Aspirin is the most widely used antiplatelet agent; its effectiveness is proven by numerous clinical studies. Antiplatelet use of aspirin has proven useful in preventing thrombotic events in patients at risk of a number of cardiovascular and cerebrovascular diseases. Clinical studies have shown, however, a risk reduction of stroke and a substantially higher benefit for some of these diseases than others. Unlike its value in secondary prevention, aspirin in primary prevention has proved effective only in preventing non-fatal myocardial infarction, having little effect on the prevention of fatal vascular events.
Analysis of 16 trials of secondary prevention in patients with old myocardial infarction, stroke, or transient ischemic attack showed that low-dose aspirin is effective in reducing by about 1/5 atherothrombotic vascular complications (myocardial infarction, non-fatal myocardial infarction or vascular death). This means a reduction in numbers by about 10 to 20 cases per 1000 patients of non-fatal vascular events and a smaller but significant reduction in vascular death. In patients under low dose aspirin for secondary prevention of cardiovascular and cerebrovascular events, its discontinuance was associated with a 40% increase in the relative risk of ischemic stroke and myocardial infarction compared with continued therapy.
Considering the primary prevention, the balance between the avoided vascular events and the major bleedings caused by aspirin is uncertain, and therefore, absolute benefits of antiplateled profilaxy are at least an order of magnitude lower than in secondary prevention.
Lately, it is suggested that the use of low-doses of aspirin for people aged 50 years or more without symptomatic cardiovascular disease, with no emphasis on patient characteristics such as age, sex, or diabetes. However, according to the European Cardiology guidelines from 2012 on cardiovascular disease prevention in clinical practice, aspirin cannot be recommended for primary prevention because of the increased risk of major bleeding (especially gastric).
Despite some suggestive evidence of a potential role of aspirin in preventing cancer, clinical guidelines currently recommend aspirin for cardiovascular only and if they exceed the potential negative effects of aspirin-induced bleeding. The benefit of reducing the risk of colorectal cancer was considered insufficient to justify treatment in people at average risk, given the risk of bleeding. There are unresolved questions about the dosing regimen of aspirin for cancer prevention and treatment.
The chemopreventive mechanism effect of aspirin against colorectal adenoma and cancer has long been related to the inhibition of COX-2 in different cell types of the gastrointestinal tract.
While the balance between the vascular benefit and the risk of gastrointestinal bleeding is clearly in favour of patients with existing coronary heart disease or cerebrovascular disease and haemorrhagic risk environment, such a balance is insecure in the case of middle-aged population with symptomatic vascular disease, and will depend on the estimated annual risk of vascular bleeding complications versus the individual ones. It is important to consider that the two risks can be viewed together as a function of common determinants. Recent studies show that low-doses of aspirin reduces deaths from cancer and overall incidence suggests that there is an overall modest short-term benefit in primary prevention, which leads to long-term use of aspirin for prevention of cancer in middle age. It is said that there is even a 10% reduction in the incidence of cancer due to prophylactic treatment with aspirin would tilt the balance of benefits and risks, and would expand the indication for treatment in medium-risk populations.
For the secondary cardiovascular prevention, the net benefits of aspirin along with other preventive measures would significantly exceed the risks of bleeding, regardless of age and sex. However, for many people without pre-existing vascular disease, cardiovascular benefits of aspirin on long-term association with other methods of primary prevention (for example, statins and antihypertensive medications) are likely to be of similar magnitude to hazards.
In the latest study that proves the benefits of aspirin, experts claim that a daily dose of aspirin for 10 years could be “the most important thing you can do to reduce the rate of cancer after quitting smoking and losing weight “.
In a new analysis of hundreds of previous studies, scientists from Queen Mary University of London could compare the benefits against the risks that could arise if several million people would take a daily dose of aspirin for 10 years, between 50 and 65 years. According to them, colon cancer deaths could fall by 40%, by 50% of esophageal cancer and stomach cancer by 35%.
If we add the smaller decreases in the number of deaths from lung cancer, prostate cancer and breast cancer and benefits in reducing the rate of heart attack and certain types of stroke, the number of lives saved per year by aspirin would total about 7,000. However, nearly 900 additional deaths would be caused by negative side effects of drug administration. Research is conducted to determine the individuals who are most likely to suffer from aspirin side effects. Smokers, those who are already taking blood thinning drugs such as warfarin, and carriers of the bacterium Helicobacter are considered as having a higher risk.