title: Abdominal aortic aneurysm expansion: risk factors and time intervals for surveillance.
abstract: BACKGROUND
  Intervention to reduce abdominal aortic aneurysm (AAA) expansion and optimization of screening intervals would improve current surveillance programs. The aim of this study was to characterize AAA growth in a national cohort of patients with AAA both overall and by cardiovascular risk factors.
  
  
  RESULTS
  In this study, 1743 patients were monitored for changes in AAA diameter by ultrasonography over a mean follow-up of 1.9 years. Mean initial AAA diameter and growth rate were 43 mm (range 28 to 85 mm) and 2.6 mm/year (95% range, -1.0 to 6.1 mm/year), respectively. Baseline diameter was strongly associated with growth, suggesting that AAA growth accelerates as the aneurysm enlarges. AAA growth rate was lower in those with low ankle/brachial pressure index and diabetes but higher for current smokers (all P<0.001). No other factor (including lipids and blood pressure) was associated with AAA growth. Intervals of 36, 24, 12, and 3 months for aneurysms of 35, 40, 45, and 50 mm, respectively, would restrict the probability of breaching the 55-mm limit at rescreening to below 1%.
  
  
  CONCLUSIONS
  Annual, or less frequent, surveillance intervals are safe for all AAAs < or =45 mm in diameter. Smoking increases AAA growth, but atherosclerosis plays a minor role.
authors.affiliation: MRC Clinical Trials Unit, London, UK.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Brady
authors.forename: Simon G
authors.initials: SG
authors.lastname: Thompson
authors.forename: F Gerald R
authors.initials: FG
authors.lastname: Fowkes
authors.forename: Roger M
authors.initials: RM
authors.lastname: Greenhalgh
authors.forename: Janet T
authors.initials: JT
authors.lastname: Powell
mesh_terms: D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D011159:Population Surveillance; D012307:Risk Factors; D012907:Smoking; D013997:Time Factors; D014463:Ultrasonography