When visiting a relative in the hospital recently, I saw a board on the wall that listed a “hospitalist” on duty. What is a hospitalist?

A hospitalist is a physician, usually an internist, who specializes in caring for people who are hospitalized. The hospitalist may work as an employee of the hospital or as part of a private group practice, with the role of admitting patients who need to be hospitalized and treating them while they’re there. This subspecialty of internal medicine is known as hospital medicine. If you have been hospitalized in the past 20 years or so, there’s a good chance you were seen by a hospitalist.

There are also hospitalists in hospital-affiliated outpatient settings (sometimes called post-discharge or follow-up clinics), who help care for recently discharged patients—especially those with difficult-to-manage medical conditions—to reduce their risk of being readmitted.

Hospital medicine is a relatively new field. Its origins date back only to the mid-1990s or so and coincided with the growth of managed health care. The idea was that a dedicated internist based at the hospital could more efficiently oversee a patient’s care than the typical office-based internist, who had to balance seeing patients at the hospital with his or her usual patient load back at the office.

Today, about three-quarters of U.S. hospitals have hospitalists on staff. Economically they’re a slam-dunk for the health care system: Research consistently shows that patients cared for by hospitalists tend to have shorter hospital stays and cost insurers less than those cared for by their own primary care doctor or other generalists.

Studies comparing the quality of care between hospitalists and non-hospitalists, however, have had inconsistent results. For example, a study of nearly 77,000 hospitalized patients found that mortality and readmission rates were about the same whether the individuals were treated by a hospitalist or by their own general internist or family doctor. But another study, of more than 560,000 Medicare beneficiaries, found that those who were cared for by their primary care doctor were less likely to die in the hospital or within 30 days than those cared for by hospitalists.

From the patient’s perspective, being seen by a hospitalist could have both benefits and drawbacks. On the positive side, if your condition worsens, say, or if you develop new symptoms, you might get seen sooner by the hospital doctor, at least in theory, than if you had to wait for your own doctor to come. On the downside, a hospitalist will be nowhere near as familiar with you as your own doctor. And being seen by yet another new practitioner when you’re already in the unfamiliar setting of the hospital could lead to more stress. If you are blessed with an outstanding internist, you may find the hospitalist’s care to be substandard in comparison. On the flip side, if your own doctor is merely mediocre and the hospitalist is excellent, you may be better off.