As doctors know, a lot of patients don’t want to hear bad news. As patients know, neither do a lot of doctors.

If there’s nothing in particular doctors can do with the information, they write it off as the patient’s neurotic fretting. So we read in a New York Times story Thursday about doctors of patients who believe they could be in the earliest stages of Alzheimer’s. Unless a doctor could see the evidence for himself, he would probably tell the patient he was wrong.

“People would complain,” said Creighton Phelps, acting chief of the dementias of aging branch of the National Institute on Aging, “and we didn’t really think it was very valid to take that into account.”

That’s finally changing. Researchers have come up with a new category called “subjective cognitive decline.” This is the perception some people have that they’re slipping . . . because they’re slipping. Who would have guessed they’d know?

Dr. Ronald Petersen, chairman of the advisory panel to the federal government’s new National Alzheimer’s Project, told the Times, “The whole field now is moving to this area, and saying ‘Hey, maybe there is something to this, and maybe we should pay attention to these people.'”

Reading the Times article reminded me of something Vladimir Horowitz supposedly once said: “If I don’t practice for a day, I know it. If I don’t practice for two days, my wife knows it. If I don’t practice for three days, the world knows it.”

This remark (sometimes attributed to other musicians) is compelling because no one doubts that Horowitz would know if he needed more practice.

Even if his doctor told him, “You sounded great to me!”