Emergency department use and subsequent hospitalizations among members of a high-deductible health plan.

CONTEXT: Patients evaluated at emergency departments often present with nonemergency conditions that can be treated in other clinical settings. High-deductible health plans have been promoted as a means of reducing overutilization but could also be related to worse outcomes if patients defer necessary care. OBJECTIVES: To determine the relationship between transition to a high-deductible health plan and emergency department use for low- and high-severity conditions and to examine changes in subsequent hospitalizations. DESIGN, SETTING, AND PARTICIPANTS: Analysis of emergency department visits and subsequent hospitalizations among 8724 individuals for 1 year before and after their employers mandated a switch from a traditional health maintenance organization plan to a high-deductible health plan, compared with 59 557 contemporaneous controls who remained in the traditional plan. All persons were aged 1 to 64 years and insured by a Massachusetts health plan between March 1, 2001, and June 30, 2005. MAIN OUTCOME MEASURES: Rates of first and repeat emergency department visits classified as low, indeterminate, or high severity during the baseline and follow-up periods, as well as rates of inpatient admission after emergency department visits. RESULTS: Between the baseline and follow-up periods, emergency department visits among members who switched to high-deductible coverage decreased from 197.5 to 178.1 per 1000 members, while visits among controls remained at approximately 220 per 1000 (-10.0% adjusted difference in difference; 95% confidence interval [CI], -16.6% to -2.8%; P = .007). The high-deductible plan was not associated with a change in the rate of first visits occurring during the study period (-4.1% adjusted difference in difference; 95% CI, -11.8% to 4.3%). Repeat visits in the high-deductible group decreased from 334.6 to 255.3 visits per 1000 members and increased from 321.1 to 334.4 per 1000 members in controls (-24.9% difference in difference; 95% CI, -37.5% to -9.7%; P = .002). Low-severity repeat emergency department visits decreased in the high-deductible group from 142.5 to 92.1 per 1000 members and increased in controls from 128.0 to 132.5 visits per 1000 members (-36.4% adjusted difference in difference; 95% CI, -51.1% to -17.2%; P