Association of Hospital Teaching Status with Neurosurgical Outcomes: An Instrumental Variable Analysis

The interpretation of the results of prior studies on the association of hospital teaching status with surgical outcomes is limited by selection bias. We investigated whether undergoing surgical operations in teaching hospitals is associated with improved outcomes.

We performed a cohort study of all patients undergoing spine and cranial operations who were registered in the New York Statewide Planning and Research Cooperative System database from 2009 to 2013. We examined the association of teaching status (defined as academic affiliation for the primary analysis) with inpatient case fatality, discharge to a facility, and length of stay (LOS). An instrumental variable analysis was used to control for unmeasured confounding and to simulate the effect of a randomized trial.

During the study period, 186,483 patients underwent surgical operations that met the inclusion criteria. Instrumental variable analysis demonstrated that hospitalization in teaching hospitals was associated with higher rates of case fatality (adjusted difference, 25%; 95% confidence interval [CI], 4%-46%), discharge to a facility (adjusted difference, 5.7%; 95% CI, 4.5%-7.0%), and longer LOS (adjusted difference, 31.4%; 95% CI, 16.0%-46.1%) in comparison with nonteaching hospitals. The same associations were present in propensity score adjusted mixed effects models. These persisted in prespecified subgroups stratified on particular operations and for different definitions of teaching hospitals.

Using a comprehensive all-payer cohort of surgical patients in New York State, we identified an association of treatment in teaching hospitals with increased case fatality, rate of discharge to rehabilitation, and longer LOS. Further research into the factors contributing to superior outcomes in nonteaching institutions is warranted.