How your internal body clock affects sleep quality each night
Sleep. It’s one of the body’s most natural processes, yet so many of us struggle with the simple act of nodding off.
We already have plenty of evidence that sleep is linked to improved mood, cognitive and physical performance and a healthy immune system. And while much of the focus has been on whether people are getting enough, a new survey suggests the timing of our sleep, and whether it aligns with our individual body clocks, is equally important.
The pandemic presented an unusual opportunity for people to get a sense of their own circadian preference, resulting in some Australians sleeping better.Credit:istock
The global survey of over 1650 people, 35 per cent of whom were from Australia, looked at people’s sleep health during the first lockdown period. Interestingly, researchers found a dichotomy between those whose sleep suffered, and those whose improved.
Seventy-three per cent of people reported poor sleep quality. “Of course, we know that stress is a major precipitant of insomnia, and a global stressful event like a pandemic is bound to bring out sleep problems in some people,” says Dr Melinda Jackson, a sleep psychologist at Monash University's Turner Institute for Brain and Mental Health and one of the survey’s lead researchers.
For these respondents, poor sleep was related to what Dr Jackson describes as “pre-sleep arousal” where people can’t wind down and switch off. This was caused by increased news and social media consumption, anxiety and worry about loved ones, and general stress, particularly around personal finance.
But what about those people who actually slept better? Forty-two per cent of respondents said their sleep was in better alignment with their body clock compared to before the pandemic.
“We each experience levels of alertness and drowsiness at slightly different times during a 24-hour period.”
“Essentially, they could go to bed and wake up at a time that suited their own internal body clocks,” says Dr Jackson, noting more flexible working arrangements and the absence of commutes and possibly alarms.
While the survey is still under review, its findings mirror similar studies conducted in both US and Europe this year, explains Dr Jackson. “It shows us the importance of being more in tune with when we’re feeling sleepy and ensuring we have flexibility in our daily lives to sleep on our own schedules.”
Are you a 'morning lark' or a 'night owl'?
Sleep researchers use the terms “morning lark” and “night owl” to describe the different chronotypes, that is, whether you are a morning or night person based on your circadian rhythm.
“We all have different circadian preferences,” explains Dr Jackson. “We each experience levels of alertness and drowsiness at slightly different times during a 24-hour period.”
For example, a night owl might struggle to feel alert in the morning but their productivity builds throughout the day and they tend to have a later bedtime compared to a morning lark.
To make things a little more complicated, we have a body clock that often, across the general population, runs slightly longer than 24 hours. “We see this when we’re on holiday, we start going to bed a little later than what we did the night before,” says Dr Dorothy Bruck, a sleep psychologist with the Sleep Health Foundation. “And if we don’t have a set time for getting up for work, you might find your body clock wants to run at 24.5 hours and that means you’re going to bed later, and getting up later.”
Dr Jackson says the pandemic presented an unusual opportunity for people to get a sense of their own circadian preference. “It’s been a really interesting naturalistic experiment to see what happens when we’re not dictated by what our work or schooling is requiring us to do,” she says. “It provides evidence that when people are allowed to sleep on their own time and they’re not dictated by societal schedules that people will potentially get more sleep and sleep on a sleep/wake schedule that better aligns with their body clocks.”
Most people will land somewhere in the middle of a morning lark and night owl. But that doesn’t necessarily mean everybody’s sleep/wake time should be the same. “While being aware of your chronotype is helpful, ultimately the quality and amount of sleep you’re getting, as well as ensuring your sleep/wake cycle is consistent within each 24-hour period, is most critical,” says Dr Jackson.
Getting in tune with your sleep/wake cycle
Our circadian rhythm responds to external cues, especially daylight, and works to regulate our sleepiness and wakefulness throughout the day.
This will change over time, for example, adolescents tend to be night owls and will sleep longer into the morning. What’s happening at a biological level, explains Dr Jackson, is the release of melatonin in the brain – the hormone responsible for sleep promotion.
“We know that melatonin is released later in the night for people who are night owls and released earlier for morning larks,” says Dr Jackson.
Darkness plays an important role in its release, which is why bright light at bedtime has long been a concern for sleep scientists. Researchers recently found the average Australian home’s lighting was so bright it suppressed melatonin by nearly 50 per cent, therefore having a negative effect on sleep.
The study, published in Scientific Reports, also found people with depression have poor light sensitivity – providing further evidence that depression may be correlated with disrupted circadian rhythms.
“We know that evening types tend to have higher rates of depression and poorer mental health,” says Dr Jackson, adding that insomnia tends to be more prevalent in this group.
“We don’t really understand why this is the case – but it might be that it’s because they are trying to conform by going to bed at a ‘normal’ time and yet they can’t because their body clock isn’t ready, so they lie awake and that presents as insomnia.”
If darkness is key to getting us ready for sleep, morning light is equally crucial for resetting our body clocks. “We’re creatures of habit and having that regularity of light each morning is really important for our bodily systems,” says Dr Jackson.
Getting to know your internal body clock will help with setting a regular sleep/wake routine, explains Dr Jackson. In order to so, she recommends taking notice of a few things: be aware of your alertness levels and when you are most productive at work, and if you didn’t set an alarm, take notice of what time you naturally wake up and what time in the evening you start to feel naturally sleepy.
Once you've got your body clock in check, it's all about routine and the timing of that routine. “Sometimes it's hard to keep a strict bedtime but as much as you can, try to keep your sleep and wake times fairly fixed,” says Dr Jackson. “And if you're someone who ruminates before bed, try and deal with any worries and concerns earlier in the day.”
And with that, you'll no longer be chasing sleep, but well on your way to reaping the many health benefits of quality sleep on a schedule that works for you.
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