Obesity has long been considered a risk factor for postoperative adverse events in surgery. We sought to study the impact of body mass index (BMI) on the clinical outcomes of the high-risk emergency general surgery (EGS) elderly patients.
All EGS ≥65 years old patients in the 2007-2016 ACS-NSQIP database, identified using the variables ’emergency’ and ‘surgspec,’ were included. Patients were classified into five groups: normal weight: BMI <25 kg/m, overweight: BMI ≥25 kg/m and <30 kg/m, Class I: BMI ≥30 kg/m and <35 kg/m, Class II: BMI ≥35 kg/m and <40 kg/m, and Class III: BMI ≥40 kg/m. Patients with BMI<18.5 kg/m were excluded. Multivariable logistic regression models were built to assess the relationship between obesity and 30-day postoperative mortality, overall morbidity, and individual postoperative complications after adjusting for demographics (e.g., age, gender), comorbidities (e.g., diabetes mellitus, heart failure), laboratory tests (e.g., white blood cell count, albumin), and operative complexity (e.g., ASA classification).
A total of 78,704 patients were included, of which 26,011 were overweight (33.1%), 13,897 (17.6%) had Class I obesity, 5904 (7.5%) had Class II obesity, and 4490 (5.7%) had Class III obesity. On multivariable analyses, compared to the nonobese, patients who are overweight or with Class I-III obesity paradoxically had a lower risk of mortality, bleeding requiring transfusion, pneumonia, stroke and myocardial infarction (MI). Additionally, the incidence of MI and stroke decreased in a stepwise fashion as BMI progressed from overweight to severely obese (MI: OR: 0.84 [0.73-0.95], OR: 0.73 [0.62-0.86], OR: 0.66 [0.52-0.83], OR: 0.51 [0.38-0.68]; stroke: OR: 0.80 [0.65-0.99], OR: 0.79 [0.62-1.02], OR: 0.71 [0.50-1.00], OR: 0.43 [0.28-0.68]).
In our study of elderly EGS patients, overweight and obese patients had a lower risk of mortality, bleeding requiring transfusion, pneumonia, reintubation, stroke, and MI. Further studies are needed to confirm and investigate the obesity paradox in this patient population.

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