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The Moving Target of Medical Knowledge

The recent recommendation from the U.S. Preventive Services Task Force that women should no longer routinely start getting screening for mammograms at age 40 is the latest example of a time-honored tradition of doctors changing their minds. While frustrating for patients, that tradition is a good thing.

A recent review found that, in general, medical advice changes about every five and a half years because of new evidence. There are many examples in the past decade alone. In 2002, the Women's Health Initiative found that hormone replacement therapy, formerly thought to protect against heart disease, actually increases the risk of heart disease and breast cancer. Since 2005, several studies have shown that, contrary to previous assumptions, B6, B12 and folic acid don't prevent heart disease. Last year, a large trial challenged the belief that selenium and vitamin E can help prevent prostate cancer.

Patients should be wary of recommendations that are set in stone. Few things frighten me more than a doctor who is not open to the possibility of being wrong. For thousands of years, holes were drilled in the skulls of patients to release pressure or evil spirits, and as recently as the 1920s people were bled to help restore the correct balance of "bodily humors."

The cocksure physician was perfectly parodied by Steve Martin, who memorably played the bloodletting, leech-applying medieval barber Theodoric of York (Watch the clip here) in a 1978 "Saturday Night Live" skit. Responding to a mother's plea to help her ill daughter, he says:

"Well, I'll do everything humanly possible. But unfortunately, we barbers are not gods. You know, medicine is not an exact science, but we are learning all the time. Why, just fifty years ago, we would have thought your daughter's illness was brought on by demonic possession or witchcraft. But nowadays we know that Isabelle is suffering from an imbalance of bodily humors, perhaps caused by a toad or a small dwarf living in her stomach."

When her daughter dies after a bloodletting, the mother lashes out at Theodoric of York:

Mother: "You charlatan! You killed my children, just like you killed the rest of my family! Why don't you admit it! You don't know what you're doing!"

Theodoric of York: "Wait a minute. Perhaps she's right. Perhaps I've been wrong to blindly follow the medical traditions and superstitions of the past centuries. Maybe we barbers should test those assumptions analytically, through experimentation and a "scientific method." Perhaps this scientific method could be extended to other fields of learning: the natural sciences, art, architecture, navigation. Perhaps I could lead the way to a new age, an age of rebirth, a Renaissance! [he thinks for a few seconds] Naaaaaahhh!"

I think this should be required viewing in all medical schools. It was the "scientific method" nearly invented by Theodoric of York that, when it finally arrived, made medical knowledge a moving target. The best physicians understand that they can never entirely master a discipline that remains an art as much as a science. They welcome new ideas, even if it means abandoning comfortable, preconceived notions. They also understand that new information is not necessarily the best information and are open to lessons from the past. In recent years, leeches have made a comeback - not for bloodletting but to help with wound-healing. Neurosurgeons still drill holes in patients' heads - to relieve pressure caused by bleeding inside the skull. And bloodletting has persisted as a treatment for iron overload in the body (hemochromatosis).

I've often thought, "What am I doing today that will seem utterly ridiculous to doctors a hundred years from now?" I recently came across a book called The Cottage Physician, written "For Individual and Family Use" by Dr. George W. Post at the end of the 19th century. It sits by the side of my bed and I read a few pages now and then - both for entertainment and perspective. In a section called "Diseases of the Heart," Dr. Post describes the recommended treatment of the era:

"In all cases of heart disease, the body and mind should be kept as easy and cheerful as possible. The diet should be well regulated, - nourishing but not stimulating. Coffee, tea, liquors, and tobacco must be dispensed with. The feet should be kept dry and warm, and occasionally rubbed with mustard.

For inflammatory diseases of the heart, the bowels, if constipated may be moved with compound tincture of jalap. To each dose add ten grains of cream of tartar. Keep up a perspiration till the pain is relieved by giving a teaspoonful of compound tincture of Virginia snakeroot; also a warm infusion of pleurisy root. Mustard plasters over the chest and spinal column are also to be employed. If the patient is troubled with sleeplessness, give eight to ten grains of compound powder of ipecac and opium (Dover's powder) at bedtime."

For this week's CBS Doc Dot Com, Dr. Christopher P. Cannon, a cardiologist at Harvard Medical School, discusses the latest recommendation for heart health described in his new book, The New Heart Disease Handbook. While watching the segment, you might ask yourself, "A hundred years from now, which suggestions will still ring true and which will go the way of ipecac and opium?"

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