Reassessing the July Effect: 30 Years of Evidence Show No Difference in Outcomes

Cheryl K. Zogg, David Metcalfe, Claire M. Sokas, Michael K. Dalton, Sameer A. Hirji, Kimberly A. Davis, Adil H. Haider, Zara Cooper, Judith H. Lichtman

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


Objective: The aim of this study was 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 before December 20, 2019, looking 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 nonteach-ing 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. Metaanalyses of mortality [odds ratio (95% confidence interval): 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. Conclusion: The preponderance of negative results over the past 30 years suggests that it might 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.

Original languageEnglish
Pages (from-to)E204-E211
JournalAnnals of Surgery
Issue number1
Publication statusPublished - 1 Jan 2023


  • July Effect
  • July Phenomenon
  • morbidity
  • mortality
  • readmission
  • resident
  • teaching


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