LOS ANGELES - Many patients like having a say in their medical care. But according to a new survey, the people who say they want to take a relatively aggressive, hands-on approach may also wind up with longer hospital stays and higher bills than their peers who leave the decision-making up to their doctors.

A team of researchers from the University of Chicago School of Medicine reported the survey's findings Monday in the journal JAMA Internal Medicine.

In the background section of their report, the team noted that "shared decision-making has been widely endorsed as a model for making complex medical decisions and may have many advantages, including improved patient satisfaction and health outcomes."

But researchers don't understand how shared decision-making affects costs, they added. Would patients who participated in the process actually use fewer resources and have lower bills, because they might decline interventions they don't want? Or would they opt for more, and more expensive, medical services?

The researchers found that nearly all of the 21,754 participants- 96.3 percent - wanted to receive information about their illnesses and treatment options, but that only 28.9 percent said they had a strong preference for making their own decisions about their care.

Those patients had longer hospital stays, by about a quarter of a day on average, than patients who preferred to let doctors take the lead. They also had greater costs - $865 more, on average.

By and large, people who were more likely to participate in medical decisions were better educated, and more likely to have private insurance coverage, than the others in the survey.

The team calculated that multiplying the 28.9 percent of patients by the 35 million hospitalizations in the U.S. each year yielded 10 million hospitalizations. If each represented an additional quarter of a day and $865, it would total 2.6 million hospital days and about $8.7 billion in costs.