Dear Dr. Lynch
I totally agree with your approach of individual versus population levels of
causation. But I have a slight criticism regarding the usual interpretation
of the equation exposureX vulnerability. Quoting you: "As Rose said, if
causes at the population level (ie the factors that cause most cases in the
population) can be removed then susceptibility to those factors ceases to
matter. (ie only certain susceptible individuals get sick - not all
individuals who are obese get diabetes)"
What I want to discuss is that this would also work the other way around: if
average population vulnerability to an environmental risk fall, than
exposure to that risk ceases to matter. And if it raises, the exacly same
ammount of exposure may result in a previously non-existing effect of it.
Notwithstanding all the discussion going on about nature-nurture
interaction, we still think of individual vulnerability as a purely
inherited (meaning "non-modifiable") trait. This has prevented us to explore
alternative hypothesis to time-trends like the rise and fall in CHD
mortality.
I have suggested that it resulted from a window of vulnerability to CHD
deaths opened among birth cohorts most affected by the 1918 Influenza
Pandemic - those born around the turn to the 20th Century. Average
population serum cholesterol fell and high-fat diets ceased to matter
regarding CHD cases when those vulnerable cohorts left the population. As
the CHD mortality declined, remaining CHD cases were more and more
representative of a different source sub-population of cases, associated
with "a second atherogenic phenotype"- hypersinsulinemia, diabetes,
obesity - which, by the way, was also dominant among cases recognized before
the rise in CHD mortality in the 1920s.
The lack of recognition of this CHD true epidemic and of its determinant,
has even prevented a better assessment of the role of social inequalities in
mortality trends. The lack os association of temporal trends (as reported in
your paper http://www.milbank.org/820204html ) may be explained by non
considering the change which happened in the mix of CHD cases during the
20th Century. -
Again we may be going through a change in population vulnerability to diet
that may be more important then the diet itself.
Best regards,
Maria Inês Azambuja, MD, PhD
School Of Medicine
Universidad Federal do Rio Grande do Sul
Porto Alegre, RS
Brazil
About Rose, I believe that he left a possibility uncovered...
----- Original Message -----
From: "John Lynch, Dr." <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, August 03, 2006 8:23 AM
Subject: Re: [SDOH] Obesity as a "cause" of diabetes?
> Actually, Dennis and Steve are both correct - but depends on your
> perspective.
>
> If your objective is to statistically explain individual variation in risk
> of diabetes or CHD then its true that only 33% is 'explained' by risk
> factors
>
> If your objective is to explain population levels of diabetes and CHD,
> then obesity and the conventional physiological/behavioral risk factors
> explain the vast majority of case load in the population. Actually I think
> Steve's estimates of half diabetes case being obese is if anything, an
> underestimate. We know that 90%+ of CHD cases have at least 1 conventional
> risk factor. Thats been shown in several large scale studies with reliable
> data and exactly what you would see in studies like Whitehall as well. The
> population attributable risk for conventional risk factors ~ 80%. See
> Yusuf in Lancet (2004)
>
> The first objective is like Geoffrey Rose's explaining 'why individuals
> get sick'; the 2nd is like his 'why do populations get sick'. These are
> quite different questions and its important to keep them clear. As Rose
> said, if causes at the population level (ie the factors that cause most
> cases in the population) can be removed then susceptibility to those
> factors ceases to matter. (ie only certain susceptible individuals get
> sick - not all individuals who are obese get diabetes)
>
> Why a particular individual gets diabetes (a clinical focus) is NOT
> necessarily the same question as why populations have high levels of
> diabetes (a population level epidemiological question).
>
> Rose G. Sick individuals and sick populations. International Journal of
> Epidemiology 1985;14(1):32-8 also reprinted and discussed in Int J
> Epidemiol (2001)
>
> So, if you prefer the idea that only 33 % is explained by risk factors
> then you prefer individual prediction over population and so it seems hard
> to me, to then try to translate that into calls for population-wide
> change.
>
> In some ways these are very basic ideas but they are a bit tricky
> sometimes and I find not all that well understood by my students. Here's
> some material I get my students to ponder on this issue:
>
> Our recent paper shows that conventional risk factors DO explain social
> inequalities in CHD
> Lynch J, Davey Smith G, Harper S, Bainbridge K. Explaining the social
> gradient in coronary heart disease: comparing relative and absolute risk
> approaches. Journal of Epidemiology and Community Health 2006;60:436-441.
>
> Our paper is related to this interchange:
> Emberson JR, Whincup PH, Morris RW, Walker M. Social class differences in
> coronary heart disease in middle-aged British men: implications for
> prevention. Int. J. Epidemiol. 2004;33(2):289-296.
