Rosalind D. Cartwright is Professor Emeritus of Rush University Medical Center’s Graduate College Neuroscience Division, and was chair of the College’s Department of Behavioral Sciences until 2008. In her new book, The Twenty-Four Hour Mind: The Role of Sleep and Dreaming in Our Emotional Lives, Cartwright brings together decades of research into the bizarre sleep disorders known as parasomnias to propose a new theory of how the human mind works consistently throughout waking and sleeping hours. In the excerpt below we learn how important it is to slow down and get the appropriate amount of sleep.
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.
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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 ci