Aspirin’s benefits and harms finely balanced
A “fine balance” exists between benefits and risks in healthy people taking regular prophylactic aspirin to ward off cardiovascular disease (CVD), according to a round-up of current scientific evidence.
Writing in the September issue of Health Technology Assessment, scientists from the University of Warwick also report that effects on cancer prevention have “a long lead time and are at present reliant on post-hoc analyses” (2013;17).
The aim of the study — funded by The National Institute for Health Research health technology assessment programme — was to identify and reanalyse randomised controlled trials, systematic reviews and meta-analyses with a focus on possible harms of prophylactic aspirin in the primary prevention of CVD and cancer.
The team found that benefits of aspirin ranged from a 6 per cent reduction in relative risk for all-cause mortality (RR 0.94, 95 per cent confidence interval 0.88 to 1.00) and a 10 per cent reduction in major cardiovascular events (RR 0.90, CI 0.85 to 0.96), to a reduction in total coronary heart disease of 15 per cent (RR 0.85, CI 0.69 to 1.06). Reported pooled odds ratios for total cancer mortality ranged between 0.76 (CI 0.66 to 0.88) and 0.93 (CI 0.84 to 1.03).
Reported increases in the relative risk of adverse events from aspirin use were 37 per cent for gastrointestinal bleeding (RR 1.37, CI 1.15 to 1.62), between 54 per cent (RR 1.54, CI 1.30 to 1.82) and 62 per cent (RR 1.62, CI 1.31 to 2.00) for major bleeds, and between 32 per cent (RR 1.32, CI 1.00 to 1.74) and 38 per cent (RR 1.38, CI 1.01 to 1.82) for haemorrhagic stroke.
Not possible to identify subgroups that will benefit
Commenting on the report, Helen Williams, consultant pharmacist for cardiovascular disease at NHS Southwark Clinical Commissioning Group, said: “Aspirin has a clear role in the prevention of CV events in patients with established CV disease. However, evidence for primary prevention of CV disease suggests the benefits and harms of aspirin in this setting may be more finely balanced than previously thought, even in individuals estimated to be at high risk of experiencing CV events — such as those with diabetes or elevated blood pressure. This study confirms that it is not currently possible to identify a specific subgroup of patients that may benefit from aspirin in primary prevention of CV disease and therefore aspirin is no longer recommended for routine use in this indication.”
She added that aspirin’s effects on cancer rates are small. “Pharmacists should be aware that currently no guidelines recommend aspirin use for the primary prevention of cancer. Patients should be made aware that the chronic use of aspirin, even in low doses, increases the risk of bleeds significantly and therefore should only be considered where there is strong evidence that the benefits outweigh the risks,” she said.
The report’s authors add: “Several potentially relevant ongoing trials will be completed between 2013 and 2019, which may clarify the extent of benefit of aspirin in reducing cancer incidence and mortality.”
Citation: The Pharmaceutical Journal DOI: 10.1211/PJ.2013.11129374