Urban and suburban areas have lost a quarter of their hospital emergency departments over the last 20 years, according to the study, in The Journal of the American Medical Association. In 1990, there were 2,446 hospitals with emergency departments in nonrural areas. That number dropped to 1,779 in 2009, even as the total number of emergency room visits nationwide increased by roughly 35 percent…

“Some people think, ‘As long as my emergency room isn’t closing, I feel O.K. and protected,’ ” said Dr. Hsia, whose research was financed by the Robert Wood Johnson Foundation. “But even if they don’t lose the E.R. in their own neighborhood, they do experience the effect of fewer emergency rooms — the waits get longer and longer, and people’s outcomes get worse.”…

Conditions in emergency rooms may be worsened by the new health care law, several experts said. The law will expand eligibility for Medicaid, the government health plan for the poor. Often beneficiaries turn to emergency rooms for care, because many physicians do not accept Medicaid payments, said Dr. Sandra M. Schneider, president of the American College of Emergency Physicians.