Protective effect of overweight status in aortic valve surgery: revisiting the obesity paradox

To investigate the relationship between body mass index (BMI) and postoperative mortality in patients undergoing aortic valve surgery, with an emphasis on exploring the presence and limits of the "obesity paradox", the phenomenon wherein overweight and mildly obese patients may experience lower mortality despite obesity's general association with adverse health outcomes.

The Nationwide Inpatient Sample (NIS) database was used to obtain data from adult patients who underwent aortic valve surgery between 2016 and 2020. BMI categories, as well as comorbidities, were identified using ICD-10 codes. Mortality rates across BMI categories were compared, and multivariate analysis was performed to adjust for comorbid conditions. This is a retrospective observational study.

We found 301,250 adult patients who underwent aortic valve surgery. Normal weight patients (n=226,490) had a mortality rate of 3.79%. Overweight (n=2,555) and obese (n=46,320) patients demonstrated significantly lower mortality rates of 1.17% (OR=0.30, 95% CI: 0.14-0.66; P=0.003) and 2.43% (OR=0.63, 95% CI: 0.55-0.73; P<0.001), respectively. Cachectic patients (n=835) had the highest mortality rate at 14.97% (OR=4.47, 95% CI: 2.87-6.96; P<0.001). Morbidly obese patients (n=25,450) had a mortality rate of 4.13%, which was not significantly different from normal-weight patients (OR=1.09, 95% CI: 0.94-1.26; P=0.23). These trends and statistical significance remained after multivariate logistic regression, accounting for demographics and comorbidities.

The partial obesity paradox is true in patients undergoing aortic valve surgery, with the lowest mortality occurring in overweight patients, followed by obese patients, and with cachexia having the highest mortality out of all groups.