The bark of the humble willow tree has made headlines again today, and not because of some new fungal infestation that's going to wipe out those fabulous weeping willows from the banks of our rivers. Hippocrates used 'salicylic tea' to reduce fevers nearly 2,500 years ago, and by the nineteenth century chemists were extracting salicylic acid - the active ingredient in aspirin - from willow bark.
The fortunes of aspirin have been up and down in recent decades in terms of its powers of prevention. Twenty years ago we all got very excited over the news that 75 mg aspirin a day cut the risk of a second heart attack or stroke in people who'd already had one of these by 23%, and over the next few years we extrapolated the advice to people who hadn't had a heart attack but who were at high risk of one. Then we realised it might not be the 'magic bullet' we thought it was, first with news that in people who hadn't had a heart attack (1) and then in people with diabetes (2), the risks of gastric bleeding were about as big as the benefits in terms of heart attack reduction.
Next came a study a couple of years ago suggesting aspirin could cut the risk of colon cancer and now this latest study, the biggest evaluation there has been of studies looking at the impact of aspirin on colon and other cancers.
It pulls together the results of about 200 studies covering hundreds of thousands of people, and concludes that taking 75 mg of aspirin a day regularly from your fifties could cut your risk of dying from colon cancer by 40%, stomach cancer by 35% and oesophageal (gullet) cancer by 35-50%. There is also some suggestion that it might cut the risk of death from other common cancers, including breast, lung and prostate.
But there are some big 'buts'. The researchers calculate that if everyone took aspirin at this dose every day for a decade from age 50-64, we could save 122,000 lives in the UK over two decades. But they admit there would be casualties, with about 18,000 people dying from side effects related to bleeding. For some people the balance of risk and benefit would be much more precarious - particularly people at high risk of bleeding, such as people with a history of stomach ulcers, or who drink or smoke heavily. It's possible that having a germ called H. pylori, which predisposes you to indigestion would increase the risk of gastric bleeding.
Secondly, as you get older, your risk of bleeding goes up, so you shouldn't take it for life if your only reason is to cut your risk of cancer. But it's not yet clear how long is good enough. The researchers showed that the benefits only started stacking up significantly after five years of regular dosing from the age of 50 - so as a compromise, they suggest a 10-year period of daily dosage in your fifties to early sixties. Their theory goes like this:
1) The researchers found no evidence of benefit in under 50-year-olds
2) While we don't know how long you have to take it for maximum effect, we do know that you need to take it for at least five years to reap the rewards
3) The benefits persist after you stop while the risks of continuing to take it rise sharply in your 70s.
Should everyone over 50 take aspirin? No - it's a drug and all drugs have side effects. Is it a substitute for healthy living? Categorically not, but the benefits are seen even if you live a wholly blameless life. Will I be taking it? I'll have to admit to myself I'm over 50 first…
1. Antithrombotic Trialists' (ATT) Collaboration. Aspirin in the primary and secondary prevention of vascular disease: collaborative meta-analysis of individual participant data from randomised trials. Lancet 2009; 373:1849-1860.
2. De Berardis G, Sacco M, Strippoli GFM, et al. Aspirin for primary prevention of cardiovascular events in people with diabetes: Meta-analysis of randomised controlled trials. BMJ 2009; DOI:10.1136/bmj.b4531. Available at: http://www.bmj.com.
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