This paper examined whether expanded access to health care, such as provided by Oregon's comprehensive Oregon Health Plan (OHP), affected rates of preventable hospitalization (PH). The authors used a retrospective study to analyze PH rates for Medicaid enrollees, an uninsured population, and a group of non-Medicaid insured people, in Oregon from 1990–2000, using 1994 to represent the starting point of OHP implementation.
Contrary to the authors' hypothesis, and to results from prior studies elsewhere, the data showed that PH rates increased from 46.1 to 54.9 per 10,000 people in Medicaid and uninsured populations following eligibility expansion. In the non-Medicaid insured population, PH rates decreased slightly. The authors termed this overall increase "paradoxical," because when the uninsured and Medicaid groups were separated, both showed declining trends in PH rates. They further analyzed their data by subdividing the populations into three groups: those eligible for Medicaid by federal mandate; low-income people living above the Federal Poverty Line (FPL); and people living under 100 percent FPL but not categorically eligible for Medicaid. The subdivision indicates that the increase in PH rates seen in the aggregated populations was due to an increase in PHs in the last group, many of whom were newly insured.
Explanations for the increase seen in the newly insured were complex and multifactorial, and included the possibility that newly insured patients might have lower thresholds for seeking care, and physicians might have lower thresholds for admitting these patients to hospitals. Other factors also may have confounded the data, such as the inability of this study to incorporate variables (race, illness severity, income) known to influence PH rates.
Although the authors cannot definitively conclude that their study shows a true rise in PH rates after expanded access to health insurance, this paper emphasizes the need for caution regarding the use of PH rates to track changes in access to health care in response to large-scale policy interventions. Increased PH rates, note the authors, may not indicate "a 'failure' of outpatient access and quality, but rather a reflection of the available services, severity of illness, and prevalence of disease in the population to which health care has been extended."