Sitting through the first lecture of our research internship program, the lecturer invited us to introduce our subjects. After Pietje (for the sake of anonymity) had spoken about his subject, the lecturer smilingly said ‘ah, one of the sitters’. Apparently, five out of 20 students were involved in the popular research topic of sedentary behaviour (i.e. sitting and lying down). You probably know the phrase “sitting is the new smoking”, but you probably did not know “the chair is out to kill us” – by James A. Levine, MD, PhD. In his new book ‘Get Up’ he makes appealing comparisons stating that sitting is more dangerous than smoking, HIV or even a parachute jump . We will now briefly overview the essentials concerning delirious health effects of sitting.
Physical activity (PA; with moderate to vigorous-intensity) is well-known for its beneficial health effects, hence its incorporation in governmental and WHO guidelines. However, sedentary behaviour time is associated with increased all-cause mortality and chronic disease incidence (cardiovascular disease, cancer and type 2 diabetes), independent of physical activity participation . Meaning, even though you meet PA guidelines (big fan of lifting tractor tires), you are still at an increased risk (because you choose the sitting life of a university student).
A growing body of research is unravelling the mechanisms underlying this association. Uninterrupted sitting acutely deteriorates values of glucose tolerance, blood pressure, lipids and mediators of vascular health (blood flow and velocity) . Luckily, frequent interruption of sitting (every 30 minutes – 1 hour) seems to prevent negative outcomes. Moreover, standing (at your desk!) and leg fidgeting (nervously tapping your foot) seem to have the same preventive effect in acute sitting experiments . However, only one study evaluated the long-term effect of reduced sitting experimentally, finding significant improvement in HDL cholesterol only .
Just like increase in somatic disease burden, sitting time is also hypothesised to affect mental wellbeing. A recent study found that a decrease in sedentary time was associated with improvement in mood, stress and sleep in a group of young adults over the span of one year .
In a nutshell, the associations between sitting and delirious health outcomes (both somatic and psychological) are evident. In short-term experiments, acute deterioration of traditional risk factors and vascular health measures can be prevented by strategies such as interrupting sitting or standing. There is still very little experimental evidence on long-term reduced sitting effects. If the current knowledge gaps are addressed, it seems likely that sitting will be incorporated in guidelines to reduce disease burden in modern sedentary society.
 Levine, J.A. Get Up! Why Your Chair is Killing You and What You Can Do About it, (Palgrave Macmillan Ltd, London, 2015).
 Biswas, A., et al.Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis. Ann Intern Med 162, 123-132 (2015).
 Carter, S., et al.Sedentary Behavior and Cardiovascular Disease Risk: Mediating Mechanisms. Exerc Sport Sci Rev 45, 80-86 (2017).
 Padilla, J. & Fadel, P.J. Prolonged sitting leg vasculopathy: contributing factors and clinical implications. Am J Physiol Heart Circ Physiol 313, H722-H728 (2017).
 Graves, E.F.L., et al.Evaluation of sit-stand workstations in an office setting: a randomised controlled trial. BMC Public Health 15, 1145 (2015).
 Ellingson, L.D., et al.Changes in sedentary time are associated with changes in mental wellbeing over 1 year in young adults. Prev Med Rep 11, 274-281 (2018).