How Inter-State Patient Migration affects the projected need for hospital services: A Case Study of Illinois?

Research Objective: Determining the projected need for hospital services based on experienced demand for services in an area is fundamental for developing state health plans serving as a statewide policy blueprint for future resource allocation decisions. A recent review of projection methodologies used by state planning agencies revealed that no state methodology takes into account inter-state migration patterns. The objective of the study was to examine the extent to which inter-state migration occurs and to test if an adjustment for inter-state migration is needed in determining the projected need for hospital medical/surgical beds.

Study Design: Based on the year 2002 discharge data from hospitals in Illinois and its 6 neighboring states (Indiana, Kentucky, Missouri, Iowa, Michigan and Wisconsin), a matrix of 41 planning areas of residence by 41 areas of hospitalization was constructed to systematically calculate in-migration number and out-migration number. The in-migration number is defined as the number of patients from outside the planning area receiving services at area hospitals; out-migration is the number of area residents receiving services at hospitals outside the planning area.

Study Population: Illinois resident discharges in 2002 from medical/surgical (MS) and Obstetrics (OB) beds of hospitals in six neighboring states in addition to discharges from Illinois hospitals.

Principal Findings: Illinois is primarily a net out-migration state, with 4 times greater (for MS) and 3.2 times greater (for OB) out-migration numbers than in-migration numbers. In region-wide estimates, downstate Illinois is a notable out-migration area. The magnitude of out-migration to neighboring states was largest among areas that share boundaries with a neighboring state. As many as eight areas had more than 20% of their resident M-S discharges from the hospitals in the neighboring six states. Six areas had more than 15% of resident OB discharges from hospitals in the neighboring six states.

Conclusions: The present methodology that Illinois uses to project acute care hospital beds does not take into consideration the fact that a substantial portion of Illinois residents receive care out of the State. Using extensive data from neighboring states, we verify many Illinois planning areas are “out migration” areas, and the days of care received at out-of-state hospitals are not re-allocated back to the planning area of origin in Illinois.

Implications for Policy, Delivery or Practice: “Recapturing” a portion of this extensive out-of-state migration into the planning areas where patients reside may be a reasonable consideration.