Lifestyle and risk of abdominal aortic aneurysm

Background: Lifestyle-related factors associated with abdominal aortic aneurysm (AAA) disease are very scarcely investigated in prospective design. Identification of such could provide better understanding of AAA epidemiology and etiology, and provide new hypotheses for studies on AAA growth rate in order to try to limit progression of the disease. The overall aim of this thesis was to study possible associations between modifiable, lifestyle-related factors and risk of AAA.

Methods and Results: Two prospective population-based cohorts of 84,890 middle-aged and elderly men and women, from Central Sweden (the Cohort of Swedish Men and the Swedish Mammography Cohort) constituted the study population for all studies in this thesis. In Study I-IV, AAA diagnosis and/or repair was identified over the 12- to 14-year follow-up in the Swedish National Patient Register, the Swedish Cause of Death Register, and the National Register for Vascular Surgery (Swedvasc). In Study V, abdominal aortic diameter (AAD) was assessed in 14,249 men screened for AAA (AAD ≥30 mm) between 65 and 75 years of age (mean 13 years after baseline, 1 January 1998). Linear regression models were used to estimate mean AAD, and Cox proportional hazards regression models were used to estimate hazard ratios (HR) of AAA as a measure of AAA risk, by comorbidities and self-reported lifestyle-related exposures, with corresponding 95% confidence intervals (CI’s).

We observed that smoking was associated with an increased risk of AAA, and with an increased mean AAD among men. Across all specific smoking strata, the absolute risks of AAA were higher among men, while the relative risks seemed to be more pronounced among women. The AAA incidence was higher among smoking women than among never smoking men. Following smoking cessation, women had a more rapid decline in excess risk associated with current smoking than men did. Furthermore, obesity seemed to be associated with an increased AAA risk; central obesity (i.e. increased waist circumference) was associated with AAA diagnosis and/or repair, while total obesity (i.e. increased BMI) was associated with screening detected AAA, and with a larger mean AAD, among men.

We also observed that consumption of fruits, but not vegetables, was associated with a decreased risk of AAA, an association that seemed to be more pronounced with ruptured AAA than with intact AAA. No association was observed between a healthy diet in general and risk of AAA detected at screening among men. A moderate consumption of total alcohol (i.e. ethanol) was associated with a lower risk of AAA diagnosis and/or repair, but not among participants free from cardiovascular disease (CVD). Alcohol consumption was also associated with a smaller mean AAD among men. The most commonly consumed alcoholic beverages – beer among men and wine among women – were inversely associated with AAA diagnosis and/or repair, whereas no association was observed for spirits. Last, when compared with those who almost never walked/bicycled, men who were walking/bicycling >40 min/day had a lower risk of having an AAA at screening. Among men, CVD was associated with a larger predicted mean AAD, and with an increased risk of AAA detected at screening.

Conclusions: Lifestyle-related exposures were prospectively associated with AAA disease, and with mean AAD. Regarding risk of AAA, current smoking may affect women to a greater extent than men, obesity may increase the risk, and consumption of fruits, a moderate consumption of alcohol, and physical activity, may reduce the risk.

List of scientific papers

I. Stackelberg O, Björck M, Larsson SC, Orsini N, Wolk A. Sex differences in the association between smoking and abdominal aortic aneurysm. British Journal of Surgery. 2014;101:1230-1237
https://doi.org/10.1002/bjs.9526

II. Stackelberg O, Björck M, Sadr-Azodi O, Larsson SC, Orsini N, Wolk A. Obesity and abdominal aortic aneurysm. British Journal of Surgery. 2013;100:360-366.
https://doi.org/10.1002/bjs.8983

III. Stackelberg O, Björck M, Larsson SC, Orsini N, Wolk A. Fruit and vegetable consumption with risk of abdominal aortic aneurysm. Circulation. 2013;128:795-802
https://doi.org/10.1161/CIRCULATIONAHA.112.000728

IV. Stackelberg O, Björck M, Larsson SC, Orsini N, Wolk A. Alcohol consumption, specific alcoholic beverages, and abdominal aortic aneurysm. Circulation. 2014;130:646-652.
https://doi.org/10.1161/CIRCULATIONAHA.113.008279

V. Stackelberg O, Wolk A, Eliasson K, Hellberg A, Bersztel A, Larsson SC, Orsini N, Wanhainen A, Björck M. Lifestyle and risk of screening-detected abdominal aortic aneurysm in men – A prospective population based cohort study. [Submitted]