Most working blokes know that the more they work, the less they sleep. What
they may not know is that the more time they
spend in their cars, the less they sleep.
Drive time — not television viewing,
computer addiction or exercise — is
second only to hours on the job as a reason
people don't get the shut-eye they need.
"The most deadly combination," says David
F. Dinges, chief of the division of sleep
and chronobiology at the University of Pennsylvania
School of Medicine, "would be long commute
time, long work hours and living in a place
where you have to get in the car and drive
to get anything."
Sound like home?
The combination is deadly because a good night's
sleep now appears to be every bit as important
to good health and long life as a nutritious
diet and regular exercise.
"Sleep is in the top three," says Dinges.
"And I think it's No. 1. Sleep is a biological
imperative and not getting enough has health-related
costs."
In April, the Institute of Medicine issued
a report confirming links between sleep deprivation
and an increased risk of hypertension, diabetes,
obesity, depression, heart attack and stroke.
Some scientists are exploring possible connections
between inadequate sleep and a decline in
immune function.
The Archives of Internal Medicine devoted
its Sept. 18 issue to the relationship between
sleep and health. An editorial called for
assessment of sleep habits as a standard part
of all medical checkups.
That's because short sleep can hasten the
arrival of the inevitable long sleep. The
largest study of sleep duration and mortality
was published in February 2002 in the Archives
of General Psychiatry. The Cancer Prevention
Study II of the American Cancer Society followed
more than a million participants for six years.
The best survival was found among those who
slept about seven hours a night, the worst
among those who slept less than 4.5 hours.
Too much sleep — nine hours or more
— also was associated with a higher
risk of mortality.
In the last decade, researchers have begun
studying sleep based on today's reality: a
country open for business virtually 24/7,
and a populace increasingly unwilling or unable
to call it a day. Sleep needs vary slightly,
but the vast majority of people, experts agree,
need just about eight hours of sleep each
night to fully recover from 16 hours of being
awake.
Yet Americans are racking up sleep debt like
a college kid with a credit card. About 40%
of Americans say they get fewer than seven
hours of sleep on weekdays, and most —
71% — get fewer than eight hours of
sleep, according to a 2005 survey by the National
Sleep Foundation. Even on weekends, they sleep
about 7.4 hours — better, but not enough
to pay back the week's loss. Every hour they
fall behind is considered an hour of sleep
debt, and Americans accumulate about two full
weeks of personal sleep debt a year.
Sleep researchers have a name for the way
the vast majority of people in this country
sleep: volitional chronic sleep deprivation,
and it is a lifestyle disorder.
Without enough sleep, the cost in reduced
memory, focus, concentration and reaction
time is well established. Incidents in the
lore of sleep research include the Exxon Valdez
oil spill and the Chernobyl nuclear power
plant disaster. In each, key decisions were
made by people who were sleep deprived.
But it's only in the last half a dozen years
that studies have begun to link chronic partial
sleep deprivation to serious physical health
consequences.
Command center signals
Sleep is essential to the workings of
every organ. And it seems that the connection
between sleep and health starts at the brain's
central command post, the hypothalamus. There,
sleep or lack of it can work to activate,
or inhibit, hormone production. There, too,
is where the body gets the signal to go to
bed, to wake up and to adjust temperature,
blood pressure, digestive secretions and immune
activity.
Inadequate sleep works on hormone production
in other areas as well. Without enough sleep,
the central nervous system becomes more active,
inhibiting the pancreas from producing adequate
insulin, the hormone the body needs to digest
glucose.
A groundbreaking study in 1999, led by Eve
Van Cauter, a professor of medicine at the
University of Chicago, showed that just six
days of sleep restricted to four hours pushed
11 healthy young male volunteers into a pre-diabetic
state. Those jaw-dropping results expanded
the field of sleep research, and convinced
scientists that chronic, partial sleep deprivation
damaged the body, not just the mind.
The young men in the same study also had reduced
levels of the stress hormone cortisol, which
normally surges just before waking from a
good night's sleep, energizing people for
the day's demands. The study participants
had the low morning levels of cortisol typical
of their grandparents.
And these volunteers also showed that, with
chronic inadequate sleep, young people might
be accelerating the beer-belly, pear-bottom
problems typically linked to middle age. They
were producing lower levels of growth hormone
after less than a week of four hours of sleep.
