Sitting idle for hours kills?

Next time you`re on a bus or train, holding on to a pole to avoid a fall, cranky that another commuter has nabbed the last seat, consider the fact that standing up could boost your longevity.

Not only do we need to get more exercise but we also need to spend less of our time sitting down, Australian researchers say.

Their study of more than 220,000 NSW residents found the longer you spend sitting down the greater your risk of dying early, even if you otherwise do regular exercise.

Professor David Dunstan, from the Baker IDI Heart and Diabetes Institute, said health workers usually focused on trying to increase people`s participation in sports, and trying to get them to do at least half an hour of exercise every day.

"We need to think more about what we do with the 15 hours of non-exercise wake time," he said.

Sitting can be detrimental for our health because when we sit down there is an absence of muscle contractions, explains Professor Dunstan. These contractions are required for the body to clear blood glucose and blood fats from the blood stream.

Studies on animals have shown that when the body stops moving for long periods of time it slows down one of the key enzymes needed to break down blood fats.
The study, published in the Archives of Internal Medicine, found adults who sat for more than 11 hours a day had a 40 per cent increased risk of dying within three years, compared with those who sat for fewer than four hours a day.

People who sat for eight to 11 hours a day increased their risk of dying by 15 per cent. Dr Hidde Van Der Ploeg from Sydney University, the lead author of the study, said research into the health effects of sitting usually put the blame on sedentary activities such as television watching. Instead, they looked at the total sitting time throughout the day regardless of the type of activity.

He and his team trawled through questionnaire data from the respected 45 and Up Study and data from the NSW`s Registry of Births, Deaths & Marriages.

They found more than 5000 participants died within three years, and about 7 per cent of those deaths could be attributed to prolonged sitting time.

"Doing at least 30 minutes of physical activity each day is still important but it`s just as critical for people to reduce their sitting time," Dr Van Der Ploeg said.

He said the average adult spends 90 per cent of their leisure time sitting down. "We sit while eating our breakfast, we sit as we drive, we sit behind our desk all day, we`re always sitting down and this is a health risk."

Professor Dunstan said the modern, urban environment was conducive to sitting behaviours.
"We need to take those opportunities to stand up, while on transport, at work, during our leisure time," he said.

He acknowledged that sitting for less than four hours a day was no mean feat. "It will require people to drastically change, which is hard," he said. "But that`s the goal."

The findings were consistent across all age groups, sexes, body mass index categories and physical activity levels. The link between prolonged sitting as a health hazard was noted as early as the 17th century by the occupational physician Ramazzini.


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