"The study provides clear, consistent evidence that low-dose aspirin can help to prevent new venous blood clots and other cardiovascular events among people who are at risk because they have already suffered a blood clot," said the study's lead author and University of Sydney Professor, John Simes.
"The treatment effect of aspirin is less than can be achieved with warfarin or other new generation direct thrombin inhibitors, which can achieve more than an 80 per cent reduction in adverse circulatory and cardiopulmonary events," added Simes.
"However, aspirin represents a useful treatment option for patients who are not candidates for anticoagulant drugs because of the expense or the increased risk of bleeding associated with anticoagulants," said Simes.
Compared to placebo patients, those who took 100mg daily of aspirin had a one-third reduction in the risk of thromboembolism, the obstruction of a blood vessel by a clot that has dislodged from another site in the circulation, and deep vein thrombosis (DVT), the formation of a blood clot in a deep vein, predominantly in the legs.
Researchers also found that aspirin also reduced the risk of pulmonary embolism, a blood clot affecting the arteries that supply blood to the lungs, and myocardial infarction (heart attack), stroke or cardiovascular death.
Long-term anticoagulant drugs are expensive and inconvenient, requiring frequent regular blood tests and adjustments to the dosage.
Further, there is an elevated risk that the treatment could cause bleeding in some patients. For people who are not able to cope with this, the viable alternative of taking regular aspirin will be a great benefit.
"This treatment is an alternative to long-term anticoagulation and will be especially useful for patients who do not want the inconvenience of close medical monitoring or the risk of bleeding," said Simes.
The study was published in the journal Circulation.