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."

Voices
The Sumatran tiger, endemic to the Indonesian island of Sumatra, is an endangered species
voicesJonathon Porritt: The wild tiger population is thought to have dropped by 97 per cent since 1900
Arts and Entertainment
Beast would strip to his underpants and take to the stage with a slogan scrawled on his bare chest whilst fans shouted “you fat bastard” at him
musicIndie music promoter was was a feature at Carter gigs
News
news
Arts and Entertainment
Story line: Susanoo slays the Yamata no Orochi serpent in the Japanese version of a myth dating back 40,000 years
arts + entsApplying the theory of evolution to the world's many mythologies
PROMOTED VIDEO
News
Performers dressed as Tunnocks chocolate teacakes, a renowned Scottish confectionary, perform during the opening ceremony of the 2014 Commonwealth Games at Celtic Park in Glasgow on July 23, 2014.
news
Life and Style
Popular plonk: Lambrusco is selling strong
Food + drinkNaff Seventies corner-shop staple is this year's Aperol Spritz
News
Gardai wait for the naked man, who had gone for a skinny dip in Belfast Lough
newsTwo skinny dippers threatened with inclusion on sex offenders’ register as naturists criminalised
News
Shake down: Michelle and Barack Obama bump knuckles before an election night rally in Minnesota in 2008, the 'Washington Post' called it 'the fist bump heard round the world'
newsThe pound, a.k.a. the dap, greatly improves hygiene
Arts and Entertainment
La Roux
music
Arts and Entertainment
Graham Fellows as John Shuttleworth
comedySean O'Grady joins Graham Fellows down his local Spar
News
people
News
ebookA unique anthology of reporting and analysis of a crucial period of history
News
Ross Burden pictured in 2002
people
News
Elisabeth Murdoch: The 44-year-old said she felt a responsibility to 'stand up and be counted’'
media... says Rupert Murdoch
Arts and Entertainment
tv
Extras
indybest
Sport
Arsenal signing Calum Chambers
sportGunners complete £16m transfer of Southampton youngster
Independent
Travel Shop
the manor
Up to 70% off luxury travel
on city breaks Find out more
santorini
Up to 70% off luxury travel
on chic beach resorts Find out more
sardina foodie
Up to 70% off luxury travel
on country retreats Find out more
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

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

iJobs Job Widget
iJobs General

ICT Teacher

£21804 - £31868 per annum: Randstad Education Chelmsford: Are you a qualified ...

DT Design and Technology Teacher

£21804 - £31868 per annum: Randstad Education Chelmsford: We are urgently for ...

Maths Teacher

£21804 - £31868 per annum: Randstad Education Chelmsford: Are you an experienc...

Junior / Graduate Application Support Engineer

£26000 per annum: Ashdown Group: A highly successful international media organ...

Day In a Page

The children were playing in the street with toy guns. The air strikes were tragically real

The air strikes were tragically real

The children were playing in the street with toy guns
Boozy, ignorant, intolerant, but very polite – The British, as others see us

Britain as others see us

Boozy, ignorant, intolerant, but very polite
Countries that don’t survey their tigers risk losing them altogether

Countries that don’t survey their tigers risk losing them

Jonathon Porritt sounds the alarm
How did our legends really begin?

How did our legends really begin?

Applying the theory of evolution to the world's many mythologies
Watch out: Lambrusco is back on the menu

Lambrusco is back on the menu

Naff Seventies corner-shop staple is this year's Aperol Spritz
A new Russian revolution: Cracks start to appear in Putin’s Kremlin power bloc

A new Russian revolution

Cracks start to appear in Putin’s Kremlin power bloc
Eugene de Kock: Apartheid’s sadistic killer that his country cannot forgive

Apartheid’s sadistic killer that his country cannot forgive

The debate rages in South Africa over whether Eugene de Kock should ever be released from jail
Standing my ground: If sitting is bad for your health, what happens when you stay on your feet for a whole month?

Standing my ground

If sitting is bad for your health, what happens when you stay on your feet for a whole month?
Commonwealth Games 2014: Dai Greene prays for chance to rebuild after injury agony

Greene prays for chance to rebuild after injury agony

Welsh hurdler was World, European and Commonwealth champion, but then the injuries crept in
Israel-Gaza conflict: Secret report helps Israelis to hide facts

Patrick Cockburn: Secret report helps Israel to hide facts

The slickness of Israel's spokesmen is rooted in directions set down by pollster Frank Luntz
The man who dared to go on holiday

The man who dared to go on holiday

New York's mayor has taken a vacation - in a nation that has still to enforce paid leave, it caused quite a stir, reports Rupert Cornwell
Best comedians: How the professionals go about their funny business, from Sarah Millican to Marcus Brigstocke

Best comedians: How the professionals go about their funny business

For all those wanting to know how stand-ups keep standing, here are some of the best moments
The Guest List 2014: Forget the Man Booker longlist, Literary Editor Katy Guest offers her alternative picks

The Guest List 2014

Forget the Man Booker longlist, Literary Editor Katy Guest offers her alternative picks
Jokes on Hollywood: 'With comedy film audiences shrinking, it’s time to move on'

Jokes on Hollywood

With comedy film audiences shrinking, it’s time to move on