> Marmot M. Commentary: Risk factors or social causes? Int. J. Epidemiol.
> 2004;33(2):297-298.
> Emberson JR, Whincup PH, Morris RW, Walker M. Reducing social inequalities
> and the prevention of coronary heart disease. Int. J. Epidemiol.
> 2004;33(5):1152-1153.
>
> Other useful stuff on "explaining" disease
> Coggon DIW, Martyn CN. Time and chance: the stochastic nature of disease
> causation. Lancet 2005;365(9468):1434-1437.
>
> Rockhill B. Theorizing about causes at the individual level while
> estimating effects at the population level - implications for prevention.
> Epidemiology 2005;16(1):124-129.
>
> John Lynch
> Dept. Epidemiology
> McGill University
>
>
>
> -----Original Message-----
> From: Social Determinants of Health on behalf of Dennis Raphael
> Sent: Thu 8/3/2006 6:33 AM
> To: [log in to unmask]
> Subject: [SDOH] Obesity as a "cause" of diabetes?
>
> Actually, the evidence concerning obesity as a causal factor in type II
> diabetes is rather equivocal. This is another example of the dominant
> behavioural paradigm distorting analyis and understanding of a health
> issue
> -- see below...
> -------------------------------------------------------------------------
> "Ninety percent of the variance in occurrence of metabolic syndrome
> observed in the Whitehall studies cannot be accounted for by conventional
> behavioural risk factors.33"
>
> "Virtually nothing is known about the causes of recent increases in
> morbidity and mortality among the Canadian population in general, and the
> low-income population in particular.28 The presence of the metabolic
> syndrome has been identified as a significant indicator of a
> predisposition
> to diabetes (as well as CVD).29 30 Conventional thinking among health
> care,
> public health workers, and disease-oriented associations attributes
> increases in the presence of the metabolic syndrome and increases in
> morbidity and mortality to changes in dietary and activity patterns among
> Canadians 31, similar to traditional thinking concerning CVD-related
> issues.12,32 Yet, this dominant "health behaviours" paradigm takes little
> account of the increasing literature concerning the importance of the
> social determinants of health in population health in general and the
> incidence and management of diseases such as diabetes in particular.
> Ninety
> percent of the variance in occurrence of metabolic syndrome observed in
> the
> Whitehall studies cannot be accounted for by conventional behavioural risk
> factors.33 "
>
> "An extensive analysis of the determinants of adults' health-related
> behaviours such as tobacco use, physical activity, and healthy diets,
> found
> these behaviours were predicted by poor childhood conditions, low levels
> of
> education, and low status employment.(37) The study also found that poor
> socioeconomic conditions during early life make it less likely that people
> feel they have control over their lives - a factor that can contribute to
> illness Identifying some of the possible pathways to diabetes mellitus
> such
> as material deprivation, excessive psychosocial stress, and adoption of
> health threatening behaviours suggests value in applying a societal
> determinants of diabetes approach. Certainly, such an analysis would
> contribute to our understanding of why and how diabetes mellitus is an
> especially important issue for low income and other vulnerable
> populations.
> And considering the increasing numbers of low income families living in
> urban Canada, such a focus seems especially important.(12)"
>
> Yu, V. & Raphael, D. (2004). Identifying and addressing the social
> determinants of the incidence and successful management of type 2 diabetes
> mellitus in Canada. Canadian Journal of Public Health, 95, 366-368.
>
> http://quartz.atkinson.yorku.ca/QuickPlace/draphael/Main.nsf/h_Library/083BA721B77F5BA485256F2E004EB029/?OpenDocument
>
> Raphael, D., Anstice, S., Raine, K., et al. (2003). The social
> determinants of the incidence and management of Type 2 Diabetes Mellitus:
> Are we prepared to rethink our questions and redirect our research
> activities? Leadership in Health Services, 16, 10-20.
>
> http://quartz.atkinson.yorku.ca/QuickPlace/draphael/Main.nsf/h_Library/2F5A8832066E485F85256D86003EE54C/?OpenDocument
>
>
>
>
>
>
> Steve Cummins <[log in to unmask]>@YORKU.CA> on 08/03/2006 05:49:06
> AM
>
> Please respond to Social Determinants of Health <[log in to unmask]>
>
> Sent by: Social Determinants of Health <[log in to unmask]>
>
>
> To: [log in to unmask]
> cc:
>
> Subject: Re: [SDOH] anti-obesity technology
>
> I find the view that obesity is an unreliable indicator of physical
> health rather a strange and potentially dangerous one.
