ANN ARBOR, Mich., Sept. 16 (UPI) -- Elderly U.S. patients living in impoverished areas are more likely to die after surgery compared to peers from higher-income ZIP codes, researchers said.

Lead study author Nancy Birkmeyer of the University of Michigan said the odds of dying were 17-39 percent higher for patients with low socioeconomic status.

"While some prior studies have documented 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 in a statement.

"Patients that live in socioeconomically disadvantaged areas have higher surgical mortality rates mainly because the quality of care is lower at hospitals where patients of lower socioeconomic status tend to be treated."

Birkmeyer and colleagues used U.S. census and Medicare data to evaluate postoperative death rates in more than 1 million elderly patients, who had undergone one of six common, high-risk surgical procedures between 1999 and 2003.

The study, published in the journal Medical Care, found all patients -- regardless of income -- who underwent treatment at the hospitals in the poorest areas were more likely to die, whereas all patients undergoing surgery in the wealthiest ZIP codes proved less likely to die.

Copyright 2008 by United Press International.

All rights reserved.