TABLE 1

Trials of aspirin as primary prevention

Trial	Year	Population	Number needed to treat or harm^a
Trial	Year	Population	Nonfatal myocardial infarction	Nonfatal ischemic stroke	Major gastrointestinal bleed
BDS¹⁴	1988	5,139 healthy male physicians	[143]	[250]	ND
PHS¹⁵	1989	22,071 healthy male physicians	67	[333]	[250]
TPT¹⁶	1998	5,085 men at high risk	40	125	[250]
HOT17	1998	18,790 people with hypertension	77	1,000	[71]
PPP¹⁹	2003	4,495 people with risk factors	143	250	333
WHS¹⁸	2005	39,876 healthy female nurses	ND	500	1,000
POPADAD²¹	2008	1,276 people with diabetes, ABI < 0.99	500	36	143
JPAD²³	2008	2,539 people with diabetes	[167]	1,000	[200]
AAA²⁴	2010	3,350 people with ABI < 0.91	200	1,000	[1,000]
JPPP²²	2014	14,000 people with > 1 risk factor	250	ND	[50]
ARRIVE⁸	2018	12,526 men with 2-4 risk factors or women with > 3 risk factors	333	333	[100]
ASCEND⁹	2018	15,480 people with diabetes	1,000	333	[167]
ASPREE^10-12	2018	19,114 healthy elderly	333	250	42

↵a The number of patients who would need to be treated for 10 years to prevent or cause 1 event, calculated as the inverse of the absolute difference in the proportion of patients with events per year between the aspirin and placebo groups. Numbers in brackets indicate harm, ie, higher rates in the aspirin group.
AAA = Aspirin for Asymptomatic Atherosclerosis; ABI = ankle-brachial index; ASCEND = A Study of Cardiovascular Events in Diabetes; ASPREE = A Study of Cardiovascular Events in Diabetes (ASCEND) and Aspirin in Reducing Events in the Elderly; ARRIVE = Aspirin to Reduce Risk of Initial Vascular Events; BDS = British Doctors Study; HOT = Hypertension Optimal Treatment; JPAD = Japanese Primary Prevention of Atherosclerosis With Aspirin for Diabetes; JPPP = Japanese Primary Prevention Project; ND = no difference; PHS = Physicians’ Health Study; POPADAD = Prevention of Progression of Arterial Disease and Diabetes; PPP = Primary Prevention Project; TPT = Thrombosis Prevention Trial; WHS = Women’s Health Study