Growth hormone is largely secreted during
the night's first round of deep sleep. As
adults age, they naturally spend less time
in deep sleep, getting less of the hormone
that, in addition to driving childhood growth,
plays a role in controlling the body's proportions
of fat and muscle.
The University of Chicago study's findings
were the first solid evidence that chronic
partial sleep deprivation could have physical
health consequences. Since then, researchers
have begun to look harder and deeper at the
links between sleep and illness. A study published
in the Dec. 7, 2004, Annals of Internal Medicine
found that when 12 healthy, young men were
restricted to four hours of sleep for just
two nights, normal levels of leptin, a hormone
that signals satiety, dropped, while levels
of ghrelin, a hormone that prompts appetite,
increased.
When the men awoke, following the sleep-deprived
state, their hunger and appetite increased
— especially for calorie-dense, high
carbohydrate foods. "Chronic short sleep is
the royal road to diabetes and obesity," says
Karine Spiegel, a sleep researcher from Brussels
and author of the study. She spoke of her
work last June at the annual meeting of the
Associated Professional Sleep Societies.
It appears, some researchers believe, that
the links between sleep deprivation and obesity
are two interacting epidemics. "A few years
ago, I would look at obese people and see
weakness of character," says Fred Turek, a
sleep researcher at Northwestern University
and director of the Center of Sleep &
Circadian Biology. "Now I believe that if
you interfere with sleep, you're interfering
with weight. If you interfere with weight,
you're interfering with sleep."
The Nurses' Health Study, an epidemiologic
study begun in 1976 monitoring the health
of more than 100,000 nurses, put poundage
to sleep loss. In a study reported in the
Aug. 16, 2006, issue of the American Journal
of Epidemiology, researchers found that after
12 to 16 years, women who slept, on average,
less than five hours per night were 5 1/2
pounds heavier than those who slept an average
of seven hours nightly.
The resting heart
The brain controls a lot, but the ever-beating
heart needs sleep too. During the night, the
heart gets a break. Most people experience
a 20% to 30% reduction in blood pressure,
and a 10% to 20% drop in heart rate when they're
asleep, according to 24-hour blood pressure
studies of more than 5,000 people by Dr. William
White at the University of Connecticut Health
Center.
Sleep is so important for the heart that,
in a study published in the Aug. 2 issue of
the journal Sleep, researcher Dr. Daniel J.
Gottlieb of Boston University School of Medicine
suggested that a good night's sleep should
be tested as a nonpharmacologic treatment
in managing high blood pressure. He questioned
more than 5,000 men and women ages 40 to 100
on their sleep habits and found that people
sleeping less than six hours had as much as
a 66% greater prevalence of hypertension.
"Sleep is good for your heart," says Dr. Virend
Somers, a cardiologist and sleep researcher
at the Mayo Clinic. "I think physicians should
always address the question of sleep with
their patients. That's particularly true if
they have cardiovascular diseases that are
not responding well to treatment."
Those most at risk for heart disease because
of sleep problems are people with apnea, a
disorder in which airways are obstructed and
the person wakes up, sometimes hundreds of
times a night, snoring and gasping for air.
The sleeper, often unaware of waking, breathes
harder and faster during the episodes, and
blood pressure and heart rate surge. Sleep
apnea puts people at higher risk of heart
attack and stroke, in part because their cardiovascular
system doesn't get its nightly dose of an
easier workload.
A good night's sleep also can stave off short-term
illness such as colds and flu, as well as
hasten the benefits of a flu shot.
In a study reported in the Sept. 25, 2002,
Journal of the American Medical Assn., 25
healthy young men, who normally slept 7.5
to 8.5 hours each night, received flu shots.
Eleven of the men were vaccinated on the fourth
of five days in which their sleep was restricted
to four hours, while the others got their
usual nights' sleep. Ten days later, blood
tests showed that those who got the shots
while sleep deprived had less than half the
protective benefits as those who slept normally.
The immune response to the vaccine of sleep-deprived
volunteers didn't catch up with that of the
well-rested subjects for more than three weeks.
Even some cancers might be rooted in sleep
deprivation — or, more precisely, to
too many hours exposed to artificial light,
according to Richard G. Stevens, cancer researcher
at the University of Connecticut Health Center.
