Table 1.

Selected recommendations on low dose aspirin for primary prevention of CVD and colorectal cancer

Disease outcome	Organization	Recommendation and assumptions made
Cardiovascular disease	European Society of Cardiology [5]	Aspirin or clopidogrel cannot be recommended in individuals without cardiovascular or cerebrovascular disease due to the increased risk of major bleeding. (Class of recommendation III = is not recommended; level of evidence weak)
		No details on assumptions or on how benefit-harm assessment was done
Cardiovascular disease	World Health Organization [4]	− Coronary heart disease 10-year risk <10 %. For individuals in this risk category, the harm caused by aspirin treatment outweighs the benefits. Aspirin should not be given to individuals in this low-risk category. (1++, A)
		− Coronary heart disease 10-year risk 10 to <20 %. For individuals in this risk category, the benefits of aspirin treatment are balanced by the harm caused. Aspirin should not be given to individuals in this risk category. (1++, A)
		− Coronary heart disease 10-year risk 20 to <30 %. For individuals in this risk category, the balance of benefits and harm from aspirin treatment is not clear. Aspirin should probably not be given to individuals in this risk category. (1++, A)
		− Coronary heart disease 10-year risk ≥30 %. Individuals in this risk category should be given low dose aspirin. (1++, A)
		No details on assumptions or on how benefit-harm assessment was done.
Cardiovascular disease	US Preventive Services Task Force [6]	Encourage men age 45 to 79 years to use aspirin when the potential benefit of a reduction in MI outweighs the potential harm of an increase in gastrointestinal hemorrhage. (“A” recommendation)
		The reduction in MI outweighs the potential harm of an increase in gastrointestinal hemorrhage:
		− 45–59 year old if ≥4 % 10-year risk of coronary heart disease
		− 60–69 year old if ≥9 % 10-year risk of coronary heart disease
		− 70–79 year old if ≥12 % 10-year risk of coronary heart disease
		Assumptions for benefit-harm assessment:
		− Equal weights given to coronary heart disease, gastrointestinal hemorrhage, and hemorrhagic stroke
		− 10-year risk for coronary heart disease considered from 0–20 %
		− Average risk per age category considered gastrointestinal hemorrhage and hemorrhagic stroke
		− Ischemic stroke not considered
		− No competing risks considered
Colorectal cancer	US Preventive Services Task Force [7]	The USPSTF recommends against the routine use of aspirin and nonsteroidal anti-inflammatory drugs to prevent colorectal cancer in individuals at average risk for colorectal cancer.