By Marissa Evans, CQ Roll Call

July 6, 2016 -- Emergency room death rates dropped 48 percent between 1997 and 2011, but researchers were unable to draw specific conclusions on how or why this happened, according to a Health Affairs study.

The report released last week found that while researchers could not give conclusive reasons for the sharp drop, it could be linked to factors such as increased use of palliative care, better management of patients with potential heart issues, as well as reduced smoking rates and improved car safety features and policies.

Researchers studied 1.3 billion emergency room visits from the National Center for Health Statistics' Hospital Ambulatory Medical Care Survey. The survey includes emergency room visits in nonfederal, general, and short-stay hospitals alongside patient demographics, reasons for the visit and if the patient survived. Researchers noted the data may have limitations due to industry changes in medical coding and other factors.

Hemal Kanzaria, assistant professor in the Department of Emergency Medicine at the University of California San Francisco and the lead author of the study, said in an interview that the subject will be an area of continued interest.

"It's nice that we're seeing these trends in reduced mortality," Kanzaria said. "We've made tremendous improvements in longevity of life...with that though, is making sure [patients] are living a high quality of life."

The study found 62.7 percent of emergency room deaths logged involved patients with cardiopulmonary arrest, unconsciousness or were dead on arrival. Meanwhile, 8.3 percent fatalities stemmed from shortness of breath, another 5.1 percent from an injury and 3.9 percent from chest pains.

Researchers pointed to an increase in palliative care as a potential reason for the reduced deaths due to "more patients dying in hospice settings outside acute care hospitals and emergency departments than in the past."

The study referenced research showing a significant increase in the proportion of home deaths and more policies requiring medical professionals to follow do not resuscitate orders.

"One of the main reasons we did the study was there's been tremendous increases in palliative care part of which is focused on patients and patient wishes," Kanzaria said. "It would be reasonable to think patients would prefer to be at home than an emergency room setting."