Table 2.

—[Section 2.1] Aspirin (75-100 mg) Compared With No Aspirin in the Primary Prevention of Cardiovascular Disease^a,9

Outcomes	Participants (Studies), Follow-up	Quality of the Evidence (GRADE)	Relative Effect (95% CI)	Anticipated Absolute Effects Over 10 y
				Risk Without Aspirin	Risk Difference With Aspirin (95% CI)
Total mortalitya	100,076 (9), 3.8-10 y	Moderate due to imprecisionb	RR 0.94 (0.88 to 1.00)	60-y-old manc
				100 deaths per 1,000c	6 fewer deaths per 1,000 (from 12 fewer to 0 fewer)
MI nonfatal events	95,000 (6), 3.8-10 y	High	RR 0.77 (0.69-0.86)	Low-cardiovascular-risk populationd
				27 MI per 1,000e	6 fewer MI per 1,000 (from 8 fewer to 4 fewer)
				Moderate-cardiovascular risk populationd
				83 MI per 1,000e	19 fewer MI per 1,000 (from 26 fewer to 12 fewer)
				High-cardiovascular-risk populationd
				136 per 1,000e	31 fewer per 1,000 (from 42 fewer to 19 fewer)
Stroke includes nonfatal ischemic and hemorrhagic strokesf	95,000 (6), 3.8-10 y	Moderate due to imprecisionb	RR 0.95 (0.85-1.06)	Low-cardiovascular-risk populationd
				23 strokes per 1,000e	No significant difference; 1 fewer stroke per 1,000 (from 3 fewer to 1 more)
				Moderate-cardiovascular-risk populationd
				65 strokes per 1,000e	No significant difference; 3 fewer strokes per 1,000 (from 10 fewer to 4 more)
				High-cardiovascular-risk populationd
				108 strokes per 1,000e	No significant difference; 5 fewer strokes per 1,000 (from 16 fewer to 8 more)
Major extracranial bleed	95,000 (6), 3.8-10 y	High	RR 1.54 (1.30-1.82)	Low-cardiovascular-risk populationg
				8 bleeds per 1,000e	4 more bleeds per 1,000 (from 2 more to 7 more)
				Moderate-cardiovascular risk populationg
				24 bleeds per 1,000e	16 more bleeds per 1,000 (from 7 more to 20 more)
				High-cardiovascular-risk populationg
				40 bleeds per 1,000e	22 more bleeds per 1,000 (from 12 more to 33 more)

GRADE = Grades of Recommendations, Assessment, Development, and Evaluation; RR = risk ratio. See Table 1 legend for expansion of other abbreviation.

^aThis systematic review reports total mortality and includes the most recent trials but does not report specific causes of mortality. Other meta-analyses that use individual patient data report relative risk estimates for vascular mortality (RR, 0.97; 95% CI, 0.87-1.09), cancer mortality (RR, 0.66; 95% CI, 0.50-0.87), and fatal intracranial bleeds (RR, 1.73; 95% CI, 0.96-3.13). The risk of a fatal bleed (including extracranial and intracranial) was low (0.3% with aspirin and 0.2% with control).

^bThe 95% CI for the absolute effect includes no benefit of aspirin. We did not rate down for risk of bias, but this was a borderline decision. Three of the trials did not blind patients, caregivers, or outcome adjudicators. Sensitivity analyses in meta-analysis by Raju et al⁴ did not show evidence of risk of bias.

^cControl group risk estimate for 10-y mortality apply to a 60-y-old man and came from population-based data from Statistics Norway. Mortality increases with age (eg, 50-y-old man; 50 deaths per 1,000 in 10 y) and is lower in women than in men (eg, 3% in women aged 50 y vs 5% in men aged 50 y).

^dRisk groups correspond to low risk (5%), medium risk (15%), high risk (25%) according to the Framingham score (or other risk tool) to estimate 10-y risk.

^eControl group risk estimates in low-, moderate-, and high-cardiovascular-risk groups are based on the Framingham score. As explained in the text, we have used data from an individual patient data meta-analysis to provide estimated risks for patient-important outcomes not covered by the Framingham risk score. We have also adjusted for 20% overestimation associated with Framingham risk score.

^fOf the strokes in the trials, 89 of 682 (13%) without aspirin were hemorrhagic and 116 of 655 (18%) with aspirin were hemorrhagic.

^gIn the individual patient data meta-analysis risk for future major bleeding correlated with risk for future cardiovascular events. Therefore, we make the assumption that a patient at low, medium, or high risk of future cardiovascular events (determined by Framingham score) will be at low, medium, or high risk for future major bleeding events, respectively.