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Genetic risk factors for Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a common chronic condition, being found in ~5% of New Zealand Caucasian males over the age of 60 years. If the aneurysm is allowed to progress to rupture between 40-80% of patients will die of this condition. Early identification of increased AAA risk would significantly widen the window for environment risk factor mitigation. In addition, identification of markers associated with increased severity could alter surveillance scheduling for those with existing AAAs.

Two NZ-based genome wide association studies, using the Affymetrix Human SNP 6.0 and Illumina Omni2.5M array platforms, have been performed to identify genetic markers that could be used as indicators of AAA susceptibility. A staged analysis was conducted on 1000 large aneurysm cases and a similar number of (AAA screened) controls, with secondary validation in 10 separate international AAA cohorts. Six reproducible AAA loci were identified. These included genes known to be associated with lipid metabolism, apoptosis, inflammation and growth factor regulation.   While 6.7% of controls were carriers of 5 or 6 of these genetic variants, 20.2% of AAA’s carried this number of risk alleles. While, individually, each genetic marker contributed only weak to modest effects, after adjustment for demographic risk factors (age, smoking, hypertension and dyslipidemia) carriers of 5 or 6 risk alleles had an odds ratio for AAA association of 3.3 (95% confidence interval 1.9-5.8, p<0.0001).

This study identified novel genetic risk markers for AAA, which were independent of established demographic risk factors.  Such reproducible genetic markers may have utility as predictors of AAA within at risk populations.

This study was supported by programme grant funding from the Health Research Council of New Zealand.