The decline in hospital readmission rates that occurred following the launch of a federal program designed to improve quality of care and reduce repeat hospitalizations has been lauded as proof of the program's effectiveness.
But a new analysis led by researchers at Harvard Medical School offers an alternative explanation for the outcome.
The findings, published in the November issue of Health Affairs, suggest that an overall decline in hospital admissions may have driven the observed drop in readmissions attributed to the Medicare Hospital Readmissions Reduction program, or HRRP. What looked like achievements of the program may have been a byproduct of factors driving a broader decrease in hospitalizations across the board.
HRRP was established as part of the Affordable Care Act in 2010 in an attempt to improve quality of care through payment incentives. When the same person is admitted to a hospital twice within 30 days, that might mean that the hospital is not doing enough to ensure safe discharges and adequate follow-up. Under the program, hospitals with higher-than-expected readmission rates are penalized.
Since the program launched, readmission rates progressively declined from 17.5% in 2009 to 15.5% in 2014. To the casual observer, this trend would seem to prove that the HRRP achieved its objective, a widely held belief among policymakers and healthcare experts, and the conclusion of many research studies on the subject.
But researchers wondered if other factors could account for this effect. To test an alternative hypothesis, the team conducted a simulation analysis. They first calculated changes in per capita admission rates from 2009 to 2014. Next, they removed random samples of admissions from the 2009 data to match the admission rate in each subsequent year. Finally, they recalculated the readmission rate to determine what would be expected at the lower admission rate and compared these expected readmission rates to what was observed.
WHAT'S THE IMPACT
Assuming that readmissions are often not due to deficient care in prior admissions, readmission rates should fall as admission rates decline because of a simple statistical relationship between the two. The probability that two unrelated hospitalizations occur within 30 days of each other decreases when there are fewer hospitalizations occurring per patient.
This assumption was borne out in the new analysis, the team said. Prior studies have generally found that, at most, 20 to 30% of readmissions are due to preventable deficits occurring during the prior admission; the rest are independent events. For example, a patient admitted for pneumonia may be admitted again within 30 days for a gastrointestinal infection.
Strikingly, the simulated drop in readmission rates that would be expected from the drop in admission rates was as large as the observed decline from 2009 to 2014.
The findings call into question the prevailing interpretation that the program caused the reduction in readmissions, the authors said, and build on other recent research questioning the HRRP's impact. For example, one study found that some of the decrease ascribed to the HRRP was explained by administrative changes in the number of diagnoses coded during the years after the program launched. Perhaps more importantly, the new study underscores the importance of questioning assumptions and examining causes and effects carefully and rigorously.
Some experts may continue to deem the HRRP responsible for much of the decline in readmissions. They may argue that the broader decline in admissions was a "spillover effect" of hospital responses to the HRRP.
The researchers say this explanation is highly unlikely. Not only did the decline in admissions predate the HRRP, but it occurred across the board -- including private insurance payers as well as Medicare. Hospitals would not sacrifice such a substantial fraction of their revenue to avoid much smaller penalties imposed by a single payer.
The researchers say the substantial decrease in admissions -- a 13% decline from 2009 to 2014 -- is likely the result of multiple factors unrelated to the HRRP, including medical innovations that allow for more conditions to be treated in an outpatient setting, an ongoing decline in available hospital beds in the U.S., and regulatory measures to crack down on unnecessary short hospital stays.
THE LARGER TREND
The findings mirror those of a report published in July, also in Health Affairs, finding that the readmission rate for patients who had hip or knee replacement surgery had already started dropping by the time the idea of readmission penalties was announced as part of the Affordable Care Act in 2010. Soon after that, the readmissions rate for these surgical patients started dropping faster -- even though the penalties announced in the ACA did not apply to surgical patients.
The rate kept dropping rapidly for several years -- even though hospitals weren't getting penalized yet for hip and knee replacement-related readmissions. But that improvement started to slow down.
After the government announced in late 2013 that penalties would expand to hip and knee replacement, the rate of readmissions for these patients kept dropping, but at nearly half the rate. In other words, improvements in surgical readmissions slowed to the same pace they had before any penalties were announced in 2010.