Advances in medical care and more end-of-life outpatient options have resulted in a sharp decline in emergency room deaths in the last 15 years, according to a new study published in the July edition of Health Affairs.

Researchers found a 48 percent drop in adult deaths in ERs between 1997 and 2011. There's no clear-cut reason for the decrease, leading researchers to cite several reasons for the results.

Study author Dr. Hemal Kanzaria said improvements in emergency medicine and public health as well as greater usage of outpatient hospice and palliative care have likely contributed to the decline.

"This was a descriptive study, essentially looking at trends," said Kanzaria, an assistant professor of emergency medicine at University of California, San Francisco. "Finding a nearly 50 percent reduction was thought-provoking, and I think there are many possible explanations. [But] dying in an emergency department is rare, and it's important to highlight how rare an event it is overall."

The researchers said patients who did die during an ER visit were older and more likely to be male and white. Patients who died were also more likely to live in a rural area or the South. In general though, they were more severely ill or injured when arriving at the hospital.

The study found that 63 percent of patients who died were either in cardiac arrest, unconscious or dead on arrival. Of the patients who died, most presented to the emergency department with shortness of breath, injury or chest pain.

"As a practicing emergency physician, I feel the ED isn't an optimal place for either a patient to die or a family member or loved one to experience such an event," Kanzaria said. "We were interested in looking at how often this actually occurs."

One reason fewer people may be dying in ERs is greater utilization of palliative care services, which allow patients to die at home or under hospice care. With more people opting for palliative care for end-stage and terminal illnesses, fewer people are dying in hospitals, Kanzaria said.

Additionally, Kanzaria said advances in emergency medicine over the past two decades has helped physicians better manage cardiac arrest, stroke, trauma and serious infections.

The Centers for Disease Control and Prevention (CDC) maintains data on emergency departments visits. The most recent year for which data is available is 2011. That year, 136 million ER visits occurred in the U.S. Of those, 40 million occurred due to injuries, and 12 percent led to a hospital admission.

Kanzaria's team looked at data from the National Hospital Ambulatory Medical Care Survey and discovered emergency room mortality rates fell from 1.48 per 1,000 adults in 1997 to 0.77 per 1,00 adults 15 years later. The team reviewed 1.3 billion ER visits that occurred during the time.

Dr. Kevin Rodgers, president of the American Academy of Emergency Medicine, said the research was laudable but it may not show the full picture.

Rodgers, also a professor of clinical emergency medicine at Indiana University, said the research couldn't determine the number of patients who were revived in the emergency room who ended up "in terrible neurologic condition and counted as survivors."

"Are we really doing a better job?" Rodgers asked. "We might be, but it's hard to know."