快猫短视频

FEELING bogged down by routine? Bored with your predictable lifestyle?
Perhaps it鈥檚 time to join the 24-hour revolution. Flexibility is the rallying
cry: you can buy your groceries at midnight, book your holiday on the Internet
at 3 am, and deal shares online at the crack of dawn. The 24-hour society offers
convenience and instant access. And, as business hours get longer, we are lured
into adopting unorthodox work and leisure patterns. But there鈥檚 a catch: a
primitive timekeeper tucked deep inside our brains stubbornly defies these new
trends.

This body clock not only dictates when we sleep, but also keeps every cell
and tissue working under a tight regime. What time we eat, rest and play, the
rhythmic surge of hormones, the cycling in body temperature鈥攁ll are in the
clock鈥檚 domain. Yet it is surprisingly easy to outsmart our body clock. With the
help of alarm clocks, we do so almost daily, without giving it a second
thought.

But scientists are warning that we ignore this biological timepiece at our
peril. Fighting our natural sleep tendencies to conform to work, family and
social pressures may be grinding away at our health, triggering a string of
maladies, from niggling aches and pains to more sinister problems such as heart
disease, perhaps even the full-blown symptoms of chronic fatigue syndrome.
Giving up the late nights and weekend lie-ins in favour of a strict daily
routine and a regular bedtime might be as important to our health as quitting
smoking or cutting back on saturated fat.

From its headquarters in the suprachiasmatic nucleus of the hypothalamus, the
biological clock controls every circadian rhythm in the body. 鈥淎nything you care
to measure will show a rhythm鈥攈ormones, temperature, alertness, immune
functions, urine excretion, sodium, potassium,鈥� says Simon Folkard, a
chronopsychologist at the University of Wales, Swansea. The clock鈥檚 job is to
synchronise all these. Like a conductor, it beats time and brings in all the
different instruments at the right moment to ensure the outcome is music, and
not just noise.

The settings of our biological clock determine whether we are early-rising
larks or night owls. 快猫短视频s have long known that morning types warm up
earlier in the day than night-adepts. On average, a lark鈥檚 body temperature
peaks around mid-afternoon, while owls reach their maximum a couple of hours
later. Drowsiness sets in when the body starts to cool down, and, since early
birds鈥� body temperature plummets earlier, the urge for shut-eye comes sooner for
them too.

Despite the clock鈥檚 control streak, it is easy to override with a late night
or an early alarm. Nudge the sleep-wake cycle often enough and the battle is
won鈥攜our internal circadian rhythm will adjust to a new schedule. But
Folkard is convinced that tampering with the clock鈥檚 natural settings is a
hazardous activity.

Folkard has studied how owls and larks cope with working shifts. 鈥淚t is
actually the opposite of what you鈥檇 predict,鈥� he says. Although owls prefer late
shifts, their health takes a serious battering. They develop a constellation of
symptoms: heart trouble, indigestion, ulcers, gut complaints, back and muscular
pain, fatigue and frequent viral infections.

Their psychological health fares no better. Folkard鈥檚 recent studies have
revealed that owls can become depressed, anxious and prone to accidents. 鈥淭he
irony is that if you ask evening types which shift they prefer, they will say
`permanent night shift鈥�,鈥� Folkard explains. 鈥淪o they self-select the very shift
that does them the most damage.鈥�

How can disrupting the brain鈥檚 sleeping habits disturb the body in so many
different ways? Harvey Moldofsky, director of the Centre for Sleep and
Chronobiology at the University of Toronto, maintains that we are organised by
interconnected rhythms. Moldofsky has observed dramatic changes in the
immune system between waking and sleeping. Natural killer cells circulate in
greater numbers during the day, while T cells are more active at night, and more
of the immune regulator interleukin-1 is churned out as we sleep. Moving the
clock settings to and fro disturbs this harmony, paving the way for the
infections that often plague shift workers.

