The first part: Apps and Wearable Devices in Sleep

Sleep-wake Disorders

Sleep occupies about one-third of a person's lifetime. It is also vital in maintaining essential bodily functions and supports people's health.

Interference with proper sleep can result in insomnia, excessive sleep, and abnormal behavior during sleep. It has also been indicated that sleep disturbance can sometimes cause a decline in physical functions, such as weakening the immune system and increase the risk of developing physical and mental illnesses. These various influences also cause a decrease in labor productivity, and health awareness of the importance of sleep has been increasing year by year.

However, the number of people suffering from sleep problems increases yearly. Among sleep-wake disorders, insomnia disorders are the most prevalent. Insomnia disorders is defined as the inability to maintain sufficient quantity or quality of sleep despite adequate opportunities for sleep, resulting in functional impairment under certain circumstances.  ¹⁾²⁾

Although many medical institutions primarily use a medical interview to diagnose sleep-wake disorders, polysomnography (PSG), which uses various sensors, is widely accepted as a test with high evaluation accuracy. PSG is used to understand sleep patterns and diagnose. Still, the testing equipment is expensive and often makes it difficult to fall asleep, as the patient must lie in bed wearing many complicated sensors in an environment that differs from the usual. For this reason, only a limited number of medical institutions have introduced these devices, and some people meet the diagnostic criteria for sleep-wake disorders but do not receive medical attention or treatment.

Depending on the classification of the sleep-wake disorder, treatment includes sleep hygiene instruction, pharmacotherapy, and cognitive-behavioral therapy when necessary. ³⁾ Cognitive-behavioral therapy for insomnia disorders, in particular, is expected to be as effective as pharmacotherapy. However, in Japan, cognitive-behavioral therapy is not widely used due to insured medical treatment issues.

Sleep and Psychiatric Disorders
Sleep-wake disorders are sometimes associated with depression, anxiety, and cognitive changes. They are also often precursors to the onset of psychiatric disorders. Early intervention to prevent severe illness or alleviate insomnia symptoms is considered depending on the severity. Correction of sleep disturbances is a priority in actual clinical psychiatric practice.

Examples of how psychiatric disorders can alter sleep status include the acute phase of depression, which has been reported to occur in as many as 90% of patients. ⁴⁾ Alzheimer's disease also causes changes in sleep and circadian rhythm control. These changes are due to degeneration of the hypothalamus and basal forebrain, associated with dementia, and disruption of the sleep-wake regulatory circuits in these areas.

Sleep problems can also affect the results of stress checks taken at the workplace, even under non-mental illness. It has been reported that 2.3% of those with a high-stress score had no sleep problems, while 16.9% had sleep problems. ⁵⁾ Thus, it is possible that sleep problems may also cause an impact on presenteeism in the workplace.

Sleep and Wearable Devices
The possibility of a simplified sleep test without compromising objectivity has been studied in sleep testing, which has been available only at a limited number of institutions. The result has been the emergence of small electroencephalographs and electromyographs. Besides, a wristwatch-type device called actigraphy, which AMI of the United States developed, is introduced. 

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