The Contemporary Impact of Body Mass Index on Open Aortic Aneurysm Repair

Obesity and the obesity paradox in abdominal aortic aneurysm

Obesity, characterized by its complexity and heterogeneity, has emerged as a significant public health concern. Its association with increased incidence and mortality of cardiovascular diseases stems not only from its complications and comorbidities but also from the endocrine effects of adipose tissue. Abdominal aortic aneurysm (AAA), a chronic inflammatory condition, has been closely linked to obesity. Intriguingly, mild obesity appears to confer a protective effect against AAA mortality, whereas severe obesity and being underweight do not, giving rise to the concept of the "obesity paradox". This review aims to provide an overview of obesity and its paradoxical relationship with AAA, elucidate its underlying mechanisms, and discuss the importance of preoperative weight loss in severely obese patients with AAA.

Impact of Serum Albumin Levels and Body Mass Index on Outcomes of Open Abdominal Aortic Aneurysm Repair in Korean Population

BACKGROUND

Although obese patients seem to be susceptible to chronic diseases, obesity paradox has been observed in the field of vascular surgery, in which many previous studies have reported that overweight patients have good postoperative outcomes and underweight patients have poor postoperative outcomes. The purpose of our study is to evaluate the impact of body mass index (BMI) and serum albumin levels, which are evaluated as indicators of nutritional status, on outcomes of open abdominal aortic aneurysm (AAA) repair.

METHODS

We reviewed the vascular surgery database of a single tertiary referral center for all patients who underwent open AAA repair due to degenerative etiology from 1996 to 2021. To analyze the effect of BMI, patients were classified into 4 groups according to the Asian-Pacific classification of BMI: underweight (UW) (<18.5 kg/m2), normal weight (NW) (18.5-22.9 kg/m2), overweight (OW) (23-24.9 kg/m2), and obese (OB) (≥25 kg/m2). The χ2, Fisher's exact, and Kruskal-Wallis tests were used to compare demographics, comorbidities, radiologic findings, surgical details, and 1-year mortality rates between the 4 groups. We also compared the preoperative serum albumin levels of each group to assess nutritional status indirectly. Cox's proportional hazards model was performed to determine factors associated with mortality. A Kaplan-Meier survival analysis was performed, and the differences were analyzed by a log-rank test. We did not perform an analysis for 30-day mortality because cases of 30-day mortality in UW patients were rare due to the unbalanced distribution of the number of patients in the 4 groups.

RESULTS

Among a total of 678 patients, 22 were classified as UW (3.2%), 200 as NW (29.5%), 183 as OW (27.1%), and 273 as OB (40.1%). The median age was 70 (64-75) years and 577 of 678 (85.1%) patients were male gender. Higher serum albumin level was associated with decreased 1-year mortality (hazard ratio [HR], 0.3; 95% confidence interval [CI], 0.15-0.63; P = 0.001). UW patients had a higher 1-year mortality rate than NW patients (HR, 3.67; 95% CI, 1.02-13.18; P = 0.046). OB patients had a lower overall mortality rate than NW patients (HR, 0.73; 95% CI, 0.53-1; P = 0.05).

CONCLUSIONS

Low BMI (<18.5 kg/m2) and low serum albumin level were associated with poor 1-year survival after elective open AAA repair. These patients also need more careful preoperative intervention, like weight gain or nutritional support, for better outcomes. The obesity paradox existed in our study; high BMI (≥25 kg/m2) was associated with better overall survival after elective open AAA repair.