Lark or Night Owl? What Your Sleep Habbits Reveal about T Your Health; from Your Weight to Your Memory -- and Even Your Risk of Cancer
Byline: KATE WIGHTON
YOU'RE up at the crack of dawn, raring to go, while your other half is dead to the world. Then, while you're ready for lights out at 10pm, they're happy to burn the midnight oil.. . and some.
Sounds familiar? It's the difference between a lark and a night owl. And it won't just affect your social life, for researchers are discovering these characteristics have implications for health, too.
This preference for morning or evening is known as your sleep chronotype, and it affects our waistline, fertility, pain levels and even cancer risk. It also affects personality - a study published last month found night owls are more likely to demonstrate dark personality traits including narcissism and deceitfulness.
Researchers from Sydney and Liverpool interviewed more than 200 people about their personalities and sleeping habits.
They suggested the selfishness of night owls might be an evolutionary hangover, because such people are more likely to scheme and steal sexual partners from others, which is best done under cover of darkness. Whether you have a morning or evening chronotype is dictated by your biological 24-hour clock, explains Dr Tim Quinnell, a respiratory consultant and sleep expert.
This, in turn, is heavily influenced by genes.
'Everything in the body - every reaction, hormone, gene switching on and off - is governed by the internal clock,' he says. 'And it's this clock that makes early types wake when they do, and late types able to carry on into the night.' Here, the experts reveal the latest research on owls or larks, and the effect on health.
LARKS FEEL MORE TIRED
BEING a night owl or lark may be largely dictated by a gene known as Period-3. Scientists discovered there are two versions of this gene - a long version and a short version. Those with the long version are larks; the short version, owls.
The gene is thought to affect 'sleep pressure'. As well as our biological clock controlling when we sleep and wake, we also have a system that builds up feelings of sleepiness throughout the day - the peak is when we are at our most tired and need to go to bed.
The Period-3 gene causes sleep pressure to affect larks and owls differently, explains Dr Simon Archer, a reader in chronobiology.
'The larks have a sleep pressure that builds up much more quickly. So as they go through a normal day, they get more tired more quickly.' We each carry two versions of the Period-3 gene - one from each parent. If you get two versions of the long or short version, you will be an 'extreme' lark or owl.
Many of us have one version of both, meaning we have tendencies for characteristics of both, says Dr Archer. 'I tested myself and found that I have one short gene and one long gene. This makes sense, as I work best in the morning, but I have the physiology of an owl and so I can't eat breakfast first thing.'
OWLS ARE HUNGRIER - AND FATTER
LARKS always eat breakfast within half an hour of waking, says Professor Jim Horne, emeritus professor of psychophysiology.
'We've found this is a very good indicator of whether a person is a morning or an evening type,' he says.
This might be because our body clock influences metabolism. But owls are more partial to a midnight feast. In a recent study on 119 obese volunteers, half who were morning types, the others evening types, the latter consumed twice as many calories after 8pm - on average 677 calories, compared with 299 for larks.
Furthermore, the morning types had their breakfast about 7.17am - the evening types ate at 8.38am.
The problem for owls is that evening meals may not be as filling as daytime meals - leading to over-eating and weight gain.
This may be due to low levels of leptin, a hormone responsible for telling our brain when we are full.
According to sleep expert Professor Russell Foster, research has shown levels of this hormone can go out of kilter when we're sleep deprived. …