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Final report on the aspirin component of the ongoing Physicians' Health Study
Insights
Low-dose aspirin significantly reduces myocardial infarction risk in men aged 50 and older. While not statistically significant, a trend towards increased stroke risk was observed. Further research is needed for cardiovascular mortality and stroke.
Area of Science:
- Cardiovascular Medicine
- Preventive Cardiology
- Clinical Trials
Background:
- Cardiovascular disease remains a leading cause of mortality.
- Primary prevention strategies are crucial for reducing cardiovascular events.
- The role of low-dose aspirin in preventing cardiovascular disease requires further elucidation.
Purpose of the Study:
- To evaluate the efficacy of low-dose aspirin in reducing cardiovascular mortality and myocardial infarction.
- To assess the impact of aspirin on stroke incidence and overall cardiovascular deaths.
- To investigate subgroup effects of aspirin based on age and cholesterol levels.
Main Methods:
- Randomized, double-blind, placebo-controlled trial (Physicians' Health Study).
- Involved 22,071 participants with an average follow-up of 60.2 months.
- Assessed outcomes including myocardial infarction, stroke, and cardiovascular mortality.
Main Results:
- A 44% reduction in myocardial infarction risk observed with aspirin (RR 0.56).
- Benefit primarily seen in participants aged 50 and older.
- No statistically significant reduction in total cardiovascular deaths; a non-significant trend towards increased hemorrhagic stroke risk.
Conclusions:
- Low-dose aspirin conclusively reduces myocardial infarction risk in older men.
- Evidence for aspirin's effect on stroke and total cardiovascular deaths is inconclusive due to limited event numbers.
- Aspirin's benefits for primary cardiovascular prevention are most evident in specific age groups and potentially influenced by cholesterol levels.
Abstract:
The Physicians' Health Study is a randomized, double-blind, placebo-controlled trial designed to determine whether low-dose aspirin (325 mg every other day) decreases cardiovascular mortality and whether beta carotene reduces the incidence of cancer. The aspirin component was terminated earlier than scheduled, and the preliminary findings were published. We now present detailed analyses of the cardiovascular component for 22,071 participants, at an average follow-up time of 60.2 months. There was a 44 percent reduction in the risk of myocardial infarction (relative risk, 0.56; 95 percent confidence interval, 0.45 to 0.70; P less than 0.00001) in the aspirin group (254.8 per 100,000 per year as compared with 439.7 in the placebo group). A slightly increased risk of stroke among those taking aspirin was not statistically significant; this trend was observed primarily in the subgroup with hemorrhagic stroke (relative risk, 2.14; 95 percent confidence interval, 0.96 to 4.77; P = 0.06). No reduction in mortality from all cardiovascular causes was associated with aspirin (relative risk, 0.96; 95 percent confidence interval, 0.60 to 1.54). Further analyses showed that the reduction in the risk of myocardial infarction was apparent only among those who were 50 years of age and older. The benefit was present at all levels of cholesterol, but appeared greatest at low levels. The relative risk of ulcer in the aspirin group was 1.22 (169 in the aspirin group as compared with 138 in the placebo group; 95 percent confidence interval, 0.98 to 1.53; P = 0.08), and the relative risk of requiring a blood transfusion was 1.71. This trial of aspirin for the primary prevention of cardiovascular disease demonstrates a conclusive reduction in the risk of myocardial infarction, but the evidence concerning stroke and total cardiovascular deaths remains inconclusive because of the inadequate numbers of physicians with these end points.