Elderly patients are more likely to die when the nearest rural hospital closes and they have to travel farther for treatment of time-sensitive conditions such as heart attacks and strokes, according to a study by a new University of Minnesota health economist.

The study is among the first nationally to link higher mortality rates with rural hospital closures, which have been happening with increasing frequency.

At least 113 rural U.S. hospitals have closed since 2010; Minnesota has mostly escaped the trend.

“When I zoom in to look at patients with time-sensitive health conditions, I find that they do worse when their [nearest] hospitals close,” said Caitlin Carroll, who conducted the research for her doctorate at Harvard University. She was recruited to the U’s School of Public Health this summer.

Carroll also found that many small hospitals averted closure by getting federal “critical access” designation, which qualifies them for higher payments from the federal Medicare program. Those hospitals saw reductions in mortality.

That is a significant finding for Minnesota, which has the fourth-most critical access hospitals in the nation.

However, those mortality reductions came at a steep cost. Her research also found that most rural hospitals probably could have stayed open without the higher payments. So it’s possible that many lives could have been saved with considerably less federal hospital spending.

Carroll’s research undercut some theories, including the proposition that rural patients might do better after a hospital closes because they would travel farther for higher-quality care.

That wasn’t the case. “The second closest hospital is another small facility that looks pretty much the same [as the first closest] on quality metrics,” she said.

Carroll’s study was based on a review of Medicare recipients who lost their closest hospitals and then needed inpatient treatment for time-sensitive conditions. She compared them with patients in the same regions for whom the closed hospitals were only second closest.

Deaths increased only among those who lost their closest hospitals, reflecting the fact that many were in their 80s and struggled to travel longer distances for medical care.

Carroll then looked specifically at patients who had to travel an additional 15 miles or more for time-sensitive care after their closest hospitals shut down. The death rate increased 10% in this group.