Transcript Title of lecture - Oxford Health Alliance

Oxford Vision 2020
Building evidence
September 2004
David R.Matthews
The Oxford Centre
for Diabetes, Endocrinology and Metabolism
“Chronic diseases are the largest cause of death in the
world. In 2002, the leading chronic diseases-cardiovascular disease, cancer, chronic respiratory
disease, and diabetes--caused 29 million deaths
worldwide. “
Derek Yach (Yach, Hawkes et al. 2004)
Evidence-base working group
Professor David Matthews (Chair), Chairman, Oxford Centre for
Diabetes, Endocrinology and Metabolism. University of Oxford
Pam Dyson, research co-ordinator, Oxford Dialogue Project
Professor James Fries, Stanford University School of Medicine
Henry Greenberg MD, consultant to the Center for Global Health and
Economic Development, Columbia University
Christine Hancock, president, International Council of Nurses
Dr Steve Leeder, visiting senior research fellow, the Center for Global
Health and Economic Development, Columbia University
Kenneth E MacWilliams, president & chief executive, Woodrow
Wilson Associates
Thomas E Novotny, Professor in Residence, Epidemiology and
Biostatistics Director, International Educational programs
University of California, San Francisco
Stig Pramming, vice-president, Global Health, Stakeholder Relations,
Novo Nordisk
Susan Raymond PhD, consultant to the Center for Global Health and
Economic Development, Columbia University
Derek Yach, special adviser to Oxford Vision 2020. Yale University.
Tim Baxter, Oxford Vision 2020 secretariat
Evidence-base working group
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We need evidence of the problem, of the size of the
problem, and of the reasons for the problem
We need evidence that the problem could be solved,
and the evidence of how this might be done
We need evidence of the cost of the solution and the
cost of failure to find a solution.
Evidence can be…
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From Randomised Controlled Trials
Epidemiological
Consensus based
Wisdom (experience) based
Anecdotal
Evidence can be…
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Of causality
Of risk
Of outcome
– Incidence of events (especially death)
– prevalence of surrogate markers
Evidence
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Meta analyses
– Biased by publication
– Confounded by heterogeneity
Cochrane reviews
– Biased by publication
– Reviews ≠ evidence
Epidemiology
– Prevalence ≠ aetiology
– Association ≠ causation
Risk factor area
Examples of published Cochrane reviews
Tobacco
Community interventions for preventing smoking in
young people
Impact of tobacco advertising and promotion on
increasing adolescent smoking behaviours
Workplace interventions for smoking cessation
Obesity
Advice on low-fat diets for obesity
Interventions for preventing childhood obesity
Diet
Reduced or modified dietary fat for preventing
cardiovascular disease
Physical activity
Exercise for preventing and treating osteoporosis in
post menopausal women
Exercise to improve self-esteem in children and young
people
Smoking
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Trials
– None. These would be, in any case, unethical. But
prospective studies amount to near-trial status and yield
strong evidence.
Epidemiology
– The epidemiology related to smoking has been studied over
fifty years. There is no real remaining debate that cigarette
smoking causes a huge burden of morbidity and mortality.
Evaluation of evidence
– Good. The size of the epidemiological changes observed
both for smoking illness and for its decline on smoking
cessation amounts to incontrovertible evidence.
Doll, Peto et al
BMJ, 2004
Doll, Peto et al BMJ, 2004
Doll, Peto et al BMJ, 2004
Physical
activity
Physical inactivity
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Trials
– Randomised controlled trials show that a healthy
lifestyle, including physical activity, reduce the
risk of diabetes. Post myocardial infarction, there
is an increasing body of evidence that mortality is
reduced.
Epidemiology
– There are some epidemiological data relating to
the protective effect of physical activity.
. Evaluation of evidence
– Strong evidence base for prevention of diabetes
and diabetic complications.
Tuomilehto et al. 2001
New England Journal of
Medicine. 344 (18): 1343
a reduction in weight of 5 percent or
more, in total intake of fat to less than 30
percent of energy consumed, and in
intake of saturated fat to less than 10
percent of energy consumed; an increase
in fiber intake to at least 15 g per 1000
kcal; and moderate exercise for at least
30 minutes per day.
Diabetes Prevention Program Research Group New England Journal of Medicine 346, 2002; (6): 393
Diabetes Prevention Program Research Group New England Journal of Medicine 346, 2002; (6): 393
(Yach, Hawkes et al. 2004)
Tobacco
High BMI
BMI
High
Physical inactivity
Obesity (or
overweight)
Diet and obesity
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Trials
– Few randomised controlled trials and none with long-term
outcome data. Some evidence of the role of changing
dietary constituents, for example type of fat There is little
evidence for the protective effect of vitamins.
