Studies show children in Singapore are sedentary more than 90per cent of the time, and doctors say adults here are likely to move even less
By Joan Chew, The Straits Times, 15 Nov 2012
People here are too sedentary - and this could kill them, going by recent research that shows prolonged sitting raises the risks of life-threatening diseases and death.
Children in Singapore were deemed physically inactive for 98.7 per cent of the time on a weekend and 90.2 per cent of the time on a weekday, in a study published in the International Scientific Journal Of Kinesiology in 2008.
That is to say, their heartbeats hardly exceeded 120 beats a minute on the three days they wore heart-rate monitors.
The study was done on 280 children aged 10 to 15 who were of normal weight.
While sitting and standing are both considered physical inactivity, it is likely they were sitting most of the time - attending lessons, doing homework and playing computer games - said the author of the study, Dr Michael Chia, a professor of paediatric exercise physiology at the National Institute of Education (NIE).
This is backed by another study he did, published in the journal Preventive Medicine in 2010, which monitored the step count of 877 children aged nine to 18 between July and September 2009.
Their daily accumulated step count fell short of the recommended 16,000 steps for boys and 13,000 steps for girls by up to 35 per cent, he found.
More recently, his study of 220 teenagers, aged 13 to 15 between last year and this year, showed they spent an average of 18 minutes on a weekday engaged in physical activity of moderate to vigorous intensity. This fell to eight minutes a day over the weekend.
No equivalent studies have been done on adults, but it is likely adults are even more sedentary because opportunities for physical play decrease as they become older, Dr Chia said.
This may be borne out by how secondary school students are less active than their primary school counterparts - a trend that is likely to continue with age, he said.
Adults' choices of jobs and leisure activities and the comforts of modern society have also significantly reduced physical activity, said Dr Jason Chia, head of the sports medicine and surgery clinic at Tan Tock Seng Hospital.
Last month, a new study on sitting, published in Diabetologia, the journal of the European Association of the Study of Diabetes, showed that the length of time a person is sedentary is associated with medical conditions and even death.
It pooled data from 18 studies involving close to 800,000 people and found that people with the highest sedentary time - meaning those who sat for the longest time - had a higher risk of certain diseases and death than those who sat for the shortest time.
Their risk of diabetes was raised by 112per cent, that of cardiovascular disease by 147 per cent, and that of death from any cause by 49 per cent.
This study said that even people who exercised and, hence, met physical activity guidelines, were not spared the risks.
This means that the risks were raised for people who sat for the longest time, even if they exercised.
Dr Yang Yifan, an assistant professor at the Physical Education and Sports Science Academic Group at NIE, said: "Traditionally, health professionals tend to view prolonged physical inactivity as the same as a lack of exercise.
"Now, for people who meet the recommended 150 minutes of moderately intensive physical activity each week but spend the rest of the time being sedentary, that itself could be a health issue."
A term called "active couch potato" has been coined to describe a segment of the population that meets or exceeds the public health guidelines for physical activity but still sits too much, said Dr Robert Sloan, the chief exercise physiologist and head of the Physical Activity Centre of Excellence at the Health Promotion Board (HPB).
In fact, there has been an explosion of studies in the last five years pointing to how sedentary behaviour is harmful for all kinds of reasons, he said.
The HPB has recently concluded its study on the association between sitting and mental health, which is due for publication in a journal in the next few months, he said.
He added: "There is not enough data to make clear recommendations on daily sitting time, but the literature clearly indicates that too much sitting is not good for one's health and well-being."
WHY SITTING IS BAD
No one knows for sure why sitting is detrimental to health - even for those who work out regularly.
What is known is that too much sitting is an independent risk factor for metabolic diseases such as obesity, diabetes and cardiovascular disease.
Dr Sloan said that the body is made up of 640 muscles and 206 bones for movement.
He said: "When we sit or lie down, the muscle work necessary to maintain a standing posture or movements comes to a halt, therefore less energy, in the form of fat and blood glucose, is used throughout the day as there is a decrease in cellular metabolism."
