June 1, 2010

health wednesday

Another not-so-sublte, thinly veiled attempt at trying to influence the health of those around me....

     If ever there was a panacea, exercise would probably fit the bill.  Ironically, it's probably also the hardest thing for a physician to prescribe.  Certainly it's well documented for its protective as well as interventional effects on heart disease and diabetes.  It's easy to see how exercise affects the heart.  The heart is a muscle.  Exercise trains muscle.  The heart improves.  It's obviously more complex than that but that it gets the point across.  But what about cancer?  Cancer is a different disease.  What in the world would training muscles have to do with cells who have gone malignant?
     There is data on exercise reducing the risk of developing cancer but that obviously doesn't interest me much at the current moment.  Those cows have already gotten out the gate.  Intervention is the more critical component here.  So what does the literature say?  I found some interesting studies.  Take this study looking at the effect of exercise on breast cancer patients after diagnosis.  This diagram pretty much says it all.

To those who don't like making graphs, let me explain it.  The vertical axis on the left is mortality.  The higher up, the higher the mortality rate.  Not good.  The horizontal axis on the bottom is time measured in years.  The three squiggly lines?  Essentially, you want to be in the line that's closest to the bottom because that means improved survival.  The study takes the women and divides them into three different categories based on METs (Metabolic Equivalence Task) which is a formulaic way for exercise physiologists to compare different exercises based on metabolic output.  A MET of 1 is what your body produces to sit there and keep breathing for 1 hour.  Walking leisurely is around 2 METs while a 13-minute mile pace for an hour expends around 6 METs.  The higher the number, the higher the intensity of exercise.  You get the picture.  If you want more information, click here
     So you can see the top squiggly dark line had less than 2.8 MET hours per week which means they didn't do much other than walk to their car or walk to McDonald's from their car.  The middle dotted line had 2.8 to 7.9 MET hours/week which means they had light to moderate activity.  They weren't couch potatoes but they weren't gym rats either.  And notice what a dramatic drop in mortality occurs with just moderate exercise.  At 6-years we're talking a relative 50% risk reduction in mortality.  That's nothing to sneeze at.  And what happens if you add more intense physical activity (not necessarily more exercise, just more intensity).  It's not crystal clear but the bottom dashded squiggly line seems to possibly indicate an even greater improvement in survival.  A similar study in JAMA back in 2005 found a similar protective effect with exercise but did not find a correlation between higher intensity and improved survival.  These incremental improvements usually take much larger and longer trials which don't tend to get answered until much later, if ever.
     Now the caveats.  These studies were only in women with breast cancer but  there are similar suggestive data in prostate and colorectal cancer.  The BIG caveat is that these studies weren't randomized.  What's that mean?  It means that it assessed people who voluntarily exercised versus those who didn't.  It didn't take people and say "you exercise, you don't."  Those people who voluntarily exercise also tend to have higher education and all the sociological beneficial trends that are associated therewith.  It may come down to something as simple as these people are better motivated to live and fight and are better equipped to do so (better medical access, better social structure, better informed, etc).  In the end for my brother, it doesn't much matter to me what the mechanism is.  He's got all those sociological factors in his favor so run with it.  Literally.  If exercise embodies some psychological/physiological will to live, then by all means exercise away.  Bottom line is that aside from improved quality of life, strength, etc., it appears that even moderate exercise may improve survival in breast cancer patients.

PS - In searching the literature for various cancer related topics, it seems to me that breast cancer seems to trump all others in breadth of trials.  That probably reflects better fund raising.  I remember the American Heart Association lamenting that the Pink and Save the Tatas campaigns did their job a little too well as heart disease still claims far more female lives than breast cancer yet women are far more educated with respect to breast cancer and relatively much less so with respect to heart disease.  They came out with their own Red Dress campaign.  It didn't work.

PPS - This blog was much easier to write after I went for my own run.  Physician, heal thyself.

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