We’re all aware of the importance of regular physical activity in maintaining good health.  Put another way, not getting regular physical activity can lead to many health problems, including heart disease, strokes, memory problems, and obesity, among many other health effects. 

But would it surprise you to find out that simply sitting – as opposed to standing and walking around  – for prolonged periods is also bad for your health?

A recent large prospective study* sponsored by the American Cancer Society of over 53,000 adult men and over 69,000 adult women – all disease-free at the time of enrollment – looked at the relationship between the amount of leisure time spent sitting and mortality over a 14 year period.  Women who reported sitting for over 6 hours per day had an approximately 40% higher death rate than those who reported sitting for less than 3 hours per day; men who reported sitting over 6 hours per day had a 20% higher death rate than those who reported sitting less than 3 hours per day.

These findings are consistent with those of at least three other studies that looked at the relationship of time spent sitting and mortality.

The researchers also looked separately at the amount of vigorous physical activity each of the participants got.  As you would expect, those participants who got the highest level of physical activity had a lower mortality than those who got little physical activity. Very interesting, however, is the fact that the association of increased sitting time and higher mortality was independent of how much regular physical activity the subject got.  This means that sitting for prolonged periods of time – even if you get in regular physical activity – can be damaging to your health. And the converse is also true: even if you don’t get in much regular exercise, your health can benefit by limiting the amount of sitting you do in a day.

As you might expect,  the combination of sitting more (greater than 6 hours per day) and being less physically active (less than 24.5 MET- hours per week)** was associated with the highest increases in death rates – 94% increase in death rates for women, and 48% increase in death rates for men – when compared to those who sat the least amount (less than 3 hours per day) and had the highest level of physical activity (greater than 52 MET-hours per week).

Do yourself a favor and notice how many hours per day you sit without getting up, including your marathon of watching your favorite television shows, sitting at your desk at work, or getting caught up in that book you’re reading for hours at a time. If you are sitting for longer than 3 hours at a time, change it! If in fact you can’t help how many hours you have to sit at work, do two things: 1) get up and walk around once every hour or two; and 2) know that it is even more important for you to get in regular physical activity in order to offset the damage to your health done by sitting.

Remember: you should be reducing your time spent sitting per day in addition to getting regular vigorous physical activity each week.

* Alpa V. Patel; Leslie Bernstein; Anusila Deka; Heather Spencer Feigelson; Peter T. Campbell; Susan M. Gapstur; Graham A. Colditz; Michael J. Thun. Posted: 09/14/2010; American Journal of Epidemiology. 2010;172(4):419-429. © 2010 Oxford University Press.

** “MET-hours” is a measurement of how vigorous physical activity is over a certain period of time.