This could increase the risk of obesity, which, in turn, increases the risk of diabetes and heart disease.
Dr Fadzil Hamzah, a resident physician at the Changi Sports Medicine Centre at Changi General Hospital, said prolonged sitting causes a lack of skeletal muscular contractions, especially in the large muscles of the lower limbs. These are needed to facilitate smooth blood circulation to various parts of the body and prevent the pooling of blood.
Thus, sitting for long periods is a major risk factor for developing deep vein thrombosis in predisposed individuals such as the elderly. Deep vein thrombosis is a life-threatening condition caused by a blood clot forming in a vein deep in the body.
Blood clots could also form in the arteries of the heart and trigger a heart attack.
Dr Yang said the lack of skeletal muscular contractions also suppresses the activity of an enzyme, known as lipoprotein lipase, in skeletal muscles that is responsible for the breakdown of fat storage into usable sources, and for the production of high-density lipoprotein (HDL) cholesterol or "good" cholesterol.
Research has shown that blood levels of HDL decreases after two hours of sitting, said Dr Joan Khoo, an endocrinologist at Changi General Hospital.
Dr Khoo said prolonged sitting has been shown to be associated with other risk factors for cardiovascular disease, such as larger waists, higher levels of triglycerides (a type of fat in the blood), and higher levels of C-reactive protein.
This protein is associated with inflammation, the immune response of the body which can itself create problems. Inflammation is associated with a host of diseases, such as cardiovascular disease and high blood pressure.
Prolonged sitting may also lead to diabetes because of its effect on the sensitivity of insulin, a hormone produced by the pancreas that allows the cells in the body to use blood glucose for energy.
Dr Khoo said inactive muscles are less able to take up glucose from the blood and will need more insulin to do so, predisposing a person to insulin resistance and the subsequent risk of developing type 2 diabetes.
Not moving can also increase one's risk of injuries.
Dr Ong Joo Haw, a registrar at the Sports Medicine Centre at Khoo Teck Puat Hospital, said the neck and shoulder muscles can get so stiff that when a person is finally ready to move, the tightness predisposes him to muscular and tendon injuries.
STAND AND WALK INSTEAD OF SIT
For these reasons, doctors say people should find opportunities to move whenever they can. They should stand instead of sit, and walk rather than stand.
Research has shown that it is not only the amount of sedentary time clocked that is important, but the manner in which it is accumulated too.
While many people may have little choice about the sedentary nature of their jobs, they should regularly interrupt their sitting with toilet breaks or meetings in which participants stand.
A study published in Diabetes Care in 2008 found that having a high number of breaks during sedentary time was associated with beneficial changes in waist circumference, body mass index, and levels of triglycerides and blood glucose.
Product marketing manager Daniel Ho, 32, is one person who knows the risks of being an "active couch potato" and has incorporated movement into his sedentary time.
He spends four to five hours working out in the gym a week, but sits for more than 10 hours a day.
He estimates that of the 10 hours at work, he sits for 81/2 hours at his desk and at meetings. At home, he sits for another three hours playing computer games and surfing the Internet.
He tries to walk to his colleagues' desks to talk to them instead of sending them e-mail.
Technical instructor Azman Kassim, 51, has reaped the benefits of moving more.
Diagnosed with type 2 diabetes in July last year, he joined the diabetes exercise programme at Khoo Teck Puat Hospital and now goes there every Friday for 11/2 hours of exercise.
In addition to eating more healthily, he incorporates more activity into his day. He parks his car on the fourth storey of the carpark so he can climb the stairs to and from the ground floor. He also goes for a walk after dinner, instead of sitting in front of the television.
The efforts have helped him shed 11kg over a year. He weighs 108kg now. His blood sugar level has fallen significantly and is now within the normal range.
He said: "I feel more energetic and no longer feel pain in the knees when I walk. My students say I now walk very fast."
HIGHER RISK OF DEATH: 49%
HIGHER RISK OF DIABETES: 112%
HIGHER RISK OF HEART DISEASES: 147%
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