The U.S. Preventive Services Task Force (USPSTF) grades its recommendations (A, B, C, D, or I) and the quality of the overall evidence for a service (good, fair, poor). The definitions of these grades can be found at the end of the “Major Recommendations” field.
- The U.S. Preventive Services Task Force strongly recommends that clinicians discuss aspirin chemoprevention with adults who are at increased risk of coronary heart disease (see the section titled "Clinical Considerations," below). Discussions with patients should address both the potential benefits and harms of aspirin therapy. [A recommendation]
The U.S. Preventive Services Task Force found good evidence that aspirin decreases the incidence of coronary heart disease in adults who are at increased risk for heart disease. They also found good evidence that aspirin increases the incidence of gastrointestinal bleeding and fair evidence that aspirin increases the incidence of hemorrhagic strokes. The U.S. Preventive Services Task Force concluded that the balance of benefits and harms is most favorable in patients at high risk of coronary heart disease (5-year risk of greater than or equal to 3%) but is also influenced by patient preferences.
Clinical Considerations
- Decisions about aspirin therapy should take into
account overall risk of coronary heart disease. Risk assessment should include
asking about the presence and severity of the following risk factors: age,
sex, diabetes, elevated total cholesterol levels, low levels of high-density
lipoprotein (HDL) cholesterol, elevated blood pressure, family history (in
younger adults), and smoking. Tools that incorporate specific information on
multiple risk factors provide more accurate estimation of cardiovascular risk
than categorizations based simply on counting the numbers of risk factors (see
the original guideline document for further references to an available
coronary heart disease risk calculator).
- Men over age 40, postmenopausal women, and younger
persons with risk factors for coronary heart disease (e.g., hypertension,
diabetes, or smoking) are at increased risk of heart disease and may wish to
consider aspirin therapy. The following table shows how estimates of the type
and magnitude of benefits and harms associated with aspirin therapy vary with
an individual's underlying risk of coronary heart disease. Although balance of
benefits and harms is most favorable in high-risk persons (5-year risk greater
than 3%), some persons at lower risk may consider the potential benefits of
aspirin to be sufficient to outweigh the potential harms.
Table. Estimates of benefits and harms of
aspirin therapy given for 5 years to 1000 individuals with various levels of
baseline risk for coronary heart disease*
| Benefits
and Harms |
Baseline
Risk for Coronary Disease Over 5 Years# |
| |
1%
|
3%
|
5%
|
| Total mortality |
No effect |
No effect |
No effect |
| Coronary heart disease
events# |
1-4
avoided |
4-12
avoided |
6-20
avoided |
| Hemorrhagic
strokes** |
0-2
caused |
0-2
caused |
0-2
caused |
| Major
gastrointestinal bleeds++ |
2-4
caused |
2-4
caused |
2-4
caused |
* These estimates are based on relative risk reduction of 28% for coronary heart disease events in aspirin-treated patients. They assume risk reductions do not vary significantly by age.
# Nonfatal acute myocardial infarction and fatal coronary heart disease. Five-year risks of 1%, 3% and 5% are equivalent to 10-year risks of 2%, 6%, and 10%, respectively.
** Data from secondary prevention trials suggest that increases in hemorrhagic stroke may be offset by reduction in other types of stroke in patients at very high risk of cardiovascular disease (greater than or equal to 10% 5-year risk).
++ Rates of gastrointestinal bleeds may be 2 to 3 times higher in persons older than 70.
(See Hayden M, Pignone M, Phillips C, Mulrow C. Aspirin for the primary prevention of cardiovascular events: a summary of the evidence. Ann Intern Med 2002 Jan 15;136[2]:161-72.)
- Discussions about aspirin therapy should focus on potential coronary heart disease benefits, such as prevention of myocardial infarction, and potential harms of gastrointestinal and intracranial bleeding. Discussions should take into account individual preferences and risk aversions concerning myocardial infarction, stroke, and gastrointestinal bleeding.
- Although the optimal timing and frequency of discussions related to aspirin therapy are unknown, reasonable options include every 5 years in middle-aged and older persons or when other cardiovascular risk factors are detected.
- Most participants in the primary prevention trials of aspirin therapy have been men between the ages of 40 and 75 years old. Current estimates of benefits and harms may not be as reliable for women and older men.
- Although older patients may derive greater benefits due to their higher risk of coronary heart disease and stroke, their risk of bleeding may be higher.
- Uncontrolled hypertension may attenuate the benefits of aspirin in reducing coronary heart disease.
- The optimum dose of aspirin for chemoprevention is not known. Primary and secondary prevention trials have demonstrated benefits of a variety of regimens including 75 mg per day, 100 mg per day, and 325 mg every other day. Doses of about 75 mg daily appear as effective as higher doses; whether doses below 75 mg daily are effective is not established. Enteric-coated or buffered preparations do not clearly reduce adverse gastrointestinal effects of aspirin. Uncontrolled hypertension and concomitant use of other nonsteroidal anti-inflammatory agents or anticoagulants increase risk for serious bleeding.
Definitions:
The U.S. Preventive Services Task Force (USPSTF) grades its
recommendations according to one of five classifications (A, B, C, D, or
I), reflecting the strength of evidence and magnitude of net benefit (benefits
minus harms).
A
The U.S. Preventive Services Task Force (USPSTF) strongly recommends that
clinicians provide [the service] to eligible patients. (The USPSTF
found good evidence that [the service] improves important health outcomes and
concludes that benefits substantially outweigh harms.)
B
The U.S. Preventive Services Task Force (USPSTF) recommends that clinicians provide [the service] to eligible patients. (The USPSTF found at least
fair evidence that [the service] improves health outcomes and concludes that
benefits outweigh harms.)
C
The U.S. Preventive Services Task Force (USPSTF) makes no recommendation for
or against routine provision of [the service]. (The US Preventive Services Task
Force found at least fair evidence that [the service] can improve health
outcomes but concludes that the balance of benefits and harms it too close to
justify a general recommendation.)
D
The U.S. Preventive Services Task Force (USPSTF) recommends against routinely
providing [the service] to asymptomatic patients. (The USPSTF found at least
fair evidence that [the service] is ineffective or that harms outweigh
benefits.)
I
The U.S. Preventive Services Task Force (USPSTF) concludes that the evidence
is insufficient to recommend for or against routinely providing [the service].
(Evidence that [the service] is effective is lacking, of poor quality, or
conflicting and the balance of benefits and harms cannot be determined.)
The U.S. Preventive Services Task Force (USPSTF) grades the quality of the
overall evidence for a service on a 3-point scale (good, fair, or poor).
Good
Evidence includes consistent results from well-designed, well-conducted
studies in representative populations that directly assess effects on health
outcomes.
Fair
Evidence is sufficient to determine effects on health outcomes, but the
strength of the evidence is limited by the number, quality, or consistency of
the individual studies; generalizability to routine practice; or indirect nature
of evidence on health outcomes.
Poor
Evidence is insufficient to assess the effects on health outcomes because of
limited number or power of studies, important flaws in their design or conduct,
gaps in the chain of evidence, or lack of information on important health
outcomes.
