Rest Assured: The Sleep Proccess

There is a time for many words, and there is also a time for sleep. — Homer (800 BC-700 BC)

We think of sleep as such a simple thing. We go to bed, we sleep, and seem to lose consciousness until the alarm sounds and we awaken. Ancient civilizations must have perceived some of the importance of sleep since we know the Greeks considered one of their lesser gods to be the god of sleep, Hypnos (also known as Somnus to the Romans), twin brother of Thanatos, god of nonviolent death.¹ One of the sons of the god of sleep was Morpheus (the god of dreams) and the other two, Phantasus and Icelus, were gods responsible for dreams of inanimate objects and animals respectively.¹ Would that it were so simple that we could assign responsibility for sleep to a few lesser deities. Sleep, however, is a far more elaborate system involving much more than just physical rest and replenishment of energy. Optimal performance, mood, and physical and mental well-being are dependent upon good, quality sleep.² Further, it has been hypothesized that dreams may be an intricate process of interpreting and reorganizing the various material accumulated in our memories during waking hours.³

Sleep is thought by some⁴ to be a time of increased metabolic activity in the brain during which the body repairs the central nervous system and other tissues. The sleep/wakefulness cycle follows a circadian rhythm and is controlled by an area of the hypothalamus that is responsive to the light vs. dark cycle.⁵

It is the prefrontal cortex (PFC) that is especially vulnerable to a lack of sleep.⁶ All of the functions of the PFC are not known, but a primary function is the maintenance of wakefulness and the "recruitment" of other cortical areas to accomplish tasks.^6,7,8,9 During sleep, the PFC, that place where most wakeful brainwork is accomplished, has its lowest period of activity during human slow-wave sleep (hSWS).⁶ It has also been shown in at least one study that women have more hSWS than men and a higher rate of metabolic activity in the PFC.⁶

Low levels of hSWS are present during depression, retardation, and stress, though it is not clear if the underlying reasons are the same or different.6 What does seem to be apparent is that hSWS is particularly important in protecting the body from psychiatric disorders and pathological aging.⁶ Moderate to severe insomnia is thought to be strongly related to mental and physical health problems¹⁰ with sleep disorders possibly considered an early symptom of major depression.^11,12 Some authors even suppose that the treatment or elimination of sleep disorders may prevent the development of a full major depression.¹¹

Insufficient or nonrestorative sleep is thought to affect somewhere between 10 and 35 percent of the general population.² Despite the finding that women seem to have more hSWS than men, women tend to report more sleep disturbances than men.^13,14 A review of all sleep disorders is beyond the scope of this review, but included here will be brief discussions of those considered to be the most common as well as changes to be expected in the normal course of aging. Insomnia, sleep apnea, restless legs syndrome, and (in the case of women) hot flushes will be addressed as well as recommendations for a better night's sleep.

Insomnia

Everyone has trouble getting to sleep from time to time. We get too jazzed up at work, we forget it's nearly 5 p.m. and have a cup of high-test coffee, or Hypnos just refuses to pay his nightly visit! But if sleep is not satisfying or doesn't last long enough to be restive, it may be classified as insomnia. One or more of the following symptoms are signs of insomnia: difficulty falling asleep, waking up often during the night and having trouble going back to sleep, waking up too early, and unrefreshing sleep.¹⁵

Several factors influence the miracle called sleep: hormonal fluctuation, drugs, alcohol, stress, smoking, and worrisome events. In one study controlled for PMS symptoms such as irritability, tearfulness, bloatedness, and/or painful periods, sleep quality was significantly impaired during the premenstrual and menstrual phases.² Not only do hormonal changes affect sleep, but urinary frequency during this time disrupts slumber as well.¹⁶ In the Baker and Driver study, women experienced poorer quality sleep three days prior to their period and during the first four days of the menstrual period.¹⁶ Estrogen was found to decrease rapid eye movement (REM) sleep during which dreaming occurs (as mentioned above, a process that may help us make sense of the chaos of life).¹⁶ Decreased REM time results in irritability for both men and women.¹⁶ Exogenous administration of progesterone, however, has been found to have a sedating effect in both sexes.^17,18

For the pregnant woman, sleep becomes even more complicated. The circadian rhythms of many hormones aside (e.g., growth hormone, prolactin, thyroid stimulating hormone, cortisol, and placental hormones), uterine activity is linked to maternal secretions of steroids, oxytocin, and melatonin (a hormone made by the pineal gland in the brain and activated by the light/dark cycle).¹⁹ This fluctuation in hormones is probably the primary contributory element to insomnia in the third trimester of pregnancy.

