The Truth about “Sitting Kills”

Wednesday, September 20, 2017 - 09:00

Between productivity losses and direct healthcare costs, the worldwide economic burden of physical inactivity was $67.5 billion in 2013. People aren’t moving enough and are sitting too much, contributing to what many call a global pandemic of physical inactivity. Results from studies in Western countries show that in general, people spend the majority of their waking time sedentary, and few meet the physical activity guidelines of 150 minutes of moderate-to-vigorous activity a week.

Most of people’s sedentary behaviour is time spent sitting, leading to headlines like “sitting kills” or “sitting is the new smoking”. For many people who sit while at work, or while travelling to or from work, eliminating or significantly reducing sitting is not feasible. Recent research suggests, however, that even if we can’t control how long we sit for, there are other things we can do to eliminate the increased risk of mortality associated with prolonged sitting.

The Protection of Physical Activity
Unsurprisingly, physical activity is the best thing we can do to mitigate the risk associated with increased sitting time. A 2016 meta-analysis investigated the combined effect of exercise and sitting time on mortality, since people generally spend parts of their day both physically active and sedentary.

People were separated into four quartiles based on their activity level, with the least active group being active for about 5 minutes per day, and the most active quartile engaging in 60-75 minutes of moderate physical activity per day. The two middle quartiles included those who followed current physical activity recommendations. Within these quartiles, people were further categorized based on the number of hours spent sitting.

• In all groups except the most active group, sitting more led to a higher risk of mortality.
• In the most active group, even sitting for more than 8 hours a day was not associated with higher mortality rates.
  
  • They also had a significantly lower risk of death than those who sat the least (less than 4 hours a day), but were the least active.
  • Large amounts of physical activity eliminates the risk of excessive sitting.
• In the second and third least active groups, while still at a higher risk than the most active group, being engaged in physical activity helped to dampen the mortality risks linked to increased sitting time.
• The least active group received no protection from physical activity, and had high mortality risk even when sitting for less than 4 hours a day.

Physical activity can weaken the effect of lengthy sitting time on risk of mortality, and for those who engage in the equivalent of 60-75 minutes of moderate exercise per day, physical activity can eliminate the effect of prolonged sitting.

These ideas could help you implement more movement and progressively work up to more intense or more frequent activity:

• Bike to work: kill two birds with one stone
• Take a walk at lunch: go outside or climb your building stairs
• Try high-intensity interval training (HIIT) to make the most of limited time
• Go for a stroll after dinner instead of sitting in front of the TV
• Encourage and include your family in physically active endeavours and games

Fitting in 60-75 minutes of moderate exercise can seem daunting, or near impossible. While there are definitely ways to incorporate them into your day if you make physical activity a priority, it’s also important to remember than even a bit of exercise is better than no exercise at all.

Sources:
Ding D, Lawson KD, Kolbe-Alexander TL, Finkelstein EA, Katzmarzyk PT, van Mechelen W, Pratt M. The economic burden of physical inactivity: a global analysis of major non-communicable diseases. 2016; 388(10051): 1311-1324.
Ekelund U, Steene-Johannessen J, Brown WJ, Wang Fagerland M, Owen N, Powell KE, Bauman A, Lee I. Does physical activity attenuate, or even eliminate, the detrimental association of sitting time with mortality? A harmonised meta-analysis of data from more than 1 million men and women. The Lancet. 2016; 388(10051): 1302-1310.
Hansen BH, Koole E, Dyrstad SM, Holme I, Anderssen SA. Accelerometer-determined physical activity in adults and older people. Medicine & Science in Sports & Exercise. 2012; 44(2): 266-272.
Matthews CE, Chen KY, Freedson PS, Buchowski MS, Beech BM, Pate RR, Troiano RP. Amount of time spent in sedentary behaviors in the United States, 2003-2004. American Journal of Epidemiology. 2008; 167(7): 875-881.

About the Author: Lily is a fourth-year student in the kinesiology program at Western University, currently interning with SIRC. With a background in synchronized swimming, she continues to be actively involved in sport as a coach and varsity athlete.