March 20 (HealthDay News) -- Doctors often play a big role in deciding where U.S. Medicare patients have their surgeries, a new study finds.

Researchers reporting in the March issue of the journal Archives of Surgery surveyed 500 Medicare patients (average age 78) in 2004 who'd had one of five elective high-risk operations about three years earlier.

The operations were for: abdominal aneurysm repair (103 patients); heart valve replacement (96); and tumor removal (119 for bladder cancer, 128 for lung cancer, and 64 for stomach cancer).

The study was conducted by researchers from the Department of Veterans Affairs Medical Center in White River Junction, Vt., and Dartmouth Medical School in Hanover, N.H.

The team found that 42 percent of patients said they decided equally with their doctor where the surgery would take place, 31 percent said their doctor was the main decision-maker, 22 percent said they made the decision, and 5 percent said a family member was the main decision-maker.

Men were more likely than women (34 percent vs. 24 percent) to report that their doctor was the main decision-maker, as were patients in poor to fair health (37 percent vs. 28 percent of patients in good to excellent health). Doctors were more likely to be the main decision-maker for cardiovascular surgery (39 percent) and for cancer surgery (26 percent).

"The process by which patients who need major surgery get directed to surgeons and hospitals is poorly understood, and the role of the patient in this process has received little attention," the study authors concluded.

"While many patients participate in the decision-making process and may desire objective information to inform their decisions, a substantial proportion of patients are not involved at all," they added. "Research is needed to help us understand whether patients would like a greater role in deciding where to have major surgery and, if so, how to facilitate such involvement."