Insomnia, defined as difficulty falling or staying asleep, is frequent in older people.1,2
In some patients, insomnia can be caused by an underlying medical condition or a medication side effect (secondary insomnia). In the absence of a causative factor, it is referred to as primary insomnia. Monane3
has estimated that insomnia affects nearly half of all those over the age of 65 years. Elderly women tend to report sleep disturbances more frequently than elderly men.4
The sleep changes noted among older women may be partly related to changes in the postmenopausal profile of sex hormones. Estrogen deficiency in particular has been postulated to contribute to the sleep difficulties that women often begin to experience in their perimenopausal period, and then increasingly with age.5
Frequent awakenings are particularly common among elderly people and may be related to their more frequent incidences of concurrent medical conditions. Among the most common causes of secondary insomnia are a variety of musculoskeletal disorders, nocturia related to benign prostatic hypertrophy in men and bladder instability with decreased urethral resistance in women, congestive heart disease, and chronic obstructive lung disease.
Depression and anxiety disorders, common among people over 65 years of age, frequently contribute to insomnia.6
Risk factors for depression in older people include loss of a spouse, retirement, social isolation, comorbid disease and onset of dementia.
Sleep disturbance or disruption is common among patients experiencing dementia, particularly those with Alzheimer's disease.7
Such patients often have difficulty not only falling asleep but also with repeated nighttime awakenings. In general, as the dementia progresses, these symptoms become increasingly severe and patients become noticeably and progressively sleepier during the daytime. They may also exhibit recurrent agitated behaviour, known as “sundowning,” during which these patients are more confused, disoriented, suspicious and restless. They may yell or exhibit violent behaviour, and are prone to wandering. Although episodes may occur at any hour, they are most common in late afternoon or evening — hence its descriptive term. For caregivers, this behaviour is extremely disruptive, and often becomes the ultimate reason for admission of a patient with dementia to an institution. Interestingly, McKibbon and colleagues8
also showed that elderly caregivers of patients with Alzheimer's disease reported more sleep problems and functional impairment from sleepiness than noncaregivers.
Insomnia is also common in people who have Parkinson's disease,9
who may experience frequent awakenings with difficulty returning to sleep. They also frequently complain of vivid dreams, nightmares and leg jerks. Restless legs syndrome and rapid eye movement (REM)-sleep behaviour disorder, described following, may also affect these patients.
Use of medication increases with age. Older, community-dwelling people commonly undergo polypharmacy and receive inappropriate prescriptions from physicians,10
which unfortunately increases the possibility of insomnia related to medication use. A careful drug history is therefore imperative when an older patient with insomnia is assessed. Many drugs and other ingested substances have been shown to cause or contribute to insomnia; examples are presented in . This is particularly important in elderly patients who may, for physiologic reasons, be more susceptible to the stimulatory effects of these agents. The stimulant effect of caffeine, for example, which can last 8–14 hours, may be more pronounced in older people, especially when decreased liver function impairs caffeine clearance. Many older people use alcohol as a sleep aid, but even moderate consumption near bedtime can cause intense dreaming and nocturnal awakenings. These arousals appear to result from sympathetic stimulation and catecholamine release associated with the eventual fall of blood alcohol levels. Older people seem to be more sensitive to these effects.
REM-sleep behaviour disorder
Normally, dreaming occurs during REM sleep. Fortunately, during this phase of sleep the voluntary muscles are actively inhibited, which renders us incapable of “acting out” our dreams. REM-sleep behaviour disorder is characterized by the loss of this normal muscle atonia. Affected people may display a variety of movements, which in extreme cases can be harmful to the patient or bed partner. A patient may get up and walk about, thrash limbs, flail arms or legs, or even engage in complex activity such as eating, while remaining in REM sleep.
