The Affordable Care Act’s Medicaid expansion was linked to better access to surgery and higher quality surgical care, according to a new study from Harvard T.H. Chan School of Public Health.

The study was published online in JAMA Surgery.

“What was most striking was that we saw significant improvements in the treatment of surgical conditions fairly quickly, less than two years after states expanded Medicaid coverage,” says lead author Andrew Loehrer, who conducted the study as a research fellow at Harvard Chan School.

Previous studies have examined the impact of the ACA’s Medicaid expansion on a range of outcomes like primary care, prescription medication use, and self-reported health, generally finding favorable results. But this is the first study showing similar benefits for serious conditions requiring surgery.

The researchers looked at five years’ worth of data from nearly 300,000 patients from 42 U.S. states who were admitted to hospitals for one of five common surgical conditions: appendicitis, cholecystitis, diverticulitis, peripheral artery disease (PAD), or aortic aneurysm. The study analyzed trends in insurance coverage, timeliness of surgical care, and care outcomes both before the ACA’s Medicaid expansion (2010-13) and after (2014-15), comparing 27 states that chose to expand their Medicaid programs with 15 that chose not to expand.

The researchers found that Medicaid expansion was associated with:

• A 7.5-percentage point decrease in the probability of patients being uninsured
• An 8.6-percentage point increased probability of patients having Medicaid
• A 1.8-percentage point increase in the probability of patients seeking care earlier, before their surgical conditions became complicated
• A 2.6-percentage point increase in patients’ probability of receiving optimal care

The researchers speculated that the ACA’s Medicaid expansion led patients with surgical conditions to seek treatment before complications set in. Being treated for these conditions earlier makes it more likely that they will have better health outcomes, the authors say.

“The fate of the ACA and Medicaid remains a key policy debate,” says senior author Benjamin Sommers, associate professor of health policy and economics at Harvard Chan School. “As policymakers continue to discuss major changes to the ACA, and the Trump administration advances reforms that could lead to fewer people covered by Medicaid, our findings provide important new evidence that Medicaid expansion is improving the quality of care for serious conditions affecting tens of thousands of Americans every year.”