Chalter 7b Flashcards
Sleep disorder
Sleep disorders are disturbances to typical sleeping and waking patterns. In this way, sleep disorders are broad and encompass many different types of sleep-related problems. This lesson will focus on circadian rhythm sleep disorders as a type of sleep disorder, as illustrated by figure 1.
Circadian sleep disorder cause and effect
Circadian rhythm sleep disorders are sleep disorders that interfere with the typical regulation of the circadian rhythm of sleep, leading to a change in the sleep-wake cycle.
Causes: Circadian rhythm sleep disorders are fundamentally caused by a disruption to the typical sleep-wake cycle. This can be due to a biological issue, such as the sleep-wake shift that occurs in adolescents, or lifestyle changes, such as shift work.
Effects: Circadian rhythm sleep disorders tend to result in an individual experiencing some form of sleep deprivation. Therefore, an individual may experience:
• amplified emotional responses • fatigue
• irritability
• reduced ability to concentrate.
Circadian rhythm sleep disorders can also be disruptive to an individual’s lifestyle. Sleeping and waking at abnormal times can result in an individual being late for certain commitments, such as school, or feeling sleepy at abnormal times, which makes it difficult to complete daily tasks.
Types of circadian sleep disorders
Delayed sleep phase syndrome (DSPS) is a type of circadian rhythm sleep disorder in which sleep and waking occur later than usual. In this way, the sleep-wake cycle is delayed. For example, if an individual typically starts sleeping at 10pm and wakes at 8am, with DSPS they may instead start sleeping at 1am and wake at 11am. DSPS is caused by a misalignment between external and internal cues that regulate the circadian rhythm. Specifically, external cues are received at an appropriate time but internal cues are not. For example, an individual with DSPS still receives the external cues of light in the morning and dark in the night, but they do not receive internal cues properly in the morning and at night. This causes melatonin secretion to occur later and therefore the individual’s sleep and wake times occur later than appropriate.
Advanced sleep phase disorder (ASPD) is a type of circadian rhythm sleep disorder in which sleep and waking occur earlier than usual. In this way, the sleep-wake cycle is advanced.For example, if an individual typically sleeps at 10pm and wakes at 8am, with ASPD they may sleep at 7pm and wake at 5am. Similar to DSPS, ASPD is caused by a misalignment between external and internal cues that regulate the circadian rhythm. Specifically, external cues are being received at an appropriate time, while internal cues are not. For example, an individual with ASPD still receives the external cues of light in the morning and dark in the night, but their internal cues are not being received properly in the morning and night. This causes the individual to sleep and wake earlier than appropriate, due to melatonin secretion occurring earlier. In this way, the difference between DSPS and ASPD is that melatonin secretion occurs later for individuals with DSPS and earlier for individuals with ASPD.
Shift work and it’s effects
Shift work is an occupation that involves working at unusual hours, such as working overnight. This can mean an individual has to sleep at unusual times, such as during the day, rather than at night. Shift work also involves rotating shift work, which may involve working a week of morning shifts, followed by a week of night shifts. Therefore, shift work impacts an individual’s sleep-wake cycle as their circadian rhythm is constantly changing and adapting to their environment. This often leads to individuals having difficulty initiating sleep and waking while adjusting from one shift to another. Shift work is considered to be a cause of sleep problems, rather than being a sleep disorder itself. In this way, shift work can result in a circadian rhythm sleep disorder, as well as or other sleep-related issues. Effects of shift work on sleep include:
• insomnia (a sleep disorder characterised by difficulty falling asleep and staying asleep). Shift work overnight can disrupt the body’s circadian rhythm and can trigger insomnia.
• fragmented sleep. Shift work often involves working unusual hours and therefore having to sleep at unusual hours. This can involve repeatedly waking up during a sleep episode and having multiple short sleep episodes during the day (naps), as opposed to one regular sleep episode (approximately 8 hours).
• circadian rhythm phase disorder. External cues from the environment are out of sync with shift work requirements, as shift workers can be in highly lit environments during night-time.
• quality and quantity of sleep can be adversely affected. Due to internal cues, such as clock gene expression and suppression, the body is programmed to sleep during the night and be wakeful during the day.
While ASPD and DSPS are caused by problems with internal cues, shift work disorders are caused by problems with external cues as an individual is required to be awake when it’s dark and sleep when it’s light.
Bright light therapy
Bright light therapy a method used to adjust a person’s circadian rhythm through exposure to a high-intensity light source
When an individual is exposed to the light source in the morning, the suprachiasmatic nucleus (SCN) will be signalled, promoting wakefulness through the release of cortisol. This will in turn trigger an earlier release of melatonin at night-time by the pineal gland. Consequently, the individual will fall asleep earlier at night-time and thus experience a longer and more restful sleep which will benefit the individual the following day.
Exposure sessions can last from about 15 minutes to a couple of hours and are conducted up to a few times a day. In order to readjust the sleep-wake cycle, a person needs to conduct these sessions for at least a few consecutive days. This helps to gradually shift a person’s sleep-wake cycle, as they can adjust the time of the exposure session each day to reach their desired waking time. Often, minor improvements can be seen in the first few days, but a few weeks of bright light therapy is required for significant results.
Factors essential for bright light therapy
Factors essential for bright light therapy :
Appropriate timing of exposure sessions Bright light therapy must occur at the right time in order to make a person feel awake at the right time. For example, people who feel sleepy earlier than appropriate, such as by 5pm, can conduct an exposure session in the late afternoon or early evening in order to help them stay awake and fall asleep later at a more appropriate time.
The right amount of light The intensity of the light and the length of exposure sessions must be appropriate to the person’s disorder and desired changes to their circadian rhythm. The intensity and length should also be built up gradually in order to avoid negative side effects like headaches.
Safe exposure A person should not look directly at the light, and their face should be an adequate distance away from the light source.
Bright light therapy effect on various sleep disorders
Bright light therapy effect on various sleep disorders:
Delayed sleep phase syndrome An individual is exposed to the bright light source in the morning at an appropriate waking time. This will act as an external cue to the suprachiasmatic nucleus and promote wakefulness, by sending signals to release cortisol. This will help the suprachiasmatic nucleus send signals for melatonin release at an earlier, more appropriate sleeping time, thus promoting sleep.
Advanced sleep phase disorder An individual is exposed to the bright light source in the evening when feeling sleepy, to act as an external cue to the suprachiasmatic nucleus and promote wakefulness. This will then help the suprachiasmatic nucleus send signals for melatonin release at a later, more appropriate sleeping time, thus promoting sleep. Additionally, this will encourage the suprachiasmatic nucleus to signal cortisol release later in the morning at a more appropriate time.
Shift work- related sleep disorder The use of bright light therapy for shift work depends on the details and timing of an individual’s work. An individual is best to be exposed to the bright light source before beginning their shift work, in order to promote wakefulness when they need to be awake and alert. This will help promote sleepiness at a later, more suitable time (when they are not required to work), whether that be during the morning or afternoon.