Drugs and alcohol are frequently used by insomniacs to assist in falling asleep, but, in the long run, they have deleterious effects. Current smokers experience "lighter" sleep (waking easier) than either ex-smokers or never smokers.²⁰ Many drugs used for insomnia either become habit-forming or lose effectiveness over time, while self-medicating with alcohol may exacerbate insomnia.²¹ Of similar concern is the possibility of insomnia-related alcoholism. The majority of patients entering treatment for alcoholism report symptoms of insomnia, and baseline insomnia continues to be a predictor of relapse into alcoholism for recovering alcoholics.²¹ Referring back to the previous discussion of sleep as it relates to mental health, the levels of severity of alcohol dependence and depression are both significantly related to insomnia.²¹

There is a strong association between family or work stress and trouble sleeping plus associated psychological symptoms.²² Trouble sleeping understandably often correlates with general somatic symptoms (like arthritis and diabetes),²² but 50 percent of those with major depressive disorders report difficulty sleeping.²³ Another way of expressing this phenomenon is that chronic insomniacs have significantly higher rates of major depression and anxiety disorder.¹¹ Putting it even more dramatically, persons with uncomplicated insomnia (not associated with physical illness) are four-and-a-half times more likely to have had depression in the past year and five times more likely to have had panic attacks than those without sleep problems or other psychiatric disorders.

When comparing women and men, women seem to experience insomnia of shorter duration than men but have more frequent episodes.¹¹ Whether short duration or long, sleep deprivation takes its toll. A deprivation of less than five hours in a 24-hour period results in a considerable overall impact on cognitive tasks and mood.²⁴ Sleep-deprived individuals perform at a significantly lower level in a motor and cognitive sense than those who are not sleep deprived, and the type of deprivation does not seem to make a difference.²⁴ In fact, partial sleep deprivation (less than five hours in a 24-hour period) may have a greater impact than a longer term of deprivation (45 hours or more), the least effect noticeable with motor tasks and the greatest effect with cognitive tasks and mood.²⁴

Sleep apnea and sleep-disordered breathing

Sleep apnea is characterized by snoring, daytime sleepiness, and periods during sleep when the sufferer may cease to breathe for 10 seconds or more.²⁵ Under the general medical umbrella of sleep-disordered breathing, sleep apnea patients are predominantly older males^25,26, but the disorder may also be found in younger populations^27,28 as well as obese and pregnant women.²⁶ Many sleep apnea patients (78 percent) have a noted inability to concentrate during the day, while 48 percent appear to suffer personality changes.²⁵ Smoking seems to be the most powerful risk factor for sleep apnea in the general population.²⁶

Sleep-disordered breathing (SDB) as a diagnosis is characterized by the simultaneous presence of frequent awakening, headache, and depression.²⁶ Relatively rare in postmenopausal women,²⁹ SDB should nevertheless be suspected if a woman displays the above symptoms in the presence of obesity since, in women, it is thought to be due to the accumulation of adipose tissue in the upper body,²⁶ a common consequence of postmenopausal body changes. In the pregnant woman, however, snoring and SDB symptoms are an even greater concern. These symptoms may signal an upper respiratory obstruction with a net effect of less oxygen in the blood and possible stress to the fetus.¹⁶

The treatments for sleep apnea can be as simple as losing weight or as complicated as upper airway surgery.^23,30,31 Other suggestions include avoiding respiratory depressants like alcohol and hypnotics and the possible use of nasal continuous positive airway pressure in extreme cases.²³

Abnormal leg movements

Periodic limb movement disorder (PLMD) and restless legs syndrome (RLS) are two sleep disorders that affect women more than men.³² PLMD, also referred to as nocturnal myoclonus, is thought to occur in approximately 3.9 percent of the general population and is characterized by involuntary leg movements during sleep.³² RLS, on the other hand, is described as disagreeable leg sensations that provoke an urge to move the legs and occur while awake, at the onset of sleep.³² Those who suffer from RLS are thought to comprise about 5.5 percent of the population and usually also experience PLMD.³² Factors that predispose individuals to PLMD and RLS are summarized in Tables 1 and 2.

Both PLMD and RLS are also associated with the presence of some musculoskeletal diseases, sleep apnea, mental disorders, and physical activity close to bedtime.³² But it may be noted that many of the predisposing factors of both PLMD and RLS are also related to insomnia and/or sleep apnea. Thus it may be difficult to separate the causative effects of one from the other.

Vasomotor symptoms

Hot flushes (also referred to as hot flashes) may not, in the strictest sense, be considered a sleep disorder, but any woman who has ever had the experience will admit they are a sleep disturbance, thus justifying their inclusion in this discussion. Those who experience an early menopause or who have had a hysterectomy seem to have an increased incidence of hot flashes.²² Women in these two categories also seem to have an increase in other somatic symptoms that may affect sleep such as "crawling skin," palpitations, headaches, and general aches and pains, though these same symptoms also seem to be present at varying frequencies during a natural, later transition to menopause.²² Other predisposing factors for vasomotor episodes are summarized in Table 3.

Oddly enough, as noted in Table 3, the study by Kuh et al. found that women who elect to participate in hormone replacement therapy (HRT) are at a higher risk for vasomotor symptoms, trouble sleeping, general aches and pains, and psychological symptoms²² ... some of the very issues that HRT is supposed to ameliorate.

