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Social Epidemiologic Methods Social Epidemiologic Methods in International Population in International Population
Health and Health Services Health and Health Services ResearchResearch
A Research Agenda Using Cancer Care as a Sentinel Indicator:
By Kevin M. Gorey
Kevin M. GoreyKevin 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
Cancer Survival in Canadian Cancer Survival in Canadian and United States and United States
Metropolitan Areas: A Series Metropolitan Areas: A Series of Studiesof Studies
Between-Country Effect Modification by Socioeconomic
Status(Health Insurance)
Research Team and ReportsResearch Team and ReportsKevin Gorey, University of Windsor
Eric Holowaty & Gordon Fehringer, CCOErich Kliewer, Cancer Care Manitoba
Ethan Laukkanen, WRCC and ColleaguesStudy series reports:
Am J Public Health 1997 & 2000Can J Public Health 1998; Milbank Q 1999
J Public Health Med 2000J Health Care Poor Underserved 2003
Ann Epidemiol 2003
IntroductionIntroduction
Mid-1980s to Mid-1990s:Historical and Theoretical
Contexts
Historical ContextHistorical Context
- Canada: Universal single payer
- US: Multi-tiered—uninsured and underinsured, Medicaid, Medicare, continuum of private coverages
- Time of great systemic changes- Managed care proliferation (US)- Federal-provincial shift (Canada)
Politics Versus SciencePolitics 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])
Cancer Survival is a Sentinel Cancer Survival is a Sentinel Health Care OutcomeHealth 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
Theoretical Context: Theoretical Context: Systematic Literature ReviewSystematic 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
SES: A Key Effect Modifier?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.
SES: An Effect Modifier? E.G.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
A Country By SES Interaction A Country By SES Interaction Hypothesis Guided Our SeriesHypothesis 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.
MethodsMethods
A Focused Series of Cancer Survival Comparisons Among Relatively Poor Residents of
Canadian and American Metropolitan Areas
Comparative Series OverviewComparative Series Overview
Toronto, Ontario vs Detroit, MichiganAn ecological exemplar
Toronto vs San Francisco, Seattle, HartfordAdjustment for absolute income
Toronto vs Honolulu, HIHealth insurance hypothesis test
Winnipeg, Manitoba vs Des Moines, IowaReplicate among smaller cities
Comparisons of Subsamples < 65 yoaHealth insurance hypothesis test
Sampling—Persons/Cancer Sampling—Persons/Cancer PatientsPatients- 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 > 95% (DCO/Autopsy < 1%)- Even better among the most public health-significant cancer types
Honolulu, Breast Cancer, 1986-1990 Honolulu, Breast Cancer, 1986-1990 SESSES MC%MC% DCO/Autopsy%DCO/Autopsy%High 100.0 0.0
100.0 0.0100.0 0.0100.0 0.0100.0 0.0100.0 0.0100.0 0.098.5 0.797.9 0.0
Low 98.9 0.0
Sampling—Places: Rationales Sampling—Places: Rationales For Metropolitan SamplingFor 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
Sampling—Places: Ecological Sampling—Places: Ecological Measures of SES Measures of SES NeighborhoodsNeighborhoods
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
Comparison of SES Quintiles: 1990/91, US$Comparison of SES Quintiles: 1990/91, US$WinnipegWinnipeg Des MoinesDes Moines
SESSES Mdn $Mdn $ Mdn $Mdn $
High $47,090$44,05039,11036,37032,26530,16526,04326,890
Low 17,50019,570
Lowest US SES quintile: 20% poor, another 45% near poor; estimated (vs highest) uninsured PR = 10.0, underinsured PR = 15.0
ResultsResults
Female Breast Cancer—5-Year Survival—As Exemplar Throughout
SRRs With 95% CIs, 1984 to 1994 SRRs With 95% CIs, 1984 to 1994 SESSES TorontoToronto DetroitDetroit
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
SRRs With 95% CIs, 1986 to 1996 SRRs With 95% CIs, 1986 to 1996 SESSES TorontoToronto HonoluluHonolulu
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
(0.95,1.11) 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)
Toronto-Honolulu Between-Toronto-Honolulu Between-Country Survival OutcomesCountry 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 < 65 yoa: SRR = 1.28 (1.07,1.53)
DiscussionDiscussion
The Screened/DevelopedHealth Insurance Hypothesis
Versus Alternative Explanations
Summary: Health InsuranceSummary: Health Insurance - Consistent SES-cancer survival associations in
US, but not Canada- Consistent country-SES interactions
- Canada advantage lowest SES strata- Particularly among those < 65 yoa
- Consistency of pattern across diverse contexts—people and places—points toward a pervasive systemic effect- 285 of 319 between-country comparisons were in support of the health insurance hypothesis
AltAlt11—Income Gap or Inequality —Income Gap or Inequality Larger in the United States?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
AltAlt22—Ethnic or Cultural —Ethnic or Cultural Explanations?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 resources—education and health care
AltAlt33—Lifestyle Factors (LS): Exercise, Diet, —Lifestyle Factors (LS): Exercise, Diet, BMI, Tobacco and Alcohol Consumption?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
AltAlt44—Different Case Mixes by —Different Case Mixes by Stage of Disease at Diagnosis?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.
AltAlt55—Cancer Registry Death Clearance? —Cancer Registry Death Clearance? National (US) vs Provincial (Canada)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.
AltAlt66—Competing Causes of Death —Competing Causes of Death (Observed vs Relative Survival)?(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
AltAlt77—Lead Time Bias?—Lead 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)
AltAlt88—Ecological Fallacy?—Ecological 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.
Future Research NeedsFuture Research Needs
Health Insurance Hypothesis Developed and Screened With An
Ecological—Income—Proxy:More Definitive Testing Needed
Central Research NeedsCentral 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
Our Research Agenda Over Our Research Agenda Over The Next 5 YearsThe Next 5 Years
Endeavoring to Filling Some of This Field’s Central Knowledge Gaps
Social, Prognostic & Therapeutic Social, Prognostic & Therapeutic Factors Associated With Cancer Factors Associated With Cancer Survival in Canada and the USSurvival in Canada and the US
Health Care Access and Effectiveness in Diverse Urban
and Rural Contexts, 1985 to 2010
Research Team Co-InvestigatorsResearch 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)
To Address Identified Research To Address Identified Research Needs, It Will: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
Cohort DesignCohort Design
Incident cohorts: 1985-1990 & 1995-2000Followed until: 2000 2010
Cox models over 1-, 3-, 5- to 10-yearsIn Canada and the USDuring a policy-interesting period- Federal-provincial shift in Canada- For-profit managed care proliferation &
prevalent increases uninsured in US
Staged AnalysesStaged AnalysesNo 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 study’s 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
Incorporation of TreatmentsIncorporation 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 study’s samples.- Surgery, radiation, chemotherapy and others- Initial course and follow-up- Type, dose, delays, timings/sequence between various therapies
Extending Generalizability: Extending Generalizability: Contexualizing KnowledgeContexualizing Knowledge
Systematic Replications in:
Ontario CaliforniaLarge cities Toronto San Fran/OaklandSmall cities Windsor SalinasRural/remote areas of Ontario & California
1,060 breast and colon cancer cases for each incident cohort in each type of place
Ecological Measurement ValidityEcological Measurement ValidityOntarian 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.
Hypotheses Related to SurvivalHypotheses 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)