After studying circadian rhythms for decades, sleep scientist Russell Foster shares his findings in the new book Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health.
Photo: Shane Reti / Unsplash
Oxford University professor of circadian neuroscience Russell Foster. Photo: Oxford University
Whether you’re a morning person or a night owl is determined by light as well as genetics and hormonal changes, Foster tells Kathryn Ryan.
“Morning light advances the clock [and] makes you want to get up earlier. Evening light delays the clock and wants to make you get up later.
“We can to some extent move our chronotype by how much morning versus evening light that we see.”
The receptors in our eyes are sensitive to shades on the blue spectrum and require a strong, lengthy exposure to it in order to regulate the circadian system, he says.
“In fact, night-shift workers do not adapt to the demands of working at night.
“What’s happening is that the levels of light in the factory or office are quite dim and we then experience bright natural light on the journey home or in fact on the drive in and the clock always refers to the brighter light signal as day time.”
Photo: Penguin Random House
As humans, the bigger the difference between our biological needs and societal demands, the more vulnerable we are to a range of problems, Foster says.
People with social jet lag - fatigue from disrupted sleep patterns - are more likely to smoke, drink heavily and have coronary heart disease.
It's tricky but ideally, we should try and match our individual biological need for sleep with our work patterns, he says.
“I think what Covid has taught us is that flexible working can actually enhance productivity in some cases. So I think that’s been very good for individualised sleep patterns.”
Even short-term sleep disruption can have a big impact on our emotional and cognitive responses, Foster says.
“Overall, sleep disruption can really reduce our cognition, our ability to process information, poor memory, poor concentration, impaired decision making, poor communication skills and reduced social connectivity, and that’s just the short-term effects.”
Circadian neuroscientist Russell Foster’s quick tips for better sleep
- Start the day with natural morning light to set your body clock and sleep-wake cycle.
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Exercise is helpful, but not too close to bedtime because a slight drop in core body temperature helps you go to sleep.
- Maintain a bedroom temperature of 18 to 20C degrees.
- Avoid excessive caffeine in the afternoon.
- Stop using electronic devices 30 minutes before you want to sleep.
- If possible, avoid prescription sedatives and alcohol
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Separate your sleeping space from work activities and TV.
- If waking in the night causes you anxiety, cover up clocks and avoid using sleep apps.
- A 20-minute afternoon nap is okay if it’s not too close to bedtime.
“That’s one of the problems with teenagers, they’re going to sleep late, they’re waking up chronically tired, they’re struggling through the school day, they then get home and have a two-hour sleep and that will then push back the [body's] pressure for sleep that night.”
- Waking up at night is normal.
The idealised norm of eight hours of consolidated sleep per night is very rare, Foster says.
- Give sleep a chance.
“People wake up thinking 'oh my goodness, that’s the end of sleep, I might as well start doing my emails and start drinking coffee, if you stay calm, keep the lights low, you can leave the bed and do something relaxing or stay in bed, and you will almost invariably fall back to sleep.”
Russell Foster is a professor of circadian neuroscience at Oxford University and the director of the Nuffield Laboratory of Ophthalmology.
