IMPORTANCE

The US Patient Protection and Affordable Care Act of 2010 (ACA) was enacted in 2010 with several provisions that targeted reducing numbers of uninsured Americans.

OBJECTIVE

To assess the numbers and proportion of emergency department (ED) visits (2006-2016) and hospital discharges (2006-2016) by uninsured patients, focusing on the 2014 ACA insurance reforms (Medicaid expansion, individual mandate, and private insurance exchanges).

DESIGN, SETTING, AND PARTICIPANTS: Cross-sectional study of visitors to US EDs and patients discharged from US hospitals using National Hospital Ambulatory Care Survey data and Healthcare Cost and Utilization Project data, respectively, from 2006 to 2016. Data analysis took place in February 2019.

MAIN OUTCOMES AND MEASURES

Numbers and proportions of total and uninsured ED visits and hospital discharges. Simple descriptive statistics and interrupted time-series analysis were used to assess changes in uninsured visits over time and after the implementation of insurance provisions in 2014.

RESULTS

There were an estimated 1.4 billion US ED visits from 2006 to 2016 and 405 million hospital discharges from 2006 to 2016. Over the study period, ED visits increased by 2.3 million per year, while hospital discharges decreased from approximately 38 million per year prior to 2009 to approximately 36 million per year after, with no clear decrease after 2013. Proportions of uninsured ED visits were largely unchanged from 2006 (16%) until 2013 (14%) (-0.2 percentage point per year; 95% CI, -0.46 to -0.01 percentage point; P = .11) but then decreased by 2.1 percentage points per year from 2014 to 2016 (95% CI, -4.3 to -1.8 percentage points; P = .003), with uninsured visits composing 8% of the total in 2016. For patients aged 18 to 64 years, uninsured ED visits declined from approximately 20% from 2006 through 2013 to 11% in 2016 (3.1% decrease per year after 2013; 95% CI, -4.3 to -1.8 percentage points; P = .003). The proportion of hospital discharges by uninsured patients remained steady at approximately 6% from 2006 to 2013, then declined to 5% in 2014 and 4% in 2016. Similar changes were seen for patients aged 18 to 64 years, with a decrease in hospital discharges from 10% to 7% over the study period.

CONCLUSIONS AND RELEVANCE

Proportions of ED visits and hospital discharges by uninsured patients decreased considerably after the implementation of the 2014 ACA insurance provisions. Despite these changes, approximately 1 in 10 ED visits and 1 in 20 hospital discharges were made by uninsured individuals in 2014 to 2016. This suggests that continued attention is needed to address the lack of insurance in US hospital visits, particularly among people aged 18 to 64 years who have less access to government-sponsored insurance.