The non-randomized study, published in The New England Journal of Medicine, followed 5,182 middle-age people over a median of 24 years.
The adjusted median life expectancy among the 2,007 volunteers who had received the surgery was 3.0 years longer than for the 2,040 patients who had received standard non-surgical obesity care.
The 1,135 people in a random sampling of the general population lived 8.5 years longer than the usual care group.
"Now, for the first time, we've got a measure of how much bariatric surgery prolongs life expectancy for the average patient," chief author Dr. Lena Carlsson of the University of Gothenburg told Reuters Health in an email.
"One important finding was that many of the causes of death in the surgery group that exceeded those in the general population are preventable," she said. "This gives doctors the opportunity to increase life expectancy after surgery even more if appropriate postoperative follow-up is offered to patients."
The surgery seemed to benefit people across the board.
"In our study we have a lot of information about the participants, and we were hoping to find markers that could help us identify patients with increased treatment benefit from bariatric surgery," said Dr. Carlsson, a professor of clinical metabolic research at Sahlgrenska Academy. "However, the treatment benefit was surprisingly similar in subgroups defined by risk factors such as BMI (body-mass index) and classical cardiovascular risk factors."
The average BMIs started off at 42.4 in the people who had chosen surgery and 40.1 in the control group recruited at the same time. A BMI of 40 or higher is considered severely obese. The BMI in the general population group was 25.1, which is borderline overweight. Thirty or higher is considered obese.
Patients who underwent surgery ended up with a mean body-mass index of about 35. For patients in the control group it was about 42. To enroll, the BMI for men to be at least 34 and for women it was at least 38.
Surgery included banding (done for 18% of patients), gastric bypass (13%), or vertical banded gastroplasty (69%).
Because the study was not randomized, there were some key differences in the groups. The patients in the surgery group were much more likely to have hypertension and diabetes, have a lower level of education, be a smoker, be younger and have a higher starting BMI than the control group.
The patients were not randomized because when the study began in 1987, postoperative mortality after bariatric surgery was high, making it unethical to randomly assign someone to that treatment group.
The Carlsson team said the number of deaths per 1,000 persons per year was 5.2 in the general population group, 10.7 in the surgery group and 13.2 in the control group.
Compared to the control group, surgery lowered mortality by 23%. It was 56% lower in the general population.
Compared to obese patients who did not undergo surgery, people who received bariatric surgery saw their risk of fatal heart problems drop by 26%, their odds of a fatal stroke plummet by 55% and their chance of death by cancer fall by 24%.
Dr. Carlsson said she hopes the study "increases the awareness that post-operative care needs a stronger focus on the preventable conditions that are responsible for the remaining excess mortality in patients who have undergone bariatric surgery."
By Gene Emery
SOURCE: https://bit.ly/33LxOcw The New England Journal of Medicine, online October 14, 2020.
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