Can infrastructure disruptions from large public events have unintended health consequences for people not participating? The authors investigated what happens to Medicare patients who suffer an acute cardiac emergency – either a heart attack or cardiac arrest – during a major marathon and are hospitalized in an area affected by the race route. They found that Medicare patients who were hospitalized for an acute cardiac emergency on the day of a marathon had substantially higher 30-day mortality (28.2%), compared to patients admitted during the weeks before and after the race (24.9%) and to patients admitted on the day of the race, but in zip codes just outside of the marathon route (24.8%). Their findings imply that, for every 100 patients who have a heart attack or cardiac arrest, an additional three people would die within one month if the cardiac event happened on the day of a marathon. This has important implications for organizers of all large public events, not just marathons.

On April 17th, Boston will host its 121st annual marathon. The Boston Marathon is the oldest long-distance road race in the United States and one of the largest marathons in the country. It is expected to attract approximately 30,000 runners and an estimated 500,000 spectators to line the marathon route and cheer them along.

Large public events like the Boston Marathon require tremendous resource investment to organize and manage the event as well as to ensure the safety of those involved. In addition to widespread road closures required to hold the marathon (by definition, more than 26.2 miles), the city enlists approximately 1,900 medical professionals and 3,500 military or police personnel to be posted along the race route.

While the focus of the city and the Boston Athletic Association (which organizes the race) will be on the health and safety of those involved, we wondered whether these infrastructure disruptions could have unintended health consequences for people not participating?

In a study just published in the New England Journal of Medicine, we investigated what happens to Medicare patients who suffer an acute cardiac emergency – either a heart attack or cardiac arrest – during a major marathon and are hospitalized in an area affected by the race route.

We compared 1,145 patients hospitalized on marathon days to 11,074 patients hospitalized on identical days in the 5 weeks before and after each marathon (so as to compare Mondays to Mondays, and so on) and those hospitalized on the same dates in surrounding non-affected areas. Our goal was to determine whether the road closures and traffic disruptions that occur during marathons could adversely affect elderly patients (not participating in marathons) trying to get to the hospital. In our sample of Medicare patients, the average age was 77 years and the majority had several chronic conditions.

We studied Medicare hospitalization data and ambulance transportation data from 11 U.S. cities that held marathons from 2002 to 2012. We found that Medicare patients who were hospitalized for an acute cardiac emergency on the day of a marathon had substantially higher 30-day mortality (28.2% of them died), compared to patients admitted during the weeks before and after the race (24.9% of them died) and to patients admitted on the day of the race, but in zip codes just outside of the marathon route (24.8% of them died). We accounted for patient demographics, clinical conditions, and hospital effects (which allowed us to compare outcomes of patients admitted to the same hospital on marathon vs non-marathon days). Our findings imply that, for every 100 patients who have a heart attack or cardiac arrest, an additional three people would die within one month if the cardiac event happened on the day of a marathon.

What could drive these results?

Perhaps road closures and immense crowds led patients to be hospitalized in different, lower quality hospitals outside the marathon city. However, we found no evidence of this; the hospitals that treated patients on marathon days were similar in quality to the hospitals that treated patients on non-marathon days. Similarly, Medicare patients tended to receive the same treatments when hospitalized on marathon and non-marathon days, including percutaneous coronary intervention (or stenting of the heart). Both findings suggest that the mortality differences we observed were due to differences in care that was provided to patients prior to hospital arrival, which includes delays in ambulance transport.

We considered the effects of delays in care imposed by marathons. Using a national database of ambulance transports, we studied the average time it took ambulances to transport patients from their home to the hospital in host cities. Our results showed that during the mornings of marathons, ambulances took 4.5 minutes longer, on average, to get to the hospital, relative to the surrounding non-marathon days. While this may seem small in absolute terms, it reflects a nearly 30% increase in travel time (the average travel time in our data was about 12 minutes). We found no corresponding increase during the evenings of the marathon date (by which point we assume most roads have re-opened), nor in neighboring areas unaffected by the marathon.

Our findings suggest that widespread road closures and other infrastructure disruptions during major marathons lead to substantive delays in care for patients. The conditions we studied – heart attack and cardiac arrest – tend to prompt patients to seek care immediately, and there is a wealth of medical literature suggesting that mere minutes can be the difference between life and death for these patients. We expect that our findings would translate to other medical emergencies which require immediate care, such as trauma and stroke.

This has important implications for organizers of all large public events, not just marathons. Primarily, it is essential that they consider and plan for the unintended side effects these events create. Municipalities and organizations already devote tremendous resources to the safety of participants, but should account for the costs imposed on bystanders as well. Additional measures to take up might include instructing emergency medical personnel to prepare alternative protocols on the dates of major events – rather than simply increasing the number of ambulances available – to help reduce the health costs imposed on others.

Moreover, residents of cities hosting large events would also do well to take note of major infrastructure disruptions. While our analysis of travel times focused on ambulances, 23% of the patients in our study arrived at the hospital by other means. It is reasonable to assume that these patients faced even larger transport delays; so residents should know to call medical personnel at the first sign of symptoms rather than attempt to drive to the hospital themselves.

Many U.S. cities enjoy a number of large public events, ranging from Fourth of July celebrations to professional sports games. While the disruptions they cause are felt by many, there are also substantive health implications for those who may require acute medical care. Both the organizers of these events and the residents living nearby should be aware of potential delays in medical care that these events can inadvertently cause.