A systematic review of studies
comparing health outcomes in Canada and the United States
Gordon H. Guyatt, et al
Open Medicine, Vol 1, No 1 (2007)
Background: Differences in medical care
in the United States compared with Canada, including greater reliance
on private funding and for-profit delivery, as well as markedly
higher expenditures, may result in different health outcomes.
Objectives: To systematically review studies
comparing health outcomes in the United States and Canada among
patients treated for similar underlying medical conditions.
Methods: We identified studies comparing
health outcomes of patients in Canada and the United States by
searching multiple bibliographic databases and resources. We masked
study results before determining study eligibility. We abstracted
study characteristics, including methodological quality and generalizability.
Results: We identified 38 studies comparing
populations of patients in Canada and the United States. Studies
addressed diverse problems, including cancer, coronary artery
disease, chronic medical illnesses and surgical procedures. Of
10 studies that included extensive statistical adjustment and
enrolled broad populations, 5 favoured Canada, 2 favoured the
United States, and 3 showed equivalent or mixed results. Of 28
studies that failed one of these criteria, 9 favoured Canada,
3 favoured the United States, and 16 showed equivalent or mixed
results. Overall, results for mortality favoured Canada (relative
risk 0.95, 95% confidence interval 0.92-0.98, p = 0.002) but were
very heterogeneous, and we failed to find convincing explanations
for this heterogeneity. The only condition in which results consistently
favoured one country was end-stage renal disease, in which Canadian
patients fared better.
Available studies suggest that health
outcomes may be superior in patients cared for in Canada versus
the United States, but differences are not consistent.
Canada and the United States are similar
in many ways, and until 40 years ago their health care systems
were nearly identical. At that time Canada adopted a national
insurance program (medicare). Simultaneously, the United States
implemented its Medicare program for elderly people.
Although both nations continue to rely
largely on private funding for drugs, they now differ substantially
in both the financing and delivery of physician and hospital services.1
With respect to financing, Canada has virtually first-dollar,
universal public coverage of hospital and physician services.
With respect to delivery, not-for-profit institutions provide
almost all hospital services, and large for-profit organizations
are almost entirely excluded from the provision of physician services.
In contrast, the United States relies on a mixture of public and
private insurance to finance health care, and leaves 16% of the
population without coverage. Investor-owned for-profit providers
play a substantial role.
The United States also spends far more
on health care, i.e., approximately 15% of its gross domestic
product versus about 10% in Canada. In 2003, Americans spent an
estimated US$5,635 per capita on health care, while Canadians
How do these alternative approaches to
health care financing and delivery affect health outcomes? Although
a number of factors beyond the health care system influence the
health of populations, for conditions amenable to medical treatment
the health care system is a major determinant of outcomes.2,3
The choices the United States and Canada have made may influence
access and quality of care, and hence morbidity and mortality.
To inform debate on this issue we undertook a systematic review
addressing the following question: Are there differences in health
outcomes (mortality or morbidity) in patients suffering from similar
medical conditions treated in Canada versus those treated in the
In this systematic review, we demonstrated
that although Canadian outcomes were more often superior to US
outcomes than the reverse, neither the United States nor Canada
can claim hegemony in terms of quality of medical care and the
resultant patient-important outcomes. In virtually all areas,
study results have demonstrated some apparent advantages for Canada
and others for the United States. In cancer, where a number of
strong studies have used population-based registries, Canadian
outcomes appear superior in head and neck cancer, and possibly
for low-income patients with a variety of cancers; American women
with breast cancer appear to have better survival rates than Canadian
women. In data from population-based registries, Canadians enjoy
better risk-adjusted survival after a variety of surgeries, but
American outcomes appear superior after hip fracture repair and
cataract surgery. Studies that do not utilize population-based
registries suggest that Americans have, possibly as a result of
more aggressive interventions, less angina after MI, but the benefit
may come at the price of increased strokes and bleeding. There
is one area in which Canadian outcomes appear consistently superior:
end-stage renal failure. Even here, however, as we shall discuss,
one cannot be certain that superior medical care is responsible
for the differences.
The strengths and limitations of this
systematic review bear on its interpretation. We established a
team that included expertise in medicine, clinical epidemiology,
health economics, health policy, and health services research
in both Canada and the United States, developed explicit eligibility
criteria, and conducted a comprehensive search that uncovered
a number of eligible articles not included in a previous systematic
review.51 We excluded studies, such as randomized trials of medical
interventions in which Canadian investigators recruited some patients
and American investigators others, in which care would be idiosyncratic
or atypical of care in usual clinical practice. Our thorough examination
of each study addressed issues of validity (selection of populations,
adjustment for confounders, loss to follow-up) and generalizability
(breadth of samples, including specifying studies that came from
Reviewers who determined eligibility and
judged validity and generalizability were blind to the results
of the study. In decision-making regarding methodologic issues
that arose as the review progressed, we recused investigators
who were aware of the study results. We made explicit a priori
hypotheses regarding possible sources of heterogeneity, and tested
these hypotheses in a thorough statistical analysis. Our results
are consistent with those of a prior systematic review that completed
its search (less comprehensive than ours) in 1997, conducted a
limited assessment of study validity, and failed to conduct a
The main limitation of our review is in
the uneven quality of the original studies, and the threats to
validity that remain even in those studies of high quality. There
were two key ways a study could fail to adequately address our
question: either the population might be small or narrow, or the
investigators might not carry out statistical adjustment for potential
differences in underlying prognosis. Most of the studies we identified
failed one of these two criteria (Tables 2, 3 and 4).
Even studies that meet these criteria,
and meet the more rigorous criterion of utilizing population-based
registries, present challenges with respect to their interpretation.
In general, a health care system can improve outcomes in two ways.
