Aspirin risks in perspective: A comparison against marathon running

The risks associated with marathon running include musculoskeletal injuries, dermatological problems and cardiac events. ¹ The rate of referral to hospital accident and emergency in marathon runners appears to be about 1 in 750.^{2, 3} About 90% of such cases are not admitted to hospital.^{2, 3} The hospital admission rate of marathon participants might thus be between about 1 in 7,500–10,000.^{2, 3}

Marathons also carry risks of serious events such as cardiac arrests and sudden death. Whilst such risks appear to be decreasing, ⁴ estimates on the current rates in marathons vary. Based on a survey of 88 marathons in the United States involving about 1.7 million participants, the incidence of sudden cardiac arrest and death has been estimated to be 1 in 57,000 and 1 in 170,000 respectively. ⁵ Men accounted for about 90% of these incidents. ⁵ In an epidemiological study of more than 10 million United States runners in marathon and half-marathon races in the decade of 2000–2010, ⁶ cardiac arrest occurred in 1 in 100,000 marathon participants, about three times higher than half-marathons. Again, about 90% of cases were men and 70% of arrests were fatal. This study concluded that marathons and half-marathons are associated with a low risk of cardiac arrest and sudden death.

The public health potential of aspirin to reduce the risk of ischaemic vascular events and sporadic cancer has been described elsewhere. ⁷ Given that risk for ischaemic vascular events and sporadic cancer rises with increasing age – indeed, age is an independent predictor – a case may be made for taking aspirin in middle age. ⁷ One objection to the wider use of aspirin for primary prevention, however, is the undesirable effects of the medicine, which include increasing risk of bleeding and haemorrhagic stroke. ⁸ Meta-analyses of randomized controlled trials suggest the annual number needed to harm from aspirin in primary prevention is approximately between 1 in 500 and 1 in 2,000.^{9, 10} Put another way, between 1 in 200,000 and 1 in 750,000 aspirin tablets need to be taken for an episode of harm which may then require hospital admission. A person running a marathon might thus be 20 to 100 times more likely to end up in hospital than a person who is taking an aspirin tablet.

Regarding deaths, individual case reports may associate aspirin with a fatality from a bleed or haemorrhage. This extreme illustration of an undesirable effect needs to be treated with caution. There is no evidence from randomised trials that aspirin increases the risk of dying ¹⁰ and there is suggestive evidence of reduced risk of death in those taking it. ¹⁰

Aspirin appears to change morbidity and mortality risk. Thus users of the medicine receive benefits but also carry risks. Whilst some individuals may react badly to the medicine and become unwell, the net benefit of wider aspirin use at a population level could be substantial. The ethics of this individual risk versus population gain with aspirin prophylaxis for primary prevention has been discussed elsewhere. ¹¹

People who enter marathons and those who choose to take aspirin for primary prevention are self-selecting and do so of their own free will. There are further parallels, namely there are benefits and risks, financial and other transactional costs and exclusion criteria, such as being a child. So if there are objections to the wider use of aspirin on the grounds of risk, then there should be even stronger objections to marathon races. Given there are no objections to the latter, there should be no reasonable objections to the former on risk grounds.

Should it be doctors that decide who takes aspirin? ¹² Doctors might be concerned that the cumulative risk of daily aspirin use for primary prophylaxis may be important. However, one option open to middle-aged individuals who want to take aspirin is to start with an infrequent regime, such as once per week, in order to then build to daily use. ¹³

Another of the objections to the wider usage of aspirin for primary prevention is that there may be unintended consequences, such as individuals may take the medicine rather than address lifestyle issues. The potential contribution of aspirin to healthy ageing must be as a complement to other measures to reduce disease risk. ¹⁴ Furthermore, there is an appetite among the general public for accurate information on aspirin to be made widely accessible to support informed decision making on the use of the medicine. ¹⁵ Indeed, about one-quarter of older adults might already be taking aspirin prophylaxis for primary prevention. ¹⁶ In closing, it is important to get all risks into perspective and comparisons can offer a challenge to any excessive risk aversion regarding the public health potential of aspirin.