People who sit for 11 hours or more a day are 40 percent more likely to die over the next three years, regardless of whether they are physically active or not, according to a new study.

Researchers analyzed self-reported data from 222,497 people in Australia aged 45 years and older and found that the death risks peak after 11 hours of total daily sitting, but the death risk is still 15 percent higher for those sitting between eight to 11 hours a day compared to people sitting less than four hours a day.

"In conclusion, prolonged sitting is a risk factor for all-cause mortality. 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 authors wrote.

However researcher stressed that the findings don’t necessarily prove that sitting killed people, but that there was a strong association between inactivity and premature mortality.

"The evidence on the detrimental health effects of prolonged sitting has been building over the last few years," said study author Hidde van der Ploeg, a senior research fellow at the University of Sydney told Healthday. "The study stands out because of its large number of participants and the fact that it was one of the first that was able to look at total sitting time. Most of the evidence to date had been on the health risks of prolonged television viewing."

Suzanne Steinbaum, a spokeswoman for the American Heart Association, who wasn't involved with the study, told HealthDay that because people have to work, it is important that people don’t go back to sitting in front of the computer or television after work.

"After the 8-hour mark, the risks go up exponentially," Steinbaum said. "It's really about what you're doing in your leisure time and making the decision to move."

Researchers said that the results have important public health implications, and public health programs should promote reductions in sitting time as well as increasing levels of physical activity.

"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

Adults typically spend 90 percent of their leisure time sitting down, and less than half of adults meet the World Health Organization physical activity recommendations of at least 150 minutes a week of moderate intensity aerobic activity like 30 minutes of fast pace walking most days of the week.

Experts in an accompanying editorial said that the evidence was strong enough for doctors to prescribe “reduced sitting time” to their patients, and researchers said that even sitting five minute less per hour can make a huge difference.

"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.

The study was published on Monday in the journal Archives of Internal Medicine.

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