It is known that sleep disturbances in old age are not only a medical but also a social problem for patients, their relatives, and society as a whole. The number of individuals who rate their sleep as unsatisfactory steadily increases with age. The present review is devoted to the evaluation of physiological changes in the sleep process due to age; the factors increasing the prevalence of sleep disorders after 60 years of age, the most frequent sleep disorders in elderly people, the peculiarities of their diagnostics and treatment.
Peculiarities of sleep process at the elderly age
Comparing the sleep of people of different age categories, we can see that older people (over 60 years old) more often report subjective difficulties related to sleep. The most common complaints are difficulty initiating (initiating) sleep, as well as a decrease in overall sleep time. Nocturnal and early-morning awakenings increase with age, and older adults are more likely to sleep during the day. Although the total duration of sleep in such cases may not differ significantly from the data typical for the general population, it is the quality of sleep and the entire sleep-wake cycle that suffers most significantly.
It is important to note that subjective changes in sleep related to age are confirmed by complaints of poor sleep quality obtained through questionnaires and questionnaires aimed at detecting sleep quality disorders.
Sleep studies carried out using objective methods - polysomnographic recording recording the stages and phases of sleep (their sequence, structure and depth, which is defined as sleep architecture) - demonstrate certain changes in these indicators, which are a reflection of age-related physiology.
A meta-analysis of these changes demonstrates the peculiarities of sleep organization after the age of 60. First of all, there is a decrease in the duration of deep stages of slow-wave sleep (so-called delta sleep), a slight decrease in the representation of the normal proportion of paradoxical sleep (sleep with rapid eye movements or REM sleep) - less than 20% of the total duration of the whole process, a variability of the surface stages of sleep (stage I or dozing), which in general leads to a decrease in the total sleep time. Some characteristics (REM-sleep, total sleep time) decrease gradually after the age of 60, characterized by a smooth decrease, the representation of slow-wave sleep in the elderly, on the contrary, decreases more sharply.
An important characteristic of sleep disorders is the presence of EEG-activation reactions. These are changes in the sleep process, in which an alpha rhythm, reflecting wakefulness, appears on the EEG for a short period of time (not more than 5 s). It turned out that the number of EEG activations is registered more often in elderly people compared to younger ones; after such events, elderly healthy people were more likely to wake up and be awake in the middle of the night, which prevented them from keeping their sleep more whole and deep.
Another reason for impaired sleep patterns and architecture in older adults may be the presence of comorbid somatic diseases. Evidence of cardiovascular disease, arterial hypertension, and stroke in the large cohort Sleep Heart Health Study has been associated with impaired sleep patterns. This study also showed that decreased sleep time or quality may have been a predisposing factor for metabolic syndrome in the elderly; and diabetic patients had decreased slow-wave sleep time, decreased sleep efficiency, and more EEG activations. In most cases, however, these associations were not as pronounced as the effects of gender, age, and ethnicity on sleep patterns.
Based on the findings on sleep patterns in the over-60 age group, it is reasonable to say that older adults spend most nights in more shallow sleep than younger and middle-aged individuals.
The multiple sleep latency test, which objectively determines the level of wakefulness during the day, shows that the elderly are significantly more sleepy compared to middle-aged individuals.
Age-related changes in sleep-wake cycle regulation systems
Many physiological systems, such as hormone secretion, regulation of blood pressure and body temperature, and the sleep-wake cycle itself, are subject to circadian rhythms with a period of about 24 hours. The circadian rhythm of sleep is disturbed when desynchronism develops between the internal circadian clock (located in the anterior hypothalamus in the suprachiasmatic nuclei area) and external behavioral factors. Older adults have several causes that can affect the desynchronism of internal and external rhythms. First, the suprachiasmatic nuclei decrease their functional activity with age, resulting in weaker and/or more pronounced disruption of circadian rhythms that regulate many processes in the body. The second cause of desynchronism is possible age-related changes in other rhythms that may affect the sleep-wake cycle. An example of such age-related changes is the nocturnal secretion of endogenous melatonin, which can be decreased many times over in the same person at a young age. Since melatonin secretion plays an important role in sleep onset in the sleep-wake cycle, this decrease can reduce sleep efficiency and increase the number of disorders related to circadian rhythm diseases (advanced sleep onset syndrome, delayed sleep onset syndrome, etc.). Various involutionary processes of the body can be the reasons for a decrease in melatonin concentrations: decrease in sympathetic tone, changes in the morphology of the epiphysis, which produces the hormone melatonin, increase in body weight, and much more. Third, circadian rhythmicity is maintained by external signals or time-sensors (zeitgebers). In the case of the sleep-wake cycle, such a signal is bright light, which coordinates the optimal timing of many daytime processes (eating, physical activity, etc.). Studies have shown that older people, especially those in need of nursing care, receive insufficient exposure to natural daylight. Daytime exposure to bright light averaged 58 minutes in young adults, 60 minutes in healthy seniors, and only 30 minutes in Alzheimer's patients living at home. Other studies have shown that bedridden elderly patients under nursing supervision at home had even less light in the room 50% of the time, averaging only 11 min of light from normal light levels. Low light levels may determine the association with subsequent nocturnal sleep fragmentation and the more frequent anticipatory circadian rhythms that occur at this age. Lack of bright daylight illumination can manifest itself in a weakening of external time-sensors that shift the circadian rhythm of the sleep-wake cycle (earlier or later onset of sleep).