For those women reading this article who have not previously been informed of the other risks of HRT, a 2002 study published in the Journal of the American Medical Association indicated that there were more harmful than beneficial results of an estrogen/progestin HRT.³³ Clinical trials in this study were prematurely halted due to increased adverse effects; e.g., breast cancer, stroke, pulmonary embolism.³³ Results from an estrogen-alone study will be available in 2005.³⁴ Nevertheless, a woman's decision to participate in HRT should be a very personal one, carefully weighing the sometimes severe symptoms of menopause and quality of life against the risks of HRT.

Sleeping as affected by age

As we age, we need not be so troubled by the thought of the inevitability of decline.²⁵ Bliwise makes a distinction between normal as opposed to "successful" aging.²⁵ Successful aging, he asserts, is an optimization of our biopsychosocial functioning beyond the limits of our genetic inheritance and our environment.²⁵ If the gentle reader will allow this digression, I hold up my 95-year-old Aunt Frieda (my greatest role model) as an example of Bliwise's assertion. She lives in an apartment building, makes new friends as residents come and go, prepares meals for those who are ill, stays active with social causes (sometimes of her own invention), stays mentally active with TV news and books-on-tape (macular degeneration halted her voracious reading), and fiercely insists on staying as independent as possible. Recently, I was concerned about her since she was hospitalized for the second time in her life; the first was for a hysterectomy when she was 17 years old. My family and I made the six-hour drive, anticipating that it might be the last time we were graced by her loving manner and sharp wit. By the time we arrived, however, she had fired two doctors and was feeling much better. Still, Aunt Frieda occasionally has trouble sleeping (perhaps the coffee or the Merlot).

Insomnia is the most common sleep disturbance in older (greater than 60 years) adults³⁵, but studies disagree on the predominance of which sex. Redline²⁰ found that increased age was more associated with impaired sleep in men (especially African-American and American Indian men), while Cricco et al.³⁵ observed more women reporting sleep disturbances. Other differences are notable, especially in the case of insomnia as it relates to cognition. Horne⁶ found that human slow-wave sleep (hSWS), that which is more restful and restoring, significantly diminishes during the aging process. Chronic insomnia carries with it a significant loss of hSWS and may independently predict a cognitive decline in men older than 65 years.³⁵ In contrast, a cognitive decline in women is only associated with insomnia when it is comorbid with high levels of depressive symptoms.³⁵

Aging and its often accompanying physical decline frequently carries with it another risk for sleep disturbances. The treatment of medical disorders in and of themselves can result in disturbances of sleep.²³ Confinement to bed can encourage extensive napping, making sleep difficult at night, and many medications, depending upon the patient's genetic signature, have disturbed sleep patterns as a consequence.²³ It is thus recommended that the elderly remain as physically active as health permits to combat not only illness but the effects of inactivity on restful sleep.²³

Treatment

As our lives become more complicated and stressful, the treatment of sleep disturbances may become more commonplace. Suggested remedies are summarized in Table 4, some familiar and some bearing elaboration.

Limiting caffeine intake is not new, but what is surprising is that the half-life of caffeine's effect on the body is three to seven hours.³⁶ Drinking only one to two cups of regular coffee in the morning has the propensity for disturbing the soundness of sleep during the subsequent night.³⁷

Physical fitness (particularly aerobic fitness) has been shown to improve the quality of sleep²³, but not within three hours of one's anticipated bedtime.

Limiting time in bed may sound self-explanatory, but many people use time in bed to watch TV, do paperwork, or just escape the chaos of an active home. If sleep disturbances are a problem, restricting time in bed to sleep or meditation may help.³⁸

Finally, in the case of the elderly, spending time in bright, outdoor light; staying socially active with clubs or religious involvement; and having a close friend were all associated with better-quality sleep.^39,40

Summary

Normal, uncomplicated, and restful sleep is a vital part of our lives. Without it, there is an increased incidence of depression,^6,10,22 alcoholism,²¹ dementia,^6,35 automobile accidents, and falling due to loss of balance.⁴¹ As women, we tend to focus our attention on the health and welfare of others, sacrificing our own rest and well-being. As women dentists, we often subject ourselves to the stresses of running a business, taking on the problems of our patients (and their resultant solutions), as well as trying to be superwomen by juggling business, family, and personal issues. Perhaps it is time to "wake up" and slow down. Take time to smell the roses, walk with a friend or family member, meditate on well-being, or just "be." We're worth it! To sleep: perchance to dream — Shakespeare: Hamlet

Judith A. Porter, DDS, MA, EdD
Dr. Porter, a general dentist, has built two solo practices during her career, taking time off in between to raise her children. She obtained a master's in secondary education in 1999 and an EdD in 2003. She is currently on the faculty at the University of Maryland Dental School.

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