Exercise

July 27, 2010

Sitting Increases Risk of Mortality…Even With Exercise?

A recent study published in the American Journal of Epidemiology (1) reported that those who sit for long periods of time each day (determined as greater than 6 hours a day) are at a significantly increased risk of mortality compared to those who don’t (determined as less than 3 hours a day). Not surprised? Understandable. After all, everyone knows that inactivity increases the risk of disease and death, right? Well, the interesting finding associated with this study was that sitting increased the risk of mortality even in those who exercise! Science Daily did a nice job summing up the findings of the study. You can read the article here: More Time Spent Sitting Linked to Higher Risk of Death

At this time, I have only been able to view the abstract of the study, and without reading the exact methodologies employed by the researchers it’s difficult for me to offer an informed opinion. However, based on available information, it would seem some caution needs to be observed before taking the study’s results at face value.

First, the study used a questionnaire format to assess exercise info. While this is a logical approach given the large sample size, it does raise questions as to the validity of the conclusions. People notoriously tend to overestimate their physical activity levels when filling out questionnaires (2). If true here, this could have skewed results with respect to the exercise group. At the very least, additional studies need to be conducted to confirm the findings.

Also, it is unclear whether the authors differentiated between training intensities, exercise volume, and/or exercise modalities of the subjects. If not, there would have been no distinction made between those whose primary form of exercise consisted of walking slowly versus those who intensely lifted weights or performed high-intensity interval training. Suffice to say, these factors could conceivably have a huge impact on morbidity and mortality.

I hope to be able to get my hands on the entire study soon and review the particulars of the research protocol. After doing so I will post a follow up with additional thoughts on the subject. In the meantime, it is certainly clear that it’s better to be active than to sit for extended time periods. It’s also clear that performing physical activity of any kind helps to decrease mortality risk, and a majority of studies show that this risk is further reduced with more vigorous exercise. Bottom line: Keeping active and sitting less is always a good strategy. More to come so stay tuned…

Stay Fit!

Brad

1) Patel, A.V., Bernstein, L., Deka, A., Feigelson, H.S., Campbell, P.T., Gapstur, S.M., Colditz, G.A., & Thun, M.J. (2010). Leisure Time Spent Sitting in Relation to Total Mortality in a Prospective Cohort of US Adults. American Journal of Epidemiology, DOI: 10.1093/aje/kwq155

2) Fogelholm M, Malmberg J, Suni J, Santtila M, Kyröläinen H, Mäntysaari M, Oja P. (2006). International Physical Activity Questionnaire: Validity against fitness. Med Sci Sports Exerc. 38(4):753-60.