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Updated: May 12, 2026
Controlled Cortical Impact Model for Traumatic Brain Injury
Published on: August 5, 2014
Evidence Against a Traumatic Brain Injury "July Effect": An Analysis of 3 160 452 Patients From the National
Avi A Gajjar1, Michael M Covell2, Rohit Prem Kumar1
1Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh , Pennsylvania , USA.
Background And Objectives:
The "July Effect" hypothesizes increased morbidity and mortality after the addition of inexperienced physicians at the beginning of an academic year. However, the impact of newer members on neurosurgical teams managing patients with traumatic brain injury (TBI) has yet to be examined. This study conducted a nationwide analysis to evaluate the existence of the "July Effect" in the setting of patients with TBI.
Methods:
The Healthcare Cost and Utilization Project Central Distributor's National Inpatient Sample data set was queried for patients with TBI using International Classification of Diseases (ICD)-9 and ICD-10 codes. Discharges were included for diagnoses of traumatic epidural, subdural, or subarachnoid hemorrhages. Only patients treated at teaching hospitals were included to ensure resident involvement in care. Patients were grouped into July admission and non-July admission cohorts. A subgroup of patients with neurotrauma undergoing any form of cranial surgery was created. Perioperative variables were recorded. Rates of different complications were assayed. Groups were compared using χ 2 tests (qualitative variables) and t -tests or Mann-Whitney U -tests (quantitative variables). Logistic regression was used for binary variables. Gamma log-linked regression was used for continuous variables.
Results:
The National Inpatient Sample database yielded a weighted average of 3 160 452 patients, of which 312 863 (9.9%) underwent surgical management. Patients admitted to the hospital in July had a 5% decreased likelihood of death ( P = .027), and a 5.83% decreased likelihood of developing a complication ( P < .001) compared with other months of the year. July admittance to a hospital showed no significant impact on mean length of stay ( P = .392) or routine discharge ( P = .147). Among patients with TBI who received surgical intervention, July admittance did not significantly affect the likelihood of death ( P = .053), developing a complication ( P = .477), routine discharge ( P = .986), or mean length of stay ( P = .385).
Conclusion:
The findings suggested that there is no "July Effect" on patients with TBI treated at teaching hospitals in the United States.
