The major causes of nonfatal and fatal cardiac arrests in marathons are related to coronary artery disease. The incidence of SCD in women is lower than it is in men. Only 15% of reported SCDs occurred in women across all marathon studies. More than half the victims had completed at least 1 previous marathon, indicating that events occur in experienced runners. Few had reported symptoms before the race. Cardiac arrests appear to cluster in the latter stages of the race, with the highest numbers in the final mile or at the finish line.
-Source: Sports Health: A Multidisciplinary Approach, July/August 2010