Don't get sick on the weekend: an evaluation of the weekend effect on mortality for
patients visiting US EDs☆,☆☆,★,★★
Adam L. Sharp MD, MSa,⁎, HwaJung Choi PhDb, Rod A. Hayward MDc
aDepartment of Emergency Medicine, Robert Wood Johnson Foundation Clinical Scholar, University of Michigan, Ann Arbor, MI 48109–2800, USA
bDepartment of Internal Medicine, Robert Wood Johnson Clinical Scholar Program, University of Michigan, Ann Arbor, MI 48109–2800, USA
cDepartment of Internal Medicine and Veteran Affairs HSR&D, Robert Wood Johnson Clinical Scholar Program, University of Michigan, Ann Arbor, MI 48109–2800, USA
a b s t r a c ta r t i c l e i n f o
Received 12 December 2012
Accepted 10 January 2013
Primary objective: The primary objective of the study is to determine if the mortality for adult patients visiting
US emergency departments (EDs) is greater on weekends than weekdays.
Secondary objectives: The secondary objective of the study is to examine whether patient factors (diagnosis,
income, insurance status) or hospital characteristics (ownership, ED volume, teaching status) are associated
with increased weekend mortality.
Methods: We used a retrospective cohort analysis of the 2008 Nationwide Emergency Department Sample.
Evaluating 4225973 adults admitted through the ED to the hospital, signifying a 20% representative sample of
US ED admissions. Logistic regression was used to examine associations of weekend mortality with patient
and hospital characteristics, accounting for clustering by hospital.
Results: Emergency department patients admitted to the hospital on the weekend are significantly more likely
to die than those admitted on weekdays (odds ratio, 1.073; 95% confidence interval, 1.061-1.084). A
significant weekend effect persisted after controlling for patient characteristics (odds ratio, 1.026; 95%
confidence interval, 1.005-1.048). The top 10 primary diagnoses for patients dying did not identify any
specific medical condition that explained the higher weekend admission mortality. The weekend effect was
also relatively consistent across patient income, insurance status, hospital ownership, ED volume, and
hospital teaching status.
Conclusion: Patients are more likely to die when admitted through the ED on the weekend. We were unable to
identify specific circumstances or hospital attributes that help explain this phenomenon. Although the
relative increased risk per case is small, our study demonstrates a significant number of potentially
preventable weekend deaths occurring annually in the United States.
© 2013 Elsevier Inc. All rights reserved.
It is widely believed that there is a weekend effect in the United
States (higher mortality risk for those presenting to emergency
departments [EDs] on weekends) resulting from lower resource
availability or quality on weekends . This belief may be driven by
health care provider's anecdotal experience or the reports of
increased mortality in other countries [2–4]. A weekend effect is
increasingly being reported for specific conditions in specific health
systems [5–13]. However, national data comparing mortality for
patients admitted on the weekend to weekdays have never been
reported in the United States.
As budget constraints continue, the prioritization of health
services becomes essential. Timely health care, one of the Institute
of Medicine's quality domains, can be expensive to maintain on
weekends, whichcould put adequatestaffingof acute care facilities on
weekends at risk. The ED is generally the primary avenue for
admission during weekends or off hours. With this in mind, we
undertook a study to examine whether higher weekend mortality for
patients admitted through the ED exists nationally in the United
States. Our secondary objective was to examine whether patient
factors (diagnosis, income, insurance status) or hospital characteris-
tics (ownership, ED volume, teaching status) are associated with
increased weekend mortality.
American Journal of Emergency Medicine 31 (2013) 835–837
☆ Data set: The Nationwide Emergency Department Sample used for analysis is
publicly available and was previously de-identified by the Agency for Healthcare
Research and Quality.
☆☆ Financial Support: ALS is supported by the Robert Wood Johnson Foundation
Clinical Scholar Program.
★ Disclosures/conflicts of interest: No authors have conflicts of interest to report.
★★ Prior Presentation: A poster for this study was presented at the American
College of Emergency Physicians Scientific Assembly in Denver Colorado October 2012.
⁎ Corresponding author. The Robert Wood Johnson Foundation Clinical Scholars
Program, North Campus Research Center (NCRC), Ann Arbor, MI 48109–2800, USA.
E-mail addresses: email@example.com, firstname.lastname@example.org (A.L. Sharp).
0735-6757/$ – see front matter © 2013 Elsevier Inc. All rights reserved.
Contents lists available at SciVerse ScienceDirect
American Journal of Emergency Medicine
journal homepage: www.elsevier.com/locate/ajem
We used a retrospective cohort analysis of the 2008 Nationwide
Emergency Department Sample (NEDS) to compare adult mortality
for patients admitted through the ED on the weekend compared with
weekdays. The NEDS is a 20% sample representative of all ED visits in
the United States. It is publicly available and de-identified as part of
the Healthcare Cost and Utilization Project sponsored by the Agency
for Healthcare Research and Quality. It is a compilation of the State
Emergency Department Databases and the State Inpatient Databases.
