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Later school start times ‘make sense’ for adolescents, who have natural tendency to fall asleep later: Experts

Later school start times ‘make sense’ for adolescents, who have natural tendency to fall asleep later: Experts
File photo of students in Singapore. (Photo: Ministry of Education)
  • Adolescents aged 13 to 19 may develop a two-hour phase delay in their body clock at the onset of puberty, causing them to fall asleep later
  • Studies have shown that delayed school start times result in increased sleep duration for students
  • More sleep for students could lead to better performance in school, and improved physical and mental health

SINGAPORE: Later school start times for adolescents could result in more sleep time and in turn better school performance, said experts. 
At the onset of puberty, adolescents may develop a two-hour phase delay in their circadian rhythm, or their "body clock", and that leads to a natural tendency to fall asleep at later times, said Associate Professor Teoh Oon Hoe, deputy head of the department of paediatrics at KK Women’s and Children’s Hospital.
A later school start time after 8am or 8.30am for secondary school students would accommodate their adolescent circadian rhythm better, he added. 
Many children in Asia sleep less than the recommended duration for their age, so a later school start time can help to increase their sleep hours, noted Assoc Prof Teoh. 
This comes as the issue of later school start times was discussed in Parliament on Tuesday (Aug 3). The Ministry of Education announced that it has commissioned two research studies on the impact of factors affecting sleep duration and sleep quality of students in Singapore. 
Schools currently start no earlier than 7.30am, said Minister of State for Education Sun Xueling. 

Adolescents aged 13 to 19 have a “natural tendency” to be active until late at night and wake up late in the morning, compared to younger children and adults, said Dr Michael Lim, senior consultant of the division of pulmonary medicine and sleep at the paediatrics department at the National University Hospital's (NUH) Khoo Teck Puat - National University Children Medical Institute.

This is due to developmental changes in their sleep regulation, Dr Lim added. 
“Behavioural and social factors, such as the nighttime use of electronic devices and social obligations, contribute to delayed sleep onset, and it is common for adolescents to have considerably less sleep than the eight to 10 hours the National Sleep Foundation recommends,” he told CNA. 
Thus, it would “make sense” for school start times to be delayed to ensure students get enough sleep, said Dr Lim. 
While some might argue that students will just sleep later if school starts later, data from several studies have shown “real gains” in sleep duration for students when later school start times for were implemented - particularly for adolescents, he added. 
For example, with school start times delayed by 20 to 85 minutes, studies have reported an increase in sleep duration of 18 to 99 minutes, he noted. 
Citing a study conducted during the “circuit breaker” period last year, Dr Lim said that with children waking up 55 minutes later on average due to enforced home-based learning, those in primary school gained an extra 30 minutes of sleep, while students in secondary school level slept 56 minutes longer compared to pre-pandemic times. 
Other physiological changes related to puberty, academic and social demands of adolescents may also affect their sleep, pushing back their bedtime, said Assoc Prof Teoh. 
“Adolescents who have adequate night sleep do not usually need afternoon naps. The tendency to take short naps when given the opportunity or fall into periods of ‘micro-sleep’ may be a sign that they have inadequate nocturnal sleep and are making up for chronic sleep deprivation,” said staff physician Dr Cheng Zai Ru, from KKH’s Respiratory Medicine Service. 
Children manifest signs of sleep deprivation differently from adults, she added. 
For example, in the short term, children who lack sleep may not appear sleepy, but exhibit problems with impulse control, hyperactivity, and difficulties controlling their emotions like aggression, tantrums and signs of anxiety or depression, said Dr Cheng. 
In the long-term, children’s academic performance may decline, with higher frequencies of falling sick from acute illnesses, she added. Growth may “falter”, as growth hormone secretion happens at night while they are asleep. 

How much sleep is recommended for children and teens?

In January 2021, the first Singapore Integrated 24-hour Activity Guidelines for Children and Adolescents was launched.

Here are its recommended sleep durations:

  • 7-13 years old – at least 9 hours
  • 14-17 years old – at least 8 hours
  • 18 years old – at least 7 hours

"Regularity is as important as duration. There needs to be consistent, early bedtime for both weekdays and weekends," said Associate Professor Teoh Oon Hoe, deputy head of the department of paediatrics at KK Women’s and Children’s Hospital. 

