Sibling risks of abdominal aortic aneurysm

There is evidence that the risk of abdominal aortic aneurysm (AAA) is greater in first-degree relatives of patients with the disorder than in the same age group of the general population. We conducted a 3-year study of siblings of AAA probands and siblings of a control group (cataract surgery patients) of the same age. Genetic information was obtained by interview from 126 probands and 100 controls; another family member was present at the interview. Medical records were obtained and further information verified before a sibling (over age 50) was assigned affected status. Of 427 siblings of probands, 19 (4·4%) had probable or definite AAA, compared with five (1·1%) of 451 siblings of controls. The lifetime cumulative risks of AAA at age 83 were 11·7% (SD 3·1) and 7·5% (4·1), respectively. The risk of AAA began at an earlier age and increased more rapidly for probandsʹ siblings than for controlsʹ siblings (p<0·01, log-rank test). A risk comparison, based on the results of ultrasound screening of 54 geographically accessible siblings of probands and the 100 controls showed a similar pattern. Ten (19%) siblings of probands and eight (8%) controls had AAA on ultrasound (lifetime cumulative risk 60·8% [18·9] vs 14·9% [5·1], P=0·01). These results show that familial factors influence the age of onset of AAA. We recommend routine ultrasound examination of siblings of patients with AAA.