Aspirin remains one of the most widely used drugs globally, yet its use as a medicinal agent can be traced to as far back as the ancient Greeks who realised its anti-inflammatory properties.
In fact, they used the bark of the willow tree from which it derives. Today, Acetylsalicyclic acid or the modern version of aspirin has been available since about 1900 as a painkiller and for treating high temperatures. Indeed, aspirin was used extensively to treat fever and rheumatic pain during the Spanish flu pandemic .
Over the last century the role for aspirin changed significantly after groundbreaking studies in the 1970s showed it reduced the risk of further heart attacks by 25% and stroke by 31% in those who already suffered same.
Indeed, low dose aspirin became a ‘life safer’ and emerged as an important drug in the treatment of heart and stroke disease. This is as a result of its effect on inhibiting platelets in our blood that normally help with clotting and so aspirin also functions as an anti-thrombotic.
So who should take aspirin? If you have suffered a heart attack, have significant coronary artery disease or have a previous (non-haemorrhagic) stroke then you will usually be put on aspirin. In fact, numerous studies over decades have consistently shown the benefits of aspirin when used for this indication.
What is less clear are the benefits of aspirin when used as a preventative in those with no known heart or stroke disease with studies providing mixed messages. Furthermore, guidelines from professional bodies vary though in general, in those at higher risk of having a stroke or heart attack (up to 10% risk in 10 years) due to a combination of risk factors such as high blood pressure, diabetes or smoking it may be considered.
In particular, although a low dose or what has been called ‘baby’ aspirin (75mg) is about a quarter of the effective amount needed as a painkiller, it can cause peptic ulcers and increase the risk of bleeding.
A review of studies in 2012 involving over 100,000 patients on aspirin as a preventative in otherwise well people confirms that it reduced the risk of nonfatal heart attacks in males but overall increased harm through risk of bleeding. In fact, good control of blood pressure and cholesterol and addressing other risk factors is more beneficial.
This year large studies on aspirin used by older adults also shed further light on the matter. In one involving about 19,000 apparently healthier, older adults (aged 65-70+) aspirin did not reduce the rate of cardiovascular events, dementia or physical disability after an average follow up of nearly five years. However, the rate of major bleeding did increase.
In a further analysis of the same study, aspirin was unexpectedly associated with a small increase in cancer mortality. While the results were surprising and must be interpreted with caution, ultimately aspirin didn’t reduce the death rate from any cause. In essence, the findings show that in a typical older person aged over 70 with no known heart or stroke disease there seems no benefit from aspirin.
Finally, a futher study of aspirin use (over about seven years) in about 15,000 adults who had diabetes but no overt cardiovascular disease resulted in a reduction in cardiac, stroke and other vascular events by an average of about 12% but increased major bleeding by about 29% off setting the benefits for many.
Unless you have a good reason to be on aspirin, it probably confers little or no benefit. In those who are younger (under 70) with multiple risk factors including diabetes but also have a low likelihood of bleeding it may be considered but’s it is crucial to address all factors including high cholesterol and blood pressure.
Interestingly, treatment with aspirin has been associated with a reduction in the incidence of colorectal cancer by over 20%, a finding that is fairly consistent in most studies. A small study in the Lancet this month also showed that aspirin was linked to a decrease in the development of colonic polys (premalignant bowel growths) in patients getting screened for bowel cancer. A probable mechanism is the aspirin inhibition of the enzyme C0X-2 that is synthesised by many bowel tumours.
Finally, aspirin is a very affective painkiller (that is sold over the counter) though has been very much superseded by safer analgesics like ibuprofen that have less risk of stomach upset, ulcers and bleeding. It is also useful for lowering a high temperature and when gargled provides relief for a sore throat.
However, a word of caution, it shouldn’t be used in those aged under 16 where it may cause the rare but potentially fatal Reyes syndrome. It can exacerbate asthma and gout and for pain relief should generally only be taken for short periods. It is also usually avoided in those with stomach or bleeding problems.
To conclude, the message of taking “an aspirin a day to keep the doctor away” is not so accurate as it once seemed!
Dr Kevin McCarroll is a Consultant Physician in Geriatric Medicine, St James’s Hospital, Dublin.