It only works if you actually go. Photographer: Alessia Pierdomenico/Bloomberg
It only works if you actually go. Photographer: Alessia Pierdomenico/Bloomberg

When it comes to health care, less is generally more. That’s doubly true of surgery. Opening up the body means introducing alien bacteria into places where bacteria aren’t supposed to be. Those bacteria may begin to multiply out of control, killing the patient. Or there may be side effects from anesthesia. Or the scar tissue you’ve created may block something that you need to be unobstructed. So although surgery can do great wonders, you generally want to do as little as possible (though no less).

But how little is possible? Often people who get a more invasive surgery do better than people who get some less invasive procedure. Patients may prefer percutaneous coronary intervention -- also known as angioplasty -- to a coronary bypass because it doesn’t involve cracking your chest open and grafting things onto your heart. But bypass patients seem to have better long-term outcomes, even though both methods increase blood flow to the heart muscle. Doctors have devoted much energy to figuring out why the more invasive procedure does better, even though it carries all the added risks of major surgery.

A new working paper from the National Bureau of Economic Research suggests a possible answer: Bypass works better precisely because it’s more invasive. The very scale of the treatment makes people more likely to change their post-operative behavior in ways that enhance their long-term chances of survival:

Over the last several decades, numerous medical studies have compared the effectiveness of two common procedures for Coronary Artery Disease: Percutaneous Coronary Intervention (PCI) and Coronary Artery Bypass Graft (CABG). Most evidence indicates that CABG -- the more invasive procedure -- leads to superior long term outcomes for otherwise similar patients, though there is little consensus as to why. In this article, we propose a novel explanation: patient offsetting behavior. We hypothesize that patients who undergo the more invasive procedure, CABG, are more likely to improve their behavior -- eating, exercise, smoking, and drinking -- in a way that increases longevity. To test our hypothesis, we use Medicare records linked to the National Health Interview Survey to study one such behavior: smoking. We find that CABG patients are 12 percentage points more likely to quit smoking in the one-year period immediately surrounding their procedure than PCI patients, a result that is robust to numerous alternative specifications.

Smoking behaviors are likely associated with other changes that may be harder to measure such as diet and exercise. And this makes a certain amount of sense. If heart disease lands you in the hospital for a minor procedure, you’re probably less worried about prevention than you would be if that disease required major surgery and a lengthy recovery.

Nor is heart disease the only area where I have heard this argument. Back surgery is the bane of health wonks everywhere, because controlled studies show that in most cases, physical therapy works just as well. So wonks love to cite this as an example of something we ought to be able to cut out of the system with little loss to patients.

I made the mistake of airing this trope in front of a back surgeon, who cornered me after my talk. This was some years ago, and I was not taking notes, so please permit me to paraphrase our conversation.

“You think we’re idiots?”

“No, of course not.”

“You think we don’t read the studies?”

“Um ..."

“We know physical therapy is better in most cases. What we don’t know is how to make the patients go to physical therapy.”

Compliance is always an issue in health care. A shocking number of patients stop taking their blood pressure medication within a year of being diagnosed with hypertension, even though the side effects of most common drugs are really minimal and can be alleviated by drug switching. Unfortunately, the symptoms of hypertension are also really minimal, until you have a stroke or a heart attack, so patients just … stop bothering to fill their prescriptions.

Physical-therapy regimes are hard for many people to keep up; you have to show up at the same place every week, or multiple times a week, for months. It’s hard to fit into a busy schedule. What the surgeon was arguing, essentially, is that physical therapy works great -- in a controlled study where everyone in the study applied or was recruited and you have top-notch staff making sure they show up to their appointments. In the real world, where you’re not dealing with such a curated group of patients or health-care workers, the alternatives are often not “surgery or physical therapy” but “surgery or nothing.” Moreover, if the results of this new study are broadly applicable, people may be more likely to go to physical therapy after they’ve had major surgery.

This presents both a conundrum and an opportunity. You don’t want to go around doing big, expensive, risky procedures as a way to get patients to quit smoking. This may suggest that we should try pairing less risky procedures with more intensive nursing support to get patients to change their lifestyles. But what do we do if that fails, and we’re left with cracking open someone’s chest in order to get them to cut back on the ice cream?

To contact the author of this article: Megan McArdle at mmcardle3@bloomberg.net.

To contact the editor responsible for this article: James Gibney at jgibney5@bloomberg.net.