Nine out of 10 patients with REM-sleep behaviour disorder are men.11,12
The disorder usually affects people older than 60.11,12
It is frequently associated with other neurodegenerative conditions such as Parkinson's disease, multiple sclerosis or Alzheimer's dementia.11,12
Interestingly, symptoms of REM-sleep behaviour disorder may precede a diagnosis of Parkinson's disease by years.13
Patients known to have Parkinson's have been found to have coexistant REM-sleep behaviour disorder in 15%–47% of cases.14
The progressive nature of this sleep disorder and its prevalence among older people and patients with Parkinsonian syndromes have led to speculation that idiopathic REM-sleep behaviour disorder is a neurodegenerative disorder of the deep nuclei and brainstem neurons involved in the integration of the sleep–wake cycle and the locomotor system.11–14
The diagnosis is made by history and supported by polysomnography: overnight multichannel monitoring in a sleep laboratory. In a Canadian study, Gagnon14
found that a third of patients with Parkinson's disease could be diagnosed with REM-sleep behaviour disorder according to polysomnographic criteria, when only half of those would have been detected through history alone. Because appropriate treatment of this disorder can be beneficial, accurate diagnosis is important. Moreover, Comella's group15
found that REM-sleep behaviour disorder was a frequent cause of sleep-related injuries of elderly patients with Parkinson's disease. Knowledge of its existence may prompt caregivers to ensure a safe and secure nocturnal environment.
A chronic neurologic disorder of unclear origin, narcolepsy results in excessive daytime somnolence and fatigue.16
The main symptoms of this condition are “sleep attacks,” during which patients experience an irresistible urge to sleep (for a few minutes or up to an hour); hypnogogic hallucinations (extremely vivid auditory or visual hallucinations experienced while falling asleep or when waking up); sleep paralysis (a temporary inability to move upon wakening or before falling asleep); and cataplexy (a sudden, temporary, often unpredictable loss of muscle tone, which leads frequently to complete collapse).
Cataplexy can occur in the absence of other features of narcolepsy. Some attacks last up to half an hour, during which the patient is awake but unable to move or, in milder cases, experiences focal muscle weakness. Cataplexic episodes are sometimes triggered by intense emotion, including crying or laughing.
Although narcolepsy usually begins during the teen years or early twenties, symptoms tend to be lifelong.16
It may therefore be seen in older patients who have had the condition for many years.16
In others, mild disease severity, misdiagnosis or long delays in cataplexy expression may prevent proper diagnosis and treatment.17,18
Chakravete and Rye18
estimated that it first comes to medical attention after the age of 40 years in nearly half of affected patients. Rye and associates19
stressed that, during differential diagnosis, narcolepsy should always be considered by physicians faced with an older patient experiencing sleepiness or with transient loss of muscle tone.
Once suspected, narcolepsy is usually evaluated by documenting the presence and severity of daytime sleepiness by means of a multiple sleep-latency test.20
Polysomnography is essential to rule out other sleep disorders.
Periodic leg movements and restless legs syndrome
Sleep-related movement disorders are an often-overlooked cause of interrupted sleep and daytime sleepiness or fatigue among older patients.
Periodic leg movements represent a unique motor disorder, in that they occur specifically during sleep. The abnormal movements range from subtle contraction of the muscles of the ankles and toes to impressive flailing of the arms and legs. This syndrome is diagnosed with polysomnography by recording bursts of electromyographic activity that recur at regular periods in the affected muscles. Its prevalence increases with age; one study21
found the condition in 45% of a randomly selected sample of elderly subjects. The syndrome can be asymptomatic and require no intercession. Among older patients with insomnia, however, the finding of periodic leg movements warrants treatment.
Restless legs syndrome is a distinct entity sometimes confused with periodic leg-movement disorder (). Patients with restless legs complain of tingling, unpleasant, crampy or even very painful sensations, usually in their lower extremities.22
Often, they describe “a crawling feeling” under the skin. The condition is characterized by an intense urge to move or massage the legs, which offers some relief. Unlike periodic leg movements, which awaken people from sleep, the symptoms of restless legs syndrome usually occur when patients get into bed, and thereby cause sleep-onset insomnia.
Restless legs syndrome is common in older people, with an estimated prevalence of 10%–35% among those over 65 years of age.23
Unlike periodic leg-movement disorder, it has a female predominance.24
The majority of patients with restless legs also have periodic leg movements, but only about a quarter of patients with a diagnosis of periodic leg movements also have restless legs syndrome.
Although it can be idiopathic, restless legs syndrome can also be associated with iron deficiency, rheumatoid arthritis, renal failure and a variety of neurologic lesions, especially peripheral neuropathy.25
About half of patients with the syndrome have a positive family history, which suggests an underlying genetic predisposition as yet poorly defined.25
The pathogenesis of restless legs syndrome is unclear, but appears to involve abnormalities in dopaminergic neural transmission or iron metabolism.23–25
There is evidence for age-related dysfunction of the descending dopaminergic pathways, possibly originating in the diencephalon or upper brainstem.26
In fact, L-dopa or dopamine agonist administration can decrease the symptoms of restless legs syndrome.25