Bariatric Surgery Improves Survival in Obese Patients

August 22, 2007 — Bariatric surgery in obese patients is linked to a reduction in overall mortality, according to the results of a prospective, controlled cohort study published in the August 23 issue of the New England Journal of Medicine.
"Obesity is associated with increased mortality," write Lars Sjöström, MD, PhD, from the Sahlgrenska Academy at Gothenburg University in Sweden, and colleagues from the Swedish Obese Subjects Study. "Weight loss improves cardiovascular risk factors, but no prospective interventional studies have reported whether weight loss decreases overall mortality. In fact, many observational studies suggest that weight reduction is associated with increased mortality."
Of 4047 obese subjects enrolled in the Swedish Obese Subjects Study, 2010 underwent bariatric surgery and 2037 received conventional treatment. The primary outcome measure was overall mortality during an average follow-up of 10.9 years, with a follow-up rate of 99.9%.
During the period in which weights were recorded (up to 15 years), average weight change in control subjects was less than ±2%. In the surgical group, maximum weight losses occurred after 1 to 2 years: 32% for gastric bypass, 25% for vertical-banded gastroplasty, and 20% for banding. Weight loss from baseline stabilized in these groups after 10 years at 25%, 16%, and 14%, respectively.
In the control group, there were 129 deaths, compared with 101 deaths in the surgery group, yielding an unadjusted overall hazard ratio (HR) of 0.76 (P = .04). After adjustment for sex, age, and risk factors, the HR was 0.71 (P = .01).
The most frequently observed causes of death were myocardial infarction, occurring in 25 subjects in the control group and in 13 subjects in the surgery group, and cancer, occurring in 47 vs 29 subjects, respectively.
"Bariatric surgery for severe obesity is associated with long-term weight loss and decreased overall mortality," the authors write. "Further studies are needed to elucidate the mechanisms through which bariatric surgery leads to decreased mortality."
Study limitations include inability to evaluate the effects of weight loss on death rate separately within the 2 study groups because of limited statistical power, insufficient power to evaluate body mass index (BMI) or age subgroups, exclusion of subjects younger than 37 years, and absence of randomization.
Hoffmann–La Roche, AstraZeneca, Cederroth, and the Swedish Medical Research Council supported this study. Some of the authors have disclosed various financial arrangements, including employment in some cases, with sanofi-aventis, Ethicon, AstraZeneca, Biovitrum, Bristol-Myers Squibb, GlaxoSmithKline, Johnson & Johnson, Lenimen, Merck, Novo Nordisk, Hoffmann–La Roche, Pfizer, Servier, Progenit, NMCT, Lenimen, PMCT, and/or Sahltech.
In an accompanying editorial, George A. Bray, MD, from the Pennington Biomedical Research Center at Louisiana State University in Baton Rouge, notes that another study in the same issue shows that weight loss saves lives in obese patients.
"Has the time come to reconsider BMI guidelines for bariatric surgery?" Dr. Bray writes. "In addition to the improvement in the risk of diabetes, the reduction in deaths from cancer may also argue in this direction.... Thus, the question as to whether intentional weight loss improves life span has been answered, and the answer appears to be a resounding yes."
Dr. Bray has disclosed receiving consulting fees and grant support from Merck, consulting fees from Amylin and Wyeth, lecture fees from sanofi-aventis, and a travel grant from GlaxoSmithKline.
N Engl J Med. 2007;357:741-752, 818-820.