Objective: To document compliance with medication, drop-out and drop-in rates, and baseline cardiovascular event rates during the pilot phase of the PACE (Prevention with low-dose Aspirin of Cardiovascular disease in the Elderly) study.
Design: Randomized, double-blind, placebo-controlled trial of low-dose aspirin therapy.
Setting: Community-based, in general practices and residential retirement villages, in Victoria, Australia.
Subjects: Four hundred persons aged 70 years and older (53% females), ambulatory and living independently, who volunteered to participate. None had significant vascular disease, peptic ulceration, hemorrhagic symptoms, or were currently taking non-steroidal anti-inflammatory drugs.
Main outcome measures: Compliance with medication (assessed by pill count and platelet function tests), self-reported drop-out and drop-in rates, and incidence of cardiovascular events reported by participants and their general practitioners during a 12-month period.
Results: Two fatal cardiovascular events, three non-fatal coronary events, and eight non-fatal cerebrovascular events were observed during the 12-month period. These incidence figures were approximately 15%, 15%, and 40%, respectively, of those in the general population of the same age and sex, based on morbidity data available from the Australian Bureau of Statistics. Compliance to medication was excellent (87%), and premature withdrawal (other than for a study end point) was limited to 14.5%. Secondary 'softer' endpoints, such as transient ischaemic attack and unstable angina, necessitated patient withdrawal from randomized therapy and possibly contributed to the small number of primary 'hard' end points observed. The projected power of the main study to detect a 20% treatment effect on overall cardiovascular mortality in 15,000 subjects over a 4-year period may, therefore, be substantially reduced.
Conclusions: These results suggest that any future primary prevention study of cardiovascular disease in the elderly examining the effect of low-dose aspirin on overall cardiovascular mortality will likely need to use much larger numbers of patients or use a combined end point of fatal and non-fatal ischemic events.