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Social Epidemiologic Methods in International Population Health and Health Services Research

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Title: Social Epidemiologic Methods in International Population Health and Health Services Research


1
Social Epidemiologic Methods in International
Population Health and Health Services Research
  • A Research Agenda Using Cancer Care as a Sentinel
    Indicator
  • By Kevin M. Gorey

2
Kevin M. Gorey
  • Kevin is a social epidemiologist and social
    welfare researcher interested in advancing
    understandings about how health care policies
    affect health. He is particularly interested in
    the impacts of various under- and uninsured
    statuses in the US.
  • His web page is www.uwindsor.ca/gorey

3
Cancer Survival in Canadian and United States
Metropolitan Areas A Series of Studies
  • Between-Country Effect Modification by
    Socioeconomic Status
  • (Health Insurance)

4
Research Team and Reports
  • Kevin Gorey, University of Windsor
  • Eric Holowaty Gordon Fehringer, CCO
  • Erich Kliewer, Cancer Care Manitoba
  • Ethan Laukkanen, WRCC and Colleagues
  • Study series reports
  • Am J Public Health 1997 2000
  • Can J Public Health 1998 Milbank Q 1999
  • J Public Health Med 2000
  • J Health Care Poor Underserved 2003
  • Ann Epidemiol 2003

5
Introduction
  • Mid-1980s to Mid-1990s
  • Historical and Theoretical Contexts

6
Historical Context
  • - Canada Universal single payer
  • - US Multi-tiereduninsured and underinsured,
    Medicaid, Medicare, continuum of private
    coverages
  • - Time of great systemic changes
  • - Managed care proliferation (US)
  • - Federal-provincial shift (Canada)

7
Politics Versus Science
  • - Political debates tend to mythologize anecdotal
    outcomes.
  • - Rhetoric often not substantiated
  • (e.g., 2 Manitoba studies)
  • - Waits for 10 surgical procedures stable or
    decreased 5 yrs post-downsizing
  • - Access to surgery actually increased after
    hospital downsizing (maintaining quality
    mortality, readmissions)

8
Cancer Survival is a Sentinel Health Care Outcome
  • - Relatively common over the life course
  • - Diverse constellation of diseases
  • - Many with good prognoses and high quality of
    survivable life
  • - Diverse screens (including primary care) and
    treatments exist and matter
  • - Timely access, referral and follow-up matter

9
Theoretical Context Systematic Literature Review
  • - In the US, ethnicity and SES are strongly
    associated with health insurance statuses (odds
    ratios OR 2.0 to 15.0).
  • - All are also strongly associated with cancer
    screens, stages at diagnosis and access to
    treatments (ORs 2.0 to 5.0).
  • - Such Canadian associations tend to be
    attenuated or nonexistent. For example
  • - US SES-cancer survival OR 1.56
  • - Canadian OR 1.04 (NS) to 1.18

10
SES A Key Effect Modifier?
  • Therefore, any Canada-US cancer outcome study
    that does not incorporate SES is unlikely to
    observe the truth.
  • - SES is so intimately connected with health in
    North America that it must be incorporated into
    all such studies.
  • - If an interaction exists, interpretations of
    main effects alone can be misleading.

11
SES An Effect Modifier? E.G.
  • - One previous study of Canada-US cancer survival
    (GAO, 1994)
  • - Found no between-country differences
  • - But, did not account for SES
  • - We have observed a substantially different
    picture within SES strata.
  • - Consistent Canadian advantages within the
    lowest SES strata

12
A Country By SES Interaction Hypothesis Guided
Our Series
  • Relatively poor Canadian cancer patients (better
    insured) would enjoy advantaged survival over
    their similarly poor counterparts in the United
    States.
  • - We think this a better guide to
    policy-interesting and important research
    questions in North America than those provided by
    main effect country-based hypotheses.

13
Methods
  • A Focused Series of Cancer Survival Comparisons
    Among Relatively Poor Residents of Canadian and
    American Metropolitan Areas

14
Comparative Series Overview
  • Toronto, Ontario vs Detroit, Michigan
  • An ecological exemplar
  • Toronto vs San Francisco, Seattle, Hartford
  • Adjustment for absolute income
  • Toronto vs Honolulu, HI
  • Health insurance hypothesis test
  • Winnipeg, Manitoba vs Des Moines, Iowa
  • Replicate among smaller cities
  • Comparisons of Subsamples lt 65 yoa
  • Health insurance hypothesis test

15
SamplingPersons/Cancer Patients
  • - Ontario and Manitoba Registries, SEER
  • - First, primary invasive cancer cases
  • - MC, not DC or autopsy only
  • - With minimum 5 years follow-up
  • - Began 15 most common cancers
  • - Since focused on most significant
  • - Estimated case ascertainments, MC, and
    follow-ups all gt 95 (DCO/Autopsy lt 1)
  • - Even better among the most public
    health-significant cancer types

