Children who go to bed late more likely to be overweightEarly risers are slimmer
Scientists found that children who went to bed late and got up late were 1.5 times more likely to become obese than those who went to bed early and got up early.
The study, published in the journal Sleep, also found that late-nighters were almost twice as likely to be physically inactive and 2.9 times more likely to sit in front of a TV , computer or play video games.
The study author, Dr Carol Maher, from the University of South Australia, said: "The children who went to bed late and woke up late, and the children who went to bed early and woke up early got virtually the same amount of sleep in total.
"Scientists have realized in recent years that children who get less sleep tend to do worse on a variety of health outcomes, including the risk of being overweight and obese.
"Our study suggests that the timing of sleep is even more important."
The researchers recorded the bedtimes and wake-up times of 2,200 Australian children, aged 9 to 16, and compared their weights and uses of free time over four days.
Dr Maher said that mornings were more conducive to physical activity for young people than nights, when children are more likely to be slumped in front of favourite TV programmes or on the computer using social network sites. This could partly explain the link between screen time and later bedtimes.
Research also shows that teenagers have a natural tendency to stay up late and wake late, she added.
"It is widely accepted that the sleep patterns of adolescents are fundamentally different from children and adults, and that it is normal for adolescents to stay up very late and sleep in late in the morning," Dr Maher said.
"Our findings show that this sleeping pattern is associated with unfavourable activity patterns and health outcomes, and that the adolescents who don't follow this sleep pattern do better."
The early-to-bed, early-to-rise children also went to bed 70 to 90 minutes earlier, woke up 60 to 80 minutes earlier and fitted in 27 more minutes of physical activity a day.
This article was published on Fri 30 September 2011
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