A British meta-analysis published in the November 2012 issue of the journal Diabetologia shows strong indications that extended time spent sitting greatly increases a person’s risk of diabetes, severe heart issues, and death. Previous studies have found a link between extended television watching and poor health, but this is the first study to specifically research the connection between any extended sedentary behavior and health.
The analysts searched previous studies for terms involving health outcomes and sedentary lifestyles. They looked at data involving 794,577 participants across 18 different studies. The data was adjusted to account for differences in measurement frequency and study length and then sorted with a random effects model.
Dr. Emma G. Wilmot of the University of Leicester, one of the study’s authors, says the research showed a particularly strong link between a sedentary lifestyle and diabetes. Analysis of the data showed that people with the highest levels of sedentary activity included in the study had twice the risk of developing diabetes than did the people with the lowest levels of sedentary behavior. People in the highly sedentary group also had 2.5 times the chance of suffering a cardiovascular event, a 90% higher chance of suffering a death related to cardiovascular problems, and a 49% greater chance of death from any cause.
Deeper analysis of the data indicated that the predictive effects were significant for diabetes, but far less so for the other health issues, which suggests that the diabetes results will be the most likely to be reproduced in future studies.
The results of the research, Wilmot says, may cause some changes in the way we think about fitness. “We've traditionally been focused on making sure we meet the physical activity guidelines of 30 minutes per day, but with that approach we've overlooked what we do with the other 23 and a half hours in the day,” she explained. “If you sit for the rest of the day, that is going to have an impact on health, and that's essentially what our meta-analysis shows.”
The health dangers of extended periods of sitting were first noted in the 1950s. Researchers realized that London bus drivers, who spend most of their day in the driver’s seat, had twice the risk of suffering a heart attack as did bus conductors, who move around inside the bus frequently. Unfortunately, the implications of this finding was more or less overlooked until recent researchers started looking for connections between lifestyle and the growing number of people diagnosed with Type 2 diabetes.
Wilmot and her colleagues estimate that on average, an adult is engaged in sedentary activities for 50% to 60% of each day. Modern lifestyles contribute to an increase in time spent sitting down. In a typical day, an adult might drive to work, sit at the office computer for hours on end, drive home, and spend the evening watching television or playing video games. "People don't realize that doing just small amounts of activity—it doesn't even need to be a proper walk—are important," she says. "If you are having a chat with a friend at your desk or the phone rings, stand up and chat. Just these small changes could make a big difference."
Sitting seems to have a negative effect on our body’s ability to metabolize glucose. Earlier studies have shown that people who sit immediately after eating have glucose levels 24% higher than do people who walk slowly after they eat. “When we sit, our muscles are not used, and we quickly become more insulin resistant," explained Wilmot. She also pointed out that people who have a genetic predisposition to diabetes may wish to be even more careful about prolonged sitting. Wilmot and her colleagues are not entirely certain of the exact mechanism by which extended sitting affects glucose metabolism.
Wilmot and her colleagues are currently undertaking a study of 200 young adults at risk for diabetes in hopes of increasing their evidence.
Journalists from around the world have been calling to ask Wilmot about the results of the study, indicating that these concerns are universal.
Future diabetes prevention programs might wish to use this evidence to start promoting less sedentary lifestyles along with traditional exercise and diet, Wilmot said. The possibilities include standing desks, treadmill desks, and alarms which can alert someone if they’ve been sitting for 40 minutes straight.
Wilmot was quick to add that physical activity is still very important to health and that people should not rush to give up their exercise programs if they start spending larger portions of the day standing. “There's a wealth of data showing that physical activity is important, but if people are spending a large percentage of their time sitting, they need to start thinking about how they can reduce this," said Wilmot.
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