Scientists Finding Out What Losing Sleep Does to a Body

[Guest guest]

By Rob Stein

With a good night's rest increasingly losing out to the Internet, e-mail,

late-night cable and other distractions of modern life, a growing body of

scientific evidence suggests that too little or erratic sleep may be taking

an unappreciated toll on Americans' health.

Beyond leaving people bleary-eyed, clutching a Starbucks cup and dozing off

at afternoon meetings, failing to get enough sleep or sleeping at odd hours

heightens the risk for a variety of major illnesses, including cancer, heart

disease, diabetes and obesity, recent studies indicate.

" We're shifting to a 24-hour-a-day, seven-day-a-week society, and as a

result we're increasingly not sleeping like we used to, " said Najib T. Ayas

of the University of British Columbia. " We're really only now starting to

understand how that is affecting health, and it appears to be significant. "

A large, new study, for example, provides the latest in a flurry of evidence

suggesting that the nation's obesity epidemic is being driven, at least in

part, by a corresponding decrease in the average number of hours that

Americans are sleeping, possibly by disrupting hormones that regulate

appetite. The analysis of a nationally representative sample of nearly

10,000 adults found that those between the ages of 32 and 49 who sleep less

than seven hours a night are significantly more likely to be obese.

The study follows a series of others that have found similar associations

with other illnesses, including several reports from the Harvard-run Nurses'

Health Study that has linked insufficient or irregular sleep to increased

risk for colon cancer, breast cancer, heart disease and diabetes. Other

research groups scattered around the country have subsequently found clues

that might explain the associations, indications that sleep disruption

affects crucial hormones and proteins that play roles in these diseases.

" There has been an avalanche of studies in this area. It's moving very

rapidly, " said Emmanuel Mignot of Stanford University, who wrote an

editorial accompanying the new obesity study in the October issue of the

journal Sleep. " People are starting to believe that there is an important

relationship between short sleep and all sorts of health problems. "

Not everyone agrees, with some experts arguing that any link between sleep

patterns and health problems appears weak at best and could easily be

explained by other factors.

" There are Chicken Little people running around saying that the sky is

falling because people are not sleeping enough, " said F. Kripke of

the University of California at San Diego. " But everyone knows that people

are getting healthier. Life expectancy has been increasing, and people are

healthier today than they were generations ago. "

Other researchers acknowledge that much more research is needed to prove

that the apparent associations are real, and to fully understand how sleep

disturbances may affect health. But they argue that the case is rapidly

getting stronger that sleep is an important factor in many of the biggest

killers.

" We have in our society this idea that you can just get by without sleep or

manipulate when you sleep without any consequences, " said Lawrence Epstein,

president of the American Academy of Sleep Medicine. " What we're finding is

that's just not true. "

While many aspects of sleep remain a mystery -- including exactly why we

sleep -- the picture that appears to be emerging is that not sleeping enough

or being awake in the wee hours runs counter to the body's internal clock,

throwing a host of basic bodily functions out of sync.

" Lack of sleep disrupts every physiologic function in the body, " said Eve

Van Cauter of the University of Chicago. " We have nothing in our biology

that allows us to adapt to this behavior. "

The amount of necessary sleep varies from person to person, with some

breezing through their days on just a few hours' slumber and others barely

functioning without a full 10 hours, experts say. But most people apparently

need between about seven and nine hours, with studies indicating that an

increased risk for disease starts to kick in when people get less than six

or seven, experts say.

Scientists have long known that sleep disorders, such as sleep apnea,

narcolepsy and chronic insomnia, can lead to serious health problems, and

that difficulty sleeping may be a red flag for a serious illness. But the

first clues that otherwise healthy people who do not get enough sleep or who

shift their sleep schedules because of work, family or lifestyle may be

endangering their health emerged from large epidemiological studies that

found people who slept the least appeared to be significantly more likely to

die.

" The strongest evidence out there right now is for the risk of overall

mortality, but we also see the association for a number of specific causes, "

said Sanjay R. Patel of Harvard Medical School, who led one of the studies,

involving more than 82,000 nurses, that found an increased risk of death

among those who slept less than six hours a night. " Now we're starting to

get insights into what's happening in the body when you don't get enough

sleep. "

Physiologic studies suggest that a sleep deficit may put the body into a

state of high alert, increasing the production of stress hormones and

driving up blood pressure, a major risk factor for heart attacks and

strokes. Moreover, people who are sleep-deprived have elevated levels of

substances in the blood that indicate a heightened state of inflammation in

the body, which has also recently emerged as a major risk factor for heart

disease, stroke, cancer and diabetes.

" Based on our findings, we believe that if you lose sleep that your body

needs, then you produce these inflammatory markers that on a chronic basis

can create low-grade inflammation and predispose you to cardiovascular

events and a shorter life span, " said andros N. Vgontzas of Pennsylvania

State University, who recently presented data at a scientific meeting

indicating that naps can help counter harmful effects of sleep loss.

Other studies have found that sleep influences the functioning of the lining

inside blood vessels, which could explain why people are most prone to heart

attacks and strokes during early morning hours.

" We've really only scratched the surface when it comes to understanding

what's going on regarding sleep and heart disease, " said Virend Somers of

the Mayo Clinic in Rochester, Minn. " I suspect as we understand more about

this relationship, we'll realize how important it really is. "

After several studies found that people who work at night appear unusually

prone to breast and colon cancer, researchers investigating the possible

explanation for this association found exposure to light at night reduces

levels of the hormone melatonin. Melatonin is believed to protect against

cancer by affecting levels of other hormones, such as estrogen.

" Melatonin can prevent tumor cells from growing -- it's cancer-protective, "

said Eva S. Schernhammer of Harvard Medical School, who has conducted a

series of studies on volunteers in sleep laboratories. " The theory is, if

you are exposed to light at night, on average you will produce less

melatonin, increasing your cancer risk. "

Other researchers are exploring a possible link to other malignancies,

including prostate cancer.

" There's absolutely no reason it should be limited to breast cancer, and it

wouldn't necessarily be restricted to people who work night shifts. People

with disrupted sleep or people who are up late at night or get up frequently

in the night could potentially have the same sort of effect, " said

of the University of Washington.

The newest study on obesity, from Columbia University, is just the latest to

find that adults who sleep the least appear to be the most likely to gain

weight and to become obese.

Other researchers have found that even mild sleep deprivation quickly

disrupts normal levels of the recently discovered hormones ghrelin and

leptin, which regulate appetite. That fits with the theory that humans may

be genetically wired to be awake at night only when they need to be

searching for food or fending off danger -- circumstances when they would

need to eat to have enough energy.

" The modern equivalence to that situation today may unfortunately be often

just a few steps to the refrigerator next door, " Mignot wrote in his

editorial.

In addition, studies show sleep-deprived people tend to develop problems

regulating their blood sugar, which may put them at increased risk for

diabetes.

" The research in this area is really just in its infancy, " Van Cauter said.

" This is really just the tip of the iceberg that has just begun to emerge. "