According to a study in the March 26 issue of Archives of Internal Medicine, researchers discovered that people who sat for 11 hours a day or more were 40 percent more likely to die – from any cause. The researchers also found the odds of dying were 15 percent higher for those who sit between eight to 11 hours a day compared to those who sit less than four hours a day.
Researchers relied on self-reported data from 22,497 individuals 45 years or older from the 45 and Up study, the largest look at aging in the Southern Hemisphere. The study has interviewed over 265,000 men and women across New South Wales and Australia, focusing on about 10 percent of that group for additional data over the coming decades. 
The researchers determined sitting was associated with a higher death risk after ruling out other factors including gender, age, education, urban/rural residence, physical activity, body mass index, smoking status, self-rated health and disability.
“The evidence on the detrimental health effects of prolonged sitting has been building over the last few years,” study author Hidde van der Ploeg, a senior research fellow at the University of Sydney. “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.”
A study last year by Harvard researchers found watching TV for two hours a day increases type 2 diabetes risk by 20 percent and heart disease risk by 15 percent. More than three hours of daily viewing and you’re upping your risk of dying from any disease, the study found.
Too much sitting or a lack of physical activity has also been linked to causing up to 43,000 cases of colon cancer and 49,000 cases of breast cancer. That report, which was presented at the American Institute for Cancer Research in Washington, D.C. in November 2011, looked at over 200 studies worldwide and concluded that physical inactivity raises risks for cancer. The World Health Organization says physical inactivity is the main cause for approximately 21-25 percent of breast and colon cancers, 27 percent of diabetes and approximately 30 percent of ischaemic heart disease burden.
Van der Ploeg said that nine out of 10 adults spend relax by sitting down and fewer than half exercise for at least 150 minutes of at least moderate-intensity physical activity each week, a standard set by the WHO.
The researchers say that reducing sitting time, in addition to increasing physical activity levels, may help alleviate sitting’s link to all-cause mortality.
Other experts agree.
“We are continuing to demonstrate time and time again in different populations that there is something real to the association between sitting time and reduced longevity,” Dr. Alpa V. Patel, an epidemiologist at the American Cancer Society in Atlanta who has published studies on the health risks associated with too much sitting. She suggests people should sit for five fewer minutes each hour.
“Small changes can have a big impact,” she said.
