Skin cells shine a light on sleep's 'larks' and 'owls'

Microscopic fragments of skin can be used to tell whether someone is an early-rising "lark" who springs to life at sunrise, or a natural "owl" who struggles to get out of bed in the morning but still feels awake late at night.

Skin cells carry an in-built timing mechanism set by the central biological clock of the body which determines whether someone is an owl or a lark, according to a study that holds out the promise of developing new treatments for sleeping disorders.

The study found that people's preferences for rising early or late are encoded in their genes - and the molecules of their skin cells - although the scientists emphasised that other factors also play a role in influencing the time that someone likes to rise in the morning.

Studies of identical and non-identical twins have shown that genes play a part in whether someone is by nature a lark or an owl but the latest research is probably the first to show that human skin cells on their own can be used to test for someone's sleeping preferences.

The findings are part of the wider effort of research into how the human body deals with the shifts in patterns of activity which are needed to cope with the 24-hour cycle of day and night. Eventually scientists hope to use the results to treat people with sleeping disorders, such as those resulting from seasonal-affected disorder.

A research team led by Steven Brown of the University of Zurich analysed the sleeping behaviour of 28 people and found that they could divide the experiment's volunteers into 11 "larks" and 17 "owls" based on a questionnaire of their normal daily routines.

After taking skin samples from the volunteers, the scientists inserted into each cell a gene that lights up in ultraviolet light when the cell is metabolically most active. The gene allowed the scientists to follow the circadian rhythm of the cells as they waxed and waned over a 24-hour period.

When the cells and the gene were at their highest activity, the intensity of the light increased. This phenomenon allowed the scientists to measure the length of activity showed by each cell and compare this to the natural sleeping tendencies of the volunteer in question.

The study, which is published in the journal Proceedings of the National Academy of Sciences, found that the skin cells from the extreme early risers has the shortest luminescence period, whereas those from the very-late risers had the longest period. This suggested that the extreme early risers had a short daily cycle and long nightly cycle, which was reversed in the late risers.

The scientists believe that a person's preferences for early or late phases of daily activity might be determined by the length of the "circadian" period, the period of roughly 24 hours that controls the biological clock of the body.

A part of the brain called the suprachiasmic nucleus acts at the body's pacemaker by analysing light levels reaching the eye and sending messages to the pineal gland at the base of the brain, which produces the sleep hormone melatonin.

The scientists believe that extreme early risers have a shorter circadian oscillation than the extreme late risers, but they also found other differences between the two groups.

"We find not only period length differences between the two classes, but also significant changes in the amplitude and phase-shifting properties of the circadian oscillator among individuals with identical 'normal' period lengths," the scientists said.

"Our observations in fibroblasts [skin cells] suggest a strong genetic contribution of an endogenous circadian clock to human daily behaviour, and show that the specific properties of this clock can be measured in peripheral cells at a molecular level."

ebooksNow available in paperback
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Austen Lloyd: Residential Property Solicitor - Hampshire

Excellent Salary : Austen Lloyd: NORTH HAMPSHIRE - SENIOR POSITION - An exciti...

Recruitment Genius: Gas Installation Engineer

£29000 per annum: Recruitment Genius: A Gas Installation Engineer is required ...

Recruitment Genius: Domestic Gas Technical Surveyor

£28000 per annum: Recruitment Genius: A Domestic Gas Technical Surveyor is req...

Recruitment Genius: HVAC & Mechanical Service Estimator

£27000 - £35000 per annum: Recruitment Genius: Yorkshire based firm looking to...

Day In a Page

Homeless Veterans Christmas Appeal: Drifting and forgotten - turning lives around for ex-soldiers

Homeless Veterans Christmas Appeal: Turning lives around for ex-soldiers

Our partner charities help veterans on the brink – and get them back on their feet
Tove Jansson's Moominland: What was the inspiration for Finland's most famous family?

Escape to Moominland

What was the inspiration for Finland's most famous family?
Nightclubbing with Richard Young: The story behind his latest book of celebrity photographs

24-Hour party person

Photographer Richard Young has been snapping celebrities at play for 40 years. As his latest book is released, he reveals that it wasn’t all fun and games
10 best stocking fillers for foodies

Festive treats: 10 best stocking fillers for foodies

From boozy milk to wasabi, give the food-lover in your life some extra-special, unusual treats to wake up to on Christmas morning
'I have an age of attraction that starts as low as four': How do you deal with a paedophile who has never committed a crime?

'I am a paedophile'

Is our approach to sex offenders helping to create more victims?
How bad do you have to be to lose a Home Office contract?

How bad do you have to be to lose a Home Office contract?

Serco given Yarl’s Wood immigration contract despite ‘vast failings’
Green Party on the march in Bristol: From a lost deposit to victory

From a lost deposit to victory

Green Party on the march in Bristol
Putting the grot right into Santa's grotto

Winter blunderlands

Putting the grot into grotto
'It just came to us, why not do it naked?' London's first nude free runner captured in breathtaking images across capital

'It just came to us, why not do it naked?'

London's first nude free runner captured in breathtaking images across capital
In a world of Saudi bullying, right-wing Israeli ministers and the twilight of Obama, Iran is looking like a possible policeman of the Gulf

Iran is shifting from pariah to possible future policeman of the Gulf

Robert Fisk on our crisis with Iran
The young are the new poor: A third of young people pushed into poverty

The young are the new poor

Sharp increase in the number of under-25s living in poverty