Even our metabolic responses to food are under the influence of the clock.
Linda Morgan from the University of Surrey has observed that upsetting a
person鈥檚 natural circadian settings will keep their levels of glucose and some
lipids in their blood dangerously high after a meal鈥攚hich may explain why
cardiovascular disease is shift workers鈥� number one hazard.

But not everyone is at equal risk from these disruptions. Surprisingly,
morning types endure the punishing schedule of late shifts better, and suffer
fewer physical problems than evening types. How can that be? According to
Folkard, it all boils down to how easy it is to reset a person鈥檚 internal clock.
Evening people can easily change their clock settings, because their circadian
cycles are longer than 24 hours (see 鈥淧arty animal or party pooper鈥�) and
need resetting daily. But adjusting and readjusting to peculiar timetables will
land them in trouble. For example, a spell on the night shift followed by a
normal sleep schedule on rest days is enough to knock an owl鈥檚 clock out of
kilter. Morning people, on the other hand, enjoy a stable endogenous clock which
needs no tuning because its cycle is almost bang on 24 hours. Even on shifts,
their clock remains beatifically constant.

Folkard鈥檚 findings spell out quite a different message from the standard
advice: they suggest night workers should try to keep the hands of their body
clocks as stable as possible. They should orient their whole life towards being
a daytime person, who just occasionally stays up all night to work. Shifts
should be broken into units of just a few days to minimise circadian disruption.
Working two successive nights, for example, is preferable to working four or
five in a row. Most chronobiologists, in contrast, believe that the way to
maintain alertness and reduce the risk of accidents is to try adapting the body
clock fully to suit the new work time, and to make shift changes less frequent,
not more.

Shift or swim

鈥淧eople have to accept that they are designed to be members of a daytime
species,鈥� says Folkard. 鈥淎sking people to work at night is a bit like throwing
them in the sea and asking them to be aquatic for a week. It is possible, but we
are not designed to do it, so there are risks.鈥�

Evening types on regular day jobs are also prone to mistreating their clocks.
An innocent lie-in鈥攁s enjoyed by most people at weekends鈥攚ill hurtle
their body clock forwards. Come Monday, they will have to get up earlier than
their internal rhythm dictates, and this is likely to make them irritable and
fed up. 鈥淚 think a lot of people are being forced to sleep and wake at the wrong
time for them, by the pressures of society, partners and children,鈥� Folkard
says. Everyone has an optimal time for sleep, and sleeping and waking at the
wrong point within the cycle can have dire consequences. And evening types, who
stay up later and later if left to their own devices, are the most
vulnerable.

Ignoring the pull of our endogenous rhythms will lead to more than just
grumpiness. It could result in physical and mental exhaustion, like that seen in
the elusive Chronic Fatigue Syndrome (CFS). Nobody yet knows what causes this
disease, but patients鈥� symptoms鈥攖iredness, poor concentration,
unrefreshing sleep and pain鈥攁re tellingly similar to those of jet lag and
shift work. At a recent meeting in London organised by the Novartis Foundation
and the Linbury Trust, chronobiologist Jim Waterhouse, from John Moores
University in Liverpool, discussed the theory that a disoriented biological
clock may perpetuate the illness.

He and Gareth Williams, a clinical endocrinologist at John Moores University,
have traced CFS patients鈥� temperature and hormone rhythms. As bedtime approaches
and over a period of an hour or two, healthy people鈥檚 body temperature drops
sharply. At the same time, the pineal gland in the brain pumps out melatonin,
the sleep-inducing hormone. This combination is the signal that triggers
sleep. In people who nod off easily, the two events are tightly synchronised,
but in chronic fatigue patients they are mismatched. 鈥淚n CFS patients, the
normal relationship between temperature rhythm and melatonin secretion is lost.
It looks like there鈥檚 a problem in the overall regulation of the body clock,鈥�
says Williams.

