Predictors of successful weight loss following bariatric surgery.

Linden A Karas, MD1, Madhu Siddeswarappa, MD1, Jean-Gabriel Coignet, BA1, Stephen D Slane, PhD2, Prashanth Ramachandra, MD1. 1Mercy Catholic Medical Center, 2Cleveland State University

Objective: Recent research has focused on both pre- and post-surgical behavioral factors as they influence weight loss outcomes after bariatric surgery, and there has been a shift away from examining demographic indicators, and intra-operative and early post-surgical factors as predictors of surgical outcome (A.H. Robinson et al in 2014, M Livhits et al in 2011). Therefore, the objective of this study was to determine which demographic and medical variables predict successful weight loss outcomes following bariatric surgery in a socially diverse patient population.

Methods: An analysis was performed of a retrospectively compiled database of all patients who have undergone bariatric surgery (including laparoscopic and open gastric banding, sleeve gastrectomy, Roux en Y gastric bypass, and revisional bariatric surgery) between February 2012 and March 2014 at a community hospital Bariatric Center of Excellence in Philadelphia, PA. Factors examined included age (mean 44.37, SD 11.9), gender, ethnicity, type of surgery, duration of anesthesia (mean 230 minutes, SD 70.8), American Society of Anesthesiologist (ASA) class, hospital length of stay (LOS) (mean 2.8 days, SD 4.7), public versus private insurance (which may indicate socioeconomic status), marital status, and number (mean 3.9, SD 2) and type of preoperative medical co-morbidity. Weight loss outcomes were collected as % excess weight loss (%EWL), % excess BMI loss (%EBMI), actual weight pre-operatively and post-operatively, and actual initial and post-operative BMI during a follow up period of three months to two years. Regression analysis was performed to determine factors predictive of better weight loss outcomes.

Results: Shorter duration of anesthesia (DOA), younger age, type of insurance (private better than public), and Caucasian race predicted significantly better weight loss following all types of bariatric surgery at one year. These three factors together accounted for 9.4% of variance in %EWL, 2.3% of variance in %EBMI, 12.8% of variance in actual weight, and 6.4% of variance in actual BMI at one year. Further, these four variables continued to be strong statistically signficant predictive factors at 1.5 years, predicting 2.1-17% of the variance the different markers of weight loss studied. Finally, a discriminative function test was performed confirming the above results; shorter DOA, younger age, private insurance, and Caucasian race correctly predicted successful post-operative weight loss at one and 1.5 years (defined as greater than or equal to 50% EWL) in 85% of cases.

Conclusion: As opposed to subjective behavioral factors, this study presents static preoperative demographic and surgical variables that can be used to predict successful weight loss following bariatric surgery. The identification of these strongly predictive elements may improve patient selection and intraoperative decision-making for bariatric surgery.

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