Rationale for a primary prevention study using low-dose aspirin to prevent coronary and cerebrovascular disease in the elderly.

The benefits of prophylactic aspirin therapy to prevent cardiovascular and cerebrovascular disease in asymptomatic individuals remains unclear. The rationale for developing a multicentered, double-blind, placebo-controlled clinical trial to determine whether low-dose aspirin (100 mg daily) prevents cardiovascular and cerebrovascular morbidity and mortality in persons aged 70 years and over with no evidence of pre-existing cardiovascular or cerebrovascular disease is described. Sample size calculations have indicated that 15,000 subjects would be required over a 4-year follow-up period in order to demonstrate a 20% reduction in overall cardiovascular mortality at the 0.01 level with a power of 0.8. Such a large-scale community-based clinical trial has never been conducted in Australia in this age group. Therefore the PACE (prevention by low-dose aspirin of cardiovascular disease in the elderly) pilot study has been developed to test recruitment strategies and methods and ascertaining disease end-points.