Graph depicting mortality  risk reduction as a function of exercise level

Mean relative risk reduction in all-cause mortality across physical activity/fitness categories.

Do You Exercise?

Most of us believe that some amount of exercise is beneficial and that we should exercise regularly. A recent article in Time Magazine caught my attention. The World Health Organization has established a target of “150 minutes of moderate physical activity each week…that’s been shown to reduce risk for all kinds of diseases and death.” But for various reasons many, maybe most, people don’t meet this target. The gist of the Time article is that less exercise also has significant benefits. A link in the Time article takes you to The BMJ (British Medical Journal) article that is the source for the article, but it requires a subscription so I could not find the referenced report.

There is also a link to an analysis of Canada’s physical activity guidelines which does work. This paper is really a study of studies. The investigators selected some 80 studies based on their criteria that “…involved a total of 1,525,377 participants; averaging 21,791 participants per study (range 302-252,925).” (That’s a lot of people, so I think the report’s findings have a lot of credence.) The study reviewed the impact of exercise on seven chronic diseases associated with a “physically inactive lifestyle”. The list includes: coronary artery disease, stroke, hypertension, colon cancer, breast cancer, type 2 diabetes and osteoporosis. This is a 220 page paper that is understandable for the most part by non-medical readers. It confirms Canada’s guidelines, which are consistent with those of the World Health Organization, that adults should exercise 150 minutes per week. The specific recommendation in this study is for “30 minutes of moderate to vigorous exercise most days of the week.” The study says “There is incontrovertible evidence that regular exercise is an effective preventative strategy against premature mortality, cardiovascular disease, stroke, hypertension, colon cancer, breast cancer and type 2 diabetes.” It also states that there is “…less conclusive but still direct compelling evidence…with respect to osteoporosis.” Benefits are significant. The graph above is Figure 3 from the study. The X-axis represents the level of physical activity based on quintiles, quartiles, or tertiles. The analysis had to be displayed this way because the various individual studies did not use consistent measures. The results though are consistent– risk reduction is “dose-dependent”. The really good news is that the curve slopes downward rather steeply at first and relatively modest amounts of consistent exercise can have a large impact. To put it more blandly: “A clear dose-response relationship was observed with marked reductions in the risk for all-cause mortality occurring with relatively small increments in physical activity.”

This is another case of a scientific study confirming what you already know. So the hard part is now to go out and do something.