deCODEme, about abdominal aortic aneurysm

introduction

When a weak area of the abdominal aorta expands or bulges, it is called an abdominal aortic aneurysm (AAA).

The aorta is the body´s largest artery, carrying blood from the heart to smaller branch arteries. An aortic aneurysm is an abnormal weakening of parts of the aorta. The pressure from blood flowing through the aorta can cause the weakened part to bulge. An aneurysm can stretch the aorta wall to the extent that it finally bursts or ruptures. A ruptured aneurysm can cause severe internal bleeding and leads to death in over 65% of instances. Fortunately, especially when diagnosed early, an aortic aneurysm can be treated, or even cured, with highly effective and safe treatments.

There are two main types of aortic aneurysms, thoracic and abdominal, depending on which part of the aorta is affected; the upper part that traverses the chest (thoracic aortic aneurysm) or the lower part that traverses the abdomen (abdominal aortic aneurysm, AAA). About three in four of all aortic aneurysms are AAA.

In most cases individuals experience no symptoms at all or only vague symptoms of AAA until the aneurysm ruptures. Therefore the true prevalence of AAA is not known, but it is estimated that 1.5-9% of men and 1-2% of women have this condition. The rupture of AAA causes roughly 15,000 deaths every year in the United States.

Research suggests that AAA has a strong familial component. This indicates that there is an important genetic contribution to the risk of developing AAA. Recently, our scientists at deCODE genetics identified a common genetic variant on chromosome 9 that is associated with increased risk of AAA.

The deCODEme Genetic Scan identifies a variant on chromosome 9 that correlates strongly (r²= 0.9) with the variant associated with increased risk of AAA and provides an interpretation of the risk of developing AAA for individuals of European ancestry. The same variant also increases the risk of heart attack in individuals of both European and Asian ancestry and intracranial aneurysms in European individuals. At the present time, information about the risk of AAA conferred by this genetic variant on individuals of other ethnicities is not available.

risk factors

Although the ultimate causes for AAA are still unclear, the known risk factors are:

Age and gender: AAA is most commonly encountered in older men. The condition is 2-5 times more common in men than women and the incidence increases with age in both sexes. In populations over age 60, estimates of prevalence range from 2% to 8%. AAA is uncommon in both men and women younger than 50 years of age.
Smoking: Smoking is the single most important environmental risk factor and the more you smoke, the greater the risk. This is probably because the underlying cause for most AAA is atherosclerosis of the aorta, which is exacerbated by smoking. Research has shown that the prevalence of AAA in tobacco smokers is more than four times that of life-long non-smokers.
Other cardiovascular risk factors: Some cardiovascular risk factors such as high blood pressure and abnormal cholesterol levels have been associated with AAA, whereas others, such as diabetes, have not.
Ethnicity: AAA is diagnosed less frequently in Asians and African-Americans than individuals of European descent.
Genetics: Genetic factors have a recognized impact on the development of AAA, with 15-20% of affected individuals reporting a family history of the condition. The lifetime risk of AAA in a first degree relative (parent, child or sibling) of a patient with AAA is 11-28% or 3-7 times that of the general population (with a lifetime risk of 4%).

more information

You can find out more information about AAA by talking with your doctor and visiting these Web sites:

scientific references

Diehm N, Dick F, Schaffner T, Schmidli J, Kalka C, Di Santo S, Voelzmann J, Baumgartner I. Novel insight into the pathobiology of abdominal aortic aneurysm and potential future treatment concepts. Prog Cardiovasc Dis. 2007 Nov-Dec;50(3):209-17. Review.
Helgadottir A, Thorleifsson G, Magnusson KP, et al. The same sequence variant on 9p21 associates with myocardial infarction, abdominal aortic aneurysm and intracranial aneurysm. Nat Genet. 2008 Feb;40(2):217-24.
Iribarren C, Darbinian JA, Go AS, Fireman BH, Lee CD, Grey DP.Traditional and novel risk factors for clinically diagnosed abdominal aortic aneurysm: the Kaiser multiphasic health checkup cohort study. Ann Epidemiol. 2007 Sep;17(9):669-78.
Kuivaniemi H, Platsoucas CD, Tilson MD 3rd. Aortic aneurysms: an immune disease with a strong genetic component. Circulation. 2008 Jan 15;117(2):242-52. Review.
Sakalihasan N, Limet R, Defawe OD. Abdominal aortic aneurysm. Lancet. 2005 Apr 30-May 6;365(9470):1577-89. Review.