NCHS Data Brief ■ No. 192 ■ March 2015

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

Emergency Department Visits and Proximity to Patients’ 

Residences, 2009–2010

Amy M. Brown, M.P.H.; Sandra L. Decker, Ph.D.; and Frederic W. Selck, Ph.D.

Key findings 

Data from the National 

Hospital Ambulatory 

Medical Care Survey

● In 2009–2010, visits to

emergency departments (EDs) 

occurred an average 6.8 miles 

from the patient’s residence, 

while the nearest ED was 

3.9 miles from the home. 

● Less than one-half of all ED

visits (43.8%) occurred at the 

ED closest to where the patient 

lived. 

● Visits within metropolitan

statistical areas were less likely 

(37.2%) to take place at the 

closest ED compared with 

visits outside of metropolitan 

statistical areas (70.1%). 

● Within metropolitan

statistical areas, visits that did 

not take place at the closest 

ED occurred more frequently 

among younger patients, at 

larger hospitals, and in EDs 

with longer waiting times, 

compared with visits to the 

closest ED.

The number of emergency department (ED) visits rose 44% from 1991 

through 2010, even as the number of hospital EDs declined 10% over the 

same period (1). As a result, EDs have increasingly experienced overcrowding 

and longer waiting times (2,3). However, little is known about which ED 

patients visit, how often patients go to the ED closest to their home, and how 

differences in geography, patient demographics, and hospital characteristics 

are associated with ED selection patterns. 

Keywords: distance • National Hospital Ambulatory Medical Care Survey

How far from patients’ residences do ED visits usually occur, 

and does this differ if visits occur within a metropolitan 

statistical area?

● Visits to EDs occurred an average 6.8 miles from the patient’s residence,

while the nearest ED was 3.9 miles from the home (Figure 1).

 
NCHS Data Brief ■ No. 192 ■ March 2015

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● Among those who visited an ED, the nearest ED was significantly closer to home 

(3.6 miles) for visits within metropolitan statistical areas (MSAs) compared with those 

outside of MSAs (5.1 miles). 

● However, the distance to the ED visited was not significantly different based on whether a 

patient visited an ED within or outside of an MSA (about 7 miles in either case). 

What percentage of visits occurred at the closest ED, and are there 

differences by patient age?

● In 2009–2010, 43.8% of all ED visits occurred at the ED closest to a patient’s home 

(Figure 2). 

● Visits to EDs within MSAs were less likely to take place at the closest ED (37.2%) 

compared with visits in non-MSAs (70.7%). This difference was also significant for each 

age group. 

● Within MSAs, visits by patients aged 18 and under (35.3%) and 19–64 (37.5%) were less 

likely to take place at the closest ED compared with visits among patients aged 65 and over 

(40.1%).

● Outside of MSAs, no significant difference was found in the percentage of visits that took 

place at the closest ED by patient age group. 

 
NCHS Data Brief ■ No. 192 ■ March 2015

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Does hospital visit volume affect whether visits take place at the closest 

ED?

● Within MSAs, a lower percentage of visits occurred at the closest ED if the ED was within 

a hospital having more than 20,000 visits per year (35.6%) compared with visits within 

hospitals having an annual volume of 20,000 or fewer visits (60.3%) (Figure 3). 

● The percentage of visits to the closest ED did not differ significantly by hospital visit 

volume outside of MSAs.

 
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Are wait times associated with whether visits take place at the closest ED?

● Within MSAs, visits to the ED closest to a patient’s home had shorter average wait times 

for being seen by a physician, physician’s assistant, or nurse practitioner (52.3 minutes) 

compared with visits to EDs that were farther away (average wait time of 62.3 minutes) 

(Figure 4). 

● Outside of MSAs, average wait time did not differ between visits to the closest ED and the 

ED visited.

 
NCHS Data Brief ■ No. 192 ■ March 2015

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Summary 

If the demand for emergency care continues to grow, understanding the circumstances in which 

patients visit an ED other than the one closest to their home may become increasingly important. 

This report uses geographic information about the location of EDs throughout the United States 

in conjunction with information about the location of patient residences to assess a) whether visits 

take place at the ED closest to where patients live and b) which factors are associated with where 

these visits occurred. 

Results suggest that ED visit patterns vary considerably by MSA status. Outside of MSAs, the 

majority of visits take place at the ED closest to a patient’s home, while within MSAs, several 

factors are associated with patients bypassing the closest ED and visiting an ED farther away. In 

2009–2010, visits to an ED farther than the closest one were more likely to occur among patients 

younger than age 65 and at hospitals with a higher visit volume. Visits within MSAs were more 

likely than visits outside of MSAs to occur at an ED farther than the closest one, despite the fact 

that EDs closest to a patient’s home had lower average wait times for seeing a clinician.

Definitions

Closest emergency department (ED): Among all EDs in the United States, the ED that has the 

minimum great-circle (orthodromic) distance between the centroid of a patient’s zip code of 

residence and the ED’s address. Zip codes for patient residences were obtained from the 2009–

2010 National Hospital Ambulatory Medical Care Survey (NHAMCS), and addresses for each 

ED in the United States were obtained from IMS Health (4). Geocoding of ED addresses was 

performed using Pitney Bowes Group 1 Geographic Coding Plus version 5.2 (Stamford, Conn.). 

