Continuous sitting for more than three hours can take a serious health toll on our bodies and it has recently become a prevalent public health topic and target for intervention, according to a new study.

The study published in the American Journal of Preventive Medicine found that sitting for more than three hours per day is responsible for 3.8% of all-cause mortality deaths.

Investigators also estimate that reducing sitting time to less than three hours per day would increase life expectancy by an average of 0.2 years.

To properly assess the damaging effects of sitting, the study analyzed behavioural surveys from 54 countries around the world and matched them with statistics on population size, actuarial tables and overall deaths.

Researchers found that sitting time significantly impacted all-cause mortality, accounting for approximately 433,000, or 3.8%, of all deaths across the 54 nations in the study.

They also found that sitting had higher impact on mortality rates in the Western Pacific region, followed by European, Eastern Mediterranean, American, and Southeast Asian countries, respectively.

Researchers now believe that periods of moderate or vigorous physical activity might not be enough to undo the detrimental effects of extended sitting.

While researchers found that sitting contributed to all-cause mortality, they also estimated the impact from reduced sitting time independent of moderate to vigorous physical activity.

“It was observed that even modest reductions, such as a 10% reduction in the mean sitting time or a 30-minute absolute decrease of sitting time per day, could have an instant impact in all-cause mortality in the 54 evaluated countries, whereas bolder changes (for instance, 50% decrease or two hours fewer) would represent at least three times fewer deaths versus the 10% or 30-minute reduction scenarios,” explained lead investigator Leandro Rezende, MSc, Department of Preventive Medicine, University of Sao Paulo School of Medicine.

Studies are beginning to show us exactly how detrimental prolonged sitting is for our health, even when coupled with exercise; however, changing habits is a difficult proposition. “Although sitting is an intrinsic part of human nature, excessive sitting is very common in modern societies,” said Rezende.

“Sedentary behavior is determined by individual, social and environmental factors, all strongly influenced by the current economic system, including a greater number of labour-saving devices for commuting, at home and work and urban environment inequalities that force people to travel longer distances and live in areas that lack support for active lifestyles.”

The results of this analysis show that reducing sitting time, even by a small amount, can lead to longer lives but lessening time spent in chairs may also prompt people to be more physically active in general.”

“Although sitting time represents a smaller impact compared with other risk factors, reducing sitting time might be an important aspect for active lifestyle promotion, especially among people with lower physical activity levels,” emphasized Rezende.

“In other words, reducing sitting time would help people increase their volumes of physical activity along the continuum to higher physical activity levels.”

Renzende said the findings support the importance of promoting active lifestyles (more physical activity and less sitting) as an important aspect for premature mortality prevention worldwide, and “therefore the need for global action to reduce this risk factor.”

In a related study led by the Institute of Psychiatry, Psychology & Neuroscience (IoPPN) at King’s College London, researchers found some promising interventions.

These include provision of sit-stand desks at work, though other techniques such as encouraging people to keep records of their own sitting time, setting individual goals for limiting sitting time and using prompts and cues to remind people to stop them sitting, were also found to help reduce sitting time, even when used in isolation.

In addition, effective interventions tended to educate people about the health benefits of reducing sitting time. The researchers recommend that sitting time should be viewed as a separate behaviour change target to physical activity.

They hope their findings can be used by public health workers and policy makers responsible for designing new interventions to reduce sitting time and improve the overall health of those who may sit for prolonged periods.