The U.S. Preventive Services Task Force (USPSTF) grades its recommendations (A, B, C, D, or I) and identifies the Levels of Certainty regarding Net Benefit (High, Moderate, and Low). The definitions of these grades can be found at the end of the "Major Recommendations" field.
Summary of Recommendations and Evidence
- The USPSTF recommends the use of aspirin for men age 45 to 79 years when the potential benefit due to a reduction in myocardial infarctions outweighs the potential harm due to an increase in gastrointestinal hemorrhage. See the "Clinical Considerations" section below for discussion of benefits and harms. This is an A recommendation.
- The USPSTF recommends the use of aspirin for women age 55 to 79 years when the potential benefit of a reduction in ischemic strokes outweighs the potential harm of an increase in gastrointestinal hemorrhage. See the "Clinical Considerations" section below for discussion of benefits and harms. This is an A recommendation.
- The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of aspirin for cardiovascular disease prevention in men and women 80 years or older. This is an I statement.
See the "Clinical Considerations" section below for suggestions for practice regarding the I statement.
- The USPSTF recommends against the use of aspirin for stroke prevention in women younger than 55 years and for myocardial infarction prevention in men younger than 45 years. This is a D recommendation.
Clinical Considerations
Patient Population Under Consideration
These recommendations apply to adult men and women without a history of coronary heart disease or stroke.
Assessment of Risk for Cardiovascular Disease
Men
The net benefit of aspirin depends on the initial risk for coronary heart disease events and gastrointestinal bleeding. Thus, decisions about aspirin therapy should consider the overall risks for coronary heart disease and gastrointestinal bleeding.
Risk assessment for coronary heart disease should include ascertainment of risk factors: age, diabetes, total cholesterol levels, high-density lipoprotein cholesterol levels, blood pressure, and smoking.
Figure 2 in the original guideline document shows the estimated number of myocardial infarctions prevented according to coronary heart disease risk level for men age 45 to 79 years—the age range with the potential for substantial net benefit from the use of aspirin. It also shows that the coronary heart disease risk level at which the absolute number of myocardial infarctions prevented by the use of aspirin is greater than the absolute number of gastrointestinal bleeding episodes and hemorrhagic strokes caused by aspirin therapy increases with age. The estimates in Figure 2 of the original guideline document were developed assuming that the men are not currently taking nonsteroidal anti-inflammatory drugs (NSAIDs) and are without other conditions that increase the risk for gastrointestinal bleeding (see below). Furthermore, the decision about the exact level of risk at which the potential benefits outweigh potential harms is an individual one. Some men may decide that avoiding a myocardial infarction is of great value, and that having a gastrointestinal bleeding event is not a major problem. The latter group would probably decide to take aspirin at a lower coronary heart disease risk level than men who are more afraid of gastrointestinal bleeding. Men who have a high likelihood of benefiting with little potential for harm should be encouraged to consider aspirin. Conversely, aspirin use should be discouraged among men who have little potential of benefiting from the therapy or have a high risk for gastrointestinal bleeding.
Shared decision making should be encouraged with men for whom the potential benefits and risks for serious bleeding are more closely balanced (see Figure 3 in the original guideline document). This discussion should explore the potential benefits and harms and patient preferences. As the potential benefit increases above potential harms, the recommendation to take aspirin should become stronger.
Evidence on the benefits in men younger than 45 years is limited, and the potential benefit in this age group is probably low because the risk for myocardial infarction is very low.
Women
The net benefit of aspirin depends on the initial risks for stroke and gastrointestinal bleeding. Thus, decisions about aspirin therapy should consider the overall risk for stroke and gastrointestinal bleeding.
Risk factors for stroke include age, high blood pressure, diabetes, smoking, a history of cardiovascular disease, atrial fibrillation, and left ventricular hypertrophy. Tools for estimation of stroke risk are available (such as the calculator available at www.westernstroke.org/PersonalStrokeRisk1.xls).
Figure 4 in the original guideline document shows the estimated number of strokes prevented according to stroke risk level in women age 55 to 79 years—the age range for which evidence shows that there could be substantial potential net benefit of aspirin use. It also shows that the stroke risk level at which the absolute number of strokes prevented is greater than the absolute number of gastrointestinal bleeding events caused increases with age. The estimates in Figure 4 in the original guideline document were developed assuming that women are not currently taking NSAIDs and are without other conditions that increase the risk for gastrointestinal bleeding (see the Risk for Gastrointestinal Bleeding section below). Furthermore, the decision about the exact stroke risk level at which the potential benefits outweigh harms is an individual one. Some women may decide that avoiding a stroke is of great value but experiencing a gastrointestinal bleeding event is not a major problem. These women would probably decide to take aspirin at a lower stroke risk level than those who are more afraid of a bleeding event. Women who have little potential of benefiting from aspirin therapy or have a high risk for gastrointestinal bleeding should be discouraged from taking aspirin.
Shared decision making should be encouraged with women for whom the potential benefits and risks for serious bleeding are more closely balanced (Figure 3 in the original guideline document). This discussion should explore potential benefits and harms and patient preferences. As the potential stroke reduction benefit increases above the potential harms, the recommendation to take aspirin should become stronger.
