A new study refutes the common claim that low death rates increase patient rehospitalization rates.

Preliminary studies, as well as a letter to the editor in 2010 in the New England Journal of Medicine, suggested that hospitals with higher patient mortality rates within 30 days of discharge tend to have lower rates of readmission within that same time period, possibly because patients most likely to die during that period are also more likely to be rehospitalized if they survive initial treatment. But a study published Feb. 13 in the Journal of the American Medical Association suggests a possible different trend. Yale researchers found little or no correlation between the death and readmission rates in hospitals nationwide in Medicare beneficiaries hospitalized for heart attack, heart failure or pneumonia, said lead author Harlan Krumholz, cardiology professor at the Yale School of Medicine

“There are many critics claiming that you can’t have both low mortality rates and low readmission rates,” Krumholz said. “But we saw many hospitals excelling in both.”

The Centers for Medicare & Medicaid Services, or CMS, evaluate hospitals’ mortality and readmission rates for patients with heart attack, heart failure and pneumonia, and issues financial penalties based on both measures by cutting Medicare reimbursements to hospitals with above-average rates. Instituted last October, the readmissions penalty is already more severe than the penalty for high mortality rates and is set to increase over the next few years. Over 2,000 hospitals have been penalized for readmissions, including many of the most renowned, such as Massachusetts General Hospital and Mayo Clinic, according to Kaiser Health News.

Krumholz said the belief that mortality and readmission rates are linked partly reflects growing concerns with the CMS’s readmissions penalty.

“Some hospitals are saying you can’t really improve it, or it’s not their fault. So some people are grasping for things that are wrong with it,” Krumholz said.

But Krumholz’s study does not completely contradict the findings of the 2010 study — his team found that mortality rates of patients suffering from heart failure were lower when readmissions rates were higher. Patrick Romano, a professor at the University of California Davis School of Medicine, added that readmissions rates may not reflect quality of care for patients with heart failure as reliably as they would for those with other conditions.

Krumholz said researchers need to examine how these CMS measures change across different types of hospitals, adding that large teaching hospitals tend to have higher readmission rates. A key challenge will be to identify the factors behind the low readmissions rates of some teaching hospitals, he added.

“We’re trying to solve the problem, not just understand the metrics,” Krumholz said. “Our real drive is to make the health care system more effective.”

Still, the readmissions penalty remains controversial. Harvard School of Public Health professor Karen Joynt said the fact that readmission and mortality rates are unrelated does not necessarily mean that readmissions reflect a hospital’s quality of care, pointing out that many established quality measures such as patient satisfaction, process quality and staffing do tend to correlate with each other.

Harvard School of Public Health professor Jha Ashish added that hospitals that are recognized for high quality of care tend to have higher readmission rates because they care for sicker, poorer patients.

“If you got sick, would you go to Yale New Haven Medical Center — which tends to have among the highest readmission rates in Connecticut — or one of the myriad of small, community hospitals that have much lower readmission rates?” Ashish said. “Readmissions are not a good quality measure [of the hospital itself], but may be a good measure” to make hospitals accountable for care after patient discharge.

Readmission rates are currently at around 20 percent for Medicare beneficiaries and cost taxpayers over $17 billion each year, according to CMS.