Abstract P203: Demographic Predictors of Long-term Weight Loss Beginning One-Year After Bariatric Surgery at Two Medical Centers

Abstract

Objective: Existing studies of predictors of weight loss after bariatric surgery suffer from simplistic statistical methods and relatively short follow-up. We sought to determine predictors of long-term weight loss up to 9.6 years after bariatric surgery using data extracted from two electronic health records (EHR) systems and linear mixed effects models. Methods: Participants were selected from patients enrolled in the NUgene biorepository at either Northwestern Memorial HealthCare or NorthShore University HealthSystem. Individuals who had undergone Roux-en-Y gastric bypass (RNY) were identified through billing or surgical history procedure codes in the electronic health records (EHRs). All available weight measurements and dates were extracted from the EHR as well as surgery date. Sex, race/ethnicity, education, marital status, and height were taken from the NUgene intake questionnaire. SAS PROC MIXED was used to create linear mixed effects models to examine weight loss from 1- 9.6 years post-surgery. To examine overall weight loss and slope of weight regain, covariates and covariate interactions with time post-surgery were included in the mixed effects models. Results: 119 individuals from Northwestern and 43 individuals from NorthShore had undergone gastric bypass and had at least 1 weight measurement 1 year post-surgery. There were 3071 weight measurements which occurred at least 1 year post-surgery in the dataset; the median number of observations per person was 10 and the median weight loss represented by these measurements was 32.7% from pre-surgical weight. The regression model indicated that, on average, individuals experienced slight weight regain of about 0.8% of pre-surgical weight per year after their first year post-surgery. Over the 1- 10 years of follow up African Americans lost nearly 5 percentage points less weight than whites ( p =.0025) . People who were older and taller also experienced less percentage weight loss, and people with higher initial weights experienced a higher percentage weight loss (all p <.05), Older age was associated with significantly (p<0.05) slower weight regain after 1 year post-surgery. Discussion: EHR records from multiple institutions can be integrated to study outcomes after bariatric surgery. Demographic factors predict overall weight loss and a rate of weight regain after 1 year post RNY surgery. This information may be useful for both surgeons and prospective patients.