As we age, changes in circadian rhythms can independently affect the timing of sleep onset. Elderly people with so-called anticipatory sleep phase syndrome feel drowsy early in the evening, starting at 7-9 h, and spontaneously awaken earlier than usual (between 3-5 h in the morning). Guided by accepted social norms, they prefer to get up later (at 7-8 a.m.), periodically falling asleep for short intervals in the morning hours. However, this sleep pattern causes partial sleep deprivation and then leads to increased sleepiness and often causes periods of short daytime sleep.
In parallel with the disturbance of the synchrony of the interaction of factors affecting the sleep process, the sleep-wake cycle amplitude itself, expressed as the difference between the minimum and maximum value of motor activity during the day and night, may decrease during aging. This can lead to an increase in the number of nocturnal awakenings and, consequently, a decrease in daytime wakefulness.
Sleep disorders in the elderly. The role of comorbid conditions and polyprogamy in older individuals with sleep disorders
Factors leading to rhythm desynchrony create conditions for the development of the most common sleep disorder: insomnia. Representative population studies (up to 9,000 included patients) indicate an increase in insomnia symptoms with age. They can occur in the study population in 40% of those over 60 years of age. The debut and consolidation of symptoms leading to desynchronization of the sleep-wake cycle occurs primarily due to non-compliance with the physiological principles of wakefulness (reduced daily physical activity, disruption of daily routines, daytime sleep, and so on). Other causes of insomnia in the elderly are comorbid conditions. For example, difficulties in turning around in bed, getting out of bed, or conversely, the desire to lie down may be due to chronic pain in fibromyalgia, which in turn leads to long awakenings and difficulty falling asleep. It is known that various pain syndromes, neurodegenerative diseases, pulmonary and cardiovascular diseases, rheumatic diseases, depression, dementia due to various afferent impulses (pain, somatoform dysfunctions and other symptoms) can lead to the development of insomnia in the elderly.
Overuse of sleeping pills also leads to the development of insomnia symptoms, which is often associated with dependence and addiction (older generations of sleeping pills are used because of their low cost). When using other drugs that may potentially cause insomnia or excessive daytime sleepiness in the elderly (most often drugs of cardiovascular, psychotropic and neurological groups), it is important to remember that these patients are usually characterized by polypragmasy and reduced metabolism. Combining drugs from these groups can lead to increased interactions and cause side effects.
Other sleep disorders are also known to be extremely common in the elderly and contribute to sleep disturbances in this population. These include sleep breathing disorders, intermittent limb movements during sleep and disorders due to paradoxical sleep behavior (REM-sleep).
Sleep breathing disorders are characterized by frequent episodes of complete or partial upper airway obstruction in sleep lasting at least 10 s. The nature of sleep apnea can be both obstructive (weakness of the palate and pharynx structures), or due to impaired central regulation of breathing (central apneas). The number of central sleep apneas increases with age, which may be due to the impact of various comorbidities in these patients (heart or lung failure, chronic renal failure, etc.). The prevalence of sleep apnea disorders is higher in the elderly than in middle-aged individuals.
According to population studies, the prevalence of sleep breathing disorders ranges from 3 to 7-10% in the middle-aged population, while it can be as high as 24-30% among the elderly.
