Changing neurosurgical workload in the United States, 1988-2001: craniotomy other than trauma in adults.
OBJECTIVE: Changes in neurosurgical workload can justify requests for hospital resources and guide planning by neurosurgical training programs. Most previous studies have used non-population-based data sources, such as surveys of professional society members, to explore the neurosurgical workload in the United States. METHODS: This is a retrospective cohort study of patients in Diagnosis Related Group (DRG) 1 ("Craniotomy other than trauma, age > 17") using the Nationwide Inpatient Sample. Statistical methods were adjusted for complex survey methodology to generate total United States caseload estimates. RESULTS: The total United States DRG 1 caseload increased from 70,800 admissions in 1988 to 105,300 admissions in 2001, a 50% relative increase (P < 0.001). For most diagnostic categories, the relative caseload increase was similar to that for the whole group. Patient age and sex distributions remained stable over time. Medical comorbidities, such as hypertension, chronic pulmonary disease, diabetes, and obesity, became more frequent. Elective admissions increased and in-hospital mortality rates decreased. Length of hospital stay decreased during the first half of the study period and then stabilized. Combined with increasing caseload, this caused total annual inpatient DRG 1 days to increase progressively after 1996. The number of United States hospitals with DRG 1 admissions decreased over time. Per-hospital annual DRG 1 caseloads increased, especially at high-volume centers. For the largest 100 hospitals by DRG 1 caseload, total admissions increased from 8.5% of all United States admissions (1988) to 9.4% (2001), whereas DRG 1 caseload increased disproportionately, from 27% to 38% of the United States aggregate caseload. This is evidence that progressive centralization of DRG 1 admissions took place during the study period. CONCLUSION: We documented an increase in total caseload and centralization of care for DRG 1 in the United States during the period 1988 to 2001. Defining the reasons for the changes in neurosurgical workload we observed will require further research.