Sleep is the basic human condition that is cyclically repeated every day as part of circadian rhythms and accompanied by the changes in physiological functions and behavior. The stages and phases of sleep provide a recovery function, process and preserve information obtained in the waking period, and optimize the functions of the internal organs. Accordingly, sleep disorders affect the daily functioning of the entire body. Sleep disorders can be the first sign of a number of mental illnesses such as neurosis, depression, and chronic stress. They reduce efficiency, social adjustment, and the quality of life of the patient with any disease. One should not underestimate sleep disorders and the importance of sleep. The quality of sleep is one of the most important components of the quality of life since it affects all aspects of the human life and the overall state of health. This paper will discuss risk factors, epidemiology, clinical features, and treatment of sleep disorders.
Many patients of psychiatrists and other specialists complain about sleep disorders. Edward O. Bixler and colleagues were the first to conduct epidemiological studies in the United States using a representative sample of the U.S. population. According to their data obtained in 1979, 42.5% of respondents complained about sleep disorders during the study period or in the past. Among them, 32.2% of the respondents had episodic insomnia, and 7.1% suffered from excessive sleep. Also, about 10% of the interviewees had chronic insomnia. These figures were sufficiently high already in 1979. It clearly demonstrated that sleep disorders turned into a major national issue that could not be ignored.
Furthermore, the occurrence of sleep disorders had been rising steadily over the following years. According to Gary K. Zammit, episodic insomnia occurs in half of the U.S. adult population while the chronic one occurs in 10-15%. The prevalence of sleep disorders in Japan is 21%, 19% in France, and 19% in Canada. Among patients who sleep poorly for several days a week, 34% feel unrefreshed in the morning, 32% often wake up at night, 23-24% report difficulties in falling asleep again or awakening too early. This data prove that sleep disorders occurrence rates continue to grow. Moreover, sleep problems are turning into an issue of global concern.
The situation is complicated by the fact that sleep disorders may be an early warning sign of a mental disorder. Another study shows that that 40% of respondents with insomnia and 46.5% with excessive sleepiness suffer from a psychiatric disorder, as compared with 16.4% of the patients without any complaints about sleep disturbance. It was revealed that anxiety disorders accompanied both insomnia and excessive sleepiness in 23.9% and 27.6% of respondents respectively. Also, there is a high incidence rate of major depression, abuse of alcohol, and other psychoactive substances in sleep disorders sufferers. Thus, sleep disorders are a common complaint among patients with a mental illness.
The frequency of sleep disorders and complaints of poor sleep have been the subject of several studies. The findings suggest that sleep disorders are, on the one hand, highly prevalent, and, on the other hand, poorly investigated and treated. Given the fact that modern production becomes increasingly complex, one can predict a subsequent increase in the prevalence of sleep disorders. The studies have also indicated a relationship between sleep disorders and mental illnesses, which can trigger sleep problems. However, mental disorders are just one of the several risk factors that can lead to difficulties falling asleep.
Patients with sleep disorders experience impairment of cognitive functions (concentration, memory), weakness during the day, increased risk of accidents, and difficulties in communicating. Sleep disorders correlate with chronic diseases, especially coronary heart disease, hypertension, diseases of the musculoskeletal system, diabetes, and arthritis.
Many risk factors for sleep disorders have been identified, but the mechanism of their action is not always clear. They include increasing age, female predisposition, somatic and mental illness, job changes and unemployment, lack of family, and obesity. According to some authors, sleep disorders may occur due to genetic factors. Sleep disorders in the family history increase the risk of insomnia often more than stress.
Epidemiological studies show that sleep disorders are becoming progressively prevalent as age increases, but many authors attribute insomnia not to the age but to the problems that occur in old age, like chronic diseases such as heart disease, stroke, hip fracture, as well as depression and other mental disorders. A number of psychological and social reasons can cause sleep disorders in the elderly and old age. They include loneliness, withdrawal from work and forced inactivity, changes in living conditions and the deterioration of the quality of life, forced restriction of activity or staying in bed due to illness, etc..
Women suffer from insomnia more than men in every age group do. Since this situation cannot be explained, various attempts were made to justify the gender characteristics of insomnia in each age period separately. In young age, female sleep disorders can be associated with the specific role of a mother, who cares for children and, therefore, has night awakenings and lack of sleep. At older ages, sleep disorders in women are explained by perimenopausal disorders with nocturnal hot flashes, sweating attacks, depression, and anxiety. After menopause, in women and men the differences in the prevalence of insomnia vanish for unknown reasons and re-appear in the senile age. The percentage of women in the population of older people increases due to the differences in life expectancy between women and men. The loss of marital status for various reasons (divorce, the death of one spouse or separation due to illness) can also cause sleep disorders.
