Impact of obesity on postoperative and long-term outcomes in a general surgery population: a retrospective cohort study

Abstract

Background: The obesity paradox has been demonstrated postoperatively in several surgical populations, but only a few studies have reported long-term survival. This study evaluates the presence of the obesity paradox in a general surgery population, reporting both postoperative and long-term survival.

Methods: This retrospective study included 10,427 patients scheduled for elective, noncardiac surgery. Patients were classified as underweight (body mass index (BMI) < 18.5 kg/m(2)); normal weight (BMI 18.5-24.9 kg/m(2)); overweight (BMI 25.0-29.9 kg/m(2)); obesity class I (BMI 30.0-34.9 kg/m(2)); obesity class II (BMI 35.0-39.9 kg/m(2)); and obesity class III (BMI ≥ 40.0 kg/m(2)). Study endpoints were 30-day postoperative and long-term mortality, including cause-specific mortality. Multivariable analyses were used to evaluate mortality risks for each BMI category.

Results: Within 30 days after surgery, 353 (3.4 %) patients died. Overweight was the only category associated with postoperative mortality, showing improved survival [odds ratio 0.7; 95 % confidence interval (CI) 0.6-0.9]. During the long-term follow-up 4,884 (47 %) patients died. Underweight patients had the highest mortality risk [hazard ratio (HR) 1.4; 95 % CI 1.2-1.6), particularly due to high cancer-related deaths. In contrast, overweight and obese patients demonstrated improved survival (overweight: HR 0.8, 95 % CI 0.8-0.9; obesity class I: HR 0.7, 95 % CI 0.7-0.8; obesity class II: HR 0.7, 95 % CI 0.6-0.9; obesity class III: HR 0.7, 95 % CI 0.5-1.0), mainly because of a strongly reduced risk of cancer-related death.

Conclusions: In this surgical population the obesity paradox was validated at the long term, mainly because of decreased cancer-related deaths among obese patients.