The problem for those whose sleep rhythm isn’t the standard – extreme early birds and night owls, for example – is that their internal body clock and the external clock to which our lives are typically timed, including 9-to-5 working or school hours, are out of sync.
There is a growing body of research about the importance, not only of getting enough sleep and the quality of our sleep, but the timing of our sleep.
“Chronobiology is this idea that there are clocks in every cell of our body,” explains Dr Amy Reynolds of the Sleep Health Foundation. “Those clocks basically tell our bodies what to do and when at the right time of day.”
They coordinate everything from our behaviour (when to sleep and wake, our hunger, energy and mood), our physiology (metabolism, hormone release, blood pressure, body temperature) and cell function (DNA repair).
While we all have clocks that run to a 24-hour rhythm, they don’t all run at the same time. Genetics, age and our external environment all play a part in determining what our individual chronotype is, essentially whether we are a morning or very early morning person, a night person or a middle of the day person.
“We know that everybody has potentially different sleep characteristics,” Reynolds says. “We suspect everybody needs about 7 hours sleep in total but when they have that sleep is becoming increasingly more of a hot topic.”
We can do things 24/7, but that doesn’t mean we should unless we have to.
This is because when we start disrupting the signals of “this really carefully orchestrated system” by not sleeping when our body needs it or by stimulating it when it is ready to wind down, we start “messing with our internal physiology,” explains Reynolds:
“Whether that’s a problem or not largely depends on how much we’re pushing our system out of whack.”
When our internal and external rhythms are chronically out of whack, it increases our risk of various illnesses including heart disease, diabetes, cancer, obesity, depression, bipolar disorder, and sleep disorders.
“Some times our choice to sleep isn’t our own,” Reynolds acknowledges. “It’s that interaction between what we need to do day-to-day for our jobs or school or for our family and what our bodies need in terms of rest.”
Although we might not always be able to change our external circumstances, understanding our body’s individual rhythm (we can figure out our chronotype by noticing what time we wake up on days we don’t have to set an alarm) can help us better align to them.
And while people commonly tell Reynolds, “Well I can’t do anything about it”, there are things we can do.
For instance, we can work our day around our individual chronotype as much as possible, we can reduce our exposure to bright light in the evenings (looking at you, phones and laptops in bed) and we can make sure we don’t eat too late at night. And if our bodies are begging us to get into bed at 8 o’clock, we can switch off Netflix for the night and listen to them.
“With rising chronic disease we [have seen] more light exposure at night and more disruption, because we can do things 24/7, but that doesn’t mean we should unless we have to,” Reynolds says. “It’s tricky. I don’t know that we get it right all the time. Just that awareness is really important.”
Sarah Berry is a lifestyle and health writer at The Sydney Morning Herald and The Age.