Thursday, 20 February 2014

Sitting linked to increased risk for disability, study shows

For people over age 60, every extra hour of the day spent sitting is linked to an increased risk for developing life-altering physical disabilities, according to a new study from Northwestern University’s Feinberg School of Medicine.

Researchers have long known that being sedentary is harmful to a person’s health – and that moderate activity has numerous health benefits. 

“But what we did not know is whether those were just two ways of looking at the same question – that is, if being sedentary meant you had insufficient activity, or whether it was a separate risk factor,” study author Dorothy Dunlop, a professor of medicine and preventive medicine .“And this study is a smoking gun that being sedentary is a separate risk factor.”

In a study published in the Journal of Physical Activity and Health, Dunlop analyzed data collected from 2,286 adults over age 60 who had participated in the National Health and Nutrition Examination Survey. From 2002 to 2005, each study participant wore an accelerometer – a device that monitors physical activity – to objectively assess their levels of activity, or inactivity.

Researchers also gathered health data from the participants to determine their risk for disability.
“The way they defined disability was limitations in basic activities you need to be able to do to stay independent – feeding yourself, bathing yourself, dressing yourself, walking from room to room,” Dunlop said.

Overall, the researchers found that for every extra hour per day that a person spent sitting, their risk for disability increased by 50 percent.

“If you take two 65-year-old women, with the same health profiles, and…one is sitting or doing very little about 12 hours a day, her chance of being in the disabled pool is about 6 percent,” Dunlop said. “If you take another person, also 65 years old, same health profile, but she sits for 13 hours a day, her chance of being disabled is 9 percent; it’s an increase of 50 percent for each hour.”

Furthermore, among people who spent the most time sitting, their increased risk for disability could not be explained by a lack of exercise. However, Dunlop cautioned that this doesn’t mean people should give up and quit the gym.

“There are two messages here – being physically active is very important, it does help you and it’s well documented that it reduces your risk of disability,” Dunlop said. “Being sedentary is a separate risk factor. You want to focus on both – be as active as possible and for people…who have desk jobs and sit [for] a large portion of daylight hours, it is beneficial to find opportunities to replace some of that sitting with other activities.”
Though the study did not examine the mechanisms behind the link between sitting and the increased risk for disability, Dunlop did have some theories.

“My clinical colleagues tell me that when a person sits for an extended time, that their muscles burn less fat and the blood is flowing more sluggishly,” Dunlop said. “And furthermore, if someone slumps in their chair then their back and stomach muscles go unused and the issue of idle muscles and slow circulation can contribute to all kinds of chronic diseases like high blood pressure, heart disease, diabetes, and also contribute to varicose veins, swollen legs and ankles.”

And though this study focused on an older population, Dunlop said the health effects of sitting on a younger population are likely similar.

“We did not look at people under age 60 because disability is so infrequent in that younger age group,” Dunlop said. “However, there is no reason to expect their experience would be different.”
Further research will be needed to definitively prove the link between sitting and an increased risk for disability – but until then, Dunlop advised people to try to replace sedentary time with light physical activity as often as possible.

“When I talk on the telephone, if I just stand up while I’m talking, that breaks up my sitting. When I go to the grocery store, if I take a walk around the store first before I start shopping, [that helps],” Dunlop said. “What you’re trying to do is simply accumulate more time where you’re not sitting or being sedentary or parked in front of a computer or television.”

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