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Nutrition LetterT H E F R I E D M A N S C H O O L O F N U T R I T I O N S C I E N C E A N O P O L I C Y

YOUR GUIDE TO LIVING HEALTHIER LONGER • OCTOBER 2004

And to All a Good Night: How SleepDeprivation May Lead to Chronic Disease

Yo u KNOW all too well what it feels like to missout on a full night's sleep: you're groggy, perhapscranky, your reaction time is slow, and you justcan't think straight. But the effects of sleeplessnessare not just limited to your brain. New research is

pointing to some potentially alarming links between sleepdeprivation and the development of serious health conditionsthat plague tens of millions of Americans: heart disease,obesity, and diabetes among them. Indeed, William Dement,MD, one of the world's most renowned sleep researchers andcofounder of the Stanford University Sleep Disorders Clinic,notes in his book. The Promise of Sleep, "there is plenty ofcompelling evidence supporting the argument that sleep is

the most important predictor of howlong you will live, perhaps moreimportant than whether you smoke,exercise, or have high blood pressureor cholesterol levels."

Sleep deprivation is epidemic."While we used to average 10 hours ofsleep a night, that number has beendwindling since the invention of thelight bulb more than 100 years ago.According to a "Sleep in America"poll taken a few years ago, nearly twothirds of adults in this country do notget the 8 hours of nightly sleep thatthe National Sleep Eoundation says isneeded for optimal health, safety, andperformance. Nearly one in threereport sleeping fewer than 7 hourseach weeknight.

Researchers are still trying to learnexactly why chronic sleep deprivationmay increase the risk for developing

various diseases. The key is probablyconnected to the effect of sleep dura-tion on vital functions that take placein the body during slumber. Someresearchers theorize that sleep is acritical time for the body to heal andrepair damage, and that diminishedsleep prevents this repair, thus leadingto a breakdown in processes essentialto health. Others point to substantialphysiologic changes that occur duringsleep, such as fluctuations in bloodpressure and changes in hormonesecretions. When the body lacks sleep,the effects of these natural fluctua-tions may be exacerbated, making itdifficult for the body to bounce backto normal. Over a long period of time,those interruptions in proper function-ing might finally push various systemsof the body into disease states. Hereare some of the most recent findings.

TIRED HEARTA recent report from Harvard foundthat women who consistently sleptjust 6 hours a night had an 18 percentgreater risk for a heart attack thanwomen who slept the recommended8 hours. For women who slept 5 orfewer hours per night, the risk for suf-fering a heart attack jumped to 39percent. (Sleeping extra hours was nota benefit, either. Women who slept 9or more hours nightly also increasedtheir heart attack risk.)

The report, part of the ongoingNurses' Health Study, was notable dueto its size and duration, providing sur-vey information on the sleeping habitsand cardiac problems of some 70,000women over a 10-year period.

Why would sleeping too little be apotential trigger for heart attacks, orfor heart disease in general?

Consider that your body experiencesmany changes not just between sleep-ing and waking but also within thevarious sleep cycles. Eor instance, dur-ing the active, or rapid-eye-movement(REM) phase of sleep, your bloodpressure increases and your heartbeats faster. And right before youawaken, a cocktail of stress hor-mones, such as adrenaline and corti-sol, all pour into your bloodstream.

Eor people who have some type ofheart disease or underlying risk factorlike hypertension, such fluctuationsmay create some stress on the hearteven if they are well rested. However,when you are sleep-deprived, the stresscould be even greater. During truncated

sleep, your heart might have to workharder, constricting blood vessels andincreasing blood pressure even more,which could conceivably result in aheart attack (or stroke).

For the estimated 18 million Amer-icans with sleep apnea, a condition inwhich the airway is obstructed duringsleep and breathing stops severaltimes during the night, the risk forsleep-related heart problems appearsparticularly critical. When the brainis deprived of oxygen during thosemoments that breathing stops, itsends a signal to the body to hyper-ventilate to obtain the necessary oxy-gen. That causes the sleeper tobreathe harder and faster. Every timethat happens, blood pressure andheart rate surge. The process may

occur dozens, or even hundreds, oftimes a night, eventually causingenough cat'diovascular damage topave the way for a heart attack orother heart-related event.

DIABETES CONNECTIONThought to afflict an estimated 17million Americans, diabetes, whichcan greatly increase the risk for vascu-lar diseases, is characterized by exces-sive levels of sugar in the blood. Andsome research has suggested that alack of sleep may play into it.