16
Honolulu, Breast Cancer, 1986-1990
SES MC DCO/Autopsy
  • High 100.0 0.0
  • 100.0 0.0
  • 100.0 0.0
  • 100.0 0.0
  • 100.0 0.0
  • 100.0 0.0
  • 100.0 0.0
  • 98.5 0.7
  • 97.9 0.0
  • Low 98.9 0.0

17
SamplingPlaces Rationales For Metropolitan
Sampling
  • - Maximize internal validity
  • - Higher MC, follow-up, geocoding rates
  • - Lower DCO or autopsy only
  • - Maximize external validity
  • - Vast majority of NAs urban residents
  • - 1 of 3 Ontarians and 1 of 7 Canadians reside
    in Toronto
  • - Control for service availability

18
SamplingPlaces Ecological Measures of SES
Neighborhoods
  • No NA registries coded personal SES.
  • - Census tracts joined cases at diagnosis to
    income data (US Census, Stats Can)
  • - Neighborhood prevalence poor
  • - Theory, insurance, practical sig.
  • - Poverty (US), low income (Canada)
  • - Both household income-based and tied to the
    consumer price index
  • - Though Canadian criterion more liberal
  • - Used to form relative SES quantiles

19
Comparison of SES Quintiles 1990/91,
US Winnipeg Des MoinesSES Mdn Mdn
  • High 47,090 44,050
  • 39,110 36,370
  • 32,265 30,165
  • 26,043 26,890
  • Low 17,500 19,570
  • Lowest US SES quintile 20 poor, another 45
    near poor estimated (vs highest) uninsured PR
    10.0, underinsured PR 15.0

20
Results
  • Female Breast Cancer5-Year SurvivalAs Exemplar
    Throughout

21
SRRs With 95 CIs, 1984 to 1994
SES Toronto Detroit
  • High 1.00 1.00
  • 1.00 (0.94,1.06) 0.94 (0.88,1.01)
  • Low 0.98 (0.93,1.04) 0.80 (0.75,0.85)
  • No significant between-country differences in the
    middle or high income areas
  • Low income areas Between-country
  • SRR 1.30 (1.23,1.38), Canadian patients
    advantaged

22
SRRs With 95 CIs, 1986 to 1996
SES Toronto Honolulu
  • High 1.00 1.00
  • 1.01 (0.93,1.10) 0.94 (0.82,1.07)
  • 1.01 (0.95,1.08) 0.93 (0.81,1.06)
  • 1.03 (0.96,1.11) 0.97 (0.86,1.09)
  • 1.04 (0.97,1.12) 0.93 (0.81,1.07)
  • 0.97 (0.90,1.04) 0.80 (0.69,0.93)
  • 1.00 (0.81,1.24) 0.90 (0.79,1.02) 1.03 (0.95,1.1
    1) 0.97 (0.87,1.09)
  • 1.05 (0.98,1.13) 0.91 (0.80, 1.04)
  • Low 1.02 (0.95,1.10) 0.78 (0.67,0.91)

23
Toronto-Honolulu Between-Country Survival Outcomes
  • The only significant decile difference was for
    the lowest income area
  • SRR 1.20 (1.06, 1.36)
  • Canadian patients advantaged
  • Among those lt 65 yoa
  • SRR 1.28 (1.07,1.53)

24
Discussion
  • The Screened/Developed
  • Health Insurance Hypothesis
  • Versus Alternative Explanations

25
Summary Health Insurance
  • - Consistent SES-cancer survival associations in
    US, but not Canada
  • - Consistent country-SES interactions
  • - Canada advantage lowest SES strata
  • - Particularly among those lt 65 yoa
  • - Consistency of pattern across diverse
    contextspeople and placespoints toward a
    pervasive systemic effect
  • - 285 of 319 between-country comparisons were
    in support of the health insurance hypothesis

26
Alt1Income Gap or Inequality Larger in the
United States?
  • - For some of our studies, the economic divide is
    actually larger in the Canadian sample.
  • - E.g., Winnipeg vs Des Moines

27
Alt2Ethnic or Cultural Explanations?
  • - Similar pattern of findings observed among
    various ethnic mixes
  • - North American studies of race/ethnicity and
    cancer screening have implicated knowledge
    (education), rather than race, per se.
  • Consistent indictment of America Inequitable
    distribution of key social resourceseducation
    and health care

28
Alt3Lifestyle Factors (LS) Exercise, Diet, BMI,
Tobacco and Alcohol Consumption?
  • - Associations with cancer survival tend to be
    extremely small
  • - Larger associations with incidence
  • - Survival findings consistent across cancers
    with diverse component causes
  • - Some LS factors very sig., others not
  • - Income is associated with lifestyle in both
    countries, but no income-survival gradients were
    observed in Canada
  • - Little to no Canada-US LS prevalence
    differences (2) have been observed

29
Alt4Different Case Mixes by Stage of Disease at
Diagnosis?
  • - Stage differences may account for some, but
    probably not all of the between-country survival
    differences.
  • - In within-US stage-adjusted analyses,
    treatment differences still account for roughly
    50 of survival variabilities.

