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CHAPTER 23 SLEEP AND AGING

CHAPTER 23 SLEEP AND AGING
Practice of Geriatrics
CHAPTER 23 SLEEP AND AGING
Sonia Ancoli-Israel, Ph.D., and Daniel F. Kripke, M.D.
Pathophysiology
Clinical Assessment
Diseases—Diagnosis and Management
Sleep Problems in Patients with Dementia
Summary
With age, many changes occur in sleep. Older people sleep less deeply, wake up more frequently during the night, and awaken earlier in the morning. In the past it was thought that older people need less sleep because they are less active. However, research has shown that physiologic sleep durations in healthy elderly people are about the same as those in younger healthy adults, whereas time in bed is often longer. This chapter examines the sleep of elderly people—how sleep changes, why it changes, and the consequences of these changes.
PATHOPHYSIOLOGY
Sleep can be divided into two types: rapid eye movement (REM) sleep and non–rapid eye movement (NREM) sleep. NREM sleep is further subdivided into four stages: stages 1, 2, 3, and 4. Stage 1 is the very lightest level of sleep, whereas stage 4 is the deepest. Traditionally, polysomnograms using electroencephalography (EEG), eye movement (electro-oculography [EOG]), and electromyographic (EMG) tension of the chin muscles have been recorded.
During NREM sleep, eye movements are slow or absent, and there is a normal degree of muscle tension (Fig. 23-1). During REM sleep, which is the dream state, eye movements are rapid (thus giving rise to the name), and there is almost no muscle tension (Fig. 23-2). In fact, during REM sleep we are paralyzed except for the eyes and the respiratory system. This is a protective mechanism that keeps us from acting out our dreams. When people wake up from their dreams, they sometimes experience a feeling of paralysis, which usually lasts only a few moments and is normal.

Figure 23-1 Non-rapid eye movement (NREM) sleep. Chin muscle tension is high, and brain waves are slow in frequency and high in amplitude. EOG, electro-oculogram; EMG, electromyogram; EEG, electroencephalogram.

Figure 23-2 Rapid eye movement (REM) sleep. Chin muscle tension is very low, and brain waves are faster in frequency and lower in amplitude than during NREM sleep. EOG, electro-oculogram; EMG, electromyogram; EEG, electroencephalogram.

During the night we cycle through the different stages of sleep. As we get older, the pattern of the cycles begins to change (Fig. 23-3).1 Older people experience less sleep in stages 3 and 4 (i.e., deep sleep), less REM sleep, and more awakenings during the night.2 Sleep efficiency (defined as the amount of time asleep divided by the amount of time in bed) is reduced. In correspondence with poor nocturnal sleep efficiency, the number of naps taken during the day increases with age.

Figure 23-3 Normal sleep cycles. As we get older, it takes us longer to fall asleep and we have less deep sleep, more awakenings, and less REM sleep.

Multiple sleep latency tests indicate that older people are sleepy during the day (i.e., have a shortened sleep-onset latency).3 This suggests that it is not the need to sleep that is reduced in the elderly but rather the ability to sleep efficiently. This reduction in ability to sleep is secondary to many factors. Two of the main ones are changes in circadian rhythms and a high prevalence of sleep disorders such as sleep-disordered breathing (sleep apnea) and periodic limb movements in sleep.
CLINICAL ASSESSMENT
Using a carefully planned sequence of history-taking and all-night polygraphic recordings (polysomnograms), it is possible to provide specific etiologic diagnoses and treatment recommendations for the majority of patients with sleep complaints.
Evaluation begins with a complete sleep history. Whenever possible, it is important to interview the bed partner because he or she often notices problems in the patient’s sleep of which the patient is unaware. A sleep history includes questions about a typical night’s sleep, daytime functioning, and details of drug and alcohol use, as well as the medical history. Key data include the following:

1.
Time to bed and lights-out time. (Is it the same every night?) Many people with troubled sleep go to bed long before they turn out the lights.

2.
Sleep latency. (How long does it take to fall asleep?)

3.
Number and duration of awakenings during the night.

4.
Final awakening time.

5.
Weekday and weekend schedule. (Are times of waking up irregular?)

6.
Estimated time spent actually sleeping at night.
These data help to determine the person’s sleep pattern. It is often advisable to ask the patient to keep a sleep diary for several weeks prior to the interview to provide a reliable perspective and to help patients learn more about their own sleep patterns.
Other questions attempt to differentiate between specific sleep disorders such as sleep-disordered breathing and periodic limb movements in sleep. Does the patient snore, gasp for breath, stop breathing, or wake up confused (e.g., does he or she show signs of sleep-disordered breathing)? Does the patient kick repetitively or have restless legs (i.e., does he or she show evidence of periodic limb movements in sleep)? It is important to remember that some patients unfortunately will not be aware of any of these symptoms.
Questions about daytime functioning include the following:

