Stand up if you want to live longer, researchers have warned.

A major study from Australia found sitting down too long increases your risk of dying within three years, even if you are already physically active.

The study of 222,000 people suggests too much sitting – as opposed to insufficient activity – may be a new risk factor for premature death.

It found adults who sat 11 or more hours per day had a 40 per cent increased risk of dying in the next three years compared with those who sat for fewer than four hours a day.

This risk remained after taking into account their physical activity, weight and general health.

People sitting for between eight and 11 hours a day had a 15 per cent increase in the risk of dying compared with those seated for fewer than four hours a day.

The findings were published in the medical journal Archives of Internal Medicine (must credit).

Lead author Dr Hidde van der Ploeg, a senior research fellow at the University of Sydney’s School of Public Health, said ‘These results have important public health implications.

‘That morning walk or trip to the gym is still necessary, but it’s also important to avoid prolonged sitting. Our results suggest the time people spend sitting at home, work and in traffic should be reduced by standing or walking more.’ The results are the first landmark findings to be published from the Sax Institute’s 45 and Up Study, the largest ongoing study of healthy ageing in the Southern Hemisphere.

Predominant position: Many people can spend the majority of the day sitting down (Posed by model)

They showed physical activity is still beneficial: inactive people who sat the most had double the risk of dying within three years than the active people who sat least.

Among the physically inactive group, those who sat the most had nearly one-third higher chance of dying than those who sat least.

Altogether there were 5,400 deaths in the three year period of follow-up, with seven per cent of the deaths attributed to sitting.

There has been growing interest in the downsides of prolonged sitting, which is a marker for a sedentary lifestyle.

Previous research found people who watch six hours of TV a day cut short their lifespan by five years compared with someone who watches no TV.

People who sit for longer have bigger waist sizes, and higher levels of cholesterol, blood sugar and triglycerides.

 The average adult spends 90 per cent of their leisure time sitting down and less than half of adults meet World Health Organization physical activity recommendations.

In the UK, adults are urged to do 150 minutes of activity a week to promote health.

In an accompanying editorial, co-author David Dunstan of the physical activity laboratory, Baker IDI Heart and Diabetes Institute, Melbourne, said individuals are exhorted to do 30 minutes of brisk walking a day to stave off chronic disease.

But ‘this still leaves 15 and a half hours of non-exercise awake time each day during which, for many adults, sitting is the predominant stance.

‘To put this in perspective, 30 minutes of physical activity is as protective an exposure as 10 hours of sitting is a harmful one’.

He said the evidence was strong enough to support doctors prescribing ‘reduced daily sitting time’ to their patients.

The research was commissioned by the Cardiovascular Research Network and supported by the NSW Division of the National Heart Foundation Australia.

Heart Foundation NSW CEO Tony Thirlwell said being inactive was a major risk factor for cardiovascular disease.

He said ‘Watching TV, using computers and electronic games can involve sitting for long periods and have become a big part of leisure time.

‘But we know that people who spend less time on these things have better health than those who spend too much time on them.’ A major five-year follow-up of 45 and Up study participants has just begun and will ask 265,000 men and women more about their health, lifestyle, and the medications and health services they use.