Heavy sleep debt extracts a price for patients

An excerpt from The Twenty-Four Hour Mind: The Role of Sleep and Dreaming in Our Emotional Lives.

by Rosalind D. Cartwright, PhD

We live in a culture that values speed; fast foods, fast cars, fast service, and fast decisions.

All of this takes a toll.  Fast food is blamed for the epidemic of obesity, fast cars for motor vehicle accidents, and the wish for fast service and decisions for an increase in the general level of frustration when we are inevitably put on hold.  This “hurry up” lifestyle also has an impact on sleep – it has notably shortened the number of hours we as a society devote to it.  When sleep experts speak to general audiences, one question they are often asked is, “How can I spend less time sleeping?”  Those who ask this question tell us that sleep is a waste of time.  Not only is that notion wrong, but the attitude behind it is largely responsible for the increase of several major public health problems.

We now turn to those whose short number of sleep hours is troubling enough for them that they seek professional help.  This is not the case for all short sleepers; some manage to live productive lives and make significant contributions to society.  These are the ones who occupy the extreme left-hand tail of a normal distribution of average hours of sleep needed to feel rested.  Most of us will fall in the middle of that curve, needing between 7 and 9 hours, with an average close to 8.  Short sleepers average 5.5 hours.  Very few people are truly physiologically and psychologically healthy with only 5 hours of sleep on a nightly basis.  Those who, as adults, were 8-hour sleepers but can no longer get that much sleep are in trouble.  Some cannot get to sleep without a prolonged struggle, while others get to sleep but wake repeatedly.  Then there are those who wake too early and cannot get back to sleep.  Insomnia is a useful model to test the contribution of sleep to keeping us healthy in mind and body.

What is the definition of “short sleep”?  Sleep experts are reluctant to answer this question by giving a specific number of hours.  As noted, there is just too much variability among individuals in the amount of sleep it takes for them to accomplish the “rest and restoration” functions of sleep.  When we are getting “enough” sleep, we wake up feeling physically refreshed, in a reasonably good mood, and able to function well throughout the day without undue sleepiness.  All of us experience a down time around mid-afternoon, called the “circadian dip,” or sometimes known by the more colorful name, “circadian slump.”  This is when our internal body temperature drops, bringing on a natural tendency to feel sleepy enough for a midday siesta.  If you can get through this without falling asleep at your desk or in your car and then feel all right for the rest of the day, your number of sleep hours is right for you.

Another indicator of how much sleep is enough is the number of hours we sleep when sleep is unscheduled – that is, when we need not wake up at a set time, like on weekends and vacations.  Since we tend to go to bed later under these circumstances we also tend to sleep later, so it is not the hour at which we wake that makes the difference but how many hours we sleep when we can take our time.  If you sleep 2 or 3 hours more on weekend nights than you do during weeknights, you are probably not getting enough sleep on a regular basis.  This is what Bill Dement calls running a “sleep debt,” and this debt mus be paid back by extending your regular sleep schedule or by including some daytime naps.

A trend among American adults is to sleep fewer hours a night during the work week and to play catch-up on the weekends.  This is proof that many who report they are short sleepers actually can sleep longer, but do not by choice.  According to information about our sleep habits gathered periodically by the Centers for Disease Control and Prevention, the old 8-hour national average per night has dropped to 7.  Evidence that this is a real problem can be found in the push to develop new drugs to treat sleep troubles.  In addition to new sleeping pills, we now see new “stay awake” pills marketed to help keep us going even longer, to work more hours without experiencing a drop in the quality of our job performance.  For those who suffer from a neurological problem such as narcolepsy, one symptom of which is sudden abrupt sleep episodes that come without warning, these medications are a life-altering boon.  But for those who are healthy, the cost to our health of working longer hours by sleeping less is not worth the benefit.

Another alarming trend we see now is the misuse by adolescents and young adults of “stay-awake” prescription medications such as Ritalin, Adderall, and modafinil originally developed to treat attention-deficit hyperactivity disorder (ADHD).  More and more frequently these drugs are being used by young people to increase their focused attention.  Is this harmful?  Yes, if it interferes with the ability to get enough sleep, and for sure if the drug was not prescribed but is “borrowed” from someone else.

Some who sleep 6 or fewer hours argue that this is not by choice but by economic necessity, the result of having to work two jobs.  Data show that the use of stay-awake medicine is strongly related to shift work.  Daytime sleep is shorter and lighter than nighttime sleep and so less refreshing.  Those who report using stay-awake medications point out that there is simply too much to do in a 16-hour day, and that an 8-hour night is luxury they can no longer afford.  The economic need may be real but the price we pay for such a heavy sleep debt should be better understood.  It is especially important for physicians to understand the risks involved in aiding their patients to reduce sleep hours with a prescription, and it is up to sleep experts to offer some sensible alternatives.

Rosalind D. Cartwright  is Professor Emeritus of Rush University Medical Center’s Graduate College Neuroscience Division and author of The Twenty-Four Hour Mind: The Role of Sleep and Dreaming in Our Emotional Lives. This post originally appeared in the Oxford University Press blog.

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