AAA screening fails to reduce mortality in men
Reduced smoking, not the implementation of abdominal aortic aneurysm screening in Sweden, largely reduced mortality caused by AAA in men, according to a study published in The Lancet.
“Previously, the balance between the benefits and harms of screening programs for abdominal aortic aneurysm was unclear, as the major harms had not been adequately considered,” Minna Johansson, MD, PhD student at University of Gothenburg in Sweden, said in a press release. “Our new findings suggest that this screening program may be outdated because the number of deaths from abdominal aortic aneurysm has been greatly reduced, likely due to lower smoking rates. As a result, the harms of this screening appear to outweigh the benefits, and our findings question the continued use of screening for abdominal aortic aneurysm in men. The results from this study are likely to be applicable to countries with similar trends in smoking rates and abdominal aortic aneurysm, which applies to many Western countries, for example the U.K.”
Screening program in Sweden
Researchers analyzed data from 25,265 men who were invited to participate in an AAA screening program between 2006 and 2009. This information was compared with data from 106,087 men who were age-matched and were not invited to the screening program. Background trends were taken into account through the analysis of all Swedish men aged 40 to 99 years from 1987 to 2015.
Men who participated in the screening program and were diagnosed with AAA were followed up at local vascular surgery clinics. Those with an aortic diameter of at least 55 mm were considered for preventive surgery.
Overdiagnosis was defined as the probability or excess risk for an AAA diagnosis in the screening cohort vs. the control cohort at 6 years. Overtreatment was defined as men who were overdiagnosed and underwent elective surgery.
Between the early 2000s and 2015, AAA mortality decreased in men aged 65 to 74 years from 36 deaths per 100,000 men to 10 deaths per 100,000 men. The decrease was similar in all Swedish counties regardless of whether a screening program was implemented or not.
Six years after the screening program was implemented, there was a nonsignificant decrease in AAA mortality in men who were screened (adjusted OR = 0.76; 95% CI, 0.38-1.51), which prevented two deaths for every 10,000 men who were screened (95% CI, –3 to 7).
The screening cohort was more likely to be diagnosed with AAA (aOR = 1.52; 95% CI, 1.16-1.99) and to undergo elective surgery (aOR = 1.59; 95% CI, 1.2-2.1) compared with the control cohort. This translated to 49 men who were overdiagnosed for every 10,000 men who were offered screening (95% CI, 25-73), 19 of whom underwent surgery that was avoidable (95% CI, 1-37).
“The increase in incidence before screening that we observed, including in age groups not invited to screening, therefore probably reflects increased use of diagnostic tests (ie, incidental finding with radiological investigations for other purposes) and opportunistic screening rather than a true increase in disease prevalence,” Johansson and colleagues wrote. “In other words, even without organized screening, a large proportion of abdominal aortic aneurysms are identified before rupture. This could partly explain why we found a smaller, nonsignificant effect on mortality than in the randomized trials. By contrast, this would underestimate the rate of overdiagnosis.”
In a related editorial, Stefan Acosta, MD, PhD, professor in the department of clinical sciences at Lund University in Malmö, Sweden, wrote: “The decreasing prevalence of smoking in Sweden (from 44% of the population in 1970, to 15% of the population in 2010) should be viewed as the main cause of the decreasing incidence and mortality of AAA. Every percentage drop in the prevalence of smoking will have a huge effect on smoking-related diseases such as cancer and AAA. Primary prevention programs to reduce the prevalence of tobacco smoking is a top priority, whereas screening for AAA is not.” – by Darlene Dobkowski
Disclosures: The authors and Acosta report no relevant financial disclosures.