Comprehensive Stroke Centers Overcome the Weekend Versus Weekday Gap in Stroke Treatment and Mortality
Background and Purpose—Hospital staffing may be reduced on weekends. Prior studies of weekend disparities in stroke care have focused on in-hospital mortality with variable results. We hypothesized that 90-day mortality was higher in patients with stroke hospitalized on weekends versus weekdays, and this difference has been minimized over time by improvements in organization and delivery of stroke care.
Methods—We used the Myocardial Infarction Data Acquisition System administrative database, which includes data on patients discharged with a primary diagnosis of cerebral infarction from all nonfederal acute care hospitals in New Jersey between 1996 and 2007. Out-of-hospital deaths were assessed by matching MIDAS records with New Jersey death registration files. New Jersey hospitals are designated by the state as comprehensive stroke centers, primary stroke centers, or nonstroke centers. The primary outcome measure was 90-day all-cause mortality after hospital admission.
Results—A total of 134 441 patients were admitted with a primary diagnosis of cerebral infarction during the study period. A total of 23.4% were admitted to a comprehensive stroke center, 51.5% to a primary stroke center, and 25.1% to a nonstroke center. Ninety-day mortality was greater in patients with stroke admitted on weekends compared with weekdays (17.2% versus 16.5%; P=0.002). The adjusted risk of death at 90 days was significantly greater for weekend admission (hazard ratio, 1.05; 95% CI, 1.02 to 1.09). No difference in 90-day mortality was observed for patients admitted to comprehensive stroke centers on weekends versus weekdays (hazard ratio, 1.01; 95% CI, 0.95 to 1.08).
Conclusions—Patients with stroke admitted on weekends to New Jersey hospitals had a significantly higher risk of death by 90 days. No such difference in mortality was observed at comprehensive stroke centers.
Disparities in care and clinical outcomes of patients exist between those hospitalized on weekends versus weekdays. Hospital staffing may be reduced in quantity and spectrum on weekends. This disparity has been shown to adversely affect treatment and outcomes in patients with myocardial infarctions.1 There have been inconsistent findings in patients admitted with stroke with most studies reporting early mortality.2–9 Canadian and Japanese studies have shown an increased risk of death and functional disability at 7 days with weekend stroke admission.2,3,9 In-hospital mortality was increased in patients admitted on “off-hours” in the Get With The Guidelines–Stroke database (OR, 1.09; 95% CI, 1.03 to 1.14).4 A report of stroke mortality in Sweden over 4 decades showed an increased risk of death with weekend admission, but the authors noted that this effect diminished over time.5 Temporal improvements in stroke care may account for this trend. A study using the Nationwide Inpatient Sample Database reported no difference in in-hospital mortality between weekend and weekday admissions for 599 087 patients with stroke from 2002 to 2007.8 Furthermore, no difference in in-hospital mortality has been observed in patients admitted to comprehensive stroke centers on weekends.6 There are little data on longer-term outcomes of patients with stroke admitted to hospitals on the weekend versus weekday.
In 2004, the State of New Jersey enacted the “Stroke Center Act,” which required the NJ Department of Health and Senior Services (DHSS) to designate hospitals that meet certain standards as primary stroke centers (PSCs) or comprehensive stroke centers (CSCs). The NJ DHSS began receiving applications and issued its first certification for both PSC and CSC in 2007. Further details are available through the NJ DHSS web site (www.state.nj.us/health/healthfacilities/documents/ac/njac43g_hoslicstd.pdf).
The aims of this study are 2-fold: (1) to compare 90-day mortality rates among patients admitted with acute ischemic stroke on weekends and those admitted on weekdays; and (2) to determine whether any differences in mortality could be explained by temporal improvements in stroke care or stroke center designation.
We used information from the Myocardial Infarction Data Acquisition System (MIDAS) administrative database for this study.1,10–12 MIDAS contains demographic and clinical data on patients discharged with a primary diagnosis of cerebral infarction (codes 433.01, 433.11, 433.21, 433.31, 433.81, 433.91, 434.01, 434.11, and 434.91 of the International Classification of Diseases, 9th Revision, Clinical Modification) from all nonfederal acute care hospitals in New Jersey. The database also includes records of treatment with intravenous (IV) thrombolysis after 1998 (International Classification of Diseases, 9th Revision code 99.10). Data for the following coexisting conditions were available: hypertension, diabetes, atrial fibrillation, and chronic renal disease. We obtained data on out-of-hospital deaths by matching MIDAS records with NJ death registration files using previously validated linkage and consolidation software (The Link King).13 Out-of-state deaths were not recorded. Outcomes were assessed by a blinded automated procedure.
