So often, when we implement new policy, I wish we had better ways to capture its effects so that we could expand our knowledge base as to how decisions change health and health care. The Oregon Health Insurance Experiment, and its older brother the RAND HIE, were RCTs designed to look at how insurance affected utilization and health. While these were impressive studies, they had their flaws.

RCTs are hard to do, though; they're also expensive. Sometimes, other designs are necessary. Recently, in Annals of Internal Medicine, Laura Wherry and Sarah Miller looked at how the Medicaid expansion has changed things. "Early Coverage, Access, Utilization, and Health Effects Associated With the Affordable Care Act Medicaid Expansions: A Quasi-experimental Study":


Background: In 2014, only 26 states and the District of Columbia chose to implement the Patient Protection and Affordable Care Act (ACA) Medicaid expansions for low-income adults.


Objective: To evaluate whether the state Medicaid expansions were associated with changes in insurance coverage, access to and utilization of health care, and self-reported health.


Design: Comparison of outcomes before and after the expansions in states that did and did not expand Medicaid.


Setting: United States.


Participants: Citizens aged 19 to 64 years with family incomes below 138% of the federal poverty level in the 2010 to 2014 National Health Interview Surveys.

Measurements: Health insurance coverage (private, Medicaid, or none); improvements in coverage over the previous year; visits to physicians in general practice and specialists; hospitalizations and emergency department visits; skipped or delayed medical care; usual source of care; diagnoses of diabetes, high cholesterol, and hypertension; self-reported health; and depression.


As we've discussed many times before, only about half of states initially decided to join the Medicaid expansion. This meant that - in those states - anyone making less than 138% of the federal poverty line could get Medicaid. In other states, many poor people were out of luck. The law provided no subsidies to people earning less than the poverty line, and without new Medicaid, many had no affordable options for insurance.

This study sought to compare how adults who would qualify for the expansion compared to those in states with and without it. The researchers used data from the 2010 and 2014 National Health Interview Surveys to compare health insurance coverage, utilization, diagnoses of some illnesses, self-reported health, and depression. They used a quasi-experimental difference-in-difference design to compensate for secular changes as well as time-invariant differences in characteristics across all states. They excluded five states that already pretty much provided expansion-like coverage before 2014.

They found that, by the second half of 2014, adults in the expansion states had seen their health insurance coverage increase 7.4%; Medicaid coverage increased 10.5%. This isn't surprising, as increased coverage was the main intent of the Affordable Care Act. Coverage was found to have "improved" as well (7.1%).

They also found that, in Medicaid expansion states, there were increased in physician visits (6.6%), hospital stays (2.4%), rates of diagnoses of diabetes (5.2%) and high cholesterol (5.7%).

Of course, this is an observational study. It's possible that other confounders exist that are the reasons for these changes. These are also very short-term data. They also couldn't find real differences in terms of access.

But, as I've discussed before, insurance coverage is just the first step in improving access. What this study adds are some data showing that expanding Medicaid through the ACA resulted in increased coverage, improved coverage, more physician visits, and more disease diagnosed.

It will be important for us to continue these types of studies as we move forward, to understand better the full impact of the ACA. But if future analyses continue to show improvements in coverage, utilization, and health from the Medicaid Expansion, it may become more difficult for the 19 remaining states to refuse it without offering alternative paths to the same achievements.


For more reading on the effects of the ACA, you might also enjoy both the HSR systemic review blog piece written earlier this week here on the AcademyHealth blog and the President's recent JAMA article.

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Aaron E. Carroll, M.D., M.S.

President and CEO - AcademyHealth

Dr. Aaron E. Carroll is President & CEO of AcademyHealth. A nationally recognized thought leader, science comm... Read Bio

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