Aspirin is an interesting medication, with a really fascinating history for the nerds among us. One of its big uses today is for so-called 'secondary prevention' of cardiovascular events, such as heart attacks or strokes. The prevention is secondary because aspirin is used after such an event has taken place, in order to keep a second event from happening. In a classic line of reasoning we see again and again, 'if some is good is more better?', this week's JAMA reports a study of aspirin for primary prevention, or before the first event takes place, to see if that, too, can be avoided.
Aspirin for Prevention of Cardiovascular Events in a General Population Screened for a Low Ankle Brachial Index took a look at close to 30,000 men and women aged 50 to 75 years living in Scotland. None of these folks had apparent cardiovascular disease, and all of them had an ankle brachial index, or ABI, screening.
Here's what happens in an ABI screening: blood pressure is taken in the arm and the leg, and a ratio is computed. Usually these blood pressures are similar, so the ratio would be high, but when the ratio is low it's an indicator of atherosclerosis. And as Rick points out in the podcast, people are more likely to develop atherosclerosis in the leg than in the arm. Those people with a low ratio were either given one 100 mg enteric coated aspirin daily, or a placebo. Then they were followed for about 8 years, and the number and type of cardiovascular events were recorded.
Disappointingly, cardiovascular events were not significantly reduced in those who took aspirin. What was increased among the group who took aspirin was the risk of a fatal bleed within the head. The likely conclusion then, is that for what appears to be a very small or nonexistent benefit, the risks are too great.
Big questions remain, of course. Why is aspirin clearly helpful in the secondary prevention capacity? I'm reminded of research in cancer genetics and natural history, which demonstrates that over time, different mutations are manifest that may enable the disease to spread and survive. Is it possible that atherosclerosis is similar in that the initial process that leads to the deposition within the arteries is one thing, while additional plaque formation is something else? And that perhaps the additional plaque formation can be ameliorated with aspirin but not the initiation? Only time, and more research (of course!) will tell.
Other topics this week include salt in our diets, screening athletes for cardiovascular problems, and treatment of blockages of the carotid arteries in The Lancet. Until next week, y'all live well.
Is there any thing that can totally prevent this illness ,because my family has a great history of this illness and im scared i might get this.
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