Variations in Inpatient Mortality among Hospitals in Different System Types, 1995 to 2000

Background: Relatively few studies focused on the impact of system formation and hospital merger on quality, and these studies reported typically little or no quality effect. Objective: To study associations among 5 main types of health systems-centralized, centralized physician/insurance, moderately centralized, decentralized, and independent-and inpatient mortality from acute myocardial infarction (AMI), congestive heart failure, stroke, and pneumonia. Data and Methods: Panel data (1995-2000) were assembled from 11 states and multiple sources: Agency for Healthcare Research and Quality State Inpatient Database, American Hospital Association Annual Surveys, Area Resource File, HMO InterStudy, and the Centers for Medicare and Medicaid Services. We applied a panel study design with fixed effects models using information on variation within hospitals. Results: We found that centralized health systems are associated with lower AMI, congestive heart failure, and pneumonia mortality. Independent hospital systems had better AMI quality outcomes than centralized physician/insurance and moderately centralized health systems. We found no difference in inpatient mortality among system types for the stroke outcome. Thus, for certain types of clinical service lines and patients, hospital system type matters. Research that focuses only on system membership may mask the impact of system type on the quality of care.