1.
How do you feel when you get up in the morning?

2.
Do you nap deliberately during the day?

3.
Do you find yourself falling asleep while reading, watching television, attending a play or a movie, while talking with friends, or while driving? At what time of day or evening are you sleepy?
These questions try to establish if the patient is falling asleep at inappropriate times, which would suggest disturbed sleep at night.
Drug, alcohol, food (caffeine), and medical histories are all important in determining interactions as well as the causes and effects of the sleep disturbance.
After the history is complete, it is sometimes necessary to refer the patient to a sleep disorders center for evaluation. A full-night recording can then be done. The traditional clinical polysomnogram includes at a minimum EEG, EOG, submental EMG, tibialis EMG, electrocardiography (ECG), two respiration channels, and blood oxygen saturation levels (oximetry). Recordings are made for at least one full night and sometimes for two nights.
Portable recording devices are also available as screening tools.4 Portable recorders may be connected to the patient in the afternoon or evening, and the patient can be sent home to sleep in his or her own bed. For hospital inpatients, the equipment can be used at the patient’s bedside. These systems are more convenient and comfortable for the patient and less expensive than a laboratory polysomnogram but are not appropriate for all situations.5
It is only with a full-night recording that one can absolutely rule out sleep apnea. If a polysomnogram cannot be obtained, the clinician must proceed with extreme caution.
DISEASES—DIAGNOSIS AND MANAGEMENT
Circadian Rhythm Changes
With age, the circadian rhythms begin to shift. The average adult begins to become sleepy around 10:00 PM to midnight and wakes up approximately 6 to 8 hours later at 6:00 to 8:00 AM. With age, this circadian rhythm often advances, and thus, older people tend to have an earlier circadian rhythm. People with an advanced sleep phase begin to get sleepy earlier in the evening, for example, around 8:00 to 9:00 PM, but they still awaken about 8 hours later, perhaps between 4:00 and 5:00 AM. Many older people, even though they may feel sleepy, try to stay up until 10:00 or 11:00 PM, yet they still awaken early and thus obtain only 5 or 6 hours of sleep. A combination of poor sleep habits and advanced rhythm may therefore reduce the older person’s ability to get a full night’s sleep.
The state-of-the-art treatment for advanced sleep phase is exposure to bright light in the evening.6 The evening light delays the circadian rhythm so that the individual begins to get sleepy later in the evening. A highly effective regimen is 2 hours of bright light (2000 to 2500 lux) from about 7:00 to 9:00 PM. Many people watch television in such dim light in the evening that simply adding additional lighting to the television area may be an effective solution to this problem.
Sleep-Disordered Breathing
Sleep-disordered breathing (SDB), also called sleep apnea, is one of the most serious sleep disorders. SDB is a repetitive process of respiratory cessation during sleep. The SDB syndrome encompasses three types of disorders: (1) obstructive sleep apnea involves the collapse of the pharyngeal airway, with partial or complete blockage of air flow; (2) central sleep apnea results from failure of the respiratory neurons to activate the phrenic and intercostal motor neurons that mediate respiratory movements; (3) mixed sleep apnea is a combination of obstructive and central sleep apnea. Hypopnea is an episode of hypoventilation that may produce anoxia or arousal even when complete sleep apnea (total cessation of air flow) does not occur. SDB is diagnosed when breathing ceases for at least 10 seconds, and at least five episodes of apnea, or 15 episodes of apnea plus hypopnea, per hour of sleep. Treatment, however, may not be needed unless the condition is more severe. Most apnea and hypopnea episodes are terminated by transient arousals.
Reviews have suggested that a variety of mechanisms, sometimes working in combination, can cause SDB. These include obesity, micrognathia, jaw or nasal deformities, thyroid, pituitary, or neurologic impairments, and alterations of respiratory reflexes during sleep.7 Epidemiologic studies, cardiac catheterization studies, and studies done before and after treatment have shown that one of the consequences of SDB is hypertension.8,9 Lugaresi and associates10 have shown that partial obstruction of snoring may also cause nocturnal hypertension. It has also been shown that SDB is associated with increased daytime sleepiness even among elderly subjects who have no sleep complaints. In addition, SDB has been associated with cognitive impairment and dementia.11 Other consequences of SDB include anoxia, excessive daytime sleepiness, cardiac arrhythmias, cardiorespiratory failure, and ultimately, death during sleep.12 Treatment options are shown in Table 23-1 for obstructive sleep apnea and Table 23-2 for central sleep apnea.

