MONDAY, Sept. 29 (HealthDay News) -- Elderly Americans who live in low-income ZIP codes are more likely to die after surgery than those who live in higher-income ZIP codes, according to new research.

The study analyzed death rates among more than one million older adults who had one of six common high-risk heart or cancer surgeries between 1999 and 2003.

The risk of death was between 17 percent and 39 percent higher for patients in low-income ZIP codes, mainly because the quality of care is lower at hospitals in lower socioeconomic areas, the study authors said.

In fact, all patients (regardless of income) who had surgery at hospitals in the poorest areas were more likely to die, while all patients who had surgery at hospitals in the richest areas were less likely to die.

"It may be that hospitals that treat patients of lower socioeconomic status have lower quality of care due to fewer resources, such as technologically advanced equipment or specialists," lead author Dr. Nancy Birkmeyer, an associate professor of surgery at the University of Michigan, said in a Center for the Advancement of Health news release.

The study was published in the September issue of the journal Medical Care.

"While some prior studies have demonstrated socioeconomic disparities in the outcomes of individual procedures, ours is the first to show that the relationship is consistent across a wide range of surgical procedures," Birkmeyer said.

While the study can improve understanding of patterns of care, it doesn't offer concrete answers for elderly patients who need surgery, said Dr. Harlan Krumholz, a professor of medicine, epidemiology and public health at Yale University.

"The study can only really raise questions about inequalities in outcomes, because the authors have limitations in their ability to know the socioeconomic status of any particular patient and the condition of the patient when they had the surgery," Krumholz said in the news release. "Nevertheless, it is time for us to look closely at whether people are getting the same care and outcomes regardless of their financial circumstances."

More information

The U.S. National Institute on Aging has more about seniors and surgery.