Saturday, January 14, 2012

Run for your life

“Who wants to live forever?”, was the rhetoric question in one of the songs of Queen which became popular after the singer Freddy Mercury had died. Forever for most people is a too long period and they prefer the fairy-tale ending to live long and happy thereafter. How to lead a happy life will be the subject of another blog, but for this moment just one tip from Betty White, 89 years old herself, in the Late Show: Get at least 8 hours of beauty sleep, 9 if you’re ugly. Whatever your looks, what would determine your lifespan, happy or not, and is there anything you can do to make the most of it? 

An interesting hypothesis on longevity is that the lifespan of an animal, including man, is determined by a fixed number of heartbeats. The hummingbird, with a heart rate of 1260 bpm (beats per minute) lives only 1-3 years. Elephants, at the other end, have a heart rate of 30 bpm and can live up to 60 years. Most elephants don’t make it to that age because their teeth fall out and they then die in fact from starvation. As compared with all other animals, the number of heartbeats for humans  is 3 times higher: 3 billion rather than 1 billion. With an average heart rate of 72 bpm you can live to become 79 years. Now is there anything you can do to change those numbers and make the most of it? Lifestyle advices for long and healthy-living include daily physical exercise for at least 30 minutes. It is difficult to establish the exact intensity level of the exercise but a rule of thumb is that the 30 minutes start from the moment you’re sweating. I am a runner myself. I try to keep the routine of running 4-8 km circuits 3 times a week and several times a year I participate in 10-15 km runs. What will all this have for an impact, if any,  on my own lifespan. During the exercise my heart rate goes up, so I am wasting valuable heartbeats.  A rough calculation learns that for every year of running you could lose a week of life. On the bright side: all that running improves your physical condition and that leads to a lower heart rate at rest. Again a rough calculation learns that for every year of running you may gain 13 weeks of life. The net effect would be that for every year of running (or cycling if you would prefer that over running) you gain 12 weeks of life. A study from Harvard even suggested that every hour spent exercising would add two hours life expectancy: Who wants to live forever? 

What has all this to do with the immune system? Everything! An optimal functioning immune system will ward off infectious diseases and prevent chronic inflammatory diseases to develop. Both effects contribute to a healthy life. It has long been established that exercise such as running and cycling improves the function of the immune system, and therefore along these routes, contributes to longevity. 

Now a recent study from Mike Gleeson’s team in the UK has found that you shouldn’t overdo it: running a marathon impairs the function of your immune system. This headline in the news is a sweeping generalization of what they actually found (which is a reduction in the activity of the so-called Natural Killer cells) but the conclusion is justified that running a marathon certainly doesn’t improve your immune system. In the weeks following a marathon the runners have a 2-6 fold increase in upper respiratory tract infections which may well be a reflection of the temporarily depressed immune system. An upper respiratory tract infection won’t kill you, so what about longevity? The participant of the first recorded marathon in history certainly didn’t prolong his life. Would the thousands of participants of modern-day marathons and half-marathons be better off? This subject has not been studied that well. A German study found that 25% of the 65- to 69-year-old runners were faster than 50% of the 20- to 54-year-old runners. So maybe  you can’t run for your life, but you can run all your life.