NCD Watch

Fighting Obesity: Let Children Sleep More

29 May 2017 (Mon)

Sleep is a basic health necessity, but many children in Hong Kong do not have enough sleep. A local study of 553 Chinese preschool children (mean age about 5.5 years) in 2011-2012 reported that only 11.0% of preschool children slept 11-12 hours per day and most (70.5%) slept 9-10 hours per day. Among adolescents, a study of over 3 700 secondary students aged between 12 and 18 years during late December 2011 to early February 2012 observed that 64.5% of students slept less than 8 hours during weekdays; more than half (58.4%) rated themselves as having inadequate sleep.

Overseas studies showed that people who were deprived of sleep had higher levels of the appetite-stimulating cortisol and ghrelin but lower levels of the satiety-inducing leptin, with a corresponding increase in hunger and appetite for foods high in carbohydrates and fats. Furthermore, insufficient sleep and associated daytime sleepiness or fatigue can compromise voluntary physical activity during the day, and thus lead to a decrease in energy expenditure and promote weight gain. There is convincing evidence that insufficient sleep is an important and independent risk factor for obesity in children. Compared with children who sleep for longer duration, those who sleep for shorter duration would have about twice the risk of being overweight or obese.

Local studies also observed an association between sleep pattern and risk of childhood obesity. A study of over 5 100 primary school children (mean age 9.25 years) found that children with shorter sleep duration had higher body mass index (BMI). Another school-based study of 327 adolescents (mean age 14.5 years) also found that shorter mean time in bed and greater weekend delay in bedtime were associated with higher BMI.

Apart from body weight issues, a systematic review of the relationships between sleep duration and health indicators in school-aged children reported that longer sleep duration was generally associated with better physical growth, better mental health outcomes, better emotion regulation, better academic performance, and better quality of life/well-being. Thus, it is of utmost importance for children to get sufficient sleep for proper body and mind development.

Here are some tips that can help children have a good night sleep —

Set age-appropriate bedtime and wake-up time for children to ensure they get enough sleep.
Reduce screen behaviours and set boundaries for use of electronic devices before bedtime.
Avoid giving children big meals within two to three hours before bedtime
Provide a sleep conducive environment, including comfortable temperature, minimal light and noise, and good ventilation.