"One must not be sleep deprived on school days, only to make up for sleep debt over the weekends." 



Later school start times have been associated with better sustained attention, school attendance and improved academic performance, said Dr Lim of NUH. 

“This is not surprising when one appreciates the function of the brain as a memory aid. It is important to get enough sleep the night before and the night after learning. Sleep restores the brain’s capacity for learning and makes rooms for new memories,” he added. 

“There is enough evidence showing that schoolchildren who sleep longer obtained better grades across the board, and the impact of later school start times would impact greatest on adolescents, as this allows for longer sleep duration on school days with a timetable that is in sync with their physiologically delayed circadian rhythm.” 

When students are well-rested and refreshed, they can pay attention, learn better and have better mental and physical health, said Assoc Prof Teoh. 

“Longer sleep time can help reduce daytime sleepiness, improve socio-emotional functioning and academic performance, and reduce risks of accidents,” he added. 

But later start times also lead to logistical issues.

Member of Parliament Leon Perera (WP-Aljunied) said in Parliament on Tuesday that in previous discussions on school start times, the possibility of traffic congestion was a concern if school buses were taking students to school at the same time as office workers heading to work. 

“Will the Government also consider that with the trend towards working from home, flexible work and so on, which may persist beyond the COVID pandemic, that is an issue that actually may be much less of a concern,” he added. 

If all schools implemented later start times, this could affect parents’ work schedule and contribute to morning traffic and public transport congestion, echoed Assoc Prof Teoh. 

“Adjustments will also be needed to stagger work hours of some parents, for food catering arrangements and other enrichment activities to cater for different start and end times at school,” he added. 

There may also be concerns about pushing extracurricular activities to later in the day, completing homework assignments later in the day, therefore resulting in later bedtimes, said Dr Lim, noting data has shown that later start times lead to longer sleep duration despite this concern. 


However, later start times do not mean parents and children do not need to cultivate and maintain good sleep hygiene habits, experts told CNA. 

If bedtime is moved later because of the later start time, this will reduce the impact of the change, said Assoc Prof Teoh. 

“The reality is that some students sleep late because of academic demands, and some due to parental work schedules which impact the family’s daily routine,” he added. 

Children should have regular sleeping hours, said Dr Kenny Pang, a ear, nose and throat specialist at Asia Sleep Centre. 

Primary school children should be in bed by 9pm to 9.30pm, and secondary school children should be in bed by 10pm to 10.30pm. Most of them wake up at around 6am to 6.15am to prepare for school, have breakfast and travel to school as most schools start at 7.30am, he noted. 

“Hence, it would be intuitive to start school at 8am, so that the kids may wake up slightly later too, this would mean more sleep for them.”

The use of digital devices can also disrupt sleep, experts stressed. At night, the pineal gland in the brain releases vast quantities of melatonin, a hormone that signals to our bodies that it is time for bed, said Dr Lim. 

Artificial light, including blue light from phones and laptops, can fool the brain into thinking that the sun has not yet set. In turn, melatonin is suppressed, and this makes it less likely to fall asleep at a reasonable time, he added. 

“Apart from delaying the timing of melatonin release and taking longer to sleep, there is poorer quality of sleep when one does get to sleep.” 

To avoid this situation, parents should establish “strict ground rules” around bedtime, and keep the timing consistent every day, including on weekends, said Dr Lim. 

Parents can also establish a regular, calming and relaxing bedtime routine 30 to 60 minutes before bed. 

“Keep all electronic devices outside the bedroom during this time. For children especially, do not allow excessive use of electronic devices in the daytime as well,” he added. 
“The short-term effects of sleep deprivation can be reversed once the child starts getting adequate good quality sleep as a matter of routine. It can take weeks to clear an accumulated sleep debt and for these symptoms to reverse,” said Dr Lim. 

“The long-term health consequences ... will often be from chronic sleep deprivation, once they are established, the window for improving these health effects is gone.”

Source: CNA/hw(ta)


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