TABLE 23-1 TREATMENT OPTIONS FOR OBSTRUCTIVE SLEEP APNEA

TABLE 23-2 TREATMENT OPTIONS FOR CENTRAL SLEEP APNEA

The prevalence of SDB in the elderly has been shown to be quite high.13 In a study of randomly selected community-dwelling elderly, Ancoli-Israel, Kripke, and colleagues showed that 24% of those aged 65 years and older had five or more apnea episodes per hour of sleep, and 81% had 10 or more episodes of apnea plus hypopnea per hour of sleep.14 In comparison, in younger adults it has been estimated that 9% of middle-aged men and 4% of middle-aged women have at least 15 episodes of apnea plus hypopnea per hour of sleep.15 Nevertheless, as with hypertension, this high prevalence does not suggest that this condition is normal with aging. Older adults with SDB should be treated no differently than younger adults with the same symptoms.16
Periodic Limb Movements in Sleep
Periodic limb movements in sleep (PLMS), also called nocturnal myoclonus, is characterized by repetitive leg kicks every 20 to 40 seconds during sleep that are followed by brief arousals. The diagnosis is made when there are five or more leg kicks per hour of sleep, each causing an arousal. In this disorder, periodic episodes of leg jerks alternate with normal sleep. Because the patients are repeatedly disturbed, they often complain of both insomnia and excessive daytime sleepiness. Other symptoms of PLMS include leg kicks and restless legs during the day and during relaxation. There is evidence that PLMS is often associated with SDB. Thus, this syndrome may have some pathophysiologic relationship with SDB as well as being an independent syndrome.
Treatment of PLMS is very difficult because the etiology is not known. Three types of medications are generally used, including the sedative-hypnotics (e.g., clonazepam or temazepam),17 the opiates (e.g., Tylenol with codeine),18 and levodopa-carbidopa (e.g., Sinemet or Sinemet CR).19 Each type of treatment has its advantages and disadvantages, and the benefit-to-risk ratio of long-term treatment is unresolved.
The prevalence of PLMS in older populations has been estimated to be 44%.20 This disorder, therefore, may account for many of the complaints reported by elderly people about difficulty in falling asleep.
Insomnia
Insomnia is defined as difficulty in falling asleep or difficulty in staying asleep. Two factors that can cause the complaint of insomnia in elderly people are medical and psychiatric illness and use of medications. Medical illness, whether it be the pain of cancer or depression, can interfere with sleep. In these situations, it is important to treat the primary medical or psychiatric problem first. Improving the symptoms of the illness should also improve the sleep complaint.
The relationship between medications and sleep should always be discussed with older patients. Medications that are depressants can cause daytime sleepiness if taken during the day. Medications that are stimulants can cause complaints of insomnia if taken near bedtime. By adjusting the time and dose of the medication, the physician may improve the problem causing the complaint. Examples of medications that can affect sleep are shown in Table 23-3. Note that some drugs, particularly antidepressants such as imipramine, nortriptyline, and desipramine, can cause both insomnia and daytime sleepiness.21

TABLE 23-3 MEDICATIONS AFFECTING SLEEP

As mentioned, treatment of insomnia in the elderly should be geared to treatment of the underlying problem. Sedative-hypnotics should be used only for temporary relief of symptoms and only for short time periods and in conjunction with behavioral techniques. Sedative-hypnotics often increase sleep only modestly. Sedative-hypnotics that have short absorption times are more appropriate for patients complaining of sleep onset difficulties (for example, triazolam or zolpidem). Sedative-hypnotics with longer half-lives are more appropriate for patients complaining of early morning insomnia (for example, temazepam). Sedative-hypnotics are never recommended for long-term use, so they have a limited role in patients with chronic sleep problems.
In summary, sedative-hypnotics should be prescribed only for elderly people with transient insomnia, and no prescription should last longer than about 3 weeks. Older patients with chronic insomnia should use sedative-hypnotics only intermittently, for example, once every two or three nights. Sedative-hypnotics should be prescribed at the lowest possible effective dose and should never be prescribed if SDB is suspected.22
Infirm people with arthritis and other chronic illnesses are often inclined to spend extra time in bed, often watching television or reading. Others spend more time in bed (e.g., 10 to 12 hours) because they are concerned that they are not getting enough sleep. A habit of going to sleep promptly after going to bed is desirable, and therefore anything that interferes with this habit may ultimately contribute to insomnia. Spending long hours lying awake in bed is very damaging to sleep patterns. It is often better to read or watch television in a recliner under a favorite quilt, on a couch, or even in another bed, and then going to sleep in one’s own bed only when sleep seems imminent. Similarly, the elderly person who awakens in the middle of the night should not remain in bed if he or she feel unable to return to sleep but should get up until he again feels sleepy. Nevertheless, the morning wake-up time should remain the same and should not be extended.
In addition, older insomniacs should be taught good sleep hygiene techniques (Table 23-4). These include exercising regularly, keeping regular hours, avoiding alcohol and caffeine at night, limiting naps, and, as mentioned, not spending excessive time in bed. In addition, because many older insomniacs are sleep advanced, spending more time out of doors to increase overall light exposure will help to stabilize their circadian rhythms.

