A Cochrane review [Abstract] 1 included 22 studies with 1798 participants. Most studies followed participants for 12, 24 or 36 months; the longest follow-up was 10 years.
All 7 RCTs comparing surgery with non-surgical interventions found benefits of surgery on measures of weight change at 1 to 2 years follow-up. Improvements for some aspects of health-related quality of life (QoL) (two RCTs) and diabetes (5 RCTs) were also found. Five studies reported data on mortality, no deaths occurred. Serious adverse events (SAEs) were reported in four studies and ranged from 0% to 37% in the surgery groups and 0% to 25% in the no surgery groups. Between 2% and 13% of participants required reoperations in the five studies that reported these data.
Three RCTs found that laparoscopic Roux-en-Y gastric bypass (LRYGB) achieved significantly greater weight loss and body mass index (BMI) reduction up to 5 years after surgery compared with laparoscopic adjustable gastric banding (LAGB). Mean end-of-study BMI was lower following LRYGB compared with LAGB: mean difference (MD) -5.2 kg/m² (95% CI -6.4 to -4.0; 265 participants; 3 trials). The LRGYB procedure resulted in greater duration of hospitalisation in 2 RCTs (4/3.1 versus 2/1.5 days) and a greater number of late major complications (26.1% versus 11.6%) in one RCT. In one RCT the LAGB required high rates of reoperation for band removal (9 patients, 40.9%).
Open RYGB, LRYGB and laparoscopic sleeve gastrectomy (LSG) led to losses of weight and/or BMI but there was no consistent picture as to which procedure was better or worse in the 7 included trials. MD was -0.2 kg/m² (95% CI -1.8 to 1.3); 353 participants; 6 trials; in favour of LRYGB. No statistically significant differences in QoL were found (one RCT). Six RCTs reported mortality; one death occurred following LRYGB. SAEs were reported by one RCT and were higher in the LRYGB group (4.5%) than the LSG group (0.9%). Reoperations ranged from 6.7% to 24% in the LRYGB group and 3.3% to 34% in the LSG group. Effects on comorbidities, complications and additional surgical procedures were neutral, except gastro-oesophageal reflux disease improved following LRYGB (one RCT). One RCT of people with a BMI 25 to 35 and type 2 diabetes found laparoscopic mini-gastric bypass resulted in greater weight loss and improvement of diabetes compared with LSG, and had similar levels of complications.
Two RCTs found that biliopancreatic diversion with duodenal switch (BDDS) resulted in greater weight loss than RYGB in morbidly obese patients. End-of-study mean BMI loss was greater following BDDS: MD -7.3 kg/m² (95% CI -9.3 to -5.4); 107 participants; 2 trials). QoL was similar on most domains. In one study between 82% to 100% of participants with diabetes had a HbA1c of less than 5% three years after surgery. Reoperations were higher in the BDDS group (16.1% to 27.6%) than the LRYGB group (4.3% to 8.3%). One death occurred in the BDDS group.
A meta-analysis 2 analyzing the association of bariatric surgery with long-term mortality and incidence of new-onset obesity-related disease included 18 studies with 269 818 patients receiving bariatric surgery and 1 270 086 controls. Follow-up varied from 18 to 144 months. Bariatric surgery was associated with a reduced rate of all-cause mortality (OR 0.62, 95% CI 0.55 to 0.69, p < 0.001) and cardiovascular mortality (OR 0.50, 95% CI 0.35 to 0.71, p < 0.001). Bariatric surgery reduced incidence of T2DM (OR 0.39, 95% CI 0.18 to 0.83, p = 0.010), hypertension (OR 0.36, 95% CI 0.32 to 0.40, p < 0.001), dyslipidaemia (OR 0.33, 95% CI 0.14 to 0.80, p = 0.010), and ischemic heart disease (OR 0.46, 95% CI 0.29 to 0.73, p = 0.001).
A meta-analysis of matched cohort and prospective controlled studies 3 included 16 sudies with 174 772 participants. Bariatric surgery was associated with a reduction in hazard rate of death of 49.2% (95% CI 46.3 to 51.9, p<0·0001) and median life expectancy was 6.1 years (95% CI 5.2 to 6.9) longer than usual care. In subgroup analyses, both individuals with (HR 0.41, 95% CI 0.37 to 0.45, p<0·0001) or without (HR 0.70, 95% CI 0.59 to 0.84, p<0·0001) diabetes had lower rates of all-cause mortality, but the treatment effect was considerably greater for those with diabetes (between-subgroup I2 95.7%, p<0·0001). Median life expectancy was 9.3 years (95% CI 7.1 to 11.8) longer for patients with diabetes in the surgery group than the non-surgical group, whereas the life expectancy gain was 5.1 years (2.0 to 9.3) without diabetes. The numbers needed to treat to prevent one additional death over a 10-year time frame were 8.4 for adults with diabetes and 29.8 for those without diabetes. Treatment effects did not appear to differ between gastric bypass, banding, and sleeve gastrectomy.
A systematic review and meta-analysis 4 included 39 studies (all prospective or retrospective cohort studies, no RCTs were available). Bariatric surgery was associated with a beneficial effect on all-cause mortality [pooled HR of 0.55; 95% CI 0.49 to 0.62, P < 0.001 vs. controls], CV mortality (HR 0.59, 95% CI 0.47 to 0.73, P < 0.001), HF (HR 0.50, 95% CI 0.38 to 0.66, P < 0.001), myocardial infarction (HR 0.58, 95% CI 0.43 to 0.76, P < 0.001), and stroke (HR 0.64, 95% CI 0.53 to 0.77, P < 0.001).
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