Chronic pain is strongly correlated with the high frequency of insomnia. It applies to patients with arthritis, musculoskeletal disorders, and other diseases associated with chronic pain. The pain can also be the cause of awakenings during sleep and intermittent sleep. However, research data indicates that sleep disorders increase pain perception.
Obesity is one of the most important risk factors for some sleep disorders such as sleep apnea. Respiratory disorders during sleep are associated with high morbidity and mortality. Obesity occurs in 60-90% of patients with sleep apnea. In turn, the combination of obesity and sleep apnea is a predictor of diseases such as hypertension, coronary artery disease, arrhythmia, myocardial infarction, stroke. Thus, obesity does not ensure a good night’s rest and the necessary amount of sleep since it is among the key factors of sleep apnea development.
More often, sleep issues occur along with mental disorders, especially depression, anxiety, and others. Patients with insomnia often have a concomitant mental illness. It was found that insomnia is associated with a mental disorder in two-thirds of the patients who come to the Center for Sleep Disorders, and more than half of them had a mood disorder. The relationship between insomnia and mental illness has been confirmed in numerous studies. Many patients suffering from mental ailments complain of sleep disorders. Thus, sleep issues can be a predictor of many mental disorders such as depression, mania, and post-stress disorders.
Many patients with sleep disorders use alcohol as a sleeping aid. The consumption of alcohol during the night decreases sleep latency since alcohol is metabolized slowly. It leads to a decrease in rapid eye movement (REM) sleep and deep sleep, more sleep fragmentation, and more episodes of awakening. Alcohol also disrupts breathing during sleep, reducing the muscle tone of the upper respiratory tract and resulting in respiratory depression and fragmented sleep.
Sleep disorders are often of a polyetiological nature and can be either an independent disorder or a symptom of many different diseases, including somatic, neurological, and mental ones. Thus, sleep disorders can precede a mental disorder and even contribute to its development or occur in the structure of psychopathologic syndrome along with any other symptoms. In practice, it is difficult (and sometimes impossible) to establish a cause-and-effect relationship between a sleep disorder and mental illness. Therefore, the only thing a specialist can do initially is to describe the clinical features of sleep disorders in a particular disease.
Sleep disorders can be experienced by people suffering from neurotic or psychotic disorders. Many clinicians believe that sleep disorders are an obligate characteristic of neurotic states. For example, Chokroverty identified an obligate set of symptoms in neurotic insomnia: difficulties in falling asleep, dissatisfaction with the duration and depth of sleep, nightmares, and lack of feeling refreshed. The author considered other symptoms of sleep disorders such as frequent night awakenings, parasomnia, early morning awakenings, and morning drowsiness as optional. Thus, disorders of a neurotic or psychotic nature can lead to sleep problems.
The clinical features of sleep disorders of a psychogenic nature include a set of various pathologies of the neurotic spectrum. The leading manifestations of sleep disorders in neurasthenia are difficulties in falling asleep, night awakenings, sleep myoclonias, and morning drowsiness. Neurotic depression is characterized by such symptoms as prolonged falling asleep, superficial and fitful sleep, nightmares, and lack of feeling rested after sleep. Disorders of the emotional and dramatic cluster are accompanied by the phenomenon of ‘sleep drunkenness’ in the morning and parasomnias as the main manifestations of sleep disorders. Obsessive-phobic disorders are characterized by frequent nightmares in general. Disorders of a hypochondriac and somatoform nature are often accompanied by dissatisfaction with the duration and quality of sleep as well as paradoxical drowsiness. Also, sleep disorders usually manifest themselves in generalized anxiety and frequent nighttime awakenings.
Many psychological and neuroscientific articles deal with sleep disorders in patients with depression. Sleep disorders in this condition are diverse and depend on the nature and severity of the depressive state. In psychogenic depression, there is a prevalence of difficulties in falling asleep with compensatory lengthening of morning sleep in the structure of sleep disorders. In endogenous depression, there are frequent nocturnal and morning awakenings. Moreover, a characteristic feature is the increase in the number of awakenings during the last third of the night. At the same time, 10-15% of patients with depression report increased sleepiness along with reduced energy and psychomotor retardation. Thus, the relationship between depression and sleep disorders has been studied extensively.
The identification of sleep disorders has never been an easy task. However, in recent years, the method called ‘polysomnography’ facilitated progress in this area. It is the most sensitive indicator of the state of sleep, which allows one to detect disorders of the sleep-wake cycle with an absolute accuracy. This method helped obtain substantial data that is characteristic of sleep disorders. The data also has a diagnostic and prognostic value. However, specialists put more emphasis on the subjective assessment methods of sleep disorders and their dynamics because individual satisfaction with sleep depends on the emotional and affective sphere more than on the physiological parameters of sleep.
