Incidence among men of asymptomatic abdominal aortic aneurysms: estimates from 500 screen detected cases

Objectives-To determine the incidence of asymptomatic abdominal aortic aneurysms and the implications for an ultrasound screening programme in England and Wales. Methods-First screen data were obtained from the Chichester and Huntingdon screening studies and used to estimate the prevalence of abdominal aortic aneurysms. The incidence of new, asymptomatic aneurysms was estimated from the prevalence rates observed in the Huntingdon screening study. Setting-Screening programmes in Huntingdon and Chichester using ultrasound to screen all men over the age of 50 and men over age 65 respectively. Results-The prevalence of abdominal aortic aneurysms ranged between 5.32% and 8.02% and between 6.18% and 9.88% of men aged between 65 and 79 in Chichester and Huntingdon respectively. Annual incidence rates, estimated by age, rose steadily reaching a peak of 0.67% of the Huntingdon population per year at age 65. Thereafter incidence falls. Estimates of the incidence of new asymptomatic abdominal aortic aneurysms, based on the observed prevalence data, were calculated and showed a peak at age 65. Conclusions-Hypotheses are offered to explain this unexpected early peak in incidence. This information should allow the definition of the optimum age for screening, and the relative benefits of screening at different intervals if widespread screening is adopted in the future.