Sitting is often touted as ‘the new smoking’, but it is unclear if it is the sitting itself or the lack of physical activity that causes the harm. It has also been unclear what level of moderate to vigorous intensity physical activity – routine activities like walking briskly to work, as well as sport and exercises – might offset this risk.

New research has examined the associations of sitting and physical activitiy with premature death and cardiovascular disease mortality, and estimated what level of moderate to vigorous intensity physical activity might offset health risks of sitting.

The researchers statistically modelled physical activity and sitting against death records of nearly 150,000 study participants aged 45 years and over and followed up over almost nine years.

The study’s key message is that physical activity is particularly important for people who sit a lot. Reducing sitting would be a good start but is not enough: the most important lifestyle change for such people would be to look for or create opportunities to move more daily.

Replacing sitting with physical activity – but not standing – reduced mortality risk among ‘high sitters’, people who sit over six hours per day, said lead author Professor Emmanuel Stamatakis, from the University of Sydney’s Charles Perkins Centre and Prevention Research Collaboration in the School of Public Health.

“In our study, sitting time was associated consistently with both overall premature mortality and cardiovascular disease mortality in the least physically active groups – those doing under 150 minutes of moderate to vigorous intensity physical activity per week,” Professor Stamatakis said.

“For example, people who were physically inactive and sat for more than eight hours per day had 107 percent higher risk for cardiovascular death compared to those who did at least one hour physical activity per day and sat less than four hours.”

“But one hour of physical activity per day is not necessary."