Mortality is much lower in obese patients who have obesity surgery compared with those who don't

Obesity is associated with increased mortality in numerous diseases. Bariatric surgery has shown to prevent obesity related mortality and morbidity. However, there is a lack of population-based prospective studies examining overall mortality in patients who undergo gastric bypass. The objective of this study was to assess overall mortality in obese individuals undergoing bariatric surgery compared to non-surgical obese patients.

From the Swedish Patient registry, a person-based register of all hospitalisations and hospital-based outpatients' visits in Sweden, the authors created a cohort including all patients with a principal diagnosis of obesity (meaning this was the main cause of their hospital visit) in Sweden from 2000 until 2011. The study population comprised 48,693 patients 18-74 years of whom 22,581 underwent bariatric surgery (gastric bypass 92.8%) while there were 26,112 obese patients who did not undergo surgery.

The mortality rate was higher in the non-surgical group (4.21%) compared to the surgical group (1.11%) (7.7 vs. 2.1 deaths per 1000 people per year). Mean follow-up time for the surgical group was 5.4 years and 5.5 for the non-surgical group. The overall mortality decreased by 57% in the surgery group (age adjusted hazard ratio 0.43) compared with the non-surgical group. This 57% reduction was the same when adjusting for age alone or age and previous comorbidity and other factors (including sex, coronary heart disease, valvular disease, cancer, hypertension, diabetes, heart failure, stroke and atrial fibrillation).

The most common cause of death in the non-surgical group was cardiovascular disease, followed by cancer. In the surgical obese patients, the most common cause of death was external causes of mortality (such as accidents and suicide), followed by cardiovascular disease and cancer. Although accidents and suicide were the main causes of death in the surgical group, the incidence of death from these causes was still lower than in the non-surgical group.

The authors conclude: "This population-based cohort observational study indicates that the overall all-cause mortality is considerably lower among obese individuals who undergo bariatric surgery compared to non-surgical obese individuals, and the differences lies mainly in cardiovascular disease and cancer."