Introduction: Mortality decreases following bariatric surgery. We explored the extent of the reduction and whether or not it reaches the general population level in a large cohort of patients with obesity. This study aimed to compare all-cause mortality between patients with obesity who undergo bariatric surgery and those who do not, with the general Iranian population during the same period.

Method: Data from Iran's National Obesity Surgery Database were used to establish a large cohort of patients registered between 2009 and 2019. The current vital status of the patients was determined by utilizing post-surgery follow-up data for those who underwent the operation. For patients without a surgery record, a predefined checklist was filled out through telephone interviews. Death data from the National General Registrar's office were obtained for all cohort members.

Results: Of 13,313 cohort members, 12,915 were eligible for analysis. The median age at the first visit was 38 years, and 78% were women. 6,190 patients (47.9%) underwent bariatric surgery, and 6,725 patients (52.1%) were not yet operated on at the time of analysis. We observed 139 deaths during 53,880 person-years follow-ups. The median follow-ups for operated-on and not operated-on groups were 4 and 4.8 years. The mortality rates among nonoperated patients were 2.89 times higher (standardized mortality ratio [SMR] = 2.89, 95% CI: 2.36-3.53) than those in the general population, while in operated patients, the mortality rate decreased to 1.82 as high (SMR = 1.82, 95% CI: 1.34-2.46).

Conclusion: The risk of death has been diminished in the operated-on group. It still remains considerably higher than the risk in the general population.