Metropolitan statistical area (MSA): A metropolitan area containing a core urban area of 50,000 

or more population (5). 
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Data source and methods

Data from the 2009–2010 NHAMCS were used. This survey is conducted annually by the Centers 

for Disease Control and Prevention’s National Center for Health Statistics. NHAMCS collects 

data on a nationally representative sample of visits to hospital outpatient departments and EDs 

of nonfederal, short-stay general hospitals and children’s general hospitals, and uses a multistage 

probability sample design that is described elsewhere (6). The analyses in this report use data on 

50,951 (unweighted) ED visits from NHAMCS 2009–2010 after excluding 16,281 visits. Most 

of the excluded visits (14,046) listed an ambulance as the mode of arrival, and were excluded 

because the patient likely had little or no choice of ED visited. Another 2,235 visits lacking valid 

zip codes of patient residences were excluded. In calculating average distances, an additional 

4.6% (unweighted) of visits were excluded that had outlier distances to the ED visited equal to 

or greater than 50 miles. These visits were excluded because they were outside of the reasonable 

distance range and likely occurred while the patient was traveling far from home. 

Estimates were considered statistically significant (p < 0.05) based on two-tailed t tests. All 

reported comparisons are statistically significant unless otherwise indicated. For Figure 2, a 

weighted least-squares regression method (7) was used to test for a linear trend in the percentage 

of visits that occurred at the closest ED by age group. Data analyses were performed using the 

statistical packages SAS version 9.3 (SAS Institute, Cary, N.C.), SUDAAN version 11.0 (RTI 

International, Research Triangle Park, N.C.), and Stata version 11.0 (College Station, Texas). 

Note that although straight-line distances between patients’ zip codes of residence and ED 

addresses were calculated, distances that accounted for available roadways and travel time 

would have been preferred. Distance also is calculated from the centroid of a patient’s zip code 

of residence because exact patient addresses were not available. Separate analyses were also 

conducted defining the closest ED as any ED within a 1–mile radius of the shortest distance 

between the centroid of the patient’s zip code and the address of every other ED in the country. 

This increased the percentage of ED visits occurring at the closest ED (to 56.7%), although all 

comparisons in this report remained similar. For example, the percentage of visits to the closest 

ED remained larger for visits outside of MSAs compared with inside MSAs. Lastly, although 

this report measured distance from home to an ED, the analyses did not take into account where 

patients were actually coming from at the time of the ED visit, because this information was not 

collected. In some instances, the patient may have been away from home (e.g., at work or school, 

or on vacation) prior to traveling to the ED. 
NCHS Data Brief ■ No. 192 ■ March 2015

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About the authors

Amy M. Brown is with CDC’s National Center for Health Statistics, Division of Health Care 

Statistics. Sandra L. Decker is with CDC’s National Center for Health Statistics, Office of 

Analysis & Epidemiology. Frederic W. Selck is with Bates White, an economic consulting firm in 

Washington, D.C. 

References

1. American Hospital Association. Trendwatch Chartbook 2012: Trends affecting hospitals 

and health systems: Chart 3.7. Available from: http://www.aha.org/research/reports/tw/

chartbook/2012chartbook.shtml.

2. Henneman PL, Garb JL, Capraro GA, Li H, Smithline HA, Wait RB. Geography and travel 

distance impact emergency department visits. J Emerg Med 40(3):333–9. 2011.

3. Sommers A, Boukus ER, Carrier E. Dispelling myths about emergency department use: 

Majority of Medicaid visits are for urgent or more serious symptoms. Center for Studying 

Health System Change research brief, no 23. 2012. Available from: http://www.hschange.com/

CONTENT/1302/.

4. National Center for Health Statistics. 2010 NHAMCS micro-data file documentation. 

Hyattsville, MD. 2010. Available from: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_

Documentation/NHAMCS/doc2010.pdf.

5. U.S. Census Bureau. Metropolitan and micropolitan statistical areas. Available from: 

http://www.census.gov/population/metro/.

6. National Center for Health Statistics. National Hospital Ambulatory Medical Care Survey 

documentation, 2009–2010. Available from: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/

Dataset_Documentation/NAMCS/.

7. Gillum BS, Graves EJ, Kozak LJ. Trends in hospital utilization: United States, 1988–92. 

National Center for Health Statistics. Vital Health Stat 13(124). 1996.
NCHS Data Brief ■ No. 192 ■ March 2015

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Suggested citation

Brown AM, Decker SL, Selck FW. 

Emergency department visits and proximity 

to patients’ residences, 2009–2010. NCHS 

data brief, no 192. Hyattsville, MD: National 

Center for Health Statistics. 2015.

Copyright information

All material appearing in this report is in 

the public domain and may be reproduced 

or copied without permission; citation as to 

source, however, is appreciated.

National Center for Health 

Statistics

Charles J. Rothwell, M.S., M.B.A., Director

Nathaniel Schenker, Ph.D., Deputy Director

Jennifer H. Madans, Ph.D., Associate 

Director for Science

Division of Health Care Statistics

Clarice Brown, M.S., Director

Office of Analysis and Epidemiology

Irma E. Arispe, Ph.D., Director

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