Study results show that patients who underwent Roux-en-Y gastric bypass surgery experienced greater and more rapid weight loss at 12- and 24 months post-surgery compared to patients who received the sleeve gastrectomy procedure. GB patients also experienced a larger decrease in hemoglobin within the first two months post-surgery and a sustained decrease in creatinine.
Roux-en-Y gastric bypass surgery (GB) and the newer sleeve gastrectomy procedure (SG) are now the most common bariatric procedures used to treat obesity and its metabolic complications. It has been proposed that these surgeries result in comparable long-term outcomes.
Using data from the UMHS Post-Bariatric Surgery Program, Corey J. Lager, MD, from the Internal Medicine Department at the University of Michigan Health System (UMHS), and colleagues performed a retrospective analysis to compare weight loss and change in blood pressure, BMI, hemoglobin A1c (HbA1c), lipids and other blood indices, as well as levels of common vitamins in patients who had undergone one of the two types of surgical procedure. Serum creatinine was evaluated as an indirect measure of lean mass, although Lager said that its value as a marker is controversial.
Data were collected at baseline and 2, 6, 12, and 24 months post-surgery for a large population of patients (n=729). The analysis did not include data on immediate surgical complications and the early (30-day) post-operative period, in general. Changes between time points and baseline were compared between groups by the Wilcoxon rank sum test. Results were reported as mean±SE.
Data from 392 patients post-GB (age 44±1 years, 81% females) and 337 patients post-SG (age 45±1 years, 77% females) who had their surgeries at UHMS from 1/1/2008 to 11/20/2013 were included. To date, 269 GB and 203 SG patients have completed at least 12 months follow-up and, of these, 186 GB and 89 SG have had 24 months follow-up.
Lager noted that baseline BMI and weight were both significantly lower in the GB group compared to the SG group (respectively 47.2±0.4 kg/m2 and 133±1 kg vs. 49.8±0.5 kg/m2 and 141±2 kg, p<0.0001). Nonetheless, GB patients experienced greater and more rapid weight loss. The GB group lost 68.6±2.6 % of excess body weight by 12 months vs. 55.0±1.4 % in the SG group (p<0.0001). This difference was preserved at 24 months (65.6±4.1% vs. 52.0 ±2.2 %, respectively, p<0.0001).
HbA1c improved in both groups with a decrease of 1.40±0.2% following GB and 0.75±0.15% following SG (p=0.01 at 12 months). Serum creatinine fell more rapidly in the GB group and was sustained over the long-term while the SG group experienced a less remarkable decrease. Serum creatinine values at 12 months were 0.10±0.01 mg/dL following GB vs 0.04±0.01 following SG (p<0.0001).
Both groups showed an initial decrease in hemoglobin (Hb) at 2 months, with GB patients displaying a significantly greater fall compared to SG (1.14±0.08 g/dL vs. 0.71±0.07 g/dL; p=0.0002). Decreases in Hb levels were not protracted and had returned to baseline values by 6 months.
The clinical team did not observe a significant difference between the two groups with respect to circulating vitamin B12 or vitamin D levels either at baseline or longitudinally. However, the number of patients completing studies, especially at later time points, was insufficient for valid statistical analysis. All patients were given vitamin supplements and Lager thought that might be a factor.
Lager said that data demonstrated greater weight loss and metabolic improvements in patients undergoing GB when compared to SG after 2 years. GB patients experienced a larger decrease in hemoglobin within the first two months and a sustained decrease in creatinine.
Evaluations of immediate post-surgical complications and prospective longitudinal data are required to properly assess the risks and benefits of GB and SG procedures. In particular, the extent of malabsorption for these two procedures requires long-term studies. Future studies could include analysis of sub-groups such as patients with sleep apnea and arthritis.
During question time following his talk, a member of the audience asked what drove the selection of one procedure over the other; whether by the patient or by the surgeon. Lager showed a slide depicting the use of various bariatric procedures over time (2006-2013). He said the decision regarding choice of procedure was multifactorial but the SG procedure might be preferred for patients with lower BMI or weight.
Another questioner in the audience picked up on the point that the baseline characteristics of the two populations were counter-intuitive in that patients in the GP group had lower mean values for BMI and weight.
The use of both gastric bypass and adjustable gastric banding has declined over this period while the use of the newer procedure, sleeve gastrectomy, has increased to a striking degree (p<0.001). Duodenal switch procedures have remained at a low frequency.
In response to another question, Lager said he was not aware of any data in the literature specific to various ethnic groups and their preferred