When University of Chicago re-searchers subjected a small group ofyoung men to 4 hours of sleep a nightfor six nights, they found that theirblood sugar, or glucose, shot up muchhigher after breakfast than when they

To Sleep, Perchance to Dream (During the REM Stage)

There are five stages of sleep. Four are non-REM (Rapid Eye Movement) stages, and one isREM. Throughout the night, a sleeper cycles through the non-REM, then the REM, stages,until awakening in the moming, usually completing four to five Vh- to 2-hour cycles.

Non-REM Stage 1 : This is the light, drowsy, "twilight zone" hetween sleeping andwaking. Your brain waves become more relaxed, and you begin slow, rolling eye move-ments. If you are awakened during this stage, you might not even think you were sleeping.This stage lasts about 10 minutes.

Non-REM Stage 2 : This is the first stage of "true" sleep time. It's a deeper stage ofrelaxation than stage 1 but is still considered light sleep, during which a person may easilybe woken. It lasts about 30 minutes per sleep cycle.

Non-REM Stages 3 a n d 4 : Also known as slow wave sleep, these stages representa state of profound relaxation and are relatively unresponsive to stimuli. During stages 3 and4, heartbeat and respiration slow, and the muscles relax. It is also during these stages thatgrowth hormone is produced to stimulate growth in children and help heal injured body tis-sues and regulate fat and muscle distribution in adults. These stages, combined, generallylast 40 to 50 minutes per cycle, although the amount of time depends on age. Children mayspend up to an hour in this stage, while some adults may spend just a few minutes.

REM Sleep: While non-REM sleep is quiet, REM sleep, when most dreaming occurs, isquite active. The eyes twitch and dart behind closed eyelids, heart rate and breathingbecome more irregular, and oxygen consumption increases, as do blood flow to the brainand brain temperature. Muscles are also temporarily paralyzed during this stage, perhapsas a way to let the mind explore active dreams without the body following suit. It is duringREM sleep, which lasts 10 to 25 minutes per cycle, that breathing becomes irregular, attimes spiking-a potential trigger for heart attacks in those who have underlying heart prob-lems. Males of all ages experience erections during REM sleep, and females experience cli-toral engorgement and vaginal lubrication.

had an adequate night's sleep. Andtheir secretion of insulin, the hormonethat allows sugar to be removed fromthe blood, slowed down, such that therate at which sugar cleared from theblood was nearly 40 percent slowerwhen the men weren't getting enoughsleep. The changes were severe enoughthat the men's elevated blood sugarlevels were typical of people who haveimpaired glucose tolerance—a gray-area condition that falls between"normal" and a diagnosis of diabetes(and is often a precursor to diabetes).

Granted, most people do not get byon only 4 hours of sleep a night, nightafter night. But even what many peopleconsider a decent night's sleep mightnot be enough to sufficiently clear sugarfrom the bloodstream. The Chicagoresearchers made the finding when theymonitored men for three days duringwhich they slept a little more than 7hours a night. On those days, the rhenhad higher levels in the afternoon of thehormone cortisol than when they sleptlonger. Elevated cortisol levels may beinvolved in elevated blood sugar levels(as well as memory impairment).

Diabetes wasn't the only potentialconcern the researchers came across.Differences also showed up in the men'snervous systems and thyroid hormoneconcentrations, rhaking them look, onlab tests, decades older than they actu-ally were. The alterations in the men'ssystems were "striking," the research-ers say. In a separate study, eventhough the men tested ranged in agefrom 27 to 42, on certain blood workthey seemed more like 61-year-olds.

Researchers at other institutionshave also noted a possible connectionbetween sleep deprivation and hormone-mediated conditions, diabetes included.Last year, the same Nurses' HealthStudy that reported a link between sleepdeprivation and heart attacks also foundthat women who reported significantlyshort (or long) nightly sleeping pat-terns were more likely to develop dia-betes than women who slept close to8 hours a night.

None of this means that if you don'tget enough sleep occasionally, you'regoing to end up with permanently

Continued on back page

Did voii know.. I carbohydrate, fat, and protein that we eat must pass from the stomach to the small Intestine hefore heing ahsorhed into the bloodstream. But about 20 pe

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Continued from second pagehigh blood sugar or some other med-ical condition. In the Chicago research,the men's levels of blood sugar andinsulin returned to normal when theycaught up on lost sleep. But the moreyou go without adequate sleep, theharder it becomes to make it up. Thus,a chronic lack of sleep, even just anhour or two a night, may make youmore vulnerable to certain conditionsas the years pass.

SLEEP AND IMMUNITYEveryone has had the experience offeeling "run down" from a lack ofsleep and, shortly thereafter, gettingsick. It doesn't appear to be a coinci-dence. There is strong evidence thatgetting enough sleep is imperative tokeeping your immune system in fight-ing shape. Conversely, your immunedefense will be increasingly compro-mised if you accumulate sleep debt.