30
Alt5Cancer Registry Death Clearance? National
(US) vs Provincial (Canada)
  • - Over the life of these studied cohorts,
  • only 1-3 of Toronto residents moved
    out-of-province.
  • - Likely fewer chronically ill moved
  • - Ontario Cancer Registry comparisons of national
    and provincial death clearances found
    inconsequential differences.

31
Alt6Competing Causes of Death (Observed vs
Relative Survival)?
  • - Life expectancy in Honolulu among both women
    and men is close to 3 years greater than in
    Toronto
  • - Therefore, our between-country SRRs (Canadian
    advantage) may actually underestimate the truth

32
Alt7Lead Time Bias?
  • - Our findings were fairly consistent across
    different cancers probably with various
    pre-clinical phase lengths.
  • - A systematic review of 87 studies (with
    adjustment for lead-time) observed stage and
    treatment effects (Richards et al., 1999, Lancet)

33
Alt8Ecological Fallacy?
  • - Even if it were merely an area effect, the
    consistently observed residence-survival
    association in the US, but not in Canada would
    still be instructive.
  • - The compositional measure ( poor and near poor
    in neighborhoods) is well known to be intimately
    associated with under-and uninsured statuses in
    the US.

34
Future Research Needs
  • Health Insurance Hypothesis Developed and
    Screened With An EcologicalIncomeProxy
  • More Definitive Testing Needed

35
Central Research Needs
  • - Study more recent retrospective and prospective
    cohorts
  • - Perform stage-stratified analyses
  • - Incorporate treatment variables
  • - Extend generalizability to smaller urban and
    rural-remote places
  • - Develop construct validity of ecological SES
    measures in Canada

36
Our Research Agenda Over The Next 5 Years
  • Endeavoring to Filling Some of This Fields
    Central Knowledge Gaps

37
Social, Prognostic Therapeutic Factors
Associated With Cancer Survival in Canada and the
US
  • Health Care Access and Effectiveness in Diverse
    Urban and Rural Contexts, 1985 to 2010

38
Research Team Co-Investigators
  • Kevin Gorey (PI) Emma Bartfay (Epidemiology)
  • Karen Fung (Biostatistics)
  • Isaac Luginaah (Geography)
  • Frances Wright (Surgical Oncology)
  • Caroline Hamm Sindu Kanjeekal
  • (Medical Oncology)
  • Eric Holowaty William Wright
  • (Cancer Surveillance Registration)

39
To Address Identified Research Needs, It Will
  • - Study more recent retrospective and prospective
    cohorts
  • - Perform stage-stratified analyses
  • - Incorporate treatment variables
  • - Extend generalizability to smaller urban and
    rural-remote places
  • - Develop construct predictive validities of
    ecological SES measures in Canada

40
Cohort Design
  • Incident cohorts 1985-1990 1995-2000
  • Followed until 2000 2010
  • Cox models over 1-, 3-, 5- to 10-years
  • In Canada and the US
  • During a policy-interesting period
  • - Federal-provincial shift in Canada
  • - For-profit managed care proliferation
    prevalent increases uninsured in US

41
Staged Analyses
  • No Canadian cancer registry routinely codes stage
    of disease at diagnosis.
  • - Thus, no previous study in this field has been
    able to account for case-mix.
  • Stage will be abstracted for this studys
    samples. Allowing for
  • - More comparable between-country comparisons
  • - Examination of the relative weightiness of
    pre- (affect later diagnosis) and
    post-diagnostic (affect lack of access to best
    treatments and follow-up) social forces

42
Incorporation of Treatments
  • No Canadian cancer registry routinely codes
    initial treatments.
  • - Thus, no previous study in this field has been
    able to account for them in survival analyses.
  • Detailed treatment variables will be abstracted
    for this studys samples.
  • - Surgery, radiation, chemotherapy and others
  • - Initial course and follow-up
  • - Type, dose, delays, timings/sequence
    between various therapies

43
Extending Generalizability Contexualizing
Knowledge
  • Systematic Replications in
  • Ontario California
  • Large cities Toronto San Fran/Oakland
  • Small cities Windsor Salinas
  • Rural/remote areas of Ontario California
  • 1,060 breast and colon cancer cases for each
    incident cohort in each type of place

44
Ecological Measurement Validity
  • Ontarian and Californian cancer cases will be
    joined via their residential census tracts to the
    following data
  • - Income (poverty prevalence) and
  • - Physician supplies (count/10,000 pop)
  • - Primary care and specialists
  • This will provide opportunities to better
    understand the meanings of such ecological
    measures, particularly in Canada, where little is
    yet known about them.

45
Hypotheses Related to Survival
  • 1. Significant country by SES interaction
    (Canadian advantage low-income only)
  • 1a. Advantage significantly increased over time
  • 2. SES-survival significant in US (not in Canada)
  • 2a. Age by SES interaction (Medicare advantage)
  • 2b. US gradient significantly increased over
    time
  • 3. Physician supplies-survival associations
    significant in both Canada US (for both primary
    care and specialists supplies)
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