NCHS Data Brief ■ No. 102 ■ August 2012

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for Health Statistics

Wait Time for Treatment in 

Hospital Emergency Departments: 2009

Esther Hing, M.P.H., and Farida Bhuiya, M.P.H.

Key findings

•	 From 2003 through 2009, 

the mean wait time in U.S. 

emergency departments (EDs) 

increased 25%, from 46.5 

minutes to 58.1 minutes.

•	 Mean wait times were longer 

in EDs that went on ambulance 

diversion or boarded admitted 

patients in hallways and in 

other spaces.

•	 Longer wait times were 

associated with EDs in urban 

areas (62.4 minutes), compared 

with nonurban areas (40.0 

minutes).

•	 The mean wait time 

increased as annual ED visit 

volume increased; from 33.8 

minutes in EDs with less than 

20,000 annual visits, to 69.8 

minutes in EDs with 50,000 or 

more annual visits.

•	 There was no difference in 

mean wait time for patients 

needing immediate or emergent 

care by ambulance diversion 

status, or by whether the ED 

boarded admitted patients while 

waiting for an inpatient bed.

From 1999 through 2009, the number of visits to emergency departments 

(EDs) increased 32%, from 102.8 million visits in 1999 to 136.1 million visits 

in 2009 (1,2). In some hospitals, increased ED visit volume has resulted in ED 

crowding and increased wait times for minor and sometimes serious problems, 

such as myocardial infarction (3–7). This report describes the recent trend in 

wait times for treatment in EDs, and focuses on how wait times for treatment 

varied by two ED crowding measures: ambulance diversions and boarding of 

admitted patients.

Keywords: emergency department crowding • ambulance diversion • boarding

Has wait time for treatment in EDs increased? 

•	 Between 2003 and 2009, mean wait time to see a provider increased 

25%, from 46.5 minutes to 58.1 minutes (Figure 1).

•	 Because wait time is highly skewed, that is, a small percentage (5%) of 

visits have very long wait times (greater than 3 hours), median wait time 

is less affected by the skewed distribution and provides an alternative 

way of describing ED wait time.

Wait time in minutes

Figure 1. Mean and median emergency department wait time to see a provider: United States, 

2003–2009 

NOTE: Dotted lines represent change in meaning of emergency department wait time. In 2009, emergency department wait time 

referred to wait time to see a physician, physician assistant, or nurse practitioner; prior to 2009, emergency department wait time 

referred to wait time to see a physician. See data source and methods for details.

SOURCE: CDC/NCHS, National Hospital Ambulatory Medical Care Survey.

46.5

27 29 31 31 33 35 33

47.5

56.1 55.8 57.2 56.7 58.1

Median 

2003 2004 2005 2006

Year

2007 2008 2009

10

0

20

30

40

50

60

70

Mean
NCHS Data Brief ■ No. 102 ■ August 2012

■  2  ■

•	 Between 2003 and 2009, median time to see a provider increased 22%, from 27 minutes to 

33 minutes. 

Does ED crowding affect wait time? 

•	 In 2009, 33% of ED visits occurred in EDs that reported they went on ambulance diversion 

at some time during the previous year; 40% of visits occurred in EDs that reported they 

did not go on ambulance diversion; and 27% of visits occurred in EDs that reported it was 

unknown whether the ED went on ambulance diversion (Figure 2).

•	 The average wait time to see an ED provider in EDs with ambulance diversions (64.3 

minutes) was longer than in EDs with no diversions (48.7 minutes), but was similar to EDs 

for which diversions were unknown (65.2 minutes).

•	 In 2009, 78% of visits occurred in EDs that reported boarding admitted patients in hallways 

and in other spaces while waiting for an inpatient bed to become available.

•	 Wait time in EDs with any boarding was longer (61.3 minutes) than wait time in EDs with 

no boarding (44.1 minutes). 

1

Significantly different from no diversion.

2

Significantly different from no boarding.

SOURCE: CDC/NCHS, National Hospital Ambulatory Medical Care Survey.

Figure 2. Mean wait time for treatment, by emergency department crowding measure: United States, 2009 

0 20 40

Wait time in minutes

60 80

Ambulance diversion

(33% of visits) 1

64.3

No diversion

(40% of visits) 48.7

Unknown

(27% of visits) 1

65.2

Boarded

(78% of visits) 2

61.3

Unknown

(3% of visits) 2

66.3

No boarding

(19% of visits) 44.1

Any ambulance diversion in 2008

Boarded admitted patients 

How does hospital location and ED crowding affect wait time?