Common sense dictates that losingsleep on a regular basis can make aperson feel lousy. But science is showingthat your immune system may startfaltering after even just one night ofpartial sleep loss. In a University ofCalifornia, San Diego, study, when 42healthy men were deprived of justpart of a single night's sleep, there was asignificant reduction in their immunecapabilities the next day. One set offighter immune cells that were critical-ly affected were "natural killer cells,"which are normally dispatched to attackwhen the body is invaded by viruses,or when cancer cells start to multiply.

The men's natural killer cells re-turned to their original strength andactivity after a night of recovery sleep,but other immune responses remainedsuppressed for a longer period of time.Since this study measured only onenight of sleep deprivation, it's impossi-ble to know the implications for peo-ple who are chronically sleep deprived.

What is known is that other smallstudies have corroborated the results ofthis one. Also, when people do developinfections, they often feel lethargic andcan do nothing but sleep. Perhaps it'snature's way of insuring that the bodygets the time and immune "resources"it needs to repair itself.

TOO LITTLE SLEEP,TOO MUCH WEIGHtA small but provocative body of re-search has demonstrated that peopledeprived of sleep end up with increasedappetites—and increased food con-sumption. For instance, in a study ofcollege students who had only 2V2 hourssleep for three nights and were also sub-jected to interrupted sleep on three othernights, all reported a greater appetite. Inanother study of young men who forseveral nights were deprived of REMsleep, during which people dream,some developed a marked increasein appetite, and a few even gained alittle weight.

The mechanism for the overeatinghas by no means been nailed down, butlevels of leptin, a hormone that helpsprovide a signal of satiety after eating,diminish when there's a lack of sleep.When leptin levels are low, carbohy-drates in particular seem to be cravedand over-consumed.

Another weight-related hormonethat diminishes in response to a lackof sleep is growth hormone. Growthhormone, its name notwithstanding,is critical to cell repair and healing inadults. But it also plays an importantrole in controlling the proportion offat and muscle in the body. It's secretedduring sleep in the REM cycle, whichis a deep stage of sleep that becomesharder to achieve for the necessarytime period as people age. Indeed, inone study that analyzed the sleep dataof 149 healthy men collected fromfour sleep laboratories, researchersfound that by the time most of themreached age 45, they could seldom fallinto a very deep sleep—and growthhormone production declined by about75 percent. (After menopause, womentend to get the same truncated amountof deep sleep.) Obviously, the all-too-typical middle-aged man's body cannotbe chalked up solely to a hormoneglitch stemming from a lack of sleep.But it could be a contributory factor.

There's more than hormones tosleep deprivation's possible effect onbody weight. Consider, for instance,that it takes more calories to beawake than asleep, since a person'senergy needs, even for turning a page

or answering the phone, are higherthan they are for lying still in bed.The body uses 10 to 15 percent morecalories during relaxation time thansleep time. The thing is, research hasshown that people compensate fortheir extra awake time by increasingtheir caloric consumption by greaterthan 15 percent.

Why? Allan Rechtschaffen, PhD, aUniversity of Chicago professor andone of the country's foremost sleepresearchers, has said that perhaps it'sbecause going on too little sleep cre-ates a kind of boredom, or tedium,that people try to dispel with eating,which doesn't take much concentra-tion or energy. Then, too, people whodon't get enough sleep may lose verysmall amounts of body heat andtherefore need to take in more energy(calories) to keep up their core tem-peratures. Simply put, overeating inthe face of a lack of sleep could be acorrection for a failure in heat regula-tion. (The effect has been particularlydramatic in lab animals.)

Finally, losing sleep may increasethe body's temperature setpoint. Thatis, even while a sleep-deprived personis losing body heat, his or her body"thermostat" might be adjustedupward so that more fuel (food) thanbefore is necessary to jack up the tem-perature to the new "setting."

Are you getting enough sleep?Although some people do in fact get afull night's sleep on a regular basis,there's a pretty good chance that you'repart of the yawning majority—andcould be setting yourself up for vulner-ability to some serious diseases, not tomention daily fatigue and inability tofunction at the top of your game.

That's true whether you're youngor old. A lot of older people automati-cally assume that they don't need asmuch deep, restful sleep as when theywere younger because their bodieswon't let them slumber as peacefully asformally. But it's not so. Older adultsneed as much good-quality sleep asyounger ones. For some tips on howto get and maintain more restorativesleep no matter what your age, turnback one page to our "Crib Sheet."

Did von know. More than 35 million pounds of candy corn will be produced this year, enough to add more than 16 million pounds to the national waistline.

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