title: Mortality among high-risk patients with acute myocardial infarction admitted to U.S. teaching-intensive hospitals in July: a retrospective observational study.
abstract: BACKGROUND
  Studies of whether inpatient mortality in US teaching hospitals rises in July as a result of organizational disruption and relative inexperience of new physicians (July effect) find small and mixed results, perhaps because study populations primarily include low-risk inpatients whose mortality outcomes are unlikely to exhibit a July effect.
  
  
  RESULTS
  Using the US Nationwide Inpatient sample, we estimated difference-in-difference models of mortality, percutaneous coronary intervention rates, and bleeding complication rates, for high- and low-risk patients with acute myocardial infarction admitted to 98 teaching-intensive and 1353 non-teaching-intensive hospitals during May and July 2002 to 2008. Among patients in the top quartile of predicted acute myocardial infarction mortality (high risk), adjusted mortality was lower in May than July in teaching-intensive hospitals (18.8% in May, 22.7% in July, P<0.01), but similar in non-teaching-intensive hospitals (22.5% in May, 22.8% in July, P=0.70). Among patients in the lowest three quartiles of predicted acute myocardial infarction mortality (low risk), adjusted mortality was similar in May and July in both teaching-intensive hospitals (2.1% in May, 1.9% in July, P=0.45) and non-teaching-intensive hospitals (2.7% in May, 2.8% in July, P=0.21). Differences in percutaneous coronary intervention and bleeding complication rates could not explain the observed July mortality effect among high risk patients.
  
  
  CONCLUSIONS
  High-risk acute myocardial infarction patients experience similar mortality in teaching- and non-teaching-intensive hospitals in July, but lower mortality in teaching-intensive hospitals in May. Low-risk patients experience no such July effect in teaching-intensive hospitals.
authors.affiliation: Department of Health Care Policy, Harvard Medical School, Department of Medicine, Massachusetts General Hospital, and the National Bureau of Economic Research, Cambridge, MA (A.B.J.); Department of Anesthesia, Stanford University Hospitals, Stanford, CA (E.C.S.); and the Leonard D. Schaeffer Center for Health Policy and Economics, University of Southern California, Los Angeles, CA and RAND Corporation, Santa Monica, CA (J.A.R.).
authors.forename: Anupam B
authors.initials: AB
authors.lastname: Jena
authors.forename: Eric C
authors.initials: EC
authors.lastname: Sun
authors.forename: John A
authors.initials: JA
authors.lastname: Romley
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D017052:Hospital Mortality / Q000639:trends*; D006761:Hospitals / Q000706:statistics & numerical data; D006784:Hospitals, Teaching / Q000706:statistics & numerical data*; D006801:Humans; D007297:Inpatients; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009203:Myocardial Infarction / Q000453:epidemiology* / Q000401:mortality*; D010820:Physicians; D011361:Professional Competence; D012189:Retrospective Studies; D012307:Risk Factors; D012621:Seasons; D014481:United States / Q000453:epidemiology
keywords: mortality; myocardial infarction