Screening for abdominal aortic aneurysm

Abstract

Abdominal Aortic Aneurysm (AAA) is a common disease with a prevalence of 1.5-2.0% in 65-year old men in Sweden. The risk of having AAA is increased with smoking, high age, family history of AAA and cardiovascular disease. Women have a lower prevalence (0.5%) and develop AAA later in life. An AAA seldom gives any symptom prior to rupture. Untreated rupture is associated with 100% mortality, while surgically treated rupture is associated with 25-70% mortality. Prophylactic surgery is associated with a relatively low risk (30-day mortality of 1-3%). Commonly, prophylactic surgery is offered at size 5.5 cm in men and 5.0 cm in women. As a result of randomized trials showing a benefit in terms of AAA-related mortality and all cause mortality, screening of 65-year old men have been implemented in Sweden. If a high proportion of invited persons chose not to participate in as creening programs, this will affect the positive effects of a screening program. Efforts to better understand and thereby to improve the participation rate should be made. This thesis is focused on different aspects of screening for AAA.

In the first and second studies we investigated siblings to AAA-patients in two different regions in Sweden. We examined 150 siblings in mid-Sweden (Stockholm) and 379 siblings in north Sweden (Norrbotten). In both regions a prevalence of 17% in brothers and 6% in sisters was found, strikingly high numbers as compared to the general population. We did not detect regional differences in prevalence. Further analysis of the 53 siblings found with AAA revealed that 32% had a large AAA and 16% had a large AAA before the age 65. Organized screening of both male and female siblings is motivated since the population-based screening is not sufficient for all of them.

The third study investigated reasons for non-participation in the population based AAA-screening program in Stockholm County. The individual socioeconomic- and health-status of 24319 men invited to screening was investigated and compared between participants and non-participants in screening. The risk of non-participation is increased with low income, low education, marital status single, immigrants and persons with long travel distance to examination-centre. The non-participants had a higher proportion of co-existing diseases. We concluded that immigrants and people with long travel-distance should be targeted in further attempts to improve screening-participation.

The fourth study concerns men with screening-detected AAA and their outcome when treated with prophylactic surgery. We compared all available treated screeningdetected men in Sweden (n=350) to age matched, non screening-detected controls. There was no differences in comorbid conditions between the groups but open repair was used more frequently than EVAR in patients with screening-detected AAA´s than in nonscreening-detected controls (56% vs 45%).

In terms of outcome, a lower 90-day mortality in screening-detected men was found, but no difference in 30-day or 1-year mortality. The overall 30-day mortality in all 700 men was very low at 1%. This gives further support to national screening programs for the detection of AAA´s in men.

Efforts should be made to find AAA’s with improved screening of siblings and groups with low participation-rates in the screening programs.