People who sit too much increase their risk factor for premature death, a new study suggests.

The study involved 222,497 people aged 45 and older in Australia suggested that regardless of physical activity levels, prolonged sitting is a risk factor for premature death, meaning people should not only get moving but also get up from their seat more often.

"Shorter sitting times and sufficient physical activity are independently protective against all-cause mortality not just for healthy individuals but also for those with cardiovascular disease, diabetes, overweight, or obesity," the study's authors concluded in Monday's issue of the Archives of Internal Medicine.

The World Health Organization recommends that adults get at least 150 minutes a week of moderate intensity aerobic activity like 30 minutes of brisk walking most days of the week.

But that still leaves about 6,500 minutes of waking time that are important to health when people tend to be sitting, either at work, in a vehicle, watching TV or using a phone or computer.

In the study, Hidde van der Ploeg of the Sydney School of Public Health and his co-authors analyzed data from participants and death registries in New South Wales between 2006 and 2010.

During that time, 5,405 deaths were registered.

The risk of death was 1.15 times higher for those who sat eight to 11 hours per day and 1.40 times higher for those sitting 11 or more hours per day compared with those who sat less than four hours a day, the researchers found.

Prolonged sitting is thought to harm metabolic and vascular health by changing cholesterol levels and decreasing insulin sensitivity, the researchers said.

"Our findings add to the mounting evidence that public health programs should focus not just on increasing population physical activity levels but also on reducing sitting time, especially in individuals who do not meet the physical activity recommendations," the authors wrote.

To put that finding in perspective, 30 minutes of physical activity is as protective as 10 hours of sitting time is harmful, David Dunstan of the Baker IDI Heart and Diabetes Institute in Melbourne, Australia, said in a journal commentary accompanying the study.

"With this new study, evidence is sufficiently strong that physicians should be advising patients to reduce daily sitting time. The good news is that increasing light-intensity activity may be a feasible goal for many and offers great health benefits," the commentary concluded.

While the Australian researchers relied on self-reports of sitting time, newer objective measurements from the U.S. also show that people spend most of their waking time in either sedentary behaviour or light-intensity activity like strolling, washing dishes and gardening.

Reducing sedentary behaviour will require workplace regulations, occupational health and safety changes, transportation planning, innovations in the design of communication technologies and public education campaigns, Dunstan suggested.

The Australian study was funded by the New South Wales Division of the National Heart Foundation of Australia.