Prevention of heart attack and stroke is an important public health challenge in Japan due to an aging population and increasing rates of some risk factors such as obesity, high cholesterol and diabetes. The Japanese Primary Prevention Project was designed to evaluate the benefit of low-dose daily aspirin in older Japanese.
This clinical trial examined whether daily, low-dose aspirin could reduce heart attacks and strokes in an older population in Japan. In 2005-2007, 14,464 patients aged 60 to 85 years (average age 71 years, 58% were women) who had high blood pressure, high cholesterol levels, or diabetes were selected by their Japanese primary care physicians. These patients were randomly assigned to receive either: 1) 100 mg of aspirin per day, or 2) no aspirin. No placebo was provided and patients were aware they were taking aspirin. Participants were followed for an average of 5 years for a range of outcomes including fatal and non-fatal heart attacks and strokes as well as bleeding complications. A total of 11% of the participants dropped out of the study before it ended.
Aspirin did not affect the study’s primary composite outcome: the risk of a fatal cardiovascular event or a non-fatal heart attack or stroke was only reduced by 6% with aspirin, a finding that could have been due to random chance. The number of heart attacks and strokes was less than expected and contributed to the non-significant results. There were no patient sub-groups where aspirin had a significant benefit.
In the aspirin group, there was a 47% reduction in non-fatal heart attacks and a 43% reduction in transient ischemic attacks or mini-strokes.
Serious bleeding outside of the brain increased by 85% in the aspirin group.
There were no differences in the risk of stroke or the risk of death from cardiovascular disease or from other causes.
Aspirin had relatively little effect on cardiovascular disease outcomes. For this older population with relatively low rates of heart attack and stroke, there was no clear overall benefit of aspirin.
While aspirin did have some benefits, it was associated with an increased risk of bleeding. Decisions about starting aspirin should assess these risks and benefits on an individual basis, but these findings suggest that aspirin should not be used in low-risk primary prevention patients where the benefits of aspirin are small.