Restless leg syndrome is characterized by repetitive urges to move predominantly in the legs, defined as paresthesias, which impair rest and pass on movement. If these movements occur in sleep, they are called periodic limb movements in sleep. They can lead to the development of EEG activation reactions and changes in sleep architecture. Patients with this nosology often have superficial sleep without deep phases and, as a consequence, excessive daytime sleepiness. The cause of the development of this movement disorder is not fully known; neurological abnormalities related to dopamine deficiency or its perception by brain receptors, iron deficiency, and catecholamine dysfunction play a role. The prevalence increases with age, rising from 4-6% in middle-aged individuals to 44% in elderly patients.
Disorders due to paradoxical sleep behavior disorder (REM-sleep) are characterized by an episode of complex motor behavioral reactions during sleep. More often such an episode occurs in the second half of the night, when REM-sleep is more represented. Nocturnal behavior in this disorder includes dreaming, dreaming, or other large-amplitude movements, some of which may be detrimental to the patient himself or his sleep partner. The etiology of this disorder is unknown. It is thought that the disorder may not only be associated with dementia and other neurodegenerative diseases, but may also be manifest in these nosologies. Current research suggests an increased likelihood of the development of paradoxical sleep behavior disorder in the elderly.
Diagnostic evaluation and treatment of sleep disorders in the elderly
In the diagnosis of insomnia, instrumental studies such as polysomnography, or actigraphy (prolonged recording of motor activity) often do not provide an objective picture of the disease. Therefore, the American Academy of Sleep Medicine recommends the use of sleep diaries, which focus primarily on subjective sensations, for diagnosis and treatment evaluation. Insomnia therapy has traditionally included medication (the use of drugs with sedative and hypnotic effects) and non-drug strategies. The latter includes sleep hygiene and two types of behavioral therapy (stimulus control and sleep restriction therapy). Behavioral therapy has a more lasting long-term effect than taking medication. If medication selection does not avoid the need to prescribe sleeping pills, it is advisable to consider the specifics of prescribing such medication therapy in elderly patients. These include preferential use of modern groups of drugs with a half-life of up to 8 hours; prescription of drugs for a short period (no more than 3-4 weeks); starting treatment with a dose that is half the usual therapeutic dose. If complaints of treatment ineffectiveness occur, polysomnography should be prescribed to detect atypical forms of insomnia, followed by withdrawal of drugs or situational prescribing of pharmacotherapy.
In diagnosing circadian rhythm disturbances, the main emphasis is placed on the analysis of sleep diary data and objective data obtained by actigraphy. Among the therapeutic interventions, bright light therapy, which can improve sleep efficiency among the elderly, occupies a special place. Current studies show some efficacy of melatonin replacement therapy, based on the fact that endogenous melatonin secretion in the elderly decreases with age. However, there is currently no general consensus on effective dosages of the drug in the elderly. Questions also remain open about drug interactions of melatonin with other pharmacological substances.
Diagnostic and therapeutic interventions in the treatment of sleep breathing disorders, periodic limb movements in sleep, and REM-sleep-related behavioral disorders are traditional for this age group.
In order to diagnose these nosologies, a polysomnographic study is necessary to make or refine the diagnosis.
In the choice of treatment strategy in elderly patients with sleep breathing disorders, ventilatory support methods (CIPAP or BiPAP therapy) should be preferred, since surgery on the soft palate and pharynx organs may have an increased risk of complications due to comorbid conditions that are common at this age. Dopaminergic drugs are the drugs of choice for intermittent limb movements in sleep, and clonazepam is most effective in cases of REM-sleep-induced behavioral disorders. When treating with clonazepam, its side effect of excessive daytime sleepiness should be considered and the dose should be chosen more carefully in the elderly.
When it is necessary to treat sleep disorders with pharmacological agents in the elderly (regardless of nosology), it is advisable to consider two important aspects. First, side effects that may affect existing sleep disorders (primarily insomnia and increased daytime sleepiness). Second, even the prescription of pathogenetic therapy requires the use of small doses of drugs due to reduced metabolism and possible drug interactions with drugs already taken.
Thus, objective changes in the main characteristics of sleep appear with age. Predisposition to sleep disorders in the elderly is due to age-related changes in the regulation of circadian rhythms. These changes may lead to the most common sleep disorder in the elderly: insomnia. Other common sleep disorders are also significantly more common in the elderly population. When prescribing standard drug therapy, the amount and interplay of medications taken by the patient must be considered. Non-drug and behavioral therapies should be preferred in the treatment of sleep disorders in the elderly.