Background: The “July effect” is a perceived increased risk of medical errors that occurs when US medical graduates begin residencies. There is substantial variability in results across studies of the “July effect” on patients who are admitted for heart attacks. Furthermore, studies that do show statistically significant increase in mortality at the start of residency year tend to compare teaching with non-teaching hospitals, belying the fact that the former have sicker patients on average. Here, we examine the association between deaths during hospitalization for ST-elevation myocardial infarction (STEMI) and the month of admission in teaching hospitals.
Methods: The HCUP’s Nationwide Inpatient Sample (NIS), which represents approximately 20% of all hospitals in the USA, was queried. A retrospective cohort study of all the patients admitted to teaching hospitals with the primary diagnosis of STEMI in the 2012 NIS database was conducted. These patients were categorized as being either admitted in the month of July or not. The primary outcome was all-cause mortality during hospitalization. We used a two-proportion z-test to determine whether there is an association between STEMI admissions during July and death during hospitalization.
Results: A total of 13,442 patients were admitted to teaching hospitals in 2012 with the primary diagnosis of STEMI. These patients were stratified by admission during July (n = 1,097) versus other months (n = 12,345) and whether death occurred during hospitalization. 91 deaths occurred during July admissions, while 1,033 deaths occurred during admissions in the other months. This is summarized in the table included. A Pearson’s chi-squared test statistics reveals no statistically significant difference in the number of death in July compared to other months (X-squared = 0.00068, p-value = 0.98, 95% CI = -0.018 – 0.017) for patients admitted with the primary diagnosis of STEMI.
Conclusions: In the 2012 NIS data, the “July effect” does not occur in the case of patients who are admitted for STEMI. Being admitted in July to teaching hospitals for STEMI is not associated with an increased risk of death during hospitalization.
