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Patient safety measures that reward hospitals for reducing preventable infections, pressure ulcers and adverse drug reactions have resulted in a 17 percent decline in these types of patient harms between 2010 and 2014, according to a federal report released Tuesday.

The measures were put in place by the Affordable Care Act. Preliminary estimates by the Department of Health and Human Services show 87,000 fewer patients died in hospitals and nearly $20 billion in health care costs were saved as a result of a reduction in these harms, known as hospital-acquired conditions, during that four-year period.

The precise causes of the cumulative decline are not fully understood, the report said. But a number of public and private health-care initiatives have been put in place in the past four years that reward or penalize hospitals based on how they perform on a variety of patient quality and safety measures.

"Patients in America's hospitals are safer today as a result of this partnership with hospitals and health care providers," said HHS Secretary Sylvia M. Burwell in a statement.

Hospital-acquired conditions include falls, adverse drug events, catheter-associated urinary tract infections, central line associated bloodstream infections, pressure ulcers, and surgical site infections, among others. HHS analyzed the incidence of a number of avoidable hospital-acquired conditions compared to 2010 rates.

Although the rate has dropped since 2010, it remained steady from 2013 to 2014, which researchers said showed that "much work remains to be done." That means in  2013 and 2014, almost 10 percent of hospitalized patients experienced one or more of the patient harms described, a rate the report said "is still too high." Most of the deaths averted occurred as a result of reductions in the rates of pressure ulcers and adverse drug events, the report said.

One notable exception was falls, which occurred at the same rate in 2014 as in 2010.

"Falls are a double-edged sword," said Richard Kronick, director of the Agency for Healthcare Research and Quality, the HHS agency that prepared Tuesday's report. No one knows for sure, he said, but one hypothesis is that hospitalized patients are encouraged to get out of bed and move around to improve their recovery, but that also increases the likelihood of falls.

Researchers said they used the "complex relationship between hospital-acquired conditions and mortality" to extrapolate the impact on deaths averted and cost savings.

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