Hong Kong children risk becoming obese because they sleep an hour less than children in developed countries, according to a study. A Chinese University survey of 1,159 children aged between five and 15 in 13 primary schools shows children sleep, on average, nine hours a day compared with the healthy norm of 10 hours. The study also indicates insufficient sleep may lead to obesity.
In general, local children go to bed around 10pm and wake up between 7am and 7.30am on weekdays. They sleep about one to 1.5 hours more during weekends and holidays. About 6 percent go to bed around midnight.
Psychiatry professor Wing Yun-kwok said children between five and 12 should get at least 10 hours' sleep, while those aged 16 or above need eight hours. To ensure children get adequate sleep, he suggests schools start classes up to one hour later.
Wing also advises parents to ensure the duration of their children's sleep is consistent.
The university said children who regularly sleep less than the norm are three times more likely to become overweight.
Department of medicine and therapeutics associate professor Alice Kong Pik-shan said sleep deprivation may also be linked to a series of metabolic and appetite-regulating hormonal changes, causing those with inadequate sleep to have "hungry feelings."
"Lack of sleep activates stress hormones to a defense state. This affects appetite," Kong said.
Such children may also find it harder to control their tempers in the morning and feel exhausted during class. Sleeping too much during weekends and holidays may cause what he describes as "Monday Blues" - feeling tired because of sleeping too long. "The best solution is to maintain consistent sleep patterns," she said.
Albert Martin Li of the university's department of pediatrics encourages children to do some sports in the daytime, and some relaxing activities before going to bed.
"Activities which require concentration and thinking, such as TV games, should be avoided half an hour before going to sleep," Li said.
"Parents should get their children to cultivate consistent sleeping habits and create a suitable environment for sleep. It is inappropriate for parents to watch TV late into the night after their children have gone to bed."
According to the the medical journal Pediatrics, children in Switzerland sleep on average 10.1 hours daily, the United States 10.64 and New Zealand 10.9.
The average in Taiwan is 8.37 hours while in South Korea it is 8.18.