MIDAS included 134 441 patients admitted between 1996 and 2007 with cerebral infarction as the primary reason for admission. Only the first discharge record for a patient was included. Subsequent records were excluded to avoid duplicating data or introducing bias from interhospital transfers or readmission for the same event. Patients who were admitted to federal hospitals or nursing homes or had a stroke during an admission for another diagnosis or procedure were excluded.
The primary outcome variable was all-cause mortality within 90 days of hospital admission. In-hospital and cumulative (inpatient and postdischarge) death rates at 30, 90, and 365 days were also examined. The primary independent variable was admission on weekends (Saturday, Sunday, and holidays) versus weekdays. Covariates included patient demographics, coexisting conditions, and treatment with IV thrombolysis. Measures of stroke severity were not available. Each hospital in MIDAS was categorized based on its current NJ DHSS designation as CSC, PSC, or as a nonstroke center (NSC).
We examined how differences in mortality between weekend and weekday admissions have changed over time. Data for the period from 1996 to 2007 were grouped into 2-year intervals. We compared weekend and weekday admissions in terms of both in-hospital and cumulative all-cause mortality. To adjust for confounders, we used Cox proportional hazard models in comparing the risk of death associated with weekend versus weekday admissions at 90 days. Multivariable logistic regression models were used to compare treatment among hospital types accounting for the measurable confounding effects of patient demographics and coexisting conditions. Statistical significance was defined as a probability value ≤0.01.
We examined whether the difference in mortality between weekend and weekday admissions could be explained by differences in stroke care temporally by year of admission or operationally by stroke center certification. Year of admission or stroke center certification would be considered to mediate the association between weekend and weekday admission and mortality if the hazard ratio decreased when included in the hazard model.
Statistical analyses were performed using SAS software. The Institutional Review Boards of the NJ DHSS and the University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School approved the study. Informed consent was not required.
There were 134 441 patients admitted between 1996 and 2007 with a primary diagnosis of cerebral infarction with 27.8% admitted on weekends. Baseline patient demographics were similar (Table 1). There was a 27.9% decline in stroke admissions over the study period; however, the ratio of weekend to weekday admissions remained unchanged (Figure 1).
Eighty-eight hospitals were represented in this analysis; 12 were CSC, 43 were PSC, and 33 were NSC. Of the total population, 23.4% (31 417) were admitted to a CSC, 51.5% (69 275) to a PSC, and 25.1% (33 746) to a NSC. Patients with stroke were significantly more likely to be admitted to a CSC on weekends (Table 1). Patients with stroke were more likely to be admitted to the hospital through the emergency department on the weekend than weekday (89.4% versus 84.4%, P<0.0001). There was a corresponding significant decline in admissions via physician referral on weekends versus weekdays (5.3% versus 9.9%, P<0.0001).
The overall 90-day mortality for patients admitted with cerebral infarction during the study was 16.7% (Table 2). Mortality 90 days after admission was significantly higher for patients admitted on weekends than on weekdays (17.2% versus 16.5%; P=0.001). In-hospital and 30-day mortality rates were also increased for patients admitted on weekends; however, this difference was diluted 1 year after admission (Table 2). Ninety-day stroke mortality declined throughout the study period for both weekend and weekday admissions (Figure 1). After adjusting for available confounding variables, 90-day mortality remained significantly higher for patients admitted on weekends than on weekdays (hazard ratio [HR], 1.05; 95% CI, 1.02 to 1.09; Table 3). Mortality was higher for patients admitted on weekends than weekdays for all time periods (Figure 1). However, the adjusted risk of death at 90 days was significantly lower for patients admitted between 2006 and 2007, the time period when New Jersey began designating stroke centers, compared with 1996 and 1997 (HR, 0.86; 95% CI, 0.82 to 0.91).
Additionally, we examined potential effects that PSC designation by The Joint Commission may have had by analyzing mortality before and after 2003, when The Joint Commission stroke center accreditation began. Adjusted 90-day mortality remained higher for patients admitted on weekends between 1996 and 2002 (HR, 1.05; 95% CI, 1.01 to 1.09) and 2003 and 2007 (HR, 1.05; 95% CI, 1.00 to 1.11).
