Road closings during marathons can be frustrating for drivers and pedestrians. Now a new study suggests they can be bad for your health.

Researchers analyzed data on Medicare patients hospitalized for heart attacks and cardiac arrest in 11 cities from 2002 to 2012. They compared them with people hospitalized in the same cities, on the same days of the week, in the five weeks before and after the races. The study is in The New England Journal of Medicine.

The number of hospitalizations was about the same on marathon days as others, and so were the health characteristics of those hospitalized. But during marathons, it took an average of 4.4 minutes longer to get to the hospital, and even after controlling for age, race and many pre-existing medical conditions, the risk of dying within 30 days of hospitalization was 13.3 percent higher.

The patients had an average age of 77 and were unlikely to be marathon participants themselves. There were no similar spikes in treatment delays or deaths in hospitals in ZIP codes surrounding the cities where marathons were being held.

“Care in the hospital is the same on marathon and nonmarathon days,” said the lead author, Dr. Anupam B. Jena, an associate professor at Harvard Medical School. “So it really looks like it’s the amount of time it takes to get to the hospital that is at issue.”