QUICKLINKS AND VIEW OPITONS
An Exercise Paradox
Sunday, March 16, 2014 11:56 am Email this article
Most people and all doctors believe that physical exercise makes you live longer. There is no evidence for this idea. In longitudinal studies, people who exercise more tend to live longer, true, but in studies where long-lived people were interviewed, the long-lifers were no more likely to have exercised than anyone else. In fact, they were less likely to have exercised.
This apparent paradox is a consequence of the healthy survivor effect, i.e. the people who were more healthy to begin with were the ones most likely to exercise. Notice, that does not imply that the exercise itself made them more healthy.
It’s an example of the reckless tendency to believe that association implies causation. Please learn that just because A and B occur together, does not mean A causes B.
Other examples. A. People with type 2 diabetes have high blood sugar. B. People with type 2 diabetes have more heart attacks. But you cannot assume that lowering blood sugar in type 2 diabetics reduces the chance of a heart attack. In fact, it doesn't. The ACCORD trial in 1992 showed it didn't.
Ditto high blood pressure.
Ditto high cholesterol.
The only way to know for sure whether exercise extends life is to do a randomized controlled trial. Assign people randomly to an exercise group or a control group and follow them over time to see how many in each group live longer. Such a study has never been done.
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