If you're depending on coffee to keep you awake, make sure you know what you're doing.
Finishing a term paper? Working the second shift? Driving late into
the night? Many of us grab hold of a coffee mug as if it were a life
raft in The Struggle To Stay Awake. Caffeine is certainly
America's stimulant of choice -- 80 to 90 percent of us take it
daily to foster alertness. Around the world java percolates and
teabags simmer in millions of homes each morning.
Yet scientists
still do not know exactly how caffeine delivers that dependable
jolt. A group of Harvard Medical School researchers has gotten
closer to the answer. What's more, they propose a more effective and
novel way to lean on caffeine when we're drowning in drowsiness. Instead
of quaffing one giant emergency venti latte, you're better off
taking frequent sips of small servings of coffee. That way, the
caffeine can work more naturally against the body's drive for sleep.
This information didn't come cheaply. It required a certain amount
of human sacrifice. Sixteen men were sequestered for a month and kept
on a brutal schedule that dictated awake periods of 28.57 straight
hours -- similar to those required of medical residents and military
and emergency services personnel.
Rooms were free of external
cues such as clocks, in order to throw off the men's circadian
system, the body's internal clock that promotes sleep rhythmically
in response to signals such as sunlight. Meanwhile, the conditions
stretched to its limit another physiological system that also
governs sleep, the homeostatic system. This system drives sleep in a
cumulative rather than cyclical manner, so that the longer one is
awake, the more it pushes for sleep.
When they awoke, and
once an hour afterwards, the men were given a caffeine pill, roughly
the equivalent of two ounces of coffee, or an identical-looking
dummy pill. The caffeinated group performed better on cognitive tests and didn't accidentally nod off as often as their placebo
counterparts. "There is no match for the restorative effects of
sleep," says Charles Czeisler, professor of sleep medicine at
Harvard. "We're not recommending that people stay up, but we're
excited to have found a novel way to avoid many of the adverse
consequences of an extended bout of wakefulness."
A more
effective way to fight off sleep is good news to the approximately 8
million people in the U.S. who regularly work at night and attempt
to sleep by day. Tiredness reduces productivity
and increases the risk of accidents; sleep loss is implicated in
more than 56,000 motor vehicle crashes each year. The environmental
disaster resulting from the grounding of the oil tanker Exxon Valdez
was ultimately blamed on the crew's sleep deprivation.
Just
as they suspected, Czeisler and his colleagues concluded that
caffeine works to blunt the homeostatic drive for sleep. Caffeine blocks
the receptor for adenosine, a critical chemical messenger involved
in the push for sleep.
But it's most effective if
administered in parallel with growing pressure from the homeostatic
system, to counter the accumulation of adenosine. "By modestly
increasing caffeine in the system as the drive for sleep was rising,
we could attenuate the increase of adenosine," Czeisler says.
What
about those of us who are not piloting oil tankers or fighting
forest fires, but who wake up groggy after a late night on the town?
Using caffeine in a way more relevant to our biology still makes
sense. Says Czeisler: "The method could certainly ward off an
afternoon crash, but it must be applied with good personal
judgment." Because caffeine stays in the body for about 6 or 7
hours, regular doses late in the day could have an adverse impact on
sleep.
Once caffeine hits the bloodstream, the brain and body enter an excited state: the mind is quicker and memory
improves (though not necessarily complex reasoning). But once the
effect wears off, fatigue sets in with a vengeance to correct for
that prolonged state of heightened alertness. Caffeine sets off a
host of reactions: heart rate increases, blood vessels constrict
(which is why it is a useful treatment for headaches) and breathing
improves as air passages relax.
Moderate caffeine intake produces
no health risks. However, because caffeine reduces blood flow to
the brain, it could precipitate panic
attacks in some people; it spurs irritability and "jitters" in
others. Pregnant women should limit caffeine intake; it may lower
infant birth weight and delay development. Be conservative
when measuring out your small doses. Czeisler warns that the
ubiquitous Starbucks and Dunkin' Donuts brands pack more caffeine
than coffees of yore. Not that there is any danger of a shortage:
"Coffee is second only to oil in global trade," he says. "It is the
most widely-used pharmaceutical in the world."
Source :
Tidak ada komentar:
Posting Komentar