Just cold incorrect

It's been cold across much of the country lately, including where I live. As a result of this fact, and my decision to go through Hal Higdon's marathon training program as a way to keep in shape this winter, I've been doing a lot of my running when the temperature is in the teens and 20s.

Now, my schedule is pretty tight, and during the week I usually change into my running clothes at the end of work and hit the streets before heading home. Of course, my coworkers notice this, and their response is pretty much universal: "You're going to get pneumonia!"

Really, it's kind of annoying, especially considering that the strongest warnings come from those who smoke ("You're *cough* *cough* going to *HACK!* catch pneumonia!"). Maybe I should jump up and confront them every time they get up to head outside for a cigarette: "You're going to catch heart disease, emphysema, COPD and cancer!"

Anyway, as a rational, thinking adult, I know that infections of the human body, including pneumonia, are caused by bacteria and viruses. A change in the temperature being responsible for producing illness would be an act of spontaneous generation, much like rotting meat magically turning into maggots, or dirt becoming plants. In other words, a total fallacy.

But while I know this, I also know the reason people used to believe in those other examples of spontaneous generation was ignorance of the full process in play. Rotting meat appears to turn into maggots because flies lay their eggs in rotting meat. Dirt appears to turn into plants because there are seeds in the dirt. Perhaps there is some larger mechanism at work that makes people exposed to cooler temperatures more susceptible to infection, creating the false notion that cold weather causes disease. So I decided to check it out.

First of all, according to the Centers for Disease Control and Prevention, pneumonia is a serious matter, resulting in 1.2 million hospitalizations and over 55,000 deaths in 2006. But all authoritative sources I've been able to find note that the illness is caused generally by bacteria, although it can also be brought on by viruses, fungi and chemicals (CDC, American Lung Association, WebMD).

WebMD comes right out and explicitly addresses the concerns about cold weather, saying, "You do not catch pneumonia by not dressing properly for cold weather or by being caught in the rain."

But what about the belief that cold weather, while not responsible for illness, could make one more susceptible to it? Turns out there might be an element of truth, albeit remote, to that fear. A 1996 article by Dr. Alan Greene investigating any potential link between cold air and the common cold notes that cold air does cause mucus to thicken, which may make it slightly more difficult for the body to prevent bacteria and viruses from entering the lungs.

As a counterpoint to that article, however, is this one, which reports on a number of studies that appear to show that brief periods of moderate exercise immediately boost the immune system over the short term, and engaging in such activities on a regular basis may prolong the effect over the long term. "During moderate exercise immune cells circulate through the body more quickly and are better able to kill bacteria and viruses," the article reads. "After exercise ends, the immune system generally returns to normal within a few hours, but consistent, regular exercise seems to make these changes a bit more long-lasting." It is important to note, however, that another study suggests that longer (e.g. 90 minutes), more strenuous exercise in the cold might actually weaken the immune response for up to 72 hours.

And then there's this article by Amby Burfoot, which appeared in Runner's World in 2004, that specifically explores whether there are any hazards to running when it's really cold, like 40-below-zero kind of cold. Told anecdotally, the article can find no real dangers, as long as proper precautions are taken to avoid such maladies as frostbite.

So, in summary, it appears that the old wives' tales about cold weather causing colds, the flu or pneumonia really have no basis in reality. In fact, while cold weather might inhibit the body's ability to prevent some microbes from entering, the immune system boost provided by exercise should actually mean that one would experience fewer illnesses of lesser severity.

As long as you take proper precautions to keep warm and don't overdo it, there is no reason why you shouldn't be able to continue enjoying your favorite outdoor activity in the winter. So, much as my sore legs and tired body might protest from time to time, I'll continue my training.

As for my smoking friends, maybe it is for the best that they be so concerned about the potential for pneumonia ... not for me, but for themselves. This 1999 Science Daily article reports on a study that year showing that those who smoke at least a pack a day are "almost three times more likely to acquire pneumonia than persons who never smoked." Maybe it's from all that time they spend outside in the cold.