Why do doctors keep changing their minds about the right thing to do?

DEAR DOCTOR K:

I have diabetes, and my doctor used to tell me my fasting blood sugar level needed to be below a certain number. Now, he says it’s OK if it’s higher. Why do doctors keep changing their minds about the right thing to do?

DEAR READER:

We doctors keep changing our minds because we’re human. Which means that we sometimes believe things that seem reasonable and for which there is some evidence — only to find out, as more and better research is done, that we were wrong.

Suppose you were living in the 15th century. Every (clear) day of your life you would see the sun rising in the morning in the east, moving higher in the sky, then at midday starting to move lower, and finally setting in the west. And every clear night of your life, you would see the moon and stars also moving across the sky. Wouldn’t common sense have told you that the sun, moon and stars — the entire universe — revolved around the Earth? I’m pretty sure that’s what I would have assumed.

I graduated medical school believing that I had learned the very best current treatments for different diseases. Of course, new and better treatments were likely to be discovered during my career. But I believed that every treatment I’d learned about was the best currently available, and clearly better than no treatment at all.

The first time I recall being disabused of that idea involved a treatment for bleeding ulcers (in the small intestine and stomach), which were a very common problem then.

A surgeon had a clever idea, called “gastric freezing.” He developed a plastic tube with a balloon at the end of it. The tube was pushed down through the mouth into the stomach. Then a bedside machine circulated cold fluid through the balloon. The very cold balloon froze the lining of the stomach. It made sense that this would reduce the production of stomach acid (which was thought to cause and worsen the bleeding ulcer). It also made sense that it would encourage the blood to clot and the bleeding to stop.

Every patient on which the surgeon tried gastric freezing told him they felt better afterward. He published the results and went around the country talking about his new treatment. Several thousand gastric freezing machines with tubes were sold around the United States. Up to 15,000 people got the new treatment.

Then several studies were done in which some people with ulcers were given the true gastric freezing treatment, and some just had the tube placed in their stomach without the freezing treatment. Thirty percent of the people given the freezing treatment improved — but 34 percent of those who did not get the treatment improved as well. In other words, the treatment was no better than (and maybe a little worse than) no treatment at all. Needless to say, the treatment ceased to be used.

In tomorrow’s column, I’ll talk more about how and why treatments sometimes fall out of favor.