Title: Social Epidemiologic Methods in International Population Health and Health Services Research
1Social Epidemiologic Methods in International
Population Health and Health Services Research
- A Research Agenda Using Cancer Care as a Sentinel
Indicator - By Kevin M. Gorey
2Kevin 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
3Cancer Survival in Canadian and United States
Metropolitan Areas A Series of Studies
- Between-Country Effect Modification by
Socioeconomic Status - (Health Insurance)
4Research 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
5Introduction
- Mid-1980s to Mid-1990s
- Historical and Theoretical Contexts
6Historical 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)
7Politics 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)
8Cancer 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
9Theoretical 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
10SES 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.
11SES 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
12A 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.
13Methods
- A Focused Series of Cancer Survival Comparisons
Among Relatively Poor Residents of Canadian and
American Metropolitan Areas
14Comparative 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
15SamplingPersons/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
16Honolulu, 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
17SamplingPlaces 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
18SamplingPlaces 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
19Comparison 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
20Results
- Female Breast Cancer5-Year SurvivalAs Exemplar
Throughout
21SRRs 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
22SRRs 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)
23Toronto-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)
24Discussion
- The Screened/Developed
- Health Insurance Hypothesis
- Versus Alternative Explanations
25Summary 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
26Alt1Income 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
27Alt2Ethnic 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
28Alt3Lifestyle 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
29Alt4Different 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.
30Alt5Cancer 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.
31Alt6Competing 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
32Alt7Lead 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)
33Alt8Ecological 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.
34Future Research Needs
- Health Insurance Hypothesis Developed and
Screened With An EcologicalIncomeProxy - More Definitive Testing Needed
35Central 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
36Our Research Agenda Over The Next 5 Years
- Endeavoring to Filling Some of This Fields
Central Knowledge Gaps
37Social, 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
38Research 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)
39To 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
40Cohort 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
41Staged 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
42Incorporation 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
43Extending 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
44Ecological 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.
45Hypotheses 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)