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Operative mortality

Bariatric surgery is not associated with reduced mortality in older patients

Study finds a significant association of surgery and survival

Bariatric surgery is not associated with decreased mortality when performed on older, severely obese patients with high baseline mortality, according to a study in the June 2011 issue of the Journal of the American Medical Association.

According to the researchers, the current evidence of the survival associated with bariatric surgery is based on cohort studies of predominantly younger women with a low inherent obesity-related mortality risk, making the association of survival and bariatric surgery for older men less clear. As a result, Dr Matthew L Maciejewski, Durham VA Medical Center, Durham, NC, and colleagues conducted a study to determine whether bariatric surgery is associated with reduced mortality in a multisite cohort of predominantly older male patients who have a high baseline mortality rate.

The investigators undertook a retrospective cohort study of bariatric surgery programs in Veterans Affairs medical centres. The main outcome measure was all-cause mortality through December 2008. Mortality was examined for 850 veterans who had bariatric surgery in January 2000 to December 2006 (mean age 49.5 years; SD 8.3; mean body mass index [BMI] 47.4; SD 7.8) and 41,244 non-surgical controls (mean age 54.7 years, SD 10.2; mean BMI 42.0, SD 5.0) from the same 12 Veteran Integrated Service Networks; the mean follow-up was 6.7 years. Four Cox proportional hazards models were assessed: unadjusted and controlled for baseline covariates on unmatched and propensity-matched cohorts. 

A total of 11 of the 850 surgical case patients (1.29%) died within 30 days of surgery. The surgical case patients had lower crude mortality rates than the non-surgical controls (at one year, 1.5 % vs. 2.2%; at two years, 2.2 % vs. 4.6%; at six years, 6.8% vs. 15.2%). In unadjusted analysis, bariatric surgery was associated with reduced mortality (hazard 
ratio [HR], 0.64; 95% confidence interval [CI], 0.51-0.80). After covariate adjustment, bariatric surgery remained associated with reduced mortality (HR, 0.80; 95% CI, 0.63-0.995). However, in further analysis that included 1,694 propensity-matched patients (using a statistical approach to compare patients who appear to be ‘similar’ in many ways, except for one of the matched patients having had the operation), bariatric surgery was not significantly associated with reduced mortality in unadjusted (HR, 0.83; 95% CI, 0.61-1.14) and time-adjusted (HR, 0.94; 95% CI, 0.64-1.39) Cox regressions.

“Our results highlight the importance of statistical adjustment and careful selection of surgical and nonsurgical cohorts, particularly during evaluation of bariatric surgery according to administrative data. Previous studies claiming a survival benefit for bariatric surgery had limited clinical information to conduct detailed risk adjustment or matching,” the authors note. “The survival differences between the bariatric surgery and control groups were modest in most previous studies, so the beneficial effects of surgery may have been attenuated if adjustment for confounders had been possible. We demonstrated that risk adjustment with regression analysis resulted in a significant association of surgery and survival that was reduced when equivalence in baseline characteristics improved via propensity matching in this high-risk patient group.”

Even though bariatric surgery is not associated with reduced mortality among older male patients, the investigator stated that many patients may still choose to undergo bariatric surgery, given the strong evidence for significant reductions in body weight and co-existing illnesses and improved quality of life.

In conclusion, the researchers note that in propensity score–adjusted analyses of older severely obese patients with high baseline mortality in Veterans Affairs medical centres, the use of bariatric surgery compared with usual care was not associated with decreased mortality during a mean 6.7 years of follow-up.

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