•	 Wait time in urban EDs (62.4 minutes) was significantly longer than in EDs outside of

metropolitan areas (40.0 minutes) (Figure 3).

•	 The mean wait time among EDs reporting ambulance diversions was not significantly

different in urban and nonurban hospitals (64.1 minutes compared with 68.4 minutes). The 

mean wait time in EDs with no ambulance diversions was longer among urban EDs (55.9 

minutes) than among nonurban EDs (38.1 minutes).
NCHS Data Brief ■ No. 102 ■ August 2012

■  3  ■

•	 Among EDs that boarded admitted patients, the mean wait time was longer in urban EDs 

(64.3 minutes) than in nonurban EDs (42.9 minutes). The difference in mean wait time by 

hospital location among EDs that did not board was not statistically significant.

1

Difference by hospital location is statistically significant (p < 0.05).

NOTE: MSA is metropolitan statistical area.

SOURCE: CDC/NCHS, National Hospital Ambulatory Medical Care Survey.

Figure 3. Mean wait time for treatment, by emergency department crowding measure and hospital location: United States, 

2009 

1

62.4

40.0

64.1

68.4

1

55.9

38.1

1

66.7

33.5

1

64.3

0.0

42.9

50.0

66.3

35.7

Non-MSA

MSA

0 10 20 30 40 50 60 70 80

Unknown

No boarding

Boarded

Unknown

No diversion

Ambulance

diversion

Total

Any ambulance

diversion in 2008

Boarded admitted

patients

Wait time in minutes

How does ED visit volume and ED crowding affect wait time?

•	 Mean wait time increased as the volume of annual ED visits increased; from 33.8 minutes in 

EDs with less than 20,000 annual visits, to 69.8 minutes in EDs with 50,000 or more annual 

visits (Figure 4). 

•	 Mean wait time to see a health care provider increased as annual ED visit volume increased 

in each ambulance diversion category. 

•	 The mean wait time in EDs that boarded patients increased as annual ED visit volume 

increased. Among EDs that did not board patients, EDs with less than 20,000 annual visits 

had shorter wait times than those with more than 20,000 annual visits; but there was no 

difference in wait times for EDs with 20,000–49,999 visits and those with 50,000 or more 

visits. 
NCHS Data Brief ■ No. 102 ■ August 2012

■  4  ■

Does patient acuity affect wait time for treatment in EDs?

•	 Two percent of ED patients were triaged as needing to be seen in less than 1 minute 

(immediate); 10% were triaged as needing to be seen within 1–14 minutes (emergent); 

41% were triaged as needing to be seen within 15–60 minutes (urgent); 35% were triaged 

as needing to be seen within 1–2 hours (semiurgent); and 7% of patients were triaged as 

needing to be seen between 2 and 24 hours (nonurgent). No triage system was used for the 

remaining 4% of patients (Figure 5).

•	 Mean wait times for patients triaged as immediate (28.9 minutes) and those with no triage 

system (38.2 minutes) were shorter than mean wait times for patients triaged as emergent 

(51.2 minutes), urgent (63.3 minutes), semiurgent (58.7 minutes), and nonurgent (53.5 

minutes).

1

Trend by annual emergency department visit volume is statistically significant. 

2

Mean wait time in emergency departments with fewer than 20,000 annual visits is significantly lower than wait times in emergency departments in other volume

categories.

SOURCE: CDC/NCHS, National Hospital Ambulatory Medical Care Survey.

Figure 4. Mean wait time for treatment, by emergency department crowding measure and volume of annual emergency 

department visits: United States, 2009 

Unknown

No boarding

Boarded

Unknown

No diversion

Total

Ambulance

diversion

Any ambulance

diversion in 2008

Boarded admitted

patients

0 10 20 30 40 50 60 70 80

Wait time in minutes

50,000 visits or more 

20,000–49,999 visits

33.8 20,000 visits or fewer 54.9 1

69.8

29.8 61.4 1

69.7

34.0 48.0 1

64.7

35.0 54.5 1

74.3

37.1 54.4 1

71.7 2

29.8 55.1

53.1

63.5 0.0

69.4
NCHS Data Brief ■ No. 102 ■ August 2012

■  5  ■

1

Difference with immediate care is statistically significant (p < 0.05).

2

Difference with no triage is statistically significant (p < 0.05).

SOURCE: CDC/NCHS, National Hospital Ambulatory Medical Care Survey.

