Screening for Infra-renal Abdominal Aortic Aneurysms in 65-year-old Men in Inland, Norway

Abdominal aortic aneurysm (AAA) is a dilatation of the main artery from the heart as it passes through the abdomen. In case of rupture, the condition is life threatening and acute surgery is required. The prevalence of AAA is four to six times higher in men as compared to women, and varies greatly between countries and regions, but is generally reported to be present in 1.5-5% of men. Over the last three decades, the prevalence of AAA has been relatively stable, despite improved medical therapy for cardiovascular disease and a declining use of tobacco in Norway and comparable countries. This may in part be a consequence of unchanged aneurysmal progression rate combined with improved life expectancy of individuals at risk of developing AAA. Approximately 1% of all deaths in men over 65 years of age in Norway is caused by a ruptured AAA. The mortality is 75-80% after rupture, and half the patients die before they reach a hospital with vascular surgery. A patient with an incidental finding of AAA will be offered surgery in an elective setting to prevent rupture. The number of AAA surgeries in Norway was 851 in 2021 according to the Norwegian Vascular Surgery Registry (NORKAR).

The key challenge in improvement of aneurysm related mortality is to detect the disease while it is still asymptomatic. Screening is required to detect an asymptomatic AAA and is considered a beneficial healthcare intervention in several European countries.

We hypothesize that the prevalence of AAA is significantly higher in Innlandet, as compared to Oslo, and further, that the discrepancies in AAA prevalence between regions may be caused by differences in prevalence of risk factors, medication, socio-economic status, or in variations in genetic susceptibility.

Several genetic markers and other biomarkers have been proposed to relate to aneurysm disease. Of the clinically applicable biomarkers D-dimer, LDL cholesterol, HDL cholesterol, Thrombocytes, Apolipoprotein B and HbA1c have been found to have the most significant association to aneurysm growth rate. Studies on biomarkers for AAA have been hampered by low number of patients and currently no specific biomarker has been identified as a tool to identify patients with AAA or to predict aneurysm growth and studies on larger populations of patients with AAA have been called for.

The number of AAA-surgeries performed per capita is 3-4 times higher in Innlandet county, as compared to Oslo. The last three years the annual incidence of AAA requiring treatment has been 21.5 / 100 000 inhabitants in Innlandet, as compared to 6.6 / 100 000 in Oslo. The indication for surgery is the same in both regions. In Oslo, a screening program was established in 2011, reporting a prevalence of AAA of 2.6 %, but in Innlandet county all AAA are either symptomatic or incidental findings and the prevalence is unknown. The aetiology of the major difference in AAA prevalence between these two regions has not been previously explored.