The overall aim is to determine the frequency by which women and men with intact abdominal aortic aneurysms (AAA) are treated with elective surgery at three vascular outpatient clinics in Europe, and to investigate whether the reasons to refrain from elective surgery differ between the sexes.

Abdominal aortic aneurysm (AAA) is a local widening of the infrarenal aorta (1). The natural history of AAA is progressive and may lead to rupture, a true surgical emergency with a mortality rate of 100% without immediate treatment. Men are more commonly affected (2, 3), however, women demonstrate a notably elevated risk of rupture (4, 5) and constitute up to 1/3 of all ruptures (4, 5). One plausible explanation could be a sex discrepancy in elective treatment rates.

There is both national and international evidence implying that AAA treatments, both elective and emergent, are withheld among women (6-14). Studies on elective treatment rates are especially scarce, as the vast majority of databases and vascular registries only include data on treated AAA patients. A few single-center studies from the UK (6, 7, 15) and one meta-analysis (8) have recorded lower treatment rates among women. We have recently analyzed the issue of elective treatment rates in our group using a population-based approach (manuscript submitted). Of all patients diagnosed with an intact AAA in Sweden during 2001-2015 (n=32 393, 21% women), a crude proportion as high as 60 % did not proceed to receive surgical treatment. The proportion of untreated women (67 %) surpassed that of men (59 %). In the multivariate analyses, female sex and advanced age emerged as the strongest predictors for remaining untreated despite other characteristics such as comorbidities, civil status and individual disposable household income. The median time from diagnosis to treatment for those treated was surprisingly short at 1.6 years.

The foremost intention-to-treat variable that determines the indication for elective surgery is the maximal diameter of the aneurysm (55 mm in men, 50 mm in women; (16, 17)). Population-based investigations, while comprehensive, fall short in terms of aneurysm-specific data. Therefore, these analyses assume comparable diameter distributions and similar morphology for men and women. Similarly, longitudinal follow-up data from the clinical setting, such as records of patient's wishes and physiological preoperative examinations, cannot be extracted for the purpose of nationwide analyses. Thus, the question remains whether the observed gender gap in elective treatment rates persists after detailed considerations of patient- and aneurysm-specific characteristics. A discrepancy in elective treatment rates could also lead to different long-term outcomes, with higher rupture and mortality rates among women.

Inclusion Criteria:

• Intact abdominal aortic aneurysm 30 mm or larger in men and women irrespective of underlying pathogenesis (atherosclerotic, mycotic, previous dissection).

Exclusion Criteria:

• Previous aortic surgery or surgical treatment for AAA
• Ruptured AAA at index contact

All men and women diagnosed with an intact abdominal aortic aneurysm (ICD10 classification I71.4) and who fulfill the inclusion diameter criterion and none of the exclusion criteria are consecutively included from January 2014 and onwards at three vascular outpatient departments in Europe (Karolinska University Hospital, Stockholm, Sweden; St. Olav Hospital, Trondheim, Norway; Medical University of Graz, Graz, Austria) until reaching prespecified study target size according to power calculation (200 women, 200 men).