Structured Abstract
Please note: In 2003, the CTF updated its Grades of
Recommendations to include an "I Recommendation" for situations where
insufficient evidence exists to allow a recommendation to be made.
(Formerly, these situations were captured under a "C
Recommendation".) This change is not retroactive, and all
"C Recommendations" made prior to 2003 have not been
reevaluated in light of the new "I" recommendation grade. For a
discussion of these recommendation grades, please link to the 2003 article in
the Canadian Medical Association Journal here.
Acetylsalicylic Acid and the Primary Prevention of Cardiovascular
Disease
Prepared by Geoffrey Anderson, MD, PhD, Senior
Scientist, Institute for Clinical Evaluation and Sciences in Ontario (ICES)
and Associate Professor, Department of Health Administration, University
of Toronto, Ontario
These recommendations were finalized by the Task Force in March 1994
Contents
Objective
To make recommendations for the use of low-dose acetylsalicylic acid (ASA)
to prevent vascular events (coronary artery disease and stroke) and death
in asymptomatic men and women in Canada. This guideline is an update of
the 1991 Canadian Task Force guideline.
Burden
of Suffering
In 1989 an estimated 80,858 deaths from circulatory disease occurred in
Canada; this resulted in 362,235 potential life-years lost. An estimated
49,148 deaths were due to coronary artery disease and 14,232 to stroke.
In 1987 there were 77,790 deaths due to circulatory disease. The rate of
death from cardiovascular disease begins to increase about 10 years earlier
among men than among women, but eventually nearly as many women as men
die from such disease (36,794 vs. 40,977 in 1987).
The overall rate of death from cardiovascular disease has shown a relatively
stable decrease since the 1950s. The age-standardized rates of death from
stroke among Canadians over 65 years of age decreased by more than 60%
among women and 50% among men between 1951 and 1986, but hospital morbidity
rates from 1971 to 1984 did not reflect the same rate of decline. Circulatory
disease accounts for 25% of all disability pensions paid by the Canada
Pension Plan before age 65.
Over 40% of deaths from coronary artery disease are sudden, and half
of the sudden deaths occur in people without a history of overt disease.
Reduction of the incidence of sudden death in asymptomatic people will
require the use of effective primary prevention strategies.
Options
Routine low-dose ASA use was considered.
Outcomes
Outcomes considered were mortality (total and from myocardial infarction,
stroke, all vascular causes, and nonvascular causes), nonfatal vascular
events (myocardial infarction, stroke and transient ischemic attacks),
and quality of life.
Evidence
MEDLINE was searched for 1966 - 1991 using the keywords: "aspirin" and
"cardiovascular disease".
Recommendations were graded as:
|
A
|
Good evidence to support the recommendation that the condition
be specifically considered in a PHE. |
|
B
|
Fair evidence to support the recommendation that the condition
be specifically considered in a PHE. |
|
C
|
Poor evidence regarding inclusion or exclusion of the condition
in a PHE, but recommendations may be made on other grounds. |
|
D
|
Fair evidence to support the recommendation that the condition
be specifically excluded from consideration in a PHE. |
|
E
|
Good evidence to support the recommendation that the condition
be specifically excluded from consideration in a PHE. |
Quality of evidence was rated according to 5 levels:
|
I
|
Evidence from at least 1 properly randomized controlled
trial (RCT). |
|
II-1
|
Evidence from well-designed controlled trials without randomization. |
|
II-2
|
Evidence from well-designed cohort or case-control analytic
studies, preferably from more than 1 centre or research group. |
|
II-3
|
Evidence from comparisons between times or places with
or without the intervention. Dramatic results in uncontrolled experiments
could also be included here. |
|
III
|
Opinions of respected authorities, based on clinical experience,
descriptive studies or reports of expert committees. |
Values
The 13-member Task Force of experts in family medicine, geriatric medicine,
pediatrics, psychiatry and epidemiology used an evidence-based method for
evaluating the effectiveness of preventive health care interventions. Recommendations
were not based on cost-effectiveness of options. Patient preferences were
not discussed.
Background papers providing critical appraisal of the evidence and tentative
recommendations prepared by the chapter author were pre-circulated to the
members. Evidence for this topic was presented and deliberated upon in
1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993.
Consensus was reached on final recommendations.
Benefits,
Harms, and Costs
2 RCTs of men (Physicians’ physicians’ Health health Studies studies in
the United States and the United Kingdom) and a large cohort study of women
(Nurses’ Health Study) were identified. In the British Aspirin Trial of
5139 male physicians (men) < 80 years of age the intention-to-treat
analysis showed that the ASA and nonASA groups did not differ for death
from all causes, myocardial infarction, stroke, all vascular causes, all
nonvascular causes, or nonfatal myocardial infarction or stroke. although
However, ASA users had a lower rate of transient ischemic attacks (relative
risk [RR] 0.58). In a similar study done in the United States the experimental
groups had decreased rates of differed for fatal (RR 0.31) and nonfatal
(RR 0.59) myocardial infarction (RR 0.31) and nonfatal myocardial infarction
(RR 0.59) but not for a reduction. The groups did not differ in death rates
from all cardiovascular disease. The large cohort study of women showed
only a reduction in nonfatal myocardial infarction when participants used
1 to 6 ASA tablets per week (RR 0 .75. 95% CI 0.58 to 0.99) but no differences
for cardiovascular death or total death. ASA use was not associated with
a reduction in cardiovascular deaths or total deaths. Potential problems
were bleeding, need for transfusions, peptic ulcer disease, and disabling
stroke. An overview of antiplatelet therapy showed that no clear evidence
exists on the balance of risks and benefits of antiplatelet this therapy
in primary prevention among low-risk participants including no lost quality
of life over the 5-year follow-up.
Recommendations
Recommendation grade [A, B, C, D, E] and level of evidence
[I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations
in support of individual recommendations are identified in the guideline
text.
-
There is insufficient evidence to include or exclude daily low-dose ASA use for the
primary prevention of cardiovascular disease in asymptomatic men
[C, I] and women
[C, II-2].
Validation
This report was externally peer reviewed. This report was externally peer
reviewed.
Sponsors
The Canadian Task Force on Preventive Health Care
developed this guideline with funding from Health Canada.
Selected
References
Source Document
Other
-
Canadian Task Force on the Periodic Health Examination: The periodic health
examination, 1991 update: 6. Acetylsalicylic acid and the primary prevention
of cardiovascular disease. Can Med Assoc J. 1991;145:1091-5.
Link to Full Text of this review
Link to Summary Table of Recommendations of this review
Link to Selected References list of this review
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