Evidence has been accumulating about the toll of prolonged sitting, and a new systematic review and meta-analysis published in the Archives of Internal Medicine shows just how harmful sedentary habits can be. University of Toronto researcher Aviroop Biswas and colleagues performed a quantitative meta-analyses on 41 studies that measured adults’ sedentary time and reported health outcomes directly associated with death, disease, or use of healthcare services.

Their findings won’t come as a surprise to anyone who’s been following this research. “Greater sedentary time was found to be positively associated with an increased risk for all-cause mortality, cardiovascular disease mortality, cancer mortality, cardiovascular disease incidence, cancer incidence, and type 2 diabetes incidence, “ Biswas and his co-authors write.

The meta-analysis also confirms something that researchers have been warning us about: Meeting the recommended guidelines for weekly physical activity isn’t enough to offset the damage from sitting still for several hours each day. We can’t just spend an hour at the gym and then go sit in front of a desk for 10 hours and think we’re leading a healthy life. The good news is that Biswar and colleagues found that adults with higher physical activity levels were able to reduce their risks of disease and death to some degree – but not entirely. They write:

Our study demonstrated that after statistical adjustment for physical activity, sedentary time (assessed as either daily overall sedentary time, sitting time, television or screen time, or leisure time spent sitting) was independently associated with a greater risk for all-cause mortality, cardiovascular disease incidence or mortality, cancer incidence or mortality (breast, colon, colorectal, endometrial, and epithelial ovarian), and type 2 diabetes in adults. However, the deleterious outcome effects associated with sedentary time generally decreased in magnitude among persons who participated in higher levels of physical activity compared with lower levels.

I’ve written before (here and here) about research that suggests breaking up stretches of sedentary time with relatively small amounts of activity may reduce the negative effects of sitting still. This suggests we need multiple forms of physical activity – both sustained aerobic activity that keeps our heart rates up, and frequent, less-intense activity so we’re not just sitting like lumps at our desks or in front of the television. For many of us, it’s not all that hard to get up and walk around periodically, but it will be challenging for anyone who drives vehicles for a living or is expected to be at a desk for hours at a stretch. Long commutes can also take a toll. The message from the research is clear, though: We need to be sitting less and moving more.

Study cited: Biswas A; Oh PI; Faulkner GE; Bajaj RR; Silver MA; Mitchell MS; Alter DA, Annals Of Internal Medicine, ISSN: 1539-3704, 2015 Jan 20; Vol. 162 (2), pp. 123-32.