for evidence that a particular policy or intervention leads to improved health outcomes, or is it sufficient to have evidence of reduction in risk factors or what might be called intermediate biological variables (like markers of allostatic load, in the context of prolonged stress) that are known to have an adverse effect on health outcomes? This question gains urgency from knowledge of the cumulative effects of negative contextual influences on health over the life course: "waiting for dead bodies" in this case, as in others, can amount to carrying out a large-scale experiment on non-consenting subjects, the results of which may not be available for a generation. Obviously, ongoing evaluation of interventions and policy changes is important, but how much more do we need to know before (for instance) doing what it takes to reduce food insecurity among people for whom eating a healthy diet while paying market rents is arithmetically impossible?

This is a rather polemical way of stating the question, but it is useful in order to get at the hard politics of debates about evidence. Many policies and interventions needed to reduce health disparities by way of social determinants of health will be explicitly redistributive – starting with reductions in income inequality, as noted in a forthcoming editorial in the American Journal of Public Health. As mentioned, companies facing costly regulation of their activities have long found it attractive to frame their opposition as based on the insufficiency of scientific evidence. Similarly, those who stand to lose from tackling "the inequitable distribution of power, money, and resources" – one of the three overarching recommendations of the Commission on Social Determinants of Health – may frame their opposition in terms of the need for more evidence rather than simple self-interest. One-percenters, and those on a fast track to that status, are not a natural constituency for redistributive policies. This is not of course the only explanation for hostility to the social determinants of health agenda, but it cannot be disregarded. Against this background, it's especially important to keep in mind that the appropriate questions are not only about the strength of evidence, but also about how uncertainty should be resolved in a context where "deferring a decision is a decision in itself." They are, in other words, rooted firmly in the domain of public health ethics. Only by insisting on this point can we be sure that debates about when and how to act involve – as they should – the language of values and social justice.

(1) Page, T. (1978) A Generic View of Toxic Chemicals and Similar Risks. Ecology Law Quarterly, 7, 207-244.

(2) Darby, W. (1979) An Example of Decision-Making on Environmental Carcinogens: The Delaney Clause. Journal of Environmental Systems , 9, 109-117.

(3) Crocker, T.D. (1984) Scientific Truths and Policy Truths in Acid Deposition Research. In T. Crocker, ed., Economic Perspectives on Acid Deposition Control (pp. 65-79). Ann Arbor Science Acid Precipitation Series vol. 8. Boston: Butterworth.

(4) See e.g. Higginson, J., Muir, C.S., Muñoz, N. (1992) Human Cancer: Epidemiology and Environmental Causes (pp. 39-44). Cambridge: Cambridge University Press.

(5) Jellinek, S. D. (1981) On the Inevitability of Being Wrong. Annals of the New York Academy of Sciences, 363, 43-47.

(6) Marmot, M. (2000). Inequalities in Health: causes and policy implications. In A. Tarlov & R. St.Peter, eds., The Society and Population Health Reader, vol. 2: A State and Community Perspective (pp. 293-309). New York: New Press.

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