A key Obamacare program intended to revolutionize the U.S. healthcare system by tying hospital compensation to medical outcomes is not working, according to a new study from researchers at Harvard University.

As part of its overhaul of the healthcare system, Obamacare made a number of changes to the way hospitals are paid through Medicare. One program, known as Hospital Value-Based Purchasing, intended to improve hospital quality by redistributing payments so that better-performing hospitals received more money. This was part of a broader strategy to pay medical providers based on performance, and part of a central promise of Obamacare to improve quality and reduce costs.

But Harvard researchers compared hospitals that participated in the program with those that did not, both before and after the introduction of the Obamacare program in 2011, and found that it was not working.

More specifically, the authors concluded, "We found that the introduction of the US HVBP program was not associated with lower 30 day mortality. This study suggests that we have yet to identify the appropriate mix of quality metrics and incentives to improve patient outcomes. As countries continue to move towards achieving value-based care, these findings hold important lessons and call for a greater understanding of how to achieve better outcomes under this framework."

The study appeared in BMJ (formerly known as the British Medical Journal). One of the authors, Ashish Jha, a professor of health policy at the Harvard T.H. Chan School of Public Health, wrote on Twitter that, "Our (pay-for-performance) effort not working. We need a new strategy."

Read the full study here.