Does bariatric surgery reduce all-cause mortality?

This nonrandomized controlled trial showed that bariatric surgery results in sustained weight loss of 14% to 25% after 10 years and also reduces all-cause mortality. (LOE = 2b)

Sjostrom L, Narbro K, Sjostrom CD, et al, for the Swedish Obese Subjects Study. Effects of bariatric surgery on mortality in Swedish obese subjects. N Engl J Med 2007;357:741-752.  [PMID:17715408]

Non-randomized controlled trial

Industry + govt

Population-based

This study reports 10-year outcomes for the largest prospective study of bariatric surgery. This is not a randomized controlled trial -- patients were recruited from the general public, and if they chose surgery, a matching control patient was selected from the group that refused surgery. Case patients and control patients were matched on 18 factors, including age, body mass index (BMI), smoking status, comorbidities, and body measurements. All men had a BMI of at least 34 kg/m2 and all women had a BMI of at least 38 kg/m2. Patients were recruited between 1987 and 2001, and were followed up for between 4 years and 18 years (mean = 10.9 years). The matching was not perfect -- there were statistical differences between groups on the matching variables -- but these differences were small and not likely to be clinically important. Deaths were determined from the Swedish population and address registry, and emigrants were successfully tracked by contacting relatives and embassies around the world. In the surgery group, 376 had banding, 1369 had vertical-banded gastroplasty (VBG), and 265 had gastric bypass. Initial weight loss differed by procedure: 20% for banding, 25% for VBG, and 32% for gastric bypass. After 10 years, patients had regained some of the weight but the weight gain stabilized at approximately 8 years. Weight loss at 10 years was 14% for banding, 16% for VBG, and 25% for gastric bypass. All-cause mortality was lower in the bariatric surgery group (5.0% vs 6.3%; P = .04; number needed to treat to prevent 1 death at 10 years = 77). A multivariate analysis also showed that bariatric surgery was an independent predictor of lower all-cause mortality (hazard ratio = 0.73; 95% CI, 0.56 - 0.95). The difference in death rates was largely due to fewer myocardial infarctions and deaths due to cancer in the bariatric surgery group.