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Você acorda cedo ou prefere dormir até tarde?

10/01/2004
Madrugador ou vespertino?

Você é do tipo que pula da cama cheio de disposição ainda de madrugada, ou prefere trabalhar à noite e dormir até tarde? Pesquisadores da Universidade de Surrey, no Reino Unido, acabam de descobrir uma variação genética que pode estar por trás da sua preferência de horário. O gene em questão chama-se Per3, de "período", e é ativo no núcleo supraquiasmático do hipotálamo - a estrutura cerebral onde "bate" nosso relógio biológico. Ainda não se sabe como funciona o produto do Per3, mas quem sabe um dia será possível usar o conhecimento da versão que cada um carrega para ajustar melhor a hora do trabalho com a hora de ir para a cama?

 

Gene tells time for bed

Night owls and early birds owe differences to clock-gene length.
20 June 2003

MICHAEL HOPKIN

Gene screens may help people make the most of their day.
© GettyImages

Whether you are a morning or an evening person could depend on a single gene, a study of extreme sleeping habits has revealed. Understanding the body clock's genetic basis may help people to make the most of their day.

Night owls and early birds tend to carry different versions of a gene called Per3, says Simon Archer of the University of Surrey in Guildford, UK. This difference may make their preferred sleep cycles longer or shorter than 24 hours.

The brain uses the cycle of light and dark to align its clock with the Earth's 24-hour cycle. "Every day we reset our clocks slightly," says Archer. People whose natural cycles are much shorter or longer than 24 hours often find themselves wakeful or sleepy at odd times.

The idea that sleeping patterns have a genetic basis is a promising one, says sleep researcher Emmanuel Mignot of Stanford University in California. "More and more we're discovering genes that influence when we feel tired," he says.

Tiring task

Archer's team surveyed the sleeping habits of hundreds of members of the British public with a quiz called the Horne-Östberg questionnaire. It features questions such as: "what time would you get up if you were entirely free to plan your day?"

They then analysed cheek cells from participants with the strongest tendency towards a morning or evening lifestyle.

Early risers generally have a longer version of Per3 than late sleepers, who tend to carry a truncated version, the researchers found. The gene is turned on in the brain's time-keeping centre, the suprachiasmatic nucleus. Its precise function is not known.

The team also analysed blood samples from patients with delayed sleep phase syndrome (DSPS), whose natural cycle is thought to be much longer than 24 hours. These people sleep late into the day and feel alert only when burning the midnight oil. They are usually treated with the sleep hormone melatonin.

There are environmental and social aspects too
Emmanuel Mignot
Stanford University

Seventy-five per cent of DSPS sufferers carry two copies of the short Per3 gene, the team found. This supports the idea that the abridged version is linked to a lengthening of the body's sleep cycle.

Sleeping patterns are not entirely dictated by genetics, however. "There are environmental and social aspects," Mignot points out. "Almost everyone is an evening person when they are 18."

But taken together, these considerations could help people to tailor their working lives to periods of maximum alertness, argues Josephine Arendt, one of Archer's Surrey colleagues. "Some day, people could choose their lifestyle according to their clock genes".

References
  1. Archer, S. N. et al. A length polymorphism in the circadian clock gene Per3 is linked to delayed sleep phase syndrome and extreme diurnal preference. Sleep, 26, 413 - 415, (2003). |Article|


© Nature News


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