Clinical question: Are the same doses of aspirin equally effective in preventing cardiovascular (CV) events and long-term colorectal risk reduction in patients of various body sizes?
Background: Strong evidence for the one-dose-fits-all approach to use of aspirin in long-term prevention of CV events is lacking. Aspirin effect may be dependent on patient’s body size. Excess dosing of aspirin in patients of small body size might negatively affect their outcomes.
Study design: Meta-analysis.
Setting: Trials from the Antithrombotic Trialists’ Collaboration, other systematic reviews of trials of aspirin, and from the Cochrane Database of Systematic Reviews.
Synopsis: The authors included 10 trials (117,279 participants altogether) and analyzed the association of body weight with the effectiveness of aspirin doses on CV event and colon cancer prevention. The greatest benefit of low-dose aspirin (75-100 mg) in reducing CV events was seen in patients weighing 50-69 kg (hazard ratio, 0.75; 95% confidence interval, 0.65-0.85; P less than .0001), with CV events increasing with increasing weights (P interaction = .0072). There was an increased rate of fatality with low-dose aspirin among patients at body weights greater than 70 kg (HR, 1.33; 95% CI, 1.08-1.64; P = .0082) or less than 50 kg (HR, 1.52; 95% CI, 1.04-2.21; P = .031). Higher doses of aspirin were more effective at higher body weights (P interaction = .017). Similar weight-dependent effects were seen in the 20-year risk of colorectal cancer.
While findings are consistent across trials looking at dose-dependent aspirin effects in patients of various body sizes, limitations included lack of generalizability of the results in secondary prevention trials, inclusion of older trials, variability of participants’ characteristics, and aspirin compliance across trials.
Bottom line: Weight-based aspirin dosing may be required for prevention of CV events, sudden cardiac death, and cancer. Based on the results of this meta-analysis, one-dose-fits-all aspirin administration strategy may not be advisable.
Citation: Rothwell PM et al. Effects of aspirin on risks of vascular events and cancer according to body weight and dose: Analysis of individual patient data from randomized trials. Lancet. 2018;392:387-99.
Dr. Burklin is an assistant professor of medicine in the division of hospital medicine at Emory University, Atlanta.