>
> It is true that how obesity is measured is contested and that
> discrimination and weightism is rife. For example BMI is not as reliable
> as Waist-Hip Ratio or Abdominal Fatness and that certain groups (such as
> athletes for example) can be heavier and still be healthy. It is also
> true that some people who are overweight are not unhealthy (in fact
> being overweight in old age is protective). You can be 'fat' and 'fit'.
>
> However the evidence that being obese causes physical health problems at
> the population level CANNOT be seriously contested at present. For
> example there is strong evidence that being overweight is implicated in
> half of all diabetes cases and reduces life expectancy by up to 7 years.
> To suggest otherwise is factually incorrect based upon current evidence
> and detracts focus from what is a very real and pressing public health
> problem
>
> A thorough evidence-based resource can be found here:
>
> http://www.cdc.gov/nccdphp/dnpa/obesity/index.htm
>
> Cochrane Reviews for obesity-related illnesses and interventions can
> also be found here:
>
> http://www3.interscience.wiley.com/cgi-bin/mrwhome/106568753/HOME
>
> Best
> Steve Cummins
>
>
> Carrie Brown wrote:
>> Thank you Graeme, I believe weight is an unreliable indicator of
>> physical health. I know many people within the "acceptable weight
>> range" with high cholesterol, high blood pressure and who are not
>> physically active or who don't eat well enough to achieve health
>> benefits. I also know many people who are above the "acceptable weight
>> range" who are physically fit and extremely healthy.
>>
>> I think in the next couple of years we're going to find that obesity
>> rates have decreased, but overall, people's physical health has not
>> improved. Because all those people who do not fall into the overweight
>> or obese category do not get the message because they are not being
>> targeted and don't feel that they are at risk.
>>
>> I'm afraid as a society we've created the situation where we look at
>> each other and judge health and character based on appearance. This is
>> extremely disconcerting, especially in a world so desperately in need of
>> acceptance, empathy and compassion.
>>
>> Carrie Brown
>> Health Promotion Liaison
>> Northern Lights Health Region
>> 11202 - 100 Ave.
>> High Level, A.B. T0H 1Z0
>> Phone: (780) 841-3204
>> Fax: (780) 926-7375
>> [log in to unmask]
>>
>> "Take care of ourselves and each other, spend time with loved ones, take
>> breaks when necessary and enjoy each moment on this lovely green and
>> blue planet." ~Tooker Gomberg~
>>
>>
>> -----Original Message-----
>> From: Social Determinants of Health [mailto:[log in to unmask]] On Behalf Of
>> Graeme Bacque
>> Sent: Wednesday, August 02, 2006 11:08 AM
>> To: [log in to unmask]
>> Subject: Re: [SDOH] anti-obesity technology
>>
>> One more serious issue to point out about this whole obesity obsession -
>>
>> this kind of excessive state and medical-sanctioned focus on impossible
>> standards of physical appearance and performance is in fact a known
>> aspect of fascism. It indicates a degree of social intolerance which is
>> becoming extreme.
>>
>> These kind of 'standards' have been used deliberately and systematically
>>
>> to denigrate and oppress women, non-Europeans, religious minorities and
>> persons with disabilities (among others) for centuries.
>>
>> The original history underlying this probably dates back to Biblical
>> times, where a person's physical characteristics were routinely
>> associated with either 'good' or 'evil'. This became highly evident in
>> Europe during the Burning Times. The Nazis escalated this form of
>> persecution to an extreme degree during their reign.
>>
>> This is a no-win situation and the worst form of victim-blaming -
>> although the person affected may actually be primarily a 'victim' of
>> society's scorn over physical attributes which are entirely beyond their
>>
>> control and which may not even specifically be a health issue. In the
>> end it boils down to other peoples' sense of aesthetics being offended
>> as opposed to being a valid indicator of someone's true state of
>> physical well-being.
>>
>> I for one find this obsessive, narrow, judgmental, out of context
>> official focus on certain physical characteristics (to the exclusion of
>> most other personal attributes) to be highly alarming. People need to be
>>
>> valued in all their diversity, no matter what color, shape or size they
>> may come in.
>>
>> Graeme
>>
>> Adam P. Coutts wrote:
>>> an innovative individual protective mechanism for the impending
>>> obesity epidemic! I think it's US based.
>>>
>>> http://www.harrietcarter.com/Detail.cfm?pth=13&Cat=111&prod=4594&sr=1
>>>
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> --
> Steven Cummins MSc PhD
> MRC Fellow
> Department of Geography
> Queen Mary, University of London
> Mile End Road
> London E1 4NS
>
> T: 44 020 7882 7653
> F: 44 020 8981 6276
> E: [log in to unmask]
>
> W: http://www.geog.qmul.ac.uk/staff/cummins.html
>
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