Aspirin is perhaps best known for its painkilling properties. But another of its actions in the body is to inhibit the ability of blood components called ‘platelets’ to stick together. It’s when platelets clump together that clots are formed. In other words, aspirin partially inhibits clot formation. Small blood clots called ‘trombi’ are essentially responsible for the blocking off of arteries that can cause heart attacks and strokes. For this reason, many individuals are advised to take aspirin regularly to help prevent these ‘cardiovascular’ events.
However, there has in recent times been some challenge to the conventional wisdom on aspirin. There has been growing awareness that many people need to be treated with aspirin for one to benefit as well the fact that aspirin can cause side-effects (like bleeding in the gut) that can be extremely hazardous and even fatal, particularly in the elderly. The ardour that the medical profession once had for aspirin has cooled of late.
Further dampening of the enthusiasm is likely to come as a result of a recent study which looked at the impact of aspirin taking in women [I]. The women in this study were essentially ‘healthy’ in that they had no history of heart attack or stroke. In medicine, prevention in this type of person is described as ‘primary prevention’. Basically, the researchers found some benefit for older women over the age of 65. However, in this group (generally deemed to be a elevated risk), it was calculated that 50 women would have be treated with aspirin for 10 years to prevent one ‘cardiovascular event’ (e.g. a heart attack or stroke). In other words, 49 people would take aspirin for 10 years with no benefit at all. And let’s not forget there is a risk of side-effects too.
For younger women, overall benefits were even less likely. The authors of this study concluded that: “Aspirin was ineffective or even harmful in the majority of patients.” These findings are in keeping with contemporary research on aspirin, so we should not be too surprised by them.
However, I had another sense of deja vu reading about this study, in that it brought back to me the evidence base regarding the ‘effectiveness’ of cholesterol-reducing statins. Here’s some stuff we know about the effectiveness of these drugs:
- In primary prevention, statins do not reduce the risk of death 
- In predominantly primary prevention, in women of any age, there is no reduced risk of cardiovascular events with statin treatment .
- This is also true for men aged 70 or over .
- In high-risk men aged 30-69 years, about 50 patients need to be treated for 5 years to prevent one cardiovascular event .
And this is before we even start to factor in potential side-effects such as liver damage, muscle pain and weakness and kidney failure.
What is it about ‘preventive medicine’ that makes it so utterly useless at prevention? One problem, I think, is that it almost certainly fails to address the true underlying causes of illness. Heart disease and strokes are not the result of deficiencies in either aspirin or statins, after all, and in this sense are unlikely to strike at the heart of the processes that drive disease.
Some people say you could make the same point regarding this ‘pill for an ill’ philosophy could be made for more natural medicine too. Maybe, though the difference here is that cardiovascular disease might actually be promoted through a deficiency of, say, omega-3 fats or vitamin D, and upping levels of these substances in the body, even from a pill, may indeed have real value in terms of disease prevention. Also, as these things are innate to the body (which things like aspirin and statins are not), the potential for adverse effects is much smaller too.
1. Dorresteijn JA, Aspirin for primary prevention of vascular events in women: individualized prediction of treatment effects. Eur Heart J 16 November 2011 [Epub ahead of print]
2. Ray KK, et at. Statins and all-cause mortality in high-risk primary prevention: a meta-analysis of 11 randomized controlled trials involving 65 229 participants. Arch Intern Med. 2010;170(12):1024-1031
3. Abramson J, et al. Are lipid-lowering guidelines evidence-based? The Lancet 2007:369:168-169