Relative to patients in 1988, patients in both nonteaching and teaching hospitals in 1991 were more likely to have been transferred from a nonacute health care facility and more likely to be nonwhite. Patients in 1991 in both types of hospitals were more likely to have other neurological disorders, complicated diabetes, renal failure, chronic pulmonary disorder, AIDS, and congestive heart failure as comorbidities, while less likely to have diabetes, peripheral vascular disorder, and hypothyroidism (). Patients in 1991 in teaching hospitals were less likely to have anemia, less likely to be admitted as an emergency case, but more likely to be female, and more likely to be transferred from another acute care facility. Patients in nonteaching hospitals in 1991 were more likely to be admitted as an emergency case, more likely to have anemia, more likely to have hypertension, less likely to have cardiac arrhythmia, and less likely to be transferred from an acute care facility relative to patients in 1988.
In-hospital Mortality (Unadjusted)
Overall unadjusted mortality for teaching and nonteaching hospitals declined between 1988 and 1991 (). Only acute myocardial infarction patients in noninvasive teaching hospitals and pneumonia patients in teaching hospitals failed to experience a significant decline in unadjusted mortality between 1988 and 1991.
Testing for a Code 405 Effect
Note that adding adjustment variables (as listed in ) had 2 effects on the results concerning changes in mortality between 1988 and 1991 (). Whereas unadjusted results showed that survival from pneumonia in teaching hospitals did not significantly change between 1988 and 1991 (), the adjusted results indicate a lower odds of death in 1991 relative to 1988. Furthermore, with respect to survival from AMI in invasive nonteaching hospitals, the unadjusted results showed a significant reduction in mortality between the study years, whereas the adjusted results () indicated no significant change in the odds of death between 1988 and 1991.
Odds of Death in 1991 Relative to 1988 for Teaching and Nonteaching Hospitals
Overall hospitalization in 1991 was associated with lower odds of death in both teaching and nonteaching hospitals. If there was a beneficial Code 405 effect, we would expect to see a greater decline in mortality among teaching hospitals than nonteaching hospitals. Teaching hospitals showed no increased improvement as compared to nonteaching hospitals for any of the 3 conditions when considered individually or when combined as a single group overall. For each of the 3 conditions examined, the ratio of the odds ratios (for mortality in 1991 vs 1988) comparing teaching to nonteaching hospitals could not be distinguished from unity and in all cases this ratio had a relatively narrow confidence interval.
Adjusting for Residency Size
We asked whether the size of the residency program may have influenced these results. We therefore adjusted our model for residency size by including a continuous variable for the combined number of internal medicine and family practice residents at each hospital. We found no difference in our results for AMI, CHF, and PNU. For AMI, the ratio (between teaching and nonteaching) of the changes in mortality (between 1988 and 1991) was 1.061; 95% confidence interval (CI), 0.969 to 1.163; for CHF 0.993; 95% CI, 0.918 to 1.074, and for PNU 0.997; 95% CI, 0.932 to 1.067. The coefficient on residency size was never significant in any model. Another approach to account for residency size was also taken. We grouped hospitals with internal medicine and family practice residents by the combined size of these 2 programs into quartiles. For each quartile we then fit a separate model to examine the relative changes in mortality (in 1988 vs 1991) between that quartile of teaching hospitals and all nonteaching hospitals. Again, there was no significant interaction between year of hospitalization and teaching status. The ratio of the change in the highest quartile (largest combined population of internal medicine and family practice residents) was 1.009; 0.866 to 1.175 for AMI, 1.037, 95% CI 0.974 to 1.190 for CHF, 1.002, 95% CI 0.896 to 1.121 for PNU. The other quartiles showed similar results.