Background: Emergency departments (EDs) nationwide are key entry points into the health care system, and their use may reflect changes in access and need in their communities. However, no studies to date have empirically and longitudinally studied how changes in a community's level of insurance coverage, a key determinant of access, affect ED utilization.
Objective: To determine the effects of changes in a community's rate of insurance coverage on its population's ED use.
Methods: We conducted a longitudinal analysis of all California counties between 2005 and 2010 using comprehensive ED visit data from the California Office of Statewide Health Planning and Development. Using Poisson regression with county and year fixed effects, we determined how changes in the rate of insurance coverage within a given county affect ED visits per 1000 residents.
Results: We found that changes in the rate of insurance coverage within a county had a slight but significant inverse relationship with ED visits per 1000 residents for both adults and children. For example, if a county's rate of insurance coverage among adults jumped from the 10th (73.22%) to the 90th percentile (84.93%), an estimated 2 fewer ED visits would occur per 1000 adult residents.
Conclusions: As the rate of insurance coverage increased within California counties, overall ED utilization declined only slightly. Thus, expanding insurance coverage may not lead to significant decreases in overall ED use.