A review of mortality data of 222,497 Australians that was published in the Archives of Internal Medicine made for some pretty grim reading for those of us that spend our days staring at computer screens.
Summary: "Sitting on your arse can be fatal."
"Its most striking finding was that people who sat more than 11 hours a day had a 40% higher risk of dying in the next three years than people who sat less than four hours a day." (quote from theatlantic.com review of study)
Review of study;
"Healthy or sick, active or inactive, the more people sat, the more likely they were to die in the next three years. Physical activity did reduce this risk significantly: the 40% higher death risk found when comparing people who sat the most to those who sat the least increased to 100% when comparing those who sat the most and exercised the least to those who sat the least and exercised the most. But while the death risk was much lower for anyone who exercised five hours a week or more, it still rose as these active people sat longer.
In other words, people still need to exercise, but it's also important to spend less time sitting."
This study was published in the Archives of Internal medicine, the full test does not seem to be available yet from my institution.
van der Ploeg, Hidde P., Chey, Tien, Korda, Rosemary J., Banks, Emily and Bauman, Adrian (2012) ‘Sitting Time and All-Cause Mortality Risk in 222 497 Australian Adults’, Arch Intern Med, 172(6), pp. 494–500.