In addition, complaints about sleep disorders do not always have substantial grounds. Several studies have shown that claims about poor sleep are often not verified by neurophysiological methods as well as the clinical ones. This fact is explained by the fact that most patients with sleep disorders have overvalued and hypochondriacal attitude to sleep, and, thereby, they usually exaggerate the severity of the disorders. It is confirmed by the fact that the duration of falling asleep according to the subjective feelings often exceeds the objective figures, and most patients cannot adequately evaluate the length of their sleep.
Treatment of sleep disorders includes two approaches, namely the etiological and the symptomatic. The first involves the elimination of the causes of sleep disorders. It implies treatment of diseases that caused a sleep disorder or impact on the external factors and circumstances that have a negative influence on the sleep-wake cycle and the process of sleep. In turn, the symptomatic approach aims directly at the regulation of sleep. In practice, both approaches are used simultaneously, especially if a sleep disorder is associated with other mental ones.
The treatment of sleep disorders implies non-drug therapy such as psychotherapy, acupuncture, and medical therapy, which includes such medications as calming herbs, barbiturates, benzodiazepines, antidepressants, sedating antipsychotics, and selective non-benzodiazepine hypnotics. Barbiturates were the first class of products created specifically for the treatment of sleep disorders. They had been widely used since the beginning of the 20th century until the advent of psychotropic drugs in the 1960s. Currently, barbiturates are used strictly under physician’s prescription since they can cause dependence and various complications. Then, benzodiazepines, which represent a large group of preparations with a unique range of psychotropic effects, replaced barbiturates.
Benzodiazepines cause sedative, hypnotic, anxiolytic, muscle relaxant, and anticonvulsant effects of varying degrees by interacting with the GABA receptors. The treatment of sleep disorders includes many medications, but specialists often use those that have a marked sedative impact like nitrazepam, flunitrazepam, midazolam, temazepam, flurazepam, triazolam, phenazepam, and others. In recent years, the use of benzodiazepines in the world has declined significantly due to the adverse effects arising from their long-term use (daytime sleepiness, muscle relaxation, mental and motor retardation, incoordination, ataxia). There is also a risk of psychological and physical dependence and withdrawal syndrome. Benzodiazepines are contraindicated in patients suffering from sleep apnea syndrome and are not recommended for elderly patients.
Antidepressants with a sedative effect such as amitriptyline, trazodone, mirtazapine, mianserin, fluvoxamine, and venlafaxine are often used in the treatment of insomnia in patients with depression. A dose is chosen individually, taking into account the nature and severity of depression and concomitant therapy. The treatment of sleep disorders in patients with psychosis implies the use of antipsychotics with sedating effects: levomepromazine, clozapine, olanzapine, and quetiapine. The use of antipsychotics in combination with other groups of medications, such as tranquilizers and antidepressants, is determined by the structure of psychopathological symptoms and the severity of the condition.
In the late 1980s, there was a new group of medications, namely selective non-benzodiazepine hypnotics such as zopiclone, zolpidem, and zaleplon, which are currently the most widely used medications in the clinical practice. The most effective of them is zolpidem and, therefore, it merits special attention. Zolpidem is a derivative of imidazopyridine and selectively inhibits the subtype of A1 receptors of the GABA complex without binding to other subtypes, both central and peripheral ones. A1 receptors are localized mainly in the cortical and subcortical regions and are responsible for the appearance of hypnotic action. Pharmacological properties of zolpidem are determined by its rapid absorption and short half-life. Due to such properties, the medication can be taken not only before bedtime but also at night. Thus, it is very useful for patients who wake up late at night, for example, at 2 AM or 3 AM. It especially concerns elderly patients. Moreover, the side effects of zolpidem are virtually absent: their incidence is similar to those in placebo. Due to its selective effect, zolpidem does not cause residual excessive sleepiness, does not reduce the daily functioning of a patient, and does not lead to dependence.
The efficacy and tolerability of zolpidem are researched in numerous studies on patients of different ages with various pathologies. Zolpidem has good tolerability, particularly at a dose of 10 mg, as compared to placebo in elderly patients. Also, zolpidem 20 mg was highly effective when compared with flunitrazepam 2 mg. Finally, another study found that there was no need for increasing the doses of zolpidem even after prolonged use within one year. The above studies decisively indicate the low probability of promoting tolerance and addiction to the medication.
Currently, research of sleep disorders is imperative in the context of raising awareness throughout the society of the need for healthy sleep. Sleep disorders is a quite widespread phenomenon. About 10-15% of the United States population experience chronic insomnia. Sleep disorders can develop at any age. Age, sex, mental problems, unemployment, single life, alcohol, and obesity are conducive to the development of sleep disorders. Treatment of sleep issues should begin with the use of non-drug therapies. Drug correction is performed if necessary. Preference should be given to medications that have a positive effect on the cognitive function. The safest and most effective type of medications is zolpidem.