Lessons learned about prevalence and growth rates of abdominal aortic aneurysms from a 25-year ultrasound population screening programme.

BACKGROUND: This study aimed to assess how the prevalence and growth rates of small and medium abdominal aortic aneurysms (AAAs) (3·0-5·4 cm) have changed over time in men aged 65 years, and to evaluate long-term outcomes in men whose aortic diameter is 2·6-2·9 cm (subaneurysmal), and below the standard threshold for most surveillance programmes. METHODS: The Gloucestershire Aneurysm Screening Programme (GASP) started in 1990. Men aged 65 years with an aortic diameter of 2·6-5·4 cm, measured by ultrasonography using the inner to inner wall method, were included in surveillance. Aortic diameter growth rates were estimated separately for men who initially had a subaneurysmal aorta, and those who had a small or medium AAA, using mixed-effects models. RESULTS: Since 1990, 81 150 men had ultrasound screening for AAA (uptake 80·7 per cent), of whom 2795 had an aortic diameter of 2·6-5·4 cm. The prevalence of screen-detected AAA of 3·0 cm or larger decreased from 5·0 per cent in 1991 to 1·3 per cent in 2015. There was no evidence of a change in AAA growth rates during this time. Of men who initially had a subaneurysmal aorta, 57·6 (95 per cent c.i. 54·4 to 60·7) per cent were estimated to develop an AAA of 3·0 cm or larger within 5 years of the initial scan, and 28·0 (24·2 to 31·8) per cent to develop a large AAA (at least 5·5 cm) within 15 years. CONCLUSION: The prevalence of screen-detected small and medium AAAs has decreased over the past 25 years, but growth rates have remained similar. Men with a subaneurysmal aorta at age 65 years have a substantial risk of developing a large AAA by the age of 80 years.