Nearly half of all US medical care is delivered by emergency departments, according to a new study by researchers at the University of Maryland School of Medicine (UMSOM). And in recent years, the percentage of care delivered by emergency departments has grown. The paper highlights the major role played by emergency care in health care in the U.S.

"I was stunned by the results. This really helps us better understand health care in this country. This research underscores the fact that emergency departments are critical to our nation's healthcare delivery system." said David Marcozzi, an associate professor in the UMSOM Department of Emergency Medicine, and co-director of the UMSOM Program in Health Disparities and Population Health. "Patients seek care in emergency departments for many reasons. The data might suggest that emergency care provides the type of care that individuals actually want or need, 24 hours a day."

Although he now focuses on population health, Dr. Marcozzi is an emergency room doctor himself, and works one or two days a week in the University of Maryland Medical Center emergency department, treating patients.

This is the first study to quantify the contribution of emergency department care to overall U.S. health care. The paper appears in the latest issue of International Journal for Health Services.

For this study, Dr. Marcozzi and his colleagues examined publicly available data from several national healthcare databases, which covered all 50 states and the District of Columbia. They studied the period between 1996 and 2010.

For 2010, the most recent your study, the study found that there were nearly 130 million emergency department visits, compared with almost 101 million outpatient visits and nearly 39 million inpatient visits. Inpatient visits typically involve a hospital stay, but are planned ahead, as opposed to emergency department visits, which are generally at least somewhat unexpected.

Over the 14-year period of the study, more than 3.5 billion health care contacts -- emergency department visits, outpatient visits, and hospital admissions took place. Over that time, emergency care visits increased by nearly 44 percent. Outpatient visits accounted for nearly 38 percent of contacts. Inpatient care accounted for almost 15 percent of visits.

Certain groups were significantly more likely to use the emergency department as their method of healthcare. African-American patients were significantly more likely to have emergency department visits than patients in other racial groups; patients in the "other" insurance category, which includes those without any type of insurance, were significantly more likely to have emergency department visits than any other group. And patients living in the South were significantly more likely to have emergency department visits than patients living in other areas of the country.

African-American patients used emergency departments at a higher rate than other groups. In 2010, this group used the emergency department almost 54 percent of the time. The rate was even higher for urban African-American patients, who used emergency care 59 percent of the time that year. Emergency department use rates in south and west were 54 percent and 56 percent, respectively. In the northeast, use was much lower, 39 percent of all visits.

Certain groups accounted for increasing percentages of overall emergency room use: African-Americans, Medicare and Medicaid beneficiaries, residents of the south and west, and women. Dr. Marcozzi says that these findings point to increasing use by vulnerable populations, which is no surprise since socioeconomic and racial inequality creates barriers to the use health care.

The use of emergency care resources for non-emergency cases has been controversial, since initial emergency care patients often end up being seen for non-emergency medical issues. Some experts argue that emergency departments are covering for deficiencies in inpatient and outpatient resources, and for a lack of effective prevention strategies. This could contribute to the high rate of emergency department use. They argue that emergency room use should be reduced.

Dr. Marcozzi says this is unlikely to happen anytime soon, given the structure of the country's health care system. He also notes that it may not be the best option. Instead, he says we should work to connect the care delivered in emergency departments with care delivered by the rest of the healthcare system.