November 29, 2004
Obey Your Body Clock: Late to Bed, Early to Rise
NATURE dictates that we are all `morning' or `evening' people, and scientists say it could be dangerous to fight your biological rhythms, reports Anjana Ahuja.
DID YOU FEEL a bit lacklustre early this morning, even though you didn't touch a drop last night? Does your alarm clock always seem to boom into life obscenely early, rousing you from a deep slumber?
Does your in-tray fester until after lunch, by which time you've perked up enough to face it?
And will you spend today dreaming about Friday, because on Fridays you can be the night owl you were born to be, crashing out at 3am and stirring on Saturday afternoon?
Scientists think that answering yes to all the above may betray more than a tendency towards slothfulness.
Sleep researchers are discovering that there is some biological truth to the adage that people come in "morning" and "evening" types, also called larks and owls.
Among other factors, such as hormonal levels, a set of about 12 genes appear to influence the time you prefer to go to bed.
Dr Simon Archer, lecturer in molecular neuroscience at the University of Surrey, has now embarked on a mission to disentangle how these genes work in concert to control our body rhythms.
He has set up a temporary laboratory in the Science Museum in London, where his colleague, Kay Jones, is taking cheek swabs and using questionnaires to gauge the wider connections between sleep preference and genes.
Such is the range of human "diurnal preference" that extreme larks can be waking as extreme owls slip between the sheets.
People are generally good at guessing which bird best describes them, although few people are very strong examples of either.
While filling in the questionnaires has a certain parlour game appeal, the implications of studies into "chronotypes" are very profound.
You might, for example, be more or less suited to your particular profession because of it.
"It doesn't make any sense for an evening person to become a milkman or a postman," Archer says.
Likewise, those who prefer to rise with the sun probably wouldn't make the cheeriest bar workers.
More seriously, fighting a strong biological instinct might carry as yet unknown perils. There is already a growing body of evidence that shift workers are more sickly than those in regular day jobs.
The Surrey team have already discovered the faint bleep of a genetic alarm clock - they found a year ago that individuals at opposite ends of the owl-lark spectrum showed marked difference in a gene called Period 3.
Among very early risers, Period 3 was more likely to come in its longer form, while late risers tended to exhibit it the alternative, shorter form.
Archer explains: "We know that the body clock is made up of a dozen genes, and these genes produce proteins that interact in a feedback mechanism.
"Our hypothesis is that it is the interaction of these genes and proteins that determines differences, and that this changes clock length."
These genes govern the central clock in the brain, the master timepiece by which every cell sets its own time.
Of the thousand people he expects to participate in his experiment, funded by the Wellcome Trust, Archer hopes to uncover a subset of extreme owls and larks.
Huge differences are easier to spot than small ones, especially in the encyclopaedic expanse of biological code that constitutes the human genome.
The expectation is that diehard larks will be, genetically speaking, noticeably different from committed owls, and that this will provide a signpost to the link between diurnal preference and genotype.
"We're hoping that once we've been through all 12 genes, we can come up with a relationship between genes and circadian rhythms."
Diurnal preference indeed appears to be a heritable trait. Identical twins, for example, who share 100 per cent of their genes display more similarities in their sleep time preferences than fraternal twins and siblings, who share 50 per cent.
As a rule, women are more larklike than men, although nobody knows why because the clock genes found so far are not sex-linked.
Maturity makes one increasingly lark-like: Archer suggests that this could be due to age-related changes in hormone production (eg, melatonin) or a difference in the way genes operate in later life.
Although children have not been studied extensively, anecdotal evidence suggests they maintain the same diurnal preference through life, except around puberty, when almost all become more owl-like.
Spouses often have mismatched chronotypes; which can lead to marital discord.
It isn't generally a problem with newlyweds, Archer points out, who have youth, adaptability and energy on their side, but older couples commonly and amicably, resolve their lack of synchrony by sleeping in separate rooms.
If clock genes are the musicians in an orchestra, then sunlight is their conductor. Moreover, social norms, such as a working routine, place additional constraints on a person's propensity to go to bed early or late.
So-called sleep debt is another factor that complicates the genetic studies.
The general rule is that adults need about eight hours a day.
Professor Till Roenneberg of the University of Munich has found that "late chronotypes" - the owls - rack up such large sleep deficits during the working week that they catch up at weekends by slumbering a few extra hours.
Only by correcting for the clouding factors of sunlight exposure and sleep debt, Roenneberg insists, can one get a true insight into underlying genetic chronotypes.
Still, our preference for certain sleep times seems a pretty clear-cut example of genetic determinism.
"Of course, genes aren't everything because we can force ourselves to get up with an alarm clock," Archer says.
"I'm not saying you can't alter behaviour - you can find ways of coping. There is evidence that some people are better at coping than others.
"But if you're an evening person you're going to find it that much harder to do things in the morning. That's determined by your genes and there's no getting away from that."
Archer is neither truly an owl nor a lark - his perfect night would run from 1O.30pm to 8am, although the lack of extreme preference means he can cope with late nights.
He is intrigued by the deeper scientific question of why human beings should have evolved with a range of preferences.
While homo sapiens is nowhere near diverging into nocturnal and diurnal species - like the night-fearing Eloi and the sun-hating Morlocks of H.G. Wells's The Time Machine - Archer speculates that a society made up of owls and larks would be more likely to survive and thus hold an evolutionary advantage:
"It would have been important in social groups for some people to be active in the morning and others at night, so someone was always on the lookout."
The biological legacy, if this is what it is, has lingered, and is battling it out with the trend towards a 24/7 society and an increase in shift work.
But according to research, the economic imperative is clashing with a circadian one, sometimes with fatal results.
Nightshift workers are more likely to have accidents than daytime counterparts; the Exxon Valdez oil spill and the Three Mile Island nuclear alert are commonly cited examples.
There is some evidence that shift workers suffer higher rates of cardiovascular disease and depression, even accounting for the fact that shift workers tend to be drawn from lower socioeconomic groups and are thus already disadvantaged in the health stakes.
Women who work irregular shifts show a higher incidence of miscarriage and some studies suggest that breast cancer is more common among shift workers.
Overall, there is nothing to suggest that overriding one's biological rhythms is beneficial and much to suggest it is detrimental.
Archer is well aware that there could be a controversial aspect to unravelling the genetics of body clocks.
In the future, a genetic test performed with a cheek swab could identify a person's chronotype.
He doesn't want to see such testing brought in to screen people in order to decide who can and cannot do shift work.
"I would be concerned, because that isn't fair. I met someone recently who was always shattered because of his changing shift schedule, but he liked the work because it paid well and he had great holidays."
However, he suggests genetic tests could be used to match people to certain shift schedules.
Just as some seem better at coping with jet lag, so some shift workers find it relatively easy to deal with quickly changing shift patterns.
For workers who lie at the extreme ends of the spectrum, and who have not already selected jobs that suit their biology, a genetic test may well be a boon.
If the emerging evidence is to be believed, those who synchronise clocks and calling could be happier and healthier as a result. - The Times