Figure 5. Mean emergency department wait time for treatment, by urgency of patient care: United States, 2009 

0 10 20 30 40 50 60 70 80

No triage (4% of visits)

Nonurgent (7% of visits)

Semiurgent (35% of visits)

Urgent (41% of visits)

Emergent (10% of visits)

Immediate (2% of visits)

Wait time in minutes

28.9

1,251.2

1,263.3

1,258.7

1,253.5

38.2

Does ED crowding affect wait time for treatment when patient acuity is 

controlled for?

•	 There were no differences in mean wait times for ED patients triaged as immediate or 

emergent between EDs that went on diversion and EDs that did not go on diversion 

(Figure 6). Similarly, there were no differences in wait times for ED patients triaged as 

immediate or emergent by whether the ED boarded any admitted patients.

•	 Patients triaged as urgent, semiurgent, or nonurgent, and patients that had no triage, had 

longer wait times in EDs that went on diversion compared with EDs that did not go on 

diversion.

•	 Patients triaged as urgent, semiurgent, or nonurgent, and patients that had no triage, had 

longer wait times in EDs that boarded any admitted patients compared with EDs that did not 

board any admitted patients.
NCHS Data Brief ■ No. 102 ■ August 2012

■  6  ■

1

Difference between ambulance diversion and no diversions is statistically significant (p < 0.05). 

2

Difference between boarding and no boarding is statistically significant (p < 0.05). 

SOURCE: CDC/NCHS, National Hospital Ambulatory Medical Care Survey.

Figure 6. Mean wait time for treatment, by urgency of patient care and whether emergency department experienced 

ambulance diversions or boarding: United States, 2009 

Unknown

No diversion

Ambulance

diversion

No triage

Semiurgent

or not urgent

Urgent

Immediate

or

emergent

No triage

Semiurgent

or not urgent

Urgent

Immediate

or

emergent

0 20 40 60 80

Wait time in minutes Wait time in minutes

49.4 48.7

41.9

52.1

2

65.8

50.4

66.3

2

61.3

42.5

69.5

2

45.2

27.8

0.0

47.5

46.8

1

68.7

52.3

72.2

1

64.2

48.3

64.5

1

58.2

26.0

44.3

0 20 40 60 80

Unknown

No boarding

Boarded

Summary 

Mean wait time to see a health care provider in EDs increased from 2003 through 2009. 

Consistent with previous research, longer wait time for treatment was associated with urban ED 

locations (inside metropolitan statistical areas) and with increased annual ED visit volume (6).

In 2009, EDs with any ambulance diversion during the previous year were associated with 

longer wait times, compared with EDs without ambulance diversions. EDs that boarded admitted 

patients inside the ED, in observation units, or outside the ED (in hallways) were also associated 

with longer wait times compared with EDs that did not board. In this analysis, mean wait times 

for treatment did not differ among urban EDs that went on ambulance diversion during the 

previous year, but mean wait times were longer among urban EDs and nonurban EDs with no 

ambulance diversions and with unknown ambulance diversion status. Among EDs that boarded 

admitted patients (either inside or outside ED spaces), mean wait times were longer in EDs with 

annual visit volumes of 20,000 or more. 

The mean wait time in EDs with unknown ambulance diversion status was similar to the wait 

time in EDs that went on ambulance diversion. The mean wait time in EDs for which boarding 

was unknown was also similar to the mean wait time in EDs that boarded patients inside or 

outside the ED. Figures 3 and 4 further indicate that ED visits missing information on ambulance 

diversions were all located in urban EDs and in EDs with annual visit volumes of 20,000 or more. 

The long mean wait times for visits in EDs missing information on ambulance diversions, as well 

as the high percentage (71%) that also reported boarding admitted patients, suggest that these 

EDs may have been on ambulance diversion.

There was no difference in mean wait time for patients triaged as immediate or emergent between 

EDs that went on diversion compared with EDs that did not go on diversion. There was also no 

difference in wait time for patients triaged as immediate or emergent by whether the ED boarded 

patients. 
NCHS Data Brief ■ No. 102 ■ August 2012

■  7  ■

This analysis indicates that EDs are continuing to experience pressure to treat more patients with 

fewer EDs and with fewer hospital beds. Patients not requiring immediate care have longer wait 

times in EDs experiencing crowding (i.e., went on ambulance diversion or boarded admitted 

patients while waiting for an inpatient bed).

Definitions

Emergency department crowding: An ED is considered crowded when inadequate resources to 

meet patient care demands lead to a reduction in the quality of care (8).