One is to facilitate early entry to care, including preventive
care, and thus avoid unnecessary morbidity and mortality. For
instance, if access to primary care is easy and without financial
obstacles, one might expect superior outcomes in hypertension
(e.g., fewer strokes). Alternatively, a system might generate
better outcomes by better treatment of serious morbidity once
it arises. For instance, stroke patients may be more likely to
receive early thrombolysis, thromboprophylaxis, and multidisciplinary
If a health system does better in early
identification and treatment, diseased patients in that system
will appear less ill. Statistical adjustment for severity of illness
is in general appropriate - one wouldn't want to attribute to
better care what is in fact due to a better prognosis. The risk,
however, is that the adjustment will obscure the benefits of early
identification and treatment.
Such issues become relevant in comparisons
of outcomes between Canada and the United States. For instance,
the United States does a better job of screening women for breast
cancer.52 To the extent that early diagnosis reduces breast cancer
deaths, one would expect a survival advantage for American women.
At the same time, any apparent increase in longevity may be largely,
or even completely, due to the length and lead-time biases inherent
in observational studies of screening.
A number of studies using the American
National Cancer Institute's Surveillance, Epidemiology, and End
Results Program (SEER) and the Ontario Cancer Registry (OCR) have
addressed breast cancer outcomes. Although studies using these
databases and examining Toronto versus a number of US cities suggest
higher breast cancer survival in low-income Canadian women than
in their American counterparts,20,21,36 several studies using
the entire database have suggested superior overall breast cancer
survival in American women.18,19,32 We rated these studies as
low quality because of failure to adjust for disease stage. If
higher screening rates or better self-detection in the US result
in the identification of earlier stage histologic cancers that
would have remained asymptomatic and dormant, studies would demonstrate
superior survival despite equivalent medical care. On the other
hand, perhaps there is a true American advantage that results
from higher rates of screening52 or from superior care after diagnosis.
The data do not allow assessment of the relative likelihood of
these possible explanations.
These studies raise another important
limitation of the current data. Canada has largely53 (though not
completely) eliminated gradients in access to care by socioeconomic
status that remain in the United States,55,56 and this may contribute
to Canada's smaller socioeconomic gradients in health outcome.57
If this were so, one would expect that studies focused on poorer
individuals would reveal superior outcomes in Canada, whereas
differences might be obscured in studies of entire populations.
Indeed, the cancer studies by Gorey and colleagues20,21,36 and
by Boyd19 suggest this may be the case. At the same time, it is
possible that being able to pay for better care might lead to
better outcomes in those with high incomes in the US versus Canada.
Indeed one of the studies in cancer patients suggested this possibility.19
Unfortunately, these are the only studies that explore gradients
in outcome across socioeconomic status.
Although the overall effect in the meta-analysis
may be of some interest (a 5% reduction in relative risk of all-cause
mortality in Canada versus the United States) the large variability
in study results (heterogeneity p < 0.0001, I2 94%, Figure
2) makes the pooled estimate difficult to interpret. Our primary
reason for conducting the statistical analysis was, through meta-regression,
to explore possible explanations of variability in results and
provide adjusted estimates of relative risk. This exploration
proved difficult to interpret. Although the multivariate model
identified apparent sources of heterogeneity and provided adjusted
estimates of relative risk (Table 5), the results were inconsistent
between univariate and multivariate approaches, and both the univariable
and multivariable models were very unstable. Thus, we do not feel
confident that the statistical modeling has provided either a
satisfactory explanation for the study-to-study variability in
results or credible estimates of adjusted relative risk.
One group of patients fared consistently
better in Canada than in the U.S., those with end-stage renal
disease.4,28-33 Whether in hemodialysis programs, peritoneal dialysis,
or after receipt of renal transplants, Canadians survive longer.
The larger proportion of Americans than Canadians who begin dialysis
treatment confounds interpretation of this finding. Perhaps Americans
fare worse because a larger number of sicker patients enter dialysis.
On the other hand, it may be that the larger proportion of Americans
on dialysis reflects a lower threshold to start dialysis, and
thus a less sick dialysis population. The limited available evidence
suggests that thresholds for dialysis are in fact similar in the
two countries.58 Furthermore, two high-quality studies that included
extensive adjustment for comorbidity29,33 still show substantially
lower mortality in Canadian patients, suggesting that imbalance
in risk cannot explain superior Canadian outcomes.
Nevertheless, the weight of the evidence
strongly suggests that Canadian end-stage renal patients truly
have higher survival than those in the US. The explanation for
this difference may lie in differences in the ownership of dialysis
facilities. Virtually all Canadian dialysis care is not-for-profit,
while for-profit providers deliver approximately 75% of American
care for end-stage renal failure. A systematic review has shown
a higher mortality in patients undergoing dialysis in for-profit
Despite the limitations of the available
studies, some robust conclusions are possible from our systematic
review. These results are incompatible with the hypothesis that
American patients receive consistently better care than Canadians.
Americans are not, therefore, getting value for money; the 89%
higher per-capita expenditures on health care in the United States
does not buy superior outcomes for the sick.
Canadian health care has many well-publicized
limitations. Nevertheless, it produces health benefits similar,
or perhaps superior, to those of the US health system, but at
a much lower cost. Canada's single-payer system for physician
and hospital care yields large administrative efficiencies in
comparison with the American multi-payer model.60 Not-for-profit
hospital funding results in appreciably lower payments to third-party
payers in comparison to for-profit hospitals61 while achieving
lower mortality rates.62 Policy debates and decisions regarding
the direction of health care in both Canada and the United States
should consider the results of our systematic review: Canada's
single-payer system, which relies on not-for-profit delivery,
achieves health outcomes that are at least equal to those in the
United States at two-thirds the cost.