Preoperative Hemoglobin A1c Predicts Postoperative Weight Loss following Bariatric Surgery in Patients with Diabetes

Consensus on whether preoperative (pre-op) hyperglycemia predicts adverse surgical outcomes is lacking. The objective of the study was to evaluate the relationship between pre-op HbA1c and postoperative (post-op) surgical outcomes in patients with diabetes mellitus (DM). Patients who underwent bariatric surgery between January 2000 and April 2017 and met the diagnostic criteria of DM and had pre-op HbA1c measures were studied. Logistic and GEE linear regression were used to examine the association between pre-op HbA1c and post-op morbidity and mortality and percentage weight loss (%WL) at 30 days and 1 year. A total of 2173 patients (mean age 48.6 ± 10.6, pre-op weight: 297.5 ± 60.3 lb, 75% females) were evaluated. Among them, 49.6% had HbA1c of < 7%, 26.4% had HbA1c 7-8%, and 23.9% had HbA1c > 8%. The incidence of 30-day complications (readmission, reoperation, bleeding, pulmonary embolism, leak) was 6.1% and 30-day mortality was 0.1%. These rates did not differ between HbA1c groups or between Roux-en-Y gastric bypass (RYGB), sleeve gastrectomy (SG), gastric band, and duodenal switch (DS) procedures. There was no significant association between pre-op HbA1c and complication rates or %WL at 30 days post-op. However, we detected an association between HbA1c and 1-year %WL (p = 0.014) in that 1% increase in pre-op HbA1c was associated with 0.74% less WL at 1 year after adjusting for confounders (95% CI: -1.08% to -0.41%, p < 0.0001). Females lost less weight than males (p = 0.0009) and patients with ≥ 1 anti-hypertensive medications pre-op lost less weight than those without (p < 0.0001) at 1 year. Furthermore, patients operated with DS lost more while those with SG and banding lost less weight than with RYGB.

In conclusion, pre-op HbA1c was not associated with post-op morbidity or mortality but it is a significant predictor for post-op WL at 1 year. Our data suggest that tighter glycemic control pre-op may lead to better weight loss outcomes after bariatric surgery in patients with DM.