Friday, February 3, 2012

Science Friday

Growing up, my parents had NPR playing constantly, so much so that I was conditioned, in a very Pavlovian way, to associate the chime the station plays before the 6 o’clock news with dinner being placed on the table. Now that I’m grown and have quit complaining about it, I’ve decided to unashamedly steal one of their segments as inspiration for this blog.  Apologies to NPR and Science Friday. Any problems can be addressed to my parents or the NPR Brainwashing Authorities.

By day, I’m an (aspiring) scientist and I hope to dedicate a least part of this space to the intersection between science and running. There are a lot of myths about running I’d like to address and I’ll try my best to keep up on some of the better controlled studies being published. 

After hearing I run marathons, people love to tell me how it might kill me. (Also, how I won’t have knees when I’m older, but that's a topic for another post.) The fear of deaths during marathons is similar to the fear of flying. It's far more dangerous to get in car and drive every day, just as it's far more destructive to your health to sit on the couch all day. But neither of those every day things get media coverage.

Every year, over half a million people run marathons. Sadly, a small number of people suffer heart attacks and die doing it. It is not a sport to be taken lightly, and the waivers you sign and endless warnings are a constant reminder. Famous cases (Ryan Shay, a competitor at the 2008 Olympic trials) and those closer to home (Sean McCarthy, who ran track with me in high school and died in a race I also ran) prove to us that no one is immune. But as a new study shows, the risk is actually quite small, especially compared to other sports. 

The study, conducted by Dr. Baggish's group at Massachusetts General Hospital and published last month in the New England Journal of Medicine, looked at statistics from a decade of marathons and half marathons (from January 2000 to May 2010.) Of 10.9 million participants in both half marathons and full marathons, 59 of them suffered a cardiac arrest (19 in halfs, 40 in fulls.) The average age of the cardiac arrest sufferers was 42 and 51 (86%) of them were male. (Men made up 61% of the marathon population and 48% of the half population.) Of these 59, 42 of them died. The death rate was 3-5 times higher in marathons and was higher in men. Survivors tended to be older, have more running experience, and have received CPR. The leading cause of death was hypertrophic cardiomyopathy (thickening of the heart muscle), a largely genetic disease known to strike young athletes, which may explain why older people fared better. As for the rest of the cases (many of whom instead had ischemic heart disease), this study goes against the theory that heart attacks during marathons result from a plaque dislodging from the artery walls. Instead they found the problem might be an imbalance of oxygen supply and demand. They mention that this could mean pre-race testing may be useful and others have noted that not speeding up dramatically at the end might help. Non-heart related problems, such as hyponatremia (the loss of too much sodium) and heat stroke, were rare. Interestingly, the fatality rate (of the cardiac arrest patients) was 71% while the fatality rate for "out of hospital cardiac arrests" is 92%. Because of the ever present spectators (willing to offer CPR!) and the medical staff on the course,  the marathon course is actually a pretty good place to have a heart attack. The only place safer is in the hospital itself! (I've heard this before, but didn't know the numbers to back it up.) 

Compared to other sports, the authors conclude the risk of death during long distance running races is low. Their data estimates 1 death in 259,000 participants, while they mention rates for collegiate athletes (1 death in 43,770), triathletes (1:52,630), and healthy middle-aged joggers (1:7,620) being much higher. So what does this all mean? Overall, the risk of death is incredibly low, but of course, you still need to be safe out there, especially if you have a family history. 

Full disclosure/potential bias: Both I and the principle investigator of this study are marathoners. He beats me though, with 30 marathons under his belt and a PR of 2:49

Dream big, 

1 comment :

  1. Runner Teal:

    Very interesting. As a too-frequent consumer of the mass media, I didn't realize the numbers were so low.

    I also was interested in the Pavlovian effect of NPR. You would be interested to know that in recent years (since the kids moved out of the house described in your opening), the NPR music has been replaced by the Jon Stewart theme at 6 pm sharp. Pavlov would be pleased to point out that the same drooling is produced, however -- at least in the mouth of one of the remaining diners at the table.

    Keep up these posts. Always fun to see a new one!