Seeking Perfect Knowledge of Bariatric Surgery

Is some knowledge ever enough? A new study in the Journal of the American Medical Association begs that question. Researchers found that patients with diabetes and obesity were less likely to die or have other major bad outcomes if they have bariatric surgery. The list of bad outcomes includes heart attacks, strokes, heart failure, kidney disease, and AFib. No doubt, these are great results. But they fall short of providing perfect knowledge. That’s because the study is an observational study. People don’t like getting a random assignment to have surgery. That’s why randomized surgery trials are challenging to do.

So, we must ask. Are these results good enough to make surgery a preferred treatment for some people with obesity and diabetes?

Voting Yes

A self-described curmudgeon, Edward Livingston says yes. “It should be the preferred treatment option for carefully selected, motivated patients,” he writes in a JAMA editorial. Cutting the risk of all these bad outcomes by nearly half is “a big deal,” he says.

The study’s senior author, Steven Nissen, seems to agree:

The differences were simply astonishing. We struggle to make small incremental improvements in cardiovascular mortality, and here’s an eight-year trial where the magnitude and absolute reduction are very large.

Yet Nissen and the other authors of the study write of the need for more research. Because they want to see a randomized controlled trial.

Reason for Doubt

The reason for doubt is the observational nature of the study. That means the patients chose whether to have surgery. Sure, the researchers used carefully matched controls for a comparison. But careful matches are not perfect matches. These two groups were different in a few ways. The control group was a little older. They smoked more. The surgery group was heavier. They had more high blood pressure and cholesterol.

Even more important is the possibility for confounding factors that researchers can’t measure. It adds the possibility for systematic bias that nobody sees.

Thus, we have folks like Harvard’s David Nathan calling for caution. “This study needs to be taken with a giant grain of salt,” he says.

Waiting for Perfect Knowledge

We will have a long wait for perfect knowledge of the benefits bariatric surgery provides. It’s not 100 percent effective. Most people respond well, but some do not. Not everyone is a good candidate. But anybody who tells you they know how to pick who will do well and who will not is kidding themselves.

It is, however, abundantly clear that bariatric surgery can be hugely beneficial for people with both obesity and type 2 diabetes. The randomized STAMPEDE trial proved that point. Does it reduce heart disease? Scholars can still debate that for now.

But clinicians have rendered judgment. A broad international consensus among clinical experts, DSS-II, tells us that metabolic surgery is a good option for people with type 2 diabetes and obesity. We’re down to debating finer points in academia.

Click here for the study, here for the editorial, and here for reporting from the New York Times.

The Muses, painting by Maurice Denis / WikiArt

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September 4, 2019