The Patient Protection and Affordable Care Act, more commonly referred to as Obamacare, aims to ensure millions of low-income Americans are able to get access to the health care they need. Earlier this year, Medicaid was expanded in some states. But how will it affect the use of inpatient surgery in the US? A new study published in JAMA Surgery investigates.

Obamacare was rolled out in 2010. Once it is fully implemented in the US, it is estimated to provide cover for up to 25 million previously uninsured individuals.

From January 1st this year, some states received additional funding to expand their Medicaid programs, meaning adults under the age of 65 who earn up to 133% of the federal poverty level could be covered.

But the research team, led by Chandy Ellimoottil of the University of Michigan, says it has not been fully considered how the reform will impact complex and expensive hospital-based care, such as inpatient surgery.

“For instance,” the researchers say, “owing to a large unmet need, insurance expansion might yield greater utilization of surgery across the board. An alternative scenario is that rates of surgery will change mainly for certain procedures and patient populations.”

Researchers used the 2006 health care reform in Massachusetts to estimate how Obamacare may impact the rates of inpatient surgery going forward.

They analyzed information from inpatient databases in Massachusetts between January 1st, 2003, and January 1st, 2010.

They also analyzed data from the inpatient databases of two other states – New Jersey and New York – to act as controls over the same time periods.

During the 7-year period, researchers identified 836,311 surgical procedures. Of these, 22.2% took place in Massachusetts, 54.7% took place in New York and 22.9% took place in New Jersey.

In Massachusetts, the team found that insurance expansion was associated with a 9.3% increase in discretionary surgical procedures and a 4.5% decrease in nondiscretionary surgical procedures. From this, the researchers estimate that Obamacare could result in 465,934 extra discretionary surgical procedures by 2017.

The researchers note that their findings build on previous studies suggesting that the use of health care increases when previously uninsured individuals become insured. But the team says this effect does not appear to be uniform for inpatient surgical care.