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Feeling tired while studying for an exam? You might be tempted to try polyphasic sleep: nap for an hour or two, wake up to continue studying and repeat this cycle until you feel prepared for your test.
However, two sleep experts warned that even if you manage to get the recommended seven to nine hours of total sleep, this strategy is ultimately risky.
Dr Kenny Pang from the Asia Sleep Centre in Singapore explained: “Sleep quantity is important, but sleep quality is also important.”
According to Dr Jacky Ho, the dean of the faculty of health sciences at the University of Saint Joseph in Macau, breaking sleep into smaller chunks prevents you from reaching deep sleep.
“Deep sleep is very important for our body to recover and rejuvenate,” said Ho, who is also an associate professor at the university. “Only a small portion of people are able to jump into deep sleep states very quickly. For the rest of us, we need that transition phase from light sleep to deep sleep.”
A 2017 study by Harvard Medical School and Brigham and Women’s Hospital in the US found that polyphasic sleep was associated with poorer academic performance, even when participants slept for the same amount of time.
Ho further noted that polyphasic sleep could lead to chronic sleep deprivation, which might “burden our body to a point beyond recovery”.
Sleep deprivation’s hidden dangers
The National Sleep Foundation in the US advises that teenagers get at least eight hours of sleep every night. But many Hong Kong students are not meeting this requirement.
A 2022 report card by Active Healthy Kids Hong Kong concluded that only 40 to 46 per cent of children were getting enough sleep. Active Healthy Kids is a network of researchers and practitioners promoting physical activity for Hong Kong youth.
Ho explained why many people do not prioritise sleep even within an otherwise healthy lifestyle.
“They think that sleep is the only thing that they can sacrifice to make room for ... other activities [and] to catch up with their own personal life,” he said.
Despite the push in Hong Kong society to be overachievers, Ho stressed the need to be “realistic”.
“We cannot do that much ... [in a] day, and we have to prioritise our life,” he said.
Ho warned against sacrificing sleep.
“It is actually damaging our brain function; bit by bit, we accumulate this big chunk of damage to our brain,” the professor said.
He listed common symptoms of sleep deprivation: daytime exhaustion, moodiness and irritability. Impaired cognitive function and an increased risk of dementia are just a few long-term effects of sleep deprivation.
Ho noted why we need to rest: “It supports our immune system ... It’s a way to help us to rejuvenate and to recover ourselves and to maintain our body to have a certain level of energy.”
Tips to optimise sleep
Pang explained that the ideal sleep time for students is related to the release of melatonin, the hormone that regulates sleep.
“Melatonin comes out from the pineal gland in the brain around 10pm to 11pm at night. [It] peaks at 1am to 2am and starts to dwindle away,” he said. “Hence, one should sleep by 11pm and wake [at] around 7am daily.”
For students who are used to sleeping late, it might take time to adjust their body clocks.
Ho added that it could be difficult for teenagers to fall asleep right away if they do not have some downtime to unwind before bed.
“Our brain is still very active; we are processing a lot of information,” he said.
Activities such as reading a book, journaling, meditating, drawing or listening to calming music can help with relaxing before bed.
While you may be tempted to take melatonin as a sleep aid, this should be considered a temporary fix.
Ho recommended several things to stay away from when you are preparing for sleep: “Avoid caffeine, screen time ... [and] intensive physical activity at least two hours before bedtime.”
He also noted that individuals whose sleep is affected by mental health challenges or stressful circumstances might need to find additional ways to address the underlying issues.
Ultimately, Ho emphasised that improving sleep for teens in Hong Kong would take “a societal approach”.
Young people’s ability to rest relies on schools, parents and governments alleviating academic pressure on students, as well as social media companies designing their platforms to discourage unhealthy engagement.
“It takes a very direct policy to manage how we should position our teenagers to develop,” Ho said. “If we are calling our young people the generation of our future, I think we should take a very serious step [towards] ... promoting better health.”
