The impact of obesity on postoperative outcomes following surgery for colorectal cancer: analysis of the National Inpatient Sample 2015-2019

Background: The global burden of obesity has reached epidemic proportions, placing great strain on the North American healthcare system. We designed a retrospective cohort database study comparing postoperative morbidity and healthcare resource utilization between patients living with and without obesity undergoing surgery for colorectal cancer. Methods: Adult patients undergoing resection for colorectal cancer were identified from the 2015 to 2019 National Inpatient Sample database. Patients were stratified according to obesity status (i.e., body mass index of 30 kg/m2). Propensity score matching (PSM) with 1:1 nearest-neighbour matching was performed according to demographic, operative, and hospital characteristics. The primary outcome was postoperative morbidity. Secondary outcomes included system-specific postoperative complications, postoperative mortality, length of stay, total admission healthcare cost, and post-discharge disposition. McNemar's and Wilcoxon matched pairs signed rank tests were performed. Results: After PSM, 7565 non-obese and 7565 obese patients were included. Patients with obesity had a 10% increase in relative risk of overall in-hospital postoperative morbidity (23.1% versus 25.6%, P = 0.0015) and a $4564 increase in hospitalization cost ($70 248 USD versus $74 812 USD, P = 0.0004). Patients with obesity were more likely to require post-operative ICU admission (5.0% versus 8.0%, P < 0.0001) and less likely to be discharged home after their index operation (68.3% versus 64.2%, P = 0.0022). Conclusion: Patients with obesity undergoing surgery for colorectal cancer may be at an increased risk of in-hospital postoperative morbidity. They may also be more likely to have increased hospitalization costs, post-operative ICU admissions, and to not be discharged directly home. Preoperative optimization via weight loss strategies should be further explored.