IV thrombolysis rates were higher for patients with stroke admitted on weekends than weekdays (1.6% versus 1.3%; P<0.0001). The adjusted odds of treatment with IV tissue-type plasminogen activator (tPA) remained significantly higher for patients admitted on weekends (OR, 1.19; 95% CI, 1.07 to 1.31; Table 4). The adjusted odds of receiving IV tPA was also increased at CSCs (OR, 5.82; 95% CI, 4.88 to 6.94) or PSCs (OR, 2.48; 95% CI, 2.07 to 2.96) compared with NSCs. Patients with atrial fibrillation and those admitted through emergency departments were more likely to receive IV tPA; whereas women, blacks, and those with diabetes or renal disease were less likely to be treated (Table 4). By the time of initial The Joint Commission (2002 to 2003) and NJ DHSS (2006 to 2007) stroke center designation, patients were approximately 4 and 10 times more likely to receive IV tPA, respectively, than between 1998 and 1999.
Stroke Center Designation
Overall, patients with stroke were more likely to be admitted to CSCs than NSCs on weekends than weekdays (P<0.001). However, weekday versus weekend admissions remained similar in all time periods studied for all hospital types, except from 2006 to 2007, when there was a significant increase in the percentage of patients admitted to a CSC on weekends versus weekdays (30.3% versus 26.8%; P<0.0001). No increase in adjusted 90-day mortality was observed in patients admitted to CSC on weekends (HR, 1.01; 95% CI, 0.95 to 1.08). However, adjusted 90-day mortality was significantly greater with weekend admission to PSCs (HR, 1.06; 95% CI, 1.02 to 1.10) and NSCs (HR, 1.08; 95% CI, 1.02 to 1.15). The odds of in-hospital death by stroke center designation were similar: CSC (OR, 1.00; 95% CI, 0.92 to 1.09), PSC (OR, 1.07; 95% CI, 1.00 to 1.13), and NSC (OR, 1.10; 95% CI, 1.01 to 1.20). Trends in stroke center admission rates, IV thrombolysis, and 90-day mortality are presented in Figure 2. IV thrombolysis rates by stroke center designation are presented in Supplemental Table I (http://stroke.ahajournals.org).
There may be disparities in hospital care on weekends when hospital staffing is reduced. Weekend admission for myocardial infarction is associated with a higher mortality and lower use of invasive cardiac procedures.1 This disparity has been termed the “weekend effect.” Previous reports examining the weekend effect in stroke care have reported variable results with most studies focusing on in-hospital mortality.2–5,7–9 Our analysis of the MIDAS database shows that patients with stroke admitted on weekends have an increased adjusted risk of death at 90 days compared with those admitted on weekdays.
Multiple studies outside of the United States have reported increased early mortality for patients with stroke admitted on weekends. The Canadian Stroke Network found an increase in 7-day mortality for patients with stroke admitted on weekends (HR, 1.12; 95% CI, 1.00 to 1.25).9 A Taiwanese study also reported increased mortality for patients with stroke admitted on weekends.14 However, a German study found no weekend effect on early stroke mortality.15
Stroke care organization and delivery may be different in the United States than abroad. An analysis of the Get With The Guidelines–Stroke Program found a small but significant increase in in-hospital mortality for “off-hours” admission (5.8% versus 5.2%; P<0.001).4 This report may underestimate the overall weekend effect in stroke care because most hospitals participating in the Get With The Guidelines–Stroke Program are CSCs.
A study of stroke care in the United States using the Nationwide Inpatient Sample Database found no difference in in-hospital mortality between weekend and weekday admission between 2002 and 2007 (OR, 1.00; 95% CI, 0.972 to 1.029).8 Contrary to this report, our study did show a significant increase in in-hospital, 30-day, and 90-day mortality for patients with stroke admitted on weekends overall and between 2003 and 2007. Differences in study design may account for the differences in observations made by Hoh et al and those in our study. The former study included all admissions for an ischemic stroke diagnosis, whereas we limited ours to the first hospitalization with a primary diagnosis of ischemic stroke. Furthermore, we were able to include holiday admissions in the weekend cohort, whereas Hoh and colleagues could not.
