He performs about 200 heart and vascular surgeries a year at Rush University Medical Center. He has given away two sets of golf clubs because he doesn't have time to play that often.

"If one is still interested and enjoys the work and the challenge, it's my opinion that one should and can continue," Goldin said. "I don't believe my stamina and interest have at all changed."

Stamina, strength, fine motor skills and sharp eyesight are traits associated with youth ¡ª and with surgery. The United States requires airline pilots to step down at age 60, but there is no mandatory retirement age for surgeons, who, like pilots hold life in their hands.

A new study raises questions about when older surgeons should quit the operating room and how they can stay at the top of their game in the final years of their careers. With the percentage of working doctors older than 65 climbing, the questions hold growing importance for patients.

Previous studies found that older doctors are less likely to know about new treatments and medications than younger doctors, and they tend to perform worse on recertification exams.

The new study, published in the September Annals of Surgery, found that for three complicated surgeries, including heart bypass, doctors older than 60 had higher patient death rates, especially if they didn't do very many of the surgeries.

Some doctors nearing retirement reduce their caseloads, but the study suggests that's not a good idea.

Practice keeps skills high, so an all-or-nothing approach to surgery in the pre-etirement years may be better than gradually fading away, said study co-author Dr. John Birkmeyer of the University of Michigan.

"Those who continue to practice in high-risk areas should maintain their caseloads, but it may be a good idea when surgeons get into the pre-retirement mode that they give up the most complicated and high-risk surgeries altogether," said Birkmeyer, who is 43.

Patients should ask how many procedures a surgeon does a year, rather than focus on the doctor's gray hair, Birkmeyer said.

Sometimes an aging surgeon is the last to recognize or admit it's time to quit. That's when hospital administrators should step in, said Dr. Andrew Warshaw, 67, chief of surgery at Massachusetts General Hospital.

The best hospitals monitor surgeons' rates of complications, infections, readmissions to the hospital and deaths and use those statistics to confront doctors about a pattern of problems. Hospitals also rely on surgeons passing their recertification exams every 10 years, but those tests gauge knowledge, not physical skills or technical mastery.

That forces hospitals to depend heavily on co-workers reporting on a doctor with failing skills, Warshaw said.

As department head, he tries to foster a work climate where colleagues can safely report their worries about a doctor, and he hopes that would be true for his own performance. Warshaw himself performs about 100 pancreas removals a year, considered a very large number for that rare procedure.

How will he know it's time to retire?

"I'm counting on the fact that, if I don't recognize it, somebody will tell me," Warshaw said. "Maybe I'll be the first to notice, maybe I won't."

His hospital requires administrators to be reappointed on a yearly basis after age 65, but it requires no similar annual reappointment for aging surgeons, he said.

The new study examined Medicare files on 461,000 patients who had one of eight different surgeries. In five of the surgeries, the researchers found surgeon age made no difference in patient death rates. But for pancreas removals, heart bypasses and surgery to clear blocked carotid arteries, the researchers found that older surgeons had higher rates of patient death within 30 days of surgery than younger surgeons.

Researchers speculated that those three surgeries are more complex and require more fine stitching.

"Surgeons are clearly not immune to the changes of aging," said study co-author Dr. Lazar Greenfield of the University of Michigan. For a forthcoming study, he is testing hundreds of aging surgeons' mental skills and reflexes.

While their mental skills such as short-term memory tend to decline with age, their reflexes are better than non-surgeons' and don't seem to slip over time.

"They do maintain remarkably good reflexes," said Greenfield, who is 71 and stopped doing surgery about four years ago when he faced new techniques for which he didn't feel adequately trained. "Surgeons of all ages seem to have reflexes well beyond the capability of control groups of people."

The percentage of working doctors 65 and older climbed from 13 percent in 1975 to 18 percent in 2004, according to data from the American Medical Association. An impending wave of baby boomers hitting age 65 may push those numbers even higher.

In the future, aging doctors might be required to prove their physical abilities, said Dr. Stephen Miller, president of the American Board of Medical Specialties, an umbrella group for the boards that test and certify specialists.

They might have to pass tests on patient simulators, the high-tech robots that some nurses and doctors now learn to practice on, Miller said.

Miller, 65, said he's personally in favor of requiring physical exams for older surgeons.

"What would be wrong with having a physician after a certain age be evaluated from standpoint of eyesight, from the standpoint of health?" Miller said. "That would probably be a good public health policy."