The US Preventive Services Task Force (USPSTF) has issued a recommendation statement on the use of aspirin in the prevention of cardiovascular disease (CVD). The recommendation shifts the use of aspirin to an earlier window, and making it an individualised decision for people in their 40s to 50s with a > 10% 10-year CVD risk.
The previous recommendation from 2016 had called for low-dose aspirin for people in their 50s with a > 10% 10-year CVD risk and individualised decisions for those in their 60s with similar risk. The update comes after new evidence emerged in a number of randomised controlled trials.
For the update, which appears in JAMA Network, a systematic review was conducted on the effectiveness of aspirin to reduce the risk of CVD events (myocardial infarction and stroke), cardiovascular mortality, and all-cause mortality in persons without a history of CVD. The effect of aspirin use on colorectal cancer incidence and mortality was also investigated in primary CVD prevention populations, as well as the harms (particularly bleeding) associated with aspirin use.
The USPSTF concludes with moderate certainty that aspirin use for the primary prevention of CVD events in adults aged 40–59 years with a 10% or greater 10-year CVD risk has a small net benefit, and starting low-dose aspirin use for CVD prevention should be an individual decision for them. Those not at increased risk for bleeding and are willing to take low-dose aspirin daily are more likely to benefit. The USPSTF recommends against initiating low-dose aspirin use for the primary prevention of CVD in adults 60 years or older.
Aspirin’s mechanism of action in CVD protection is well known. Aspirin at low doses is an irreversible cyclooxygenase 1 (COX-1) enzyme inhibitor, and at higher doses, it also inhibits COX-2. By inhibiting platelet function through COX-1, aspirin reduces atherothrombosis risk, and has been used widely for the prevention of CVD events, particularly for secondary prevention. However the COX-1 is also involved with protection of the gastrointestinal mucosa, and inhibition of it can promote gastrointestinal bleeding. The mechanism for the possible antineoplastic effects of aspirin is not as well understood.
Older age is one of the strongest risk factors for CVD, and men have a higher overall CVD disease burden and tend to experience CVD events earlier in life. Race and ethnicity affects CVD burden, with Black persons having the highest prevalence of CVD.
Similar CVD benefits appear for a low aspirin dose (≤ 100mg/d) and for all doses that have been studied in CVD prevention trials (50 to 500mg/d). A pragmatic approach would be to use 81 mg/d, which is the most commonly prescribed dose in the US.
Because CVD risk estimation is imprecise and imperfect at the individual level, the USPSTF suggests using these risk estimates as a starting point to discuss with appropriate candidates their desire for daily aspirin use. The benefits of initiating aspirin use are greater for individuals at higher risk for CVD events (eg, those with > 15% or > 20% 10-year CVD risk).
In addition to age and estimated level of CVD risk, decisions about initiating aspirin use should be based on shared decision-making between clinicians and patients about the potential benefits and harms, based on the relative values the patient places on these (reduced CVD risk vs increased bleeding and stroke risk).
Annual bleeding events in individuals without risk factors for increased bleeding (eg, history of gastrointestinal bleeding risk, history of peptic ulcer disease, or use of nonsteroidal anti-inflammatory drugs or corticosteroids) are rare, but risk for bleeding increases modestly with advancing age. For persons who have initiated aspirin use, the net benefits continue to accrue over time in the absence of a bleeding event. However, benefits shrink with advancing age because of increased bleeding risk, with modelling data suggesting stopping aspirin use around age 75.