bariatric surgery reduces death rates overall - but what are the caveats?

Many studies have reported lower death rates in people who have had bariatric surgery, compared with BMI-matched patients who haven’t had surgery.

A recent retrospective database study from Utah, USA, looked at up to 40 years of data (median 13 years) in patients who had undergone bariatric surgery between 1982 and 2018, providing the largest and longest data on the effects of bariatric surgery on death rates. They matched patients by BMI, age, and gender with controls from the database who did not have bariatric surgery.

In this database of over 21,000 patients who had bariatric surgery, most had gastric bypass surgery (69%), 14% had sleeve gastrectomy, 12% gastric banding, and 5% duodenal switch. They found that amongst people who had bariatric surgery, compared to people who hadn’t had surgery:

all-cause mortality (death) was reduced by 16% (14% in women, 21% in men)
death from cardiovascular disease was reduced by 29%
death from cancer was reduced by 43%
diabetes-related death was reduced by 72%
death from chronic lung disease was reduced by 39%
mean survival time was 1.3 years longer

However, some concerning findings arose as well:

The reduction in all cause mortality was only in people over age 34 at the time of surgery. People age 18-34 at the time of bariatric surgery had a higher death risk, due to higher risk of death from external causes (which were categorized in the database to include things like injury, poisoning, and suicide).
The risk of suicide was 2.4 times higher in people who had bariatric surgery, driven by a higher risk in people who were 18-34 years old at the time they had bariatric surgery.
Death from chronic liver disease was 83% higher amongst people who had bariatric surgery, driven by a higher risk in patients age 18-34 at the time of bariatric surgery (in whom the risk was over 7 times higher than those of the same age who hadn’t had surgery).

While the study findings are encouraging and positive overall, the findings of higher suicide risk, in people who were younger at the time of surgery in particular, are clearly concerning.

The Canadian Obesity Guidelines chapter that guides us on the post bariatric surgery journey advises:

Clinicians should be aware of the potential post-bariatric psychological issues that may arise, including depression, suicide, body image disorder, eating disorders, and substance and alcohol abuse. Reuslts from bariatric surgery may not meet a patient’s expectations or may not lead toward hoped improvements in quality of life, thus impacting mood.

It is unclear why people who were younger at the time of surgery also had a higher long term risk of death from liver disease. Weight loss from bariatric surgery is generally associated with improvement in liver health, due to improvement in fatty liver disease. However, there is a higher risk of alcohol abuse after bariatric surgery due to increased absorption rates from the intestine, as well as increased impulsivity and disinhibition, and mental health concerns that have been noted in other studies after bariatric surgery. It is also possible that those who died from liver disease may have had liver cirrhosis prior to surgery, which would be less likely to benefit from surgically-induced weight loss. Details about liver disease and alcohol were not available in this study.

BOTTOM LINE: The long term benefits of bariatric surgery suggested by this study to decrease overall death risk as well as death specifically from diabetes, cancer, cardiovascular disease, and lung disease, are impressive. Extra caution should be taken in younger folks to continue to support mental health in the long term after surgery. More data is needed to understand the effect of bariatric surgery on the liver, and the potential role of alcohol consumption.

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