Armed with this knowledge, the team attempted to resynchronise patients鈥�
flailing clocks with two different therapies. One was an evening dose of
melatonin, in similar amounts to those used to treat jet lag. The other
treatment exposed patients to a bright light first thing in the morning. But so
far the results are discouraging. Some patients reported feeling more energetic,
yet neither treatment seemed to fully restore their health.

This has led Waterhouse to suggest that CFS is not caused by a 鈥渂roken
clock鈥�, but rather that patients鈥� erratic lifestyles are jumbling up their
internal rhythms. Regular behaviour patterns are essential for keeping our
biological cycles in sync. Except in the most precise of larks, the clock cycle
is never exactly 24 hours, so we rely on outside cues to adjust it. Daylight and
darkness, when we go to bed and wake up, meal times, exercise and social
activities reset it daily. The trouble is that 鈥渇ew of us get enough light to
have an impact on the biological clock鈥�, says Greg Tooley, a clinical
psychologist at Deakin University in Victoria, Australia, citing studies
conducted in the 1980s. 鈥淚t means that our behaviour becomes so much more
important. It is so much more important that it is regular.鈥�

People with chronic fatigue are even less exposed to the light-dark cycle
than most of us. Feeling drained of energy and in pain, they find it almost
impossible to stick to a daily routine. Patients鈥� sleep is interrupted, they nap
during the day, and tend to stay indoors. 鈥淲e found that the sleep patterns in
CFS participants were far more variable than in healthy individuals. Healthy
people fall asleep within a couple of hours of each other, while in people with
CFS, it may be 4 hours between the first one and the last one going to sleep,鈥�
says Tooley. With such unpredictable sleep timings, the circadian system has a
tough time synchronising itself, both internally and with the outside world.

Loose cogs

If erratic behaviour has the potential to loosen the cogs in the biological
clock of chronic fatigue patients, can a regular lifestyle tighten them up
again? Many clinicians believe so. Cognitive behaviour therapy, which encourages
patients to lead a routine-driven life, helps up to 80 per cent to recover.
Getting up at a fixed time, and spending half an hour doing gentle exercise
might help retune a lot of things, including the biological clock.

For the rest of us, routine remains a dirty word. But can we afford to shun
it entirely? Now that we have devised effective ways of waking ourselves up, and
ways of lighting up the night, we might like to think of the biological clock as
redundant. 鈥淎s a species, we鈥檇 like to get rid of it,鈥� admits Folkard. 鈥淏ut
after millions of years of evolution, we can鈥檛 suddenly ignore the body clock
and become members of the 24-hour society without incurring penalties.鈥�

If you wake every morning at the crack of dawn, ready to tackle an exam or a
marathon, then you鈥檙e probably a lark. If you crawl out of bed after battling
with the snooze button, on the other hand, you鈥檙e probably an owl. But why do
morning and evening types naturally wake at different times?

One factor may be the cycle length of their circadian rhythm, says Jeanne
Duffy of Harvard Medical School in Boston. Duffy has estimated the cycle length
in moderate owls and larks by isolating them in an artificial environment where
all time cues have been removed. Measuring their temperature, and levels of
melatonin and cortisol in their blood, she has found that owls鈥� cycles are
longer than 24 hours. Larks, on the other hand, have cycles that closely follow
a 24-hour pattern.

How fast our circadian pacemaker ticks is beyond our control. The spontaneous
firing rate of body clock neurons in the suprachiasmatic nucleus is likely to
result from many genes working together. Scrutinising CLOCK鈥攐ne
of the human genes involved in circadian rhythms鈥攈as revealed that a
single nucleotide change can predict whether a person tends towards being a
morning or an evening type.

Yet stereotypical early-birds and night-lovers are in the minority, warns
Simon Folkard. Only between 5 and 10 per cent of the population falls at either
end of the spectrum, most lie in the middle. But extreme types are easy to spot.
Look out for the poor lark who nods off at a dinner party or the owl who
clumsily gravitates towards the coffee machine in the morning.