C. K. Zogg1,2,3, D. Metcalfe3, S. A. Hirji2, K. A. Davis1, A. H. Haider2 1Yale University School Of Medicine,New Haven, CT, USA 2Brigham And Women’s Hospital,Center For Surgery And Public Health,Boston, MA, USA 3University of Oxford,Oxford, United Kingdom
Introduction: The arrival of new residents at the beginning of the academic year has long been associated with perceived adverse patient outcomes. Numerous studies in recent years have sought to prove/disprove the ‘July Effect.’ The objective of this study was to provide a definitive answer, combining data on mortality, morbidity, and unplanned readmission through a systematic review/meta-analysis and expanded difference-in-difference (DID) analysis of seasonal variation in outcomes for teaching vs non-teaching hospitals across seven common medical and surgical conditions.
Methods: 1) Systematic review and meta-analysis of studies published prior to July 31, 2018. 2) DID analysis of adult patients, ≥18y, with primary diagnosis/procedure codes for AMI, CVA, pneumonia, elective CABG, elective colectomy, craniotomy, or hip fracture contained within the 2012-2015 Nationwide Readmissions Database. Weighted models compared disease-specific differences in 30- and 90-day mortality, readmission, and median index hospital length of stay (LOS) between patients admitted to teaching vs non-teaching hospitals in July-August vs September-June and April-May.
Results: A total of 85 studies met inclusion criteria. Of these, 12 (14.1%) reported evidence in support of a July Effect for any outcome (1/13 high-quality studies). An additional 14 (16.5%) suggested that evidence was mixed (3/13 high-quality studies). 57/85 assessed mortality, of which 25 were eligible to be included in the random effects meta-analysis (Figure), OR(95%CI): 1.00(0.97-1.03). 48/85 assessed major morbidity, of which 26 were included in the random effects meta-analysis, 1.02(0.99-1.05). One met inclusion for readmission, 0.90(0.80-1.23). Data assessment similarly revealed no significant differences in 30- or 90-day mortality when comparing teaching vs non-teaching hospitals in July-August vs April-May (e.g. absolute 30-day DID[95%CI] hip fracture: +0.1[-0.7 to +0.9] percentage-points). When compared relative to September-June, AMI showed a slight 30-day difference, +0.4(0.1-0.8) percentage-points, that was not significant for p<0.001. Similar results were observed for 30- and 90-day readmission (e.g. 30-day hip fracture: -0.2[-2.0 to +1.6] percentage-points) and median index hospital LOS (0.0[0.0-0.0] days).
Conclusion: An influx of recent studies has challenged pre-existing notions of the July Effect for major adverse outcomes: mortality and morbidity. While evidence refuting the July Effect in readmission is scarcer, DID assessment of common medical and surgical conditions demonstrated that the July Effect does not exist. Taken together, the results suggest that fears surrounding the July Effect are unfounded and that further studies might be unwarranted.
