Exercise, even a little per day, did tend to lower the mortality risk tied to sitting, the team noted. However, sitting's influence on death risk remained significant even when activity was factored in.
On the other hand, people who sat a lot and did not exercise or stay active had an even higher mortality risk: 94 percent for women and 48 percent for men.
Study lead author Dr. Alpa Patel, an epidemiologist with the American Cancer Society, said that the obvious reason for the connection is that "the more time you spend sitting, the less total energy expended and you can have consequences such as weight gain and increased obesity." And that affects your metabolism as well as risk factors for various diseases, she said.
But there could be other biological factors beyond simply getting fatter that explain the link.
There's a burgeoning literature evolving around "inactivity physiology," Patel said. When muscles, especially those in the legs, are "sitting," they stimulate or suppress various hormones which then affect triglycerides, cholesterol and other markers for heart and other diseases, she explained.
Find out more about the healthy effects of exercise at the U.S National Cancer Institute.
SOURCES: Jay Brooks, M.D., chairman, hematology/oncology, Ochsner Health System, Baton Rouge, La; Alpa Patel, Ph.D., epidemiologist, American Cancer Society, Atlanta; July 22, 2010, online edition, American Journal of Epidemiology
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