Healy, G. N., Matthews, C. E., Dunstan, D. W., Winkler, E. A. H., & Owen, N. Sedentary time and cardio-metabolic biomarkers in US adults: NHANES 2003–06. European Heart Journal. January 2011
The study referenced above was only recently completed and published on line this month. It is very important and adds to a growing body of evidence that is linking sedentary (inactive/sitting) behavior, in and of itself, with risk for disease. This is emerging and important work. I want you to wrap your head around that a bit. This is like when scientists first began to report that second hand smoke could cause heart disease and lung cancer. It took many years before policies to protect people from SHS were put into place. Most did not think the science was convincing but today you would be hard pressed to find any US building (or UK, or France, Ireland, etc) that allows indoor smoking.
The association between sitting and heart disease IS new. This is not about the protective result of exercise, but the damaging effect of sitting for over an hour at a time and the even worse outcomes from having those hours of sitting add up in a day. I am reading the research studies and they are well done and valid. The most recent one was even more convincing as the persons involved wore accelerometers - devices that tracked their movements and logged the amount of time that they were sedentary(not moving). The accelerometer tracked counts per minute and was only worn during waking hours
The results of the study are important on several levels.
The researchers wanted to know if total time sitting/sedentary impacted certain biological measures of disease and if there was a dose response effect.
The markers that were assessed (clinically - with lab tests) were blood pressure, blood fat, HDL, several blood sugar and insulin measures, C reactive protein levels, and waist circumference.
They wanted to know if there would be a difference on these markers (blood sugar, blood fats, etc) if the total sedentary time was broken up with any amount of break time (1 min to 15 minutes, for example)
Lastly, they compared the above across certain demographic differences like sex, age and ethnicity.
The findings were that YES the people who sat the most time compared to the people who sat the least, had worse readings across those markers (in degrees or dose response) with significant and pronounced differences on waist circumference (white only), blood fat levels and blood sugar levels. This has been seen in previous research, but new for this study was that CRP was also adversely effected by sitting.
The scientists found that the differences between sitting without taking a break and sitting for the same total time with breaks were profound enough to recommend that a National Health Message on Sedentary Activity should include the benefits of taking breaks every hour or so. In fact, they suggest that a substantial decrease in heart disease in this country could occur if people did NOT sit at their desk all day!
Take that to the boss tomorrow - the study is available here :)
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