26.2 miles is a long way to run. The training leading up to the race and the race itself can take a toll on a body. Do marathons lead to more deaths from heart attacks? Yes.
The rise in deaths is from non-participants.* A recent study published in the New England Journal of Medicine found that deaths from heart attacks increase by 15% in cities on days they have marathons mainly due to road closures and traffic delays. This translates into four additional people dying for every 100 heart attacks that occur on marathon days. The study found that it takes about four minutes longer to get to the hospital on average on marathon days. The study examined health records on marathon days vs. non-marathon days in 11 cities.
The findings likely apply to other events that cause road closures, like parades, major sporting events, concerts and dog walk events.
*Whether marathons cause an increase in deaths of participants is a different and complex topic.