We limited our analysis to the 4225973 adult ED encounters that
ended with death or hospital admission.
Our primary outcome measure was death. This was evaluated in
aggregate as well as stratified by those dying in the ED and those that
died after admission to the hospital. We used logistic regression
controlling for patient level variation of age, sex, income, and
comorbidities. Comorbidities were accounted for using the Chronic
Condition Indicator categorizing all International Classification of
Diseases, Ninth Edition, Clinical Modification, diagnosis codes as chronic
or not chronic.
We obtained robust standard errors, accounting for clustering at
the hospital level. To examine for potential heterogeneity in the
weekend effect in subpopulations, we examined for interactions
(using interaction terms) between weekend presentation and patient
income and insurance status and between weekend presentation and
ED volume, hospital teaching status, and hospital ownership. We also
evaluated for variations in weekend mortality differences for each of
the top 10 primary diagnoses. Final analyses accounted for weighting
used in the sampling design of the NEDS 2008. All analyses were done
using STATA version 12.
Of the 4225973 ED patients admitted (Table 1), 1076937 (25.5%)
presented on the weekend, and 170218 (4.03%) died in the ED or after
admission. In assessing for differences between patients admitted on
weekdays and weekends, no meaningful differences were apparent.
Patient ages, comorbidities, sex, income, and insurance status can be
evaluated by weekday and weekend presentation in Table 1.
Before adjusting for potential confounders, mortality was higher for
Table 2). A statistically significant higher odds of dying for those
presenting on the weekend was maintained after controlling for patient
characteristics (OR, 1.026 [P = .014, 95% CI, 1.005-1.048]; see Table 2).
Of note, the entire weekend effect was due to a higher risk of
dying after hospital admission (OR, 1.026; P = .014), with no
significant weekend effect found for the risk of dying in the ED itself
(OR, 0.945; P N .2). There was no indication that the weekend effect
was isolated to just a few diagnoses because there was no
significant variation in the weekend effect for the 10 most prevalent
primary diagnoses (cardiac and pulmonary arrest, sepsis, acute
cerebrovascular accident, acute myocardial infarction, pneumonia,
congestive heart failure, aspiration pneumonitis, acute unspecified
renal failure, intracranial injury, and secondary malignancies).
Similarly, there was no evidence that the weekend effect differed
by hospital characteristics, such as teaching status, hospital
ownership status and ED volume (P N .2 for all interactions), or
for patient social demographics, such as income and insurance
status (P N .2 for both interactions).
No randomization occurred; therefore, the limitations of all
retrospective observational studies apply to our analysis. Our study
found a significant weekend effect for patients admitted on the
weekend but was unable to identify specific areas to target for
improvement. Individual characteristics used for analysis did not
explain the difference, including the top 10 diagnoses, insurance
status, or income level. Hospital level variables to pursue also did not
present a clear point for improvement including ED volume,
evaluation of hospital ownership, or teaching status.
Another limitation is the relatively small effect size (adjusted OR,
1.026). Our finding is statistically significant and, consistent with
similar analyses, would be less important if not for such large
numbers of people admitted through the ED on weekends. Because of
the high volume of patients seen in the ED, this small effect size has a
potentially large impact.
Our study confirms a weekend effect in the United States,
concluding patients are at somewhat higher risk of dying when
admitted on the weekend. Although a limitation of all observational
studies is the possibility of confounding by unmeasured severity, our
findings are consistent with results reported from California, Spain,
and Canada [2–4]. Although the relative increased risk per case is
small, the level of increased risk observed in our study represents a
significant number of excess deaths annually in the United States.
Identifying the cause of this weekend effect is beyond the scope or
our analysis, but others have produced evidence suggesting some
possible causes. Decreased weekend hospital staffing and less access
to diagnostic and therapeutic interventions on the weekend are
A comparison of individual characteristics for patients admitted through the ED on
weekdays versus weekends
N = 4225973
Mean age (y)
Incomea(% in lowest quartile)
Chronic conditionsb(mean number)
n = 3149036
n = 1076937
aRepresents the proportion of patients with ZIP codes with median household
income between $1 and $39999.
bThe number of chronic conditions is calculated using the Chronic Condition
Indicator, an Healthcare Cost and Utilization Project variable used to categorize
International Classification of Diseases, Ninth Edition, Clinical Modification, codes as
chronic or nonchronic.
A comparison of weekend versus weekday mortality based on patient insurance status
and hospital characteristics
Hospital teaching status
For profit private
Unadjusted OR (95% CI)
Adjusted OR (95% CI)
A.L. Sharp et al. / American Journal of Emergency Medicine 31 (2013) 835–837
possible contributors . This explanation is supported by previous Download full-text
research from the UK attributing parity in mortality rates between
weekends and weekdays to “consistent staffing levels and 24-hour
access to diagnostics for the early phase of critical illness” .