Epidemiology
– Good demographic evidence of differences in diet,
associated with differences in morbidity and mortality..
Epidemiological data supports the role of obesity in chronic
disease development.
Evaluation of evidence
– The evidence of association of high energy, high fat, high
sugar diets with obesity is good. The association of obesity
with diabetes, CVD and some cancers is demonstrable in all
epidemiological analyses.
Diabetes attributable to weight gain
Regional estimates for diabetes (20-79
age group) 2003 and 2025
Fatal events: Ukpds
Cancer
Other
Unknown
Sudden
Renal
PVD
Stroke
Cardiac
Diet
=700 bananas per year
Dietary evidence-base
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There is little evidence for the effects of intervention
at population level, although there are examples of
successful interventions such as the North Karelia
project in Finland, that has resulted in a 70%
reduction in deaths from coronary heart disease over
30 years.
Relative Risk for type 2 diabetes
2 diabetes
RR for type16
84,941 nurses:
years follow-up
40
35
Relative risk
30
25
20
15
10
5
0
<23
to 25
to 30
to 35
>35
Body Mass Index
NEJM 345;2001:790-7
Weight distribution at diagnosis of type
2 diabetes: females
UKPDS IV: Diabetic
Medicine 1988;5:154159.
% ideal body weight
Other issues
Value of human life
It is not simply sufficient to say that all life can be
preserved indefinitely. The monetary value has
evolved from cost effectiveness studies and
generally is about £30,000 per life year –
interventions which are cheaper than this are thought
to be good value and interventions costing more than
this have tended to be seen as expensive. Moral
and theological arguments can be applied to the
individual, while, generally, economic arguments are
applied to policies of intervention. There is
reluctance or abhorrence in applying specific
economic arguments to specific cases.
Freedom of the individual
Smoking might cause an inconvenience to others and
thereby be cause for restraint. Similarly an unhealthy
diet might be ethically appropriate to indulge in by
oneself, but inflicting such diet on one’s family and
especially one’s children is progressively being
regarded as unethical.
The ethics of this “local responsibility” might be termed
“good citizenship”.
Social responsibility
Social responsibility demonstrates itself, for example, in
a desire for fair and ethical trade, and is part of the
groundswell of opinion against the exploitation of the
developing world by western organisations marketing
fast food and tobacco products. Although infrequent
in company practice there is a growing realisation
that social responsibility should be part of the ethos
of a company.
Women
Women are themselves at risk. Indeed, in some areas,
women’s death rates from CVD exceed those of men
in labour force ages. As development proceeds,
women’s risk factors from smoking, diet, and lifestyle
increase, and CVD morbidity and mortality will follow.
Even now in many middle income countries, the
percentage of deaths among women aged 15-45 is
2-3 times that attributable to the combination of
maternal deaths and deaths from HIV.
(data calculated from WHO Mortality Database)
Summary
Tobacco
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The knowledge base:
Cigarette smoking causes early death (by 10 years on average for
life-long smokers). (Doll, Peto et al. 2004)
Stopping smoking reduces the risk. (Doll, Peto et al. 2004)
Much of the epidemic could be averted if we stopped everyone
smoking by the age of 30 (Doll, Peto et al. 2004)
Nicotine is addictive.
Giving up smoking is difficult for some.
Intervention at fiscal, legislative, social and personal levels can
reduce the prevalence of smoking.
Identifying the gaps
why do some people become more addicted than others?
what is the optimal strategy for smoking cessation?
why are some races/populations more or less susceptible to
addiction, complications or death?
Physical activity
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The knowledge base:
There is strong epidemiological evidence that low
levels of physical activity are associated with chronic
disease (especially diabetes).
Increasing activity delays the onset of diabetes in atrisk groups.
Identifying the gaps
What is the optimal exercise level to recommend for
a population?
Do exercise programs prevent chronic disease in all
populations or just in those identified as being at
risk?
Diet and obesity
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The knowledge base:
High calorie intake is associated with obesity
High fat intake is associated with obesity
Obesity is associated with chronic disease including diabetes,
and gross obesity is associated with high morbidity and
mortality
Diabetes is associated with early death, and multiple
complications
Identifying the gaps
What is the cost or effectiveness of population-based strategies
to prevent obesity?
What are the necessary, quantified, dietary interventions,
including increased fruit and vegetable intake, reducing salt
intake and changing fat intake, that will prevent chronic disease
Evidence
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The specifics of the evidence – especially relating to
interventions – are poor.
But the totality of the evidence is overwhelming
The evidence for action is already beyond
reasonable doubt:
– We should not procrastinate while p values
accumulate
– we no longer have the luxury of time for
intervention