One afternoon in clinic, a patient’s wife stopped me in the hallway. I had just finished describing an operation to her and her husband, obtaining his consent and answering their questions, but I wasn’t surprised that the woman was still worried. Despite her easy smile and infectious throaty laugh, she had appeared anxious throughout the visit, the corners of her mouth twitching and her hands flitting from her hair to her face to her pocketbook and back to her hair again.

In the hall, she opened her mouth to speak but stopped abruptly when one of the residents, a doctor-in-training, passed by. Once the resident was out of earshot, she cleared her throat. “Please don’t bring any students into the operating room,” she said, looking toward where the resident was standing. “It’s not that I don’t like these young doctors. I just don’t want one practicing on my husband.”

I hear that request often regarding doctors-in-training, whether they are in their first year of training after medical school as interns, or are in the middle of their training or about to finish as residents or chief residents. But I’ve never developed an adequate response. A part of me understands these concerns. As talented and as earnest as residents can be, it’s true that they are still learning to operate. At the same time, I’m also fully aware that I am the doctor I am because other patients once allowed me to participate in their operations and care.

That afternoon a comment about the training process or my residency experiences would not have directly addressed the concerns of my patient’s wife. Or, frankly, my own disquietude. While my colleagues and I might have believed that our supervision of residents in the operating room ensured patient safety and quality of care, none of us really knew that for sure.

Now we do.

This month The Journal of the American College of Surgeons published the results of a study on how well patients come through when a surgeon-in-training is involved in the operation. Analyzing the results of more than 600,000 operations at more than 225 hospitals across the country, researchers found that while resident involvement was indeed associated with slightly higher complication rates and longer operating times, those patients who had trainees participating in their operations also experienced decreased mortality rates.

In other words, having a resident scrub in on your operation is not only safe but might also offer a bit of protection against death.

“Patients have the right to have whomever they want in the operating room,” said Dr. Mehul V. Raval, the lead author, a senior surgical resident at the Northwestern University Feinberg School of Medicine in Chicago. “But on an individual level, it’s hard to prove that there’s any significant difference in safety or quality of care when there are no residents involved.”

Previous research has been limited to the experiences of a single hospital or to broad comparisons in a geographic region or among Veterans Affairs hospitals. This study, however, looked at figures from the American College of Surgeons National Surgical Quality Improvement Program, a national database of information gathered directly from hospital charts or from phone calls and letters with patients, rather than from administrative or insurance claims reports.

“There’s an old adage about research and data: ‘garbage in, garbage out,’ ” said Dr. Clifford Y. Ko, senior author and a professor of surgery and health services at the David Geffen School of Medicine at the University of California, Los Angeles. “This study definitively answers the question of whether or not it makes a difference to have a resident involved in surgery because it is based on the best data currently available.”

That data revealed that while patients who had residents participating in surgery did develop more complications, those complications were not necessarily serious. And once one complication occurred, those patients with residents involved in their care were more likely to recover and less likely to fall prey to the so-called domino effect of complications, where one leads to another and ultimately to death. “It may be the fact of having a whole team of surgeons rather than just one that ‘rescues’ patients from these complications and even death,” Dr. Ko observed.

For example, for every 1,000 people who underwent colon surgery with trainees present, 30 patients experienced complications who wouldn’t have if they had undergone the same operation without residents. But five patients who would have died ended up surviving because trainees were involved in their surgery and care. “The question might then become,” Dr. Raval added, “‘Would you accept the risk of a urinary tract infection that required an antibiotic for several days if you knew it might save your life?’”

Researchers acknowledge that in the end, the most important factor for patients and their families is not the quality of the available data or the results of any study. It’s the relationship they have with their surgeon. “After all of this over-the-top statistical analysis to prove or not prove something, patients still have to be able to trust their surgeon.” Dr. Raval said. “They have to trust that their surgeon will take responsibility for their care and won’t give it to a resident or to anyone else.”

But they can also relax if they see a young doctor following their gurney into the operating room. She or he is really there to help, and the data proves it.