NEW YORK - The risk of cardiac arrest during a marathon or half-marathon is low, but it has increased over the past decade, according to a new study of nearly 11 million race entries.
Men faced a greater risk than women, and full marathons were more dangerous than half-marathons, according to a report published in the New England Journal of Medicine.
Hypertrophic cardiomyopathy and atherosclerotic coronary disease were pegged as the biggest causes.
The findings suggest that runners and their doctors need to realise that heart disease can take its toll even on runners who otherwise would seem to be the picture of health, co-author Dr Aaron Baggish of Massachusetts General Hospital told Reuters Health in a telephone interview.
Running reduces risk of heart disease
"Being a runner is one of the best ways to stay healthy and reduce your risk of disease. But it's not 100% protective," he said. "The people who get into trouble are the people who are either born with, or develop, through the normal ageing process, heart disease."
The results come at a time when participation in long-distance races in the US has doubled over the past decade to about two million participants in 2010.
The new findings are based on an ongoing database of all US marathons (26.2 miles) and half-marathons (13.1 miles) run from January 2000 through May 2010. It includes information on 10.9 million race registrations.
In all, there were 59 cases of cardiac arrests – 42 of them fatal – during the races or within an hour afterwards.
Fatal cardiac cases in younger runners common
That translates to a risk of 1 in 184,000 runners for developing cardiac arrest during or just after a run. The risk of sudden death was 1 in 259,000, which the researchers characterised as "a low overall risk."
It compares to 1 death per 43,770 college athletes per year and 1 in 7,620 seemingly-healthy middle-age joggers.
The average age at cardiac arrest was 42, plus or minus 13 years. The fatal cases tended to be among younger runners and those who did not get cardiopulmonary resuscitation (CPR) right away.
"We showed quiet convincingly that one of the most important determinants of survival from a cardiac arrest is whether or not one gets immediate bystander CPR," said Dr Baggish.
In response, just prior to the Boston Marathon this coming April, "We're going to be offering the first CPR education program for runners over the weekend to actually teach them how to do this," he said.
Older runners at same risk as non-runners
The researchers also found that the rate of cardiac arrest among males nearly tripled from the first five years of the study to the last five years, from 7.1 to 20.3 per million entrants (p=0.01).
The likely reason? "The demographic, of men in particular, turning to marathons has changed considerably over the last 10 years," Dr Baggish said. "It used to be the purview of only healthy fit athletes. Now more folks who had been previously sedentary, have cardiovascular risk factors, and may have histories they wish to personally abort are turning to marathon running at an older age. They are probably the ones accounting for the increased risk."
Doctors need to be aware that 50-year-old runners who cover 15 miles a day can have some of the same risk factors as their couch-potato contemporaries.
"I run a referral practice for athletes with heart issues and I can't tell you how many people walk through the door and say, 'My doctor looked at me and said, "You're so healthy, nothing can be wrong with you,'" Dr Baggish said.
Risk five times higher in men
The rate of 10.1 cardiac arrests per million entrants in full marathons was nearly four times higher than the rate of 2.7 per million for half marathons. The rate of death during full marathons was more than twice as high.
The risk of cardiac arrest was more than five times higher for men vs women (9.0 per vs 1.6 per million entrants).
Among the 59 runners with cardiac arrest, the cause was only available for 31, including 23 who died. Fifteen deaths were blamed on hypertrophic cardiomyopathy or possible hypertrophic cardiomyopathy. Among the eight who didn't die, five apparently had cardiac arrest from ischaemic heart disease, yet none of the five had evidence of plaque rupture or thrombus.
The results from the Race Associated Cardiac Arrest Even Registry (RACER) Study Group are similar to a 1996 analysis of more than 200,000 marathon runners done at the Minneapolis Heart Institute Foundation, which pegged the risk of sudden cardiac arrest while running a marathon at 0.002%.
By Gene Emery
(Reuters Health, January 2012)
Sudden cardiac arrest
Marathons and your heart