Association Between Stroke Center Hospitalization for Acute Ischemic Stroke and Mortality

Study Questions:

What is the association between admission to stroke centers for acute ischemic stroke and mortality?

Methods:

This was an observational study using data from the New York Statewide Planning and Research Cooperative System. The authors compared mortality for patients admitted with acute ischemic stroke (n = 30,947) between 2005 and 2006 at designated stroke centers and nondesignated hospitals using differential distance to hospitals as an instrumental variable to adjust for potential prehospital selection bias. Patients were followed up for mortality for 1 year after the index hospitalization through 2007. To assess whether their findings were specific to stroke, the investigators also compared mortality for patients admitted with gastrointestinal hemorrhage (n = 39,409) or acute myocardial infarction (n = 40,024) at designated stroke centers and nondesignated hospitals. The primary outcome measure was 30-day all-cause mortality.

Results:

Among 30,947 patients with acute ischemic stroke, 15,297 (49.4%) were admitted to designated stroke centers. Using the instrumental variable analysis, admission to designated stroke centers was associated with lower 30-day all-cause mortality (10.1% vs. 12.5%; adjusted mortality difference, −2.5%; 95% confidence interval [CI], −3.6% to −1.4%; p < 0.001) and greater use of thrombolytic therapy (4.8% vs. 1.7%; adjusted difference, 2.2%; 95% CI, 1.6% to 2.8%; p < 0.001). Differences in mortality also were observed at 1-day, 7-day, and 1-year follow-up. The outcome differences were specific for stroke, as stroke centers and nondesignated hospitals had similar 30-day all-cause mortality rates among those with gastrointestinal hemorrhage (5.0% vs. 5.8%; adjusted mortality difference, +0.3%; 95% CI, −0.5% to 1.0%; = 0.50) or acute myocardial infarction (10.5% vs. 12.7%; adjusted mortality difference, +0.1%; 95% CI, −0.9% to 1.1%; p = 0.83).

Conclusions:

The authors concluded that among patients with acute ischemic stroke, admission to a designated stroke center was associated with modestly lower mortality and more frequent use of thrombolytic therapy.

Perspective:

The study suggests that patients admitted to stroke centers are more likely to receive thrombolytic therapy and have lower 30-day mortality rates when compared with patients admitted to nondesignated hospitals. This survival benefit was sustained for up to 1 year after stroke occurrence and was independent of patient and hospital characteristics. Also, the lower mortality at designated stroke centers was specific to stroke and was not evident for other acute life-threatening conditions, suggesting that the mortality benefit was related to stroke center designation and specific quality improvement initiatives, rather than to generalized or overall quality improvement efforts at designated stroke center hospitals.

Keywords: Hospitals, Outcome Assessment (Health Care), Quality Improvement, Thrombolytic Therapy, Myocardial Infarction, Stroke, Follow-Up Studies, Selection Bias, Gastrointestinal Hemorrhage, New York, Hospitalization


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