Sleep disturbance - Epidemiology

Epidemiology of sleep disorders

The prevalence of sleep disturbances and complaints of poor sleep has been the subject of several studies. Surveys in the United States, Europe, and Australia have shown that 30 to 40% of adults report sleep disturbances or at least some degree of sleep dissatisfaction during the previous year. For example, a 1985 study of 3,000 adults in the United States found insomnia to be 35%, with 17% reporting severe or persistent insomnia (Mellinger et al., 1985). Of those with severe or persistent insomnia, 85% were not receiving any treatment.

In 1991 and 1995, the National Sleep Research Foundation and the Gallup Institute surveyed 1,000 and 1,027 people, respectively, to determine the frequency and nature of sleep disorders. The results of these surveys were generally comparable and contained a number of important and interesting observations. Like previous studies, the surveys showed that between one-third and one-half of the adult population report at least occasional sleep problems. Moreover, 9-12% of respondents suffered from insomnia systematically or frequently. The 1995 survey also showed that adults with severe sleep disorders rate their general health lower. Of course, this relationship can be explained in various ways:

1. poor sleep quality can actually have adverse effects on physical health;
2. People with chronic sleep disorders tend to rate their health more negatively;
3. Poor physical health has a negative impact on the quality of sleep.

Daytime sleepiness is reported by 40% of adults, with 12% of respondents stating that they can doze off during daytime activity. Interestingly, only 30% of adults with sleep disorders have discussed the problem with their doctors or other health care professionals. Moreover, people with sleep disorders rarely make an appointment to see a doctor about it. A separate study noted that only half of general practitioners ask patients about their sleep in detail, even after they complain of poor sleep. Thus, the data obtained indicate, on the one hand, the high prevalence of sleep disorders, and on the other hand, that they are poorly recognized and treated.

Although insomnia is the most common sleep disorder, several other conditions should be considered when assessing the prevalence of sleep disorders. Although insomnia is widely present, it should be distinguished from other sleep disorders, such as obstructive sleep apnea. Obstructive sleep apnea, described in the early 1970s, is a fairly common disorder in the adult population associated with a high risk of a number of diseases and increased mortality. One epidemiological study (Wisconsin Sleep Cohort Study) noted that obstructive sleep apnea is detected (according to very strict criteria) in 2-4% of the adult population.

Although the prevalence of narcolepsy is relatively low (125,000 to 250,000 people live in the United States), it is a serious public health problem due to its chronic nature and adverse impact on the lives of patients.

Periodic limb movements of sleep (PLMS) is another important disorder. Although its exact prevalence is difficult to estimate, it is known to increase with age. According to a 1995 Gallup poll, 18% of adults report significant leg movements or twitching during sleep.

Another group of sleep disorders is associated with disruption of the sleep-wake cycle (circadian rhythm disorders). For example, poor sleep quality and daytime sleepiness are found in 26% of men and 18% of women engaged in shift work. Jet lag is also a common cause of poor sleep and daytime sleepiness. Given that modern production is becoming increasingly complex, we can predict an increase in the prevalence of this type of occupational sleep disorder in the future.

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Consequences of sleep disorders

The impact of sleep disorders on general health, quality of life, and various economic indicators has been assessed in several studies. Knowing the high physiological significance of sleep, one can assume that its disturbances will significantly affect health. However, it is difficult to assess the consequences of sleep disorders, although there is a lot of evidence that poor sleep quality is fraught with serious complications. It was already mentioned that in a 1995 Gallup poll, people with chronic sleep disorders rated their overall physical condition lower than people with no disorders or with mild sleep disorders. Other studies noted that insomnia adversely affected a number of aspects of quality of life, such as life satisfaction, relationships with other people, and professional activity. Studies devoted to the study of the impact of sleep disorders on industrial activity revealed a link between drowsiness and frequent absenteeism, decreased performance and quality of work, and an increase in the number of accidents. Transport accidents are of particular importance for public health. People who suffer from insomnia are 2-3 times more likely to be involved in traffic accidents. According to a 1995 Gallup poll, 31% of adults reported feeling sleepy while driving. Moreover, about 4% of respondents reported having been involved in a traffic accident because they fell asleep at the wheel.

A number of studies have attempted to link insomnia with various diseases. It has been found that insomnia is associated with an increased risk of heart disease, hypertension, stroke, and diabetes. It has been proven that patients with obstructive sleep apnea have an increased risk of hypertension and stroke. Higher mortality has been reported in people with insomnia. However, it remains unclear whether these relationships are causal. Therefore, additional research is needed on the impact of sleep disorders on health.

Several researchers have attempted to estimate the economic costs of sleep-wake disorders. Although such estimates are approximate, they do provide an estimate of the scale of the damage. One such study estimated the total economic costs at approximately $100 billion. Another study estimated the potential costs of accidents related to sleep disorders at $50 billion.

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