Evidence on benefits in women younger than 55 years is limited, and the potential benefit in this age group is probably low because the risk for stroke is very low.
Assessment of Risk for Gastrointestinal Bleeding
Evidence shows that the risk for gastrointestinal bleeding with and without aspirin use increases with age. For the purposes of making this recommendation, the USPSTF considered age and sex to be the most important risk factors for gastrointestinal bleeding. Other risk factors for bleeding include upper gastrointestinal tract pain, gastrointestinal ulcers, and NSAID use. NSAID therapy combined with aspirin approximately quadruples the risk for serious gastrointestinal bleeding compared with the risk with aspirin alone. The rate of serious bleeding in aspirin users is approximately 2 to 3 times greater in patients with a history of a gastrointestinal ulcer. Men have twice the risk for serious gastrointestinal bleeding than women. These risk factors increase the risk for bleeding substantially and should be considered in the overall decision about the balance of benefits and harms of aspirin therapy. Enteric-coated or buffered preparations do not clearly reduce the adverse gastrointestinal effects of aspirin. Uncontrolled hypertension and concomitant use of anticoagulants also increase the risk for serious bleeding.
Treatment
The optimum dose of aspirin for preventing cardiovascular disease events is not known. Primary prevention trials have demonstrated benefits with various regimens, including dosages of 75 and 100 mg/d and 100 and 325 mg every other day. A dosage of approximately 75 mg/d seems as effective as higher dosages. The risk for gastrointestinal bleeding may increase with dose.
Intervention Intervals
Although the optimal timing and frequency of discussions related to aspirin therapy are unknown, a reasonable option might be every 5 years in middle age and later and also whenever other cardiovascular risk factors are detected.
Suggestions for Practice Regarding the I Statement
The incidence of myocardial infarctions and strokes are high in persons 80 years or older and thus the potential benefit of aspirin is large. The relationship between increasing age and gastrointestinal bleeding is also well established and thus the potential harms are also large. The net benefit of aspirin use in persons older than 80 years is probably best in those without risk factors for gastrointestinal bleeding (other than older age) and in those who could tolerate a gastrointestinal bleeding episode (for example, those with normal hemoglobin levels, good kidney function, and easy access to emergency care). Clinicians should inform patients about the adverse consequences of gastrointestinal bleeding because they might be mitigated by a patient's early recognition of the signs and symptoms of bleeding (that is, dark stools, vomiting blood, bright red blood per rectum, syncope, and lightheadedness). If clinicians decide to prescribe aspirin in adults older than 80 years, they should do so only after a discussion with the patient that includes the potential harms and uncertain benefits.
Useful Resources
The USPSTF made recommendations on other interventions for the primary and secondary prevention of cardiovascular disease, including recommendations on screening for abdominal aortic aneurysms, carotid artery stenosis, coronary heart disease, high blood pressure, lipid disorders, and peripheral arterial disease. These are available at www.preventiveservices.ahrq.gov.
Definitions:
What the United States Preventive Services Task Force (USPSTF) Grades Mean and Suggestions for Practice
| Grade |
Grade Definitions |
Suggestions for Practice |
| A |
The USPSTF recommends the service. There is high certainty that the net benefit is substantial. |
Offer or provide this service. |
| B |
The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial. |
Offer or provide this service. |
| C |
The USPSTF recommends against routinely providing the service. There may be considerations that support providing the service in an individual patient. There is moderate or high certainty that the net benefit is small. |
Offer or provide this service only if there are other considerations in support of the offering/providing the service in an individual patient. |
| D |
The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits. |
Discourage the use of this service. |
I
Statement
|
The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality or conflicting, and the balance of benefits and harms cannot be determined. |
Read "Clinical Considerations" section of USPSTF Recommendation Statement (see "Major Recommendations" field). If offered, patients should understand the uncertainty about the balance of benefits and harms. |
USPSTF Levels of Certainty Regarding Net Benefit
Definition: The U.S. Preventive Services Task Force defines certainty as "likelihood that the USPSTF assessment of the net benefit of a preventive service is correct." The net benefit is defined as benefit minus harm of the preventive service as implemented in a general, primary care population. The USPSTF assigns a certainty level based on the nature of the overall evidence available to assess the net benefit of a preventive service.
| Level of Certainty |
Description |
| High |
The available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. These studies assess the effects of the preventive service on health outcomes. This conclusion is therefore unlikely to be strongly affected by the results of future studies. |
| Moderate |
The available evidence is sufficient to determine the effects of the preventive service on health outcomes, but confidence in the estimate is constrained by factors such as:
- The number, size, or quality of individual studies
- Inconsistency of findings across individual studies
- Limited generalizability of findings to routine primary care practice
- Lack of coherence in the chain of evidence
As more information becomes available, the magnitude or direction of the observed effect could change, and this change may be large enough to alter the conclusion.
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| Low |
The available evidence is insufficient to assess effects on health outcomes. Evidence is insufficient because of:
- The limited number or size of studies
- Important flaws in study design or methods
- Inconsistency of findings across individual studies
- Gaps in the chain of evidence
- Findings not generalizable to routine primary care practice
- A lack of information on important health outcomes
More information may allow an estimation of effects on health outcomes.
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