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Determination of who may derive most benefit from aspirin in primary prevention: subgroup results from a randomised controlled trial

BMJ 2000; 321 doi: https://doi.org/10.1136/bmj.321.7252.13 (Published 01 July 2000) Cite this as: BMJ 2000;321:13
  1. T W Meade, director (t.w.meade{at}mds.qmw.ac.uk),
  2. P J Brennan, statistician the MRC General Practice Research Framework.
  1. MRC Epidemiology and Medical Care Unit, Wolfson Institute of Preventive Medicine, London, EC1M 6BQ
  1. Correspondence to: T Meade
  • Accepted 16 March 2000

Abstract

Objective: To determine which groups of patients may derive particular benefit or experience harm from the use of low dose aspirin for the primary prevention of coronary heart disease.

Design: Randomised controlled trial.

Setting: 108 group practices in the Medical Research Council's general practice research framework who were taking part in the thrombosis prevention trial.

Participants: 5499 men aged between 45 and 69 years at entry who were at increased risk of coronary heart disease.

Main outcome measures: Myocardial infarction, coronary death, and stroke.

Results: Aspirin reduced coronary events by 20%. This benefit, mainly for non-fatal events, was significantly greater the lower the systolic blood pressure at entry (interaction P=0.0015), the relative risk at pressures 130 mm Hg being 0.55 compared with 0.94 at pressures >145 mm Hg. Aspirin also reduced strokes at low but not high pressures, the relative risks being 0.41 and 1.42 (P=0.006) respectively. The relative risk of all major cardiovascular events—that is, the sum of coronary heart disease and stroke—was 0.59 at pressures <130 mm Hg compared with 1.08 at pressures >145 mm Hg (P=0.0001).

Conclusion: Even with the limitations of subgroup analyses the evidence suggests that the benefit of low dose aspirin in primary prevention may occur mainly in those with lower systolic blood pressures, although it is not clear even in these men that the benefit outweighs the potential hazards. Men with higher pressures may be exposed to the risks of bleeding while deriving no benefit through reductions in coronary heart disease and stroke.

Footnotes

  • Funding Medical Research Council, British Heart Foundation, DuPont Pharma, and Bayer Corporation. GlaxoWellcome and Boehringer-Ingelheim provided warfarin free of charge during the pilot stage. DuPont Pharma provided warfarin, and Bayer Corporation provided aspirin free of charge during the main trial.

  • Competing interests DuPont Pharma and Bayer have given financial assistance with attendance at meetings and honoraria for speaking to Professor Meade and paid into a discretionary fund to supplement the unit's allocation.

  • Accepted 16 March 2000
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