We’ve all been told that to function best, we need between seven and nine hours of sleep nightly.
But how many adults actually get this daily dosage?
An estimated 300 million people in South-East Asia suffer from insomnia, narcolepsy (excessive daytime drowsiness and sudden attacks of sleep), sleep apnoea, circadian phase disorder (the internal body clock is delayed with respect to the external day/night cycle) and seasonal affective disorder.
“I don’t know where that eight-hour sleep number came from because I cannot find it in any research journal or publication,” remarks Dr David Samson, assistant professor of anthropology at the University of Toronto, Mississauga, Canada.
“There are many factors that affect sleep quality. You can have 10 hours of sleep and if it’s all restless or light sleep, you won’t feel rested. Some people need five hours, others need nine – it really varies. Ideally, we need 15% to 20% of deep sleep and 20% to 25% in the REM (rapid eye movement) phase. The rest can be split up.”
The REM phase occurs in the first 70 to 90 minutes after you fall asleep and this is when your brain and body are energised, and dreaming occurs.
The three elements of good quality sleep are duration, continuity and depth. And most Malaysians are not getting it.
“Sleep is critical for a strong mind as poor sleep has been linked to mental disorders. It’s also a neccessity needed for healthy ageing because quality sleep protects adults from age-related cognitive decline, and reduces the physical signs of ageing.
“Interestingly, humans have the most REM: if someone whispered your name while you’re asleep, you’d wake up. In traditional population, they sleep shorter but their circadian rhythm is stronger,” he says.
Your circadian rhythm is a 24-hour internal clock that cycles between sleepiness and alertness at regular intervals. It’s also known as your sleep/wake cycle.
For most adults, the biggest dip in energy happens in the middle of the night (somewhere between 2am and 4am, when they’re usually fast asleep) and just after lunchtime (around 1pm to 3pm, when they tend to crave a post-lunch nap). Those times can be different if you’re naturally a night owl or a morning person.
You also won’t feel the dips and rises of your circadian rhythm as strongly if you’re all caught up on sleep. It’s when you are sleep- deprived that you’ll notice bigger swings of sleepiness and alertness.
A scientist, educator and lecturer who has worked with wild chimpanzees, zoo-dwelling orang utans, and sanctuary- living lemurs, Dr Samson was speaking at the World Sleep Day media event organised by AmLife International Sdn Bhd here last week.
“Yes, I search the globe for apes, monkeys, and humans that can inform us how we came to be,” he says, laughing.
Apes sleep more
Humans rely on sleep for cognitive function, yet we sleep less than any primate. Among the primates, owl monkeys sleep the longest – 17 hours! Mouse lemurs rank second at 15.5 hours.
He offers: “They also have differences in sleep architecture, just like we do, so they’ll have light sleep and deep sleep.”
Until recently, scientists knew very little about how primates slept. To document orang utan slumber, Dr Samson collaborated with primatologist Robert W. Shumaker to rig up infrared cameras at the Indianapolis Zoo and stayed up each night to watch the apes nod off.
By observing their movements, they tracked when the orang utans fell in and out of REM sleep.
“Orang utans are more contemplative and will look into a problem before acting on it, which is why we wanted to test how sleep affects them. In cognitive tests, they are the most patient. Chimpanzees are more impulsive.
“Orang utans are prolific bed builders; they usually build their beds 30m in the air.
“We gave them a bunch of sleeping materials such as pillows, memory foam mattresses, sheets, hay and cardboards. I would measure their beds during the day.
“The next day, we did cognitive tests and found that when they had access to these materials, they scored much higher than apes that slept on straws. This feature of needing this comfort is not unique to humans, but (exists in) all primates,” recalls Dr Samson, who once climbed about 100 chimpanzee nests in Uganda for his doctoral dissertation.
Their research findings, “Shining Evolutionary Light on Human Sleep and Sleep Disorders”, were published in the journal Evolutionary Anthropology in 2016.
Light pollution and sleep hygiene
While artificial light has been necessary for the progress of mankind, it has also created many negative effects.
Dr Samson says two thirds of the world live in “light polluted” areas, and 99% of them are in developed countries.
The use of electronic gadgets which emit blue light confuses the body by suppressing melatonin production.
According to the United States-based National Sleep Foundation, when the body is exposed only to natural light of the sun, the hypothalamus area of the brain sets its sleep patterns in response to whether it is light or dark outside.
Light is detected by the retina, which sends signals to the hypothalamus. When it starts getting dark outside, the hypothalamus signals to the body to release sleep hormones such as melatonin, and to drop the body temperature to prepare for sleep.
Artificial lights are also disturbing the physiology of the sea turtles and confusing them. Lighting near the shore is causing hatchlings to become disoriented and wander inland, where they often die of dehydration or fall prey to predators.
“We have evolved so much. Single cell organisms have strong circadian rhythms and the fact that humans have started screwing with our light environment is not a good thing.
“For good sleep, it’s best to model the light in your internal environment to best reflect what is going on outside. So if it’s dark outside, make it as dark as possible inside; if it’s light outside, bombard yourself with as much natural light as possible because that’s a signal to your body. This signal keeps us going like a clock – when the clock is wound tight and cleanly, sleep is easy, when it is screwed with light environment, it’s hard,” he says.
Just like body hygiene, we need sleep hygiene and Dr Samson suggests we switch off our gadgets an hour before bedtime.
He adds: “You don’t want to get emotionally aroused before sleep by looking at social media. It takes a little discipline but you have to make a conscious decision to wind things down to introduce a sleep routine.”
In the past, natural light was the primary driver of sleep but scientists are now discovering that environmental temperature influences sleep, too.
“The old fashion way was to crack the window a little to get the ambient temperature outside as at night, the temperature drops. When the temperature spikes, that’s a powerful predictor of when you wake up. Temperature drives your sleep architecture at night.
“We have to leverage on some technology to aid in sleep. If you have artificial intelligence that’s controlling the temperature throughout the night, that’s the future. Temperature shifts – you want it cooler to sleep and warmer to wake up,” says Dr Samson, adding that sleep debts accumulated during the week cannot be paid
off during a marathon weekend sleeping session.