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Yang et al. Mini-invasive Surg 2021;5:11 I http://dx.doi.org/10.20517/2574-1225.2021.06 Page 3 of 12

METHODS
Study design
This was a retrospective cohort study in Chinese patients who underwent an RYGB procedure between
April 2009 and December 2014 at five Chinese academic urban hospitals and returned for follow-up
approximately one-year post-surgery. This study was approved by each site’s ethics committee, including
a waiver for informed consent due to the retrospective nature of this study. The study was registered at
ChiCTR.org.cn (#ChiCTR-OOC-15006387). The study was reported in accordance with the STROCSS
[14]
guideline checklist .
The inclusion criteria were: (1) underwent an RYGB procedure; (2) aged 20-60 years; and (3) had outcome
data recorded [at least one of glycated hemoglobin (HbA1c), fasting plasma glucose, or fasting insulin
levels] in their medical charts at approximately 12 months after surgery.

Study interventions
All participating hospitals assessed each patient who underwent RYGB through a multidisciplinary and
integrated health unit, including a bariatric surgeon, endocrinologist, psychiatrist, cardiologist, and
dietician. Weight, BMI, T2DM duration, anthropometric measures, systolic and diastolic blood pressures,
glycemic control (HbA1c, fasting blood glucose, and insulin), lipid profile, and other laboratory and clinical
evaluations recorded in the patient’s medical record were analyzed. Given the retrospective design, not all
outcome measures were available for all patients, and those outcomes available were not always available at
all study time points.

Outcomes
The primary outcome was the resolution of T2DM. The secondary outcomes were weight reduction,
improvements in glycemic control, vital signs, blood lipids, liver function, and adverse events (AEs).

Statistical analysis
The study was not statistically powered, and data from all patients who had an RYGB procedure during
the study period and met the eligibility criteria were analyzed. For the total study population, interest
focused on changes in anthropometric characteristics, vital signs, glycemic parameters, serum lipids, and
liver function tests. In addition, for subjects with T2DM, changes in concomitant T2DM medication were
of interest as well as the remission of T2DM, which was defined as fasting glucose levels < 110 mg/dL and
HbA1c < 6.0% without the use of anti-hyperglycemic agents (AHAs) at 12 months after surgery.

Summary statistics for the outcome parameters were calculated, as well as their change from baseline. For
all analyses, baseline was defined as the last available measurement taken on or before the date of RYGB
surgery. For the mean change from baseline, 95% confidence intervals were estimated, and the one-sample
t-test or the Wilcoxon rank-sum test was applied. No multiplicity adjustments were made to P-values for
testing the change from baseline. Given the retrospective design of the study and sparseness of data at
all available time points post-surgery for some parameters, the last observation carried forward (LOCF)
approach was used. For each parameter, the latest value observed in the first 12 months after surgery was
identified and used to evaluate the change from baseline to Month 12. Change in BMI was summarized
by baseline BMI subgroup based on the WHO cutoff points. A significance level of 0.05 was considered
statistically significant, and all reported p-values are nominal P-values.

To explore which factors could be associated with T2DM remission or non-remission, univariable
and multivariable analyses were performed. Summary statistics for baseline demographic and clinical
characteristics as well as post-surgery weight and BMI change were generated for patients with and without