Patients admitted on weekends were more likely to receive treatment with IV tPA in this analysis. Although this trend was not found in an analysis of thrombolytic use in Europe, it is consistent with other previously published reports of stroke care in the United States.7,8,16 Previously proposed explanations include: decreased traffic volume and work obligations that may decrease delays in hospital arrival; quicker access to diagnostic imaging and neurological evaluation outside of weekday work schedules; and more severe strokes on weekends.7,8 An alternative explanation is that many physicians' offices are closed on weekends, forcing patients to access health care through emergency medical services and emergency departments thereby reducing delays in hospital presentation. In our study, there was a 4.6% increase in stroke admission by physician referral during the week. This difference would account for >6000 patients who had potential delays in stroke diagnosis and treatment because medical care was not accessed by calling 911 and using established systems for delivering acute care. Furthermore, emergency medical services may triage patients with suspected stroke to stroke centers where they are more likely to be treated on weekends. The increase in weekend emergency department presentation and CSC admission observed in this study may account for increased rates of weekend IV tPA administration and deserves further study. In contrast to other states, New Jersey does not have a statute requiring emergency medical services to take patients with suspected stroke to designated stroke centers. Encouragingly, overall IV tPA rates increased 10-fold throughout the study period. This marked increase in acute stroke treatment is likely multifactorial, but undoubtedly ongoing community and healthcare provider education, stroke center designation by federal and state regulatory agencies, and hospital-based quality assurance and performance improvement initiatives are largely responsible.
Albright et al reported no difference in 90-day mortality between weekend and weekday stroke admission to 2 CSCs and concluded that around the clock availability of stroke specialists, advanced neuroimaging, and specialized nursing care may account for this difference.6 In our analysis of the MIDAS database, there was no increased risk of 90-day death with CSC admission on weekends. However, a weekend effect was present for patients with stroke admitted to PSCs or NSCs. We do not feel that this simply reflects hospital volume. In the multivariable model, admission to the highest volume centers was associated with an increase in risk of death, whereas CSC designation was associated with lower mortality. In New York State, patients admitted to designated stroke centers have a significant reduction in 30-day mortality compared with patients admitted to NSCs even after adjusting for hospital volume.17
There are several limitations to the present study. The principal limitation is that unmeasured confounders may have contributed to the reported differences in mortality between patients admitted on weekends and those admitted on weekdays. It is possible that some of these unmeasured variables may explain or mask some of the observations. Furthermore, we applied current stroke center designations to hospitals during the study period. It is possible that these centers did not provide CSC-level care during the study period. However, we feel that the majority of CSCs in New Jersey functioned as comprehensive centers before the development of the state designation. Ten of the 12 centers received CSC designation within the first year of review (2007), and our results speak to the existence of superior care at CSC. Interestingly, there was a significant reduction in 90-day risk of death (HR, 0.86; 95% CI, 0.82 to 0.91) during the time period of NJ state stroke center designation that was not seen in other time periods. This could indicate that the statewide designation process had a positive effect on stroke care as a whole across New Jersey and deserves further study.
An additional limitation is the retrospective nature of the study, which has potential for selection bias. The recently developed New Jersey Acute Stroke Registry will prospectively collect data on all stroke admissions and allow for future studies.
Neither of these limitations should detract from the primary finding that 90-day mortality was increased with weekend stroke admission. Our data were collected between 1996 and 2007, and it is possible that current stroke care has improved further. This study has several important strengths, namely the large sample size that includes all patients admitted to a NJ acute care hospital over a 12-year period for a first-time diagnosis of an ischemic stroke, which may reduce or eliminate selection bias.
The observation that weekend stroke admission independently increases the risk of 90-day death by 5% is both significant and clinically meaningful. This increase in mortality could account for several thousand deaths annually in the United States. More appropriate hospital staffing and organization of stroke care such as that provided by CSC may negate the weekend effect and save lives.
In the MIDAS database, 1996 to 2007, patients with stroke admitted on weekends had a significantly higher risk of death by 90 days. No difference in mortality was observed at CSCs.
Sources of Funding
This study was funded in part by the Robert Wood Johnson Foundation and the Schering-Plough Foundation.
The online-only Data Supplement is available at http://stroke.ahajournals.org/lookup/suppl/doi:10.1161/STROKEAHA.110.612317/-/DC1.
- Received December 23, 2011.
- Revision received March 4, 2011.
- Accepted March 7, 2011.
- © 2011 American Heart Association, Inc.
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