Twenty-four-hour access to specialized trauma systems, stroke
centers, and pediatric intensive care unit teams has all shown the
ability to eliminate the weekend effect in the United States [16–19].
Although our analysis specifically targeted weekends, variations have
been reported for patients admitted in the evening as well .
Furthermore, other factors that overburden the system (including
high hospital occupancy, lower nurse staffing levels, and seasonal
influenza epidemics) have been shown to be associated with
increased in-hospital mortality . This presumptively caused by
creating a mismatch in patient needs and resource availability.
These findings have challenging but important policy implications.
As rising health care expenditures are under scrutiny, deciding which
health care resources are available requires important considerations.
Policy makers and providers should be aware that costs saved by
limiting weekend health services may increase mortality and likely
have other associated morbidity adversely effecting health outcomes.
Inconvenient hours, holidays, and weekends must be accounted for as
quality measures are established and evaluated. Policies to encourage
timely health care cannot rely wholly on 24/7 ED availability. Our
system can do better to assure our loved ones receive the care they
need, even on the weekend.
 Conley M. More stroke patients die after weekend hospital admissions. ABC News
Available at: http://abcnews.go.com/Health/stroke-patients-die-hospitalized-
weekend/story?id=16742707. Accessed July 10, 2012.
 Bell CM, Redelmeier DA. Mortality among patients admitted to hospitals on
weekends as compared with weekdays. N Engl J Med 2001;345(9):663–8.
 Cram P, Hillis SL, Barnett M, et al. Effects of weekend admission and hospital
teaching status on in-hospital mortality. Am J Med 2004;117(3):151–7.
 Barba R, Losa JE, Velasco M, et al. Mortality among adult patients admitted to the
hospital on weekends. Eur J Intern Med 2006;17(5):322–4.
 Kostis WJ, Demissie K, Marcella SW, et al. Weekend versus weekday admission
and mortality from myocardial infarction. N Engl J Med 2007;356(11):1099–109.
 Saposnik G, Baibergenova A, Bayer N, et al. Weekends: a dangerous time for
having a stroke? Stroke 2007;38(4):1211–5.
 Ananthakrishnan AN, McGinley EL, Saeian K. Outcomes of weekend admissions for
upper gastrointestinal hemorrhage: a nationwide analysis. Clin Gastroenterol
 Aujesky D, Jimenez D, Mor MK, et al. Weekend versus weekday admission and
mortality after acute pulmonary embolism. Circulation 2009;119(7):962–8.
 Crowley RW, Yeoh HK, Stukenborg GJ, et al. Influence of weekend versus weekday
hospital admission on mortality following subarachnoid hemorrhage. Clinical
article. J Neurosurg 2009;111(1):60–6.
 Crowley RW, Yeoh HK, Stukenborg GJ, et al. Influence of weekend hospital
admission on short-term mortality after intracerebral hemorrhage. Stroke
 McKinney JS, Deng Y, Kasner SE, et al. Comprehensive stroke centers overcome the
weekend versus weekday gap in stroke treatment and mortality. Stroke
 Barba R, Zapatero A, Losa JE, et al. The impact of weekends on outcome for acute
exacerbations of COPD. Eur Respir J 2012;39(1):46–50.
 Palmer WL, Bottle A, Davie C, et al. Dying for the weekend: a retrospective cohort
study on the association between day of hospital presentation and the quality and
safety of stroke care. Arch Neurol 2012:1–7.
 Bell CM, Redelmeier DA. Waiting for urgent procedures on the weekend among
emergently hospitalized patients. Am J Med 2004;117(3):175–81.
 Schmulewitz L, Proudfoot A, Bell D. The impact of weekends on outcome for
emergency patients. Clin Med 2005;5(6):621–5.
 Hixson ED, Davis S, Morris S, et al. Do weekends or evenings matter in a pediatric
intensive care unit? Pediatr Crit Care Med 2005;6(5):523–30.
 Laupland KB, Ball CG, Kirkpatrick AW. Hospital mortality among major trauma
victims admitted on weekends and evenings: a cohort study. J Trauma Manag
 Carr BG, Reilly PM, Schwab CW, et al. Weekend and night outcomes in a statewide
trauma system. Arch Surg 2011;146(7):810–7.
 Albright KC, Raman R, Ernstrom K, et al. Can comprehensive stroke centers erase
the “weekend effect”? Cerebrovasc Dis 2009;27(2):107–13.
 Arias Y, Taylor DS, Marcin JP. Association between evening admissions and higher
mortality rates in the pediatric intensive care unit. Pediatrics 2004;113(6):
 Schilling PL, Campbell Jr DA, Englesbe MJ, et al. A comparison of in-hospital
mortality risk conferred by high hospital occupancy, differences in nurse
staffing levels, weekend admission, and seasonal influenza. Med Care
A.L. Sharp et al. / American Journal of Emergency Medicine 31 (2013) 835–837