His work is based on the theory that the increase
in breast cancer in the industrialized world
is linked to the disruption of hormone cycles.
Light, he says, suppresses production of the
hormone melatonin, which allows levels of
estrogen to rise. And, when lights are on
long after dark, it confuses women's circadian
clocks, the roughly 24-hour internal rhythm
that keeps hormones and organs on their daily
schedule. "Cells don't know when not to divide,"
he says.
His theory was bolstered by a 1991 Centers
for Disease Control and Prevention report
showing that blind women are about half as
likely as sighted women to get breast cancer.
An Oct. 15, 2005, study in Cancer Research
looked at sleep patterns of more than 12,000
women. Although researchers found no statistically
significant increase in cancer risk among
short sleepers, says Stevens, an author of
the study, the risk estimates were consistently
lower in long sleepers.
"We don't know why breast cancer is increasing
in industrialized societies," he says. Until
more is known, he advises women to get adequate
sleep — and to do it in a very dark
room.
It's essential
Adequate sleep may be essential for good
health but it's every bit as hard to pull
off as eating a healthy, well-balanced diet
or finding an hour a day to exercise.
"The most common sleep disorder is insufficient
sleep," says Dr. Dennis Nicholson, director
of the Pomona Valley Hospital Medical Center's
Sleep Disorders Center. "People come in and
say they're sleepy. It's because they're not
getting enough sleep." The connection seems
like a no-brainer, but many people don't see
it, he says. They want a sleep study and a
pill.
Just as Americans can lay part of the blame
for their eating patterns on the food processing
industry, and part of the blame for their
sedentary lifestyle on unwalkable suburbs
and sprawling cities, part of the blame for
not quite enough sleep lies with congested
highways and homes located far from work.
The University of Pennsylvania's Dinges studied
numbers from the U.S. Department of Labor's
American Time Use Survey, conducted in 2003,
to find what Americans were doing instead
of sleeping. He thought that, after time spent
working, the next biggest temptation would
come from television, computers and entertainment.
Not so. "Here's the big surprise. The more
time you spend in the car, for any reason,
the less you sleep," Dinges said.
Someone who spends a total of 40 minutes in
the car each day — that's a round-trip
commute plus all daily car errands —
gets a good seven to eight hours of sleep.
He reported those unpublished findings at
the June meeting of Associated Professional
Sleep Societies. And he found that for each
eight minutes in the car beyond that, sleep
time drops by about 15 minutes.
So if a long commute, traffic congestion or
a lot of short trips to pick up kids or take
dogs to the vet adds just 15 minutes of travel
time to that 40 minutes, it means half an
hour less sleep. Commuters in the counties
of Los Angeles, Ventura, Orange, Riverside
and San Bernardino are chalking up hundreds
of millions of miles each day on freeways
and highways that cover 7,200 miles. It's
safe to assume there are a lot of sleep-deprived
drivers on the road.
One of them is costume designer Deena Appell,
43, of West Los Angeles. Her day can start
with the alarm going off at 4:30 a.m. and
take her from one end of the county to the
other in a never-ending quest for the perfect
shirt, skirt or accessory for characters in
a TV series or film. For months at a time,
including work on weekends, she might drop
into bed around 11 p.m., only to be startled
awake 5 1/2 hours later to start all over
again.
Appell knows her schedule takes a mental toll.
"You really do feel a diminished capacity,
like your brain has literally been suctioned
out of your head," she says. "And it's not
just at night. You're mesmerized by the traffic.
I've nodded off at lights, and suddenly you're
rolling into the car in front of you. It's
not a bad accident. You're just dazed."
The National Highway Traffic Safety Administration
estimates that 100,000 accidents and 1,500
traffic fatalities annually are caused by
drowsy driving, far more than those attributed
to cellphone use. "Those are the people who
are driving next to you and me," says Nicholson.
Sleeplessness is a safety issue and a health
problem. "Sleep is as important as breathing,
drinking and eating," says Dr. Meir Kryger,
a sleep scientist at the University of Manitoba.
"Animals who are deprived of sleep die, but
they don't die because their memory is poor.
They die a metabolic death: Their fur falls
out, they lose weight. Things that happen
are over and above just the brain being sleepy.
It's critical to health, but it takes longer
to notice."