Ambulance diversion: An ambulance is diverted when hospitals request that ambulances bypass 

their ED and transport patients to other medical facilities (4).

Boarding: A patient remains in the ED after the decision to admit or transfer the patient has been 

made (e.g., because an inpatient bed elsewhere in the hospital is not yet available) (4). 

Data source and methods

All estimates are from the National Hospital Ambulatory Medical Care Survey (NHAMCS), an 

annual nationally representative survey of visits to nonfederal, general, and short-stay hospital 

emergency and outpatient departments. ED visit response rate was 83% in 2009. More details 

about NHAMCS methodology are available (9). 

In 2009, ED wait time data were reported for visits seen by a physician, physician assistant, or 

nurse practitioner (n = 30,904). Prior to 2009, only wait time to see a physician was reported. 

The trend in mean wait times was minimally affected by the wording change; the 2009 mean wait 

time to see a physician (57.2 minutes) was not statistically different from mean wait time to see a 

physician, physician assistant, or nurse practitioner (58.1 minutes). The median wait time to see a 

physician (33 minutes) was also not affected by the wording change in NHAMCS. In this report, 

wait times were not presented for visits not seen by a physician, physician assistant, or nurse 

practitioner (4.1%).

Data analyses were performed using the statistical packages SAS version 9.2 (SAS Institute, Cary, 

N.C.) and SUDAAN version 9.0 RTI International, Research Triangle Park, N.C.). Differences 

in average wait times for treatment by ED and patient visit characteristics were examined using t

tests for differences at the 0.05 level. 

About the authors

Esther Hing and Farida Bhuiya are with the Centers for Disease Control and Prevention’s 

National Center for Health Statistics, Division of Health Care Statistics.

References

1. McCaig LF, Burt CW. National Hospital Ambulatory Medical Care Survey: 1999 emergency 

department summary. Advance data from vital and health statistics; no 320. Hyattsville, MD: 

National Center for Health Statistics. 2001.
U.S. DEPARTMENT OF

HEALTH & HUMAN SERVICES

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National Center for Health Statistics

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Hyattsville, MD 20782

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2. National Center for Health Statistics. National Hospital Ambulatory 

Medical Care Survey: 2009 emergency department summary tables. 

Available from: http://www.cdc.gov/nchs/ahcd/web_tables.htm#2009.

3. Institute of Medicine, Committee on the Future of Emergency Care in 

the United States Health System. Hospital-based emergency care: At the 

breaking point. Washington, DC: National Academies Press. 2007.

4. U.S. Government Accountability Office. Hospital emergency

departments: Crowding continues to occur, and some patients wait longer 

than recommended time frames. A report to the Chairman, Committee on 

Finance, U.S. Senate. Washington, DC: Publication No. GAO–09–347 2009. 

5. McCaig LF, Burt CW. National Hospital Ambulatory Medical Care 

Survey: 2003 emergency department summary. Advance data from vital 

and health statistics; no 358. Hyattsville, MD: National Center for Health 

Statistics. 2005.

6. Burt CW, McCaig LF, Valverde RH. Analysis of ambulance diversions in 

U.S. emergency departments. Ann Emerg Med 47(4):317–26. 2006. 

7. Wilper AP, Woolhandler S, Lasser KE, McCormick D, Cutrona SL, Bor 

DH, Himmelstein DU. Waits to see an emergency department physician: U.S. 

trends and predictors, 1997–2004. Health Aff 27(2):W84–95. 2008.

8. American College of Emergency Physicians Crowding Resources Task 

Force. Responding to emergency department crowding: A guidebook for 

chapters. Dallas, TX. 2002.

9. National Center for Health Statistics. NHAMCS Micro-data File 

Documentation. 2009. Available from: ftp://ftp.cdc.gov/pub/Health_

Statistics/NCHS/Dataset_Documentation/NHAMCS/doc09.pdf.

Suggested citation

Hing E, Bhuiya F. Wait time for treatment 

in hospital emergency departments: 2009. 

NCHS data brief, no 102. Hyattsville, MD: 

National Center for Health Statistics. 2012.

Copyright information

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the public domain and may be reproduced 

or copied without permission; citation as to 

source, however, is appreciated.

National Center for Health 

Statistics

Edward J. Sondik, Ph.D., Director

Jennifer H. Madans, Ph.D., Associate 

Director for Science

Division of Health Care Statistics

Clarice Brown, M.S., Director

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