A new study in the "New England Journal of Medicine" is suggesting that the risk of cardiac arrest while running a marathon or half-marathon is increasing.  While the risks are still considered to be low, the number of cases has been rising over the last ten years.

According to the study, men face a risk factor five times larger than women who run marathons or half-marathons.  The study points to things like blocked arteries and enlarged hearts being the most prevalant triggers of heart attacks.

Aaron Baggish who works for Massachusetts General Hospital is a co-author of the study.  Baggish says the while many people love running to stay in shape or for the fun of it, it's not a guarantee of perfect health.  He says from the people they have studied, the information suggests that they people who end up dying are marathoners who are either born with some sort of heart disease or heart issue, and those who develop heart disease just by aging.  For more on the study, you can find them in the "New England Journal of Medicine".