Reassessing the July effect: 30 years of evidence show no difference in outcomes

Document Type



Medical College Pakistan; General Surgery


Objective: To critically evaluate whether admission at the beginning-versus-end of the academic year is associated with increased risk of major adverse outcomes.
Summary background data: The hypothesis that the arrival of new residents and fellows is associated with increases in adverse patient outcomes has been the subject of numerous research studies since 1989.
Methods: We conducted a systematic review and random-effects meta-analysis of July Effect studies published prior to December 20, 2019, for differences in mortality, major morbidity, and readmission. Given a paucity of studies reporting readmission, we further analyzed 7 years of data from the Nationwide Readmissions Database to assess for differences in 30-day readmission for US patients admitted to urban teaching-versus-non-teaching hospitals with 3 common medical (acute myocardial infarction, acute ischemic stroke, and pneumonia) and 4 surgical (elective coronary artery bypass graft surgery, elective colectomy, craniotomy, and hip fracture) conditions using risk-adjusted logistic difference-in-difference regression.
Results: A total of 113 studies met inclusion criteria; 92 (81.4%) reported no evidence of a July Effect. Among the remaining studies, results were mixed and commonly pointed toward system-level discrepancies in efficiency. Meta-analyses of mortality (OR[95%CI]: 1.01[0.98-1.05]) and major morbidity (1.01[0.99-1.04]) demonstrated no evidence of a July Effect, no differences between specialties or countries, and no change in the effect over time. A total of 5.98 million patient encounters were assessed for readmission. No evidence of a July Effect on readmission was found for any of the 7 conditions.
Conclusions: The preponderance of negative results over the past 30 years suggests that it may be time to reconsider the need for similarly-themed studies and instead focus on system-level factors to improve hospital efficiency and optimize patient outcomes.


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Publication (Name of Journal)

Annals of Surgery