TABLE 23-4 RULES FOR GOOD SLEEP HYGIENE

Behavioral therapies, such as stimulus-control therapy,23 sleep restriction therapy,24 and cognitive-behavior therapy,25 can all be effectively taught to older insomniacs because sleep complaints almost always have behavioral components. Spending less time in bed is one of the most effective treatments for insomnia. It is easy to understand that an elderly person who is advised to restrict time in bed to 6 or 7 hours may become sleepier after a few nights and therefore will fall asleep more rapidly and sleep more soundly. Restricting time in bed is a good treatment because it results in feeling sleepier at bedtime and a greater ability to sleep deeply. What is more surprising to the patient is that restricting time in bed, by correcting bad habits, may actually result in more physiologic sleep and correspondingly less sleepiness during the day. Often the insomniac who spends 10 to 12 hours in bed can correct the problem by reducing time in bed to 6 to 7 hours, always maintaining a regular wake-up time no matter how little sleep was achieved the night before. Sleep restriction appears to be a safe and lasting treatment.
SLEEP PROBLEMS IN PATIENTS WITH DEMENTIA
Dementia and Institutionalization
Sleep in patients with dementia can be extremely disturbed. These patients have decreased sleep efficiency, and often the circadian rhythms are reversed, with patients sleeping during the day and awake and wandering at night.11,26 This extreme disruption of the sleep-wake cycle is the second leading cause of institutionalization, incontinence being the first.27 Confusion, disorientation, and agitation affect 10% to 30% of institutionalized demented elderly.
In the nursing home, sleep fragmentation is extremely common. Nursing home patients, on average, are never asleep for a full hour and never awake for a full hour. Rather, they are constantly falling asleep and waking up. In one study, nursing home patients were never asleep for more than 40 minutes per hour throughout each hour of the day and night.28 Many factors contribute to this fragmented sleep. Chronic bed rest is common because the patient is too sick to get out of bed, because of boredom, or because well-meaning staff put the patient to bed too early. Yet the longer one stays in bed, the more fragmented sleep becomes. Sleep-disordered breathing is also extremely common in this population, in which more than 40% of patients meet at least the minimum criteria for diagnosis.29 Circadian rhythm disturbances are common and are most likely exacerbated by low light exposure. The average amount of bright light exposure in one nursing home was only 11 minutes a day.30
Environmental issues also affect the sleep of nursing home patients. Patients in rooms with disruptive roommates tend to have disturbed sleep. Patients who need nursing care during the night will have their sleep disturbed (as will their roommates).
Treating Sleep Problems in the Nursing Home
Treatment of sleep problems in this population should involve a combined approach of behavioral interventions with pharmacologic treatments when necessary. When possible, time in bed should be limited to the night hours only; naps should be restricted to one short nap in the early afternoon, a daily routine should be established with meals served at a table and never in bed, caffeine should be restricted (encourage family members to bring flowers, not chocolate), night-time noise and light should be kept to a minimum, roommates should be matched on the basis of night-time as well as daytime behaviors. Recently, several investigators have begun to examine the use of bright light to treat sleep problems31,32 and agitation33 in the nursing home. Although the full effect of these studies is not yet known, increasing light exposure by taking patients outside more often or increasing the light levels inside may well help many patients.
SUMMARY
When considering sleep problems in the elderly, it is important to remember that the decreased ability to sleep causes sleeplessness, which causes daytime drowsiness and less than optimal functioning. Circadian rhythms naturally advance a few hours with age. Older people may feel sleepy earlier and wake up earlier. Physical activity and natural light exposure can promote better sleep because light exposure may help reset the circadian clock. Sticking to a regular schedule also helps to stabilize the circadian clock. Not sleeping well at night and then napping during the day can cause a disturbed sleep-wake cycle.
Aging by itself does not cause sleep problems. The need for sleep does not decrease with age, although sleep patterns do change. Rather, the ability to sleep decreases with age, due primarily to changes in circadian rhythms and the presence of sleep disorders.
ACKNOWLEDGMENT Supported by NIA AG02711, NIA AG08415, NHLBI HL44915, NIMH MH49671, NIMH MH00117, NIA AG12364, Stein Institute for Research on Aging and the Research Service of the Veterans Affairs Medical Center.
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