Circadian Rhythm Sleep Disorders

Deborah M. Brooks, MD, and Lee J. Brooks, MD, FAAP

Introduction

•Circadian rhythm basics

•Circadian rhythms are the body’s (typically) 24-hour clock, controlled by the suprachiasmatic nucleus (SCN) in the brain.

•Circadian rhythm sleep disorders (CRSDs)

—CRSDs are a timing problem with wake and sleep—either a problem with the internal body clock or a mismatch between the internal clock and the environment.

—Symptoms include trouble falling asleep, trouble staying asleep, waking up too early, or poor quality of sleep—functioning must be impaired for it to be considered a disorder.

—Common to these disorders is inflexibility: Even when physically tired or sleep deprived, sufferers cannot make up for lost sleep outside of their endogenous sleep times.

—Types of CRSDs include

▪Advanced sleep phase

▪Delayed sleep phase

▪Jet lag

▪Shift work

▪Irregular sleep phase

▪Non–24-hour sleep-wake rhythm disorder

Advanced Sleep Phase

Basics

•Sleep and wake times are habitually early when compared with conventional times, such as in “morning people” or “larks.”

•This is more common in older adults.

Etiology

•Possibly a shortened circadian rhythm

Symptoms

•Extreme sleepiness in the late afternoon or early evening

•Involuntary early-morning awakening

Delayed Sleep Phase

Basics

•It is more common among adolescents and young adults, with a reported prevalence of 7%–16%.

—Forty percent of affected individuals have a positive family history.

Etiology

•An etiologic origin is possibly an exaggerated reaction to the normal shift in the internal clock that is seen in adolescents after puberty.

•Because of the delay in falling asleep and yet still needing to get up at the required time for work or school, children or adolescents often experience excessive daytime drowsiness as a result of not getting enough sleep (this is most evident on weekdays). The delayed rhythm is coupled with a delay in the cycle of the night hormone melatonin, which lingers in the morning and makes it harder to wake up.

Symptoms

•The patient awakens late.

•Inability to fall asleep at the desired time usually manifests as insomnia complaints. It may be exacerbated by the social pressures teenagers feel to stay up late (eg, to do homework or to use the Internet or a cell phone).

•Inability to wake up at the desired time and excessive daytime sleepiness are usually the most common complaint because it is more readily evident to parents than the nighttime insomnia.

Basics

•Jet lag occurs when long travel by airplane quickly puts a person in another time zone and the person must sleep and wake at times that are misaligned with his or her body clock.

—The body clock is slightly longer than 24 hours. This makes it easier to travel westward than eastward because it is easier to delay sleep than to advance sleep.

•Jet lag affects all age groups.

Symptoms

•Disturbed sleep

•Decreased alertness and impaired daytime function

•Occasionally, gastrointestinal distress and general malaise

•Depressed mood, irritability, and anxiety

Shift Work

Basics

•This occurs when a person’s work hours are scheduled during the normal sleep period.

•It is not common in children.

•The primary etiologic origin is the opposition of required sleep and wake times to one’s endogenous circadian rhythm of sleep and waking.

Symptoms

•Sleepiness during the work shift

•Difficulty sleeping while others are awake

•Shortened sleep duration by 1–4 hours

Irregular Sleep Phase

Basics

•This is characterized by lack of a clearly defined circadian rhythm of sleep and waking.

•It is commonly associated with developmental disorders in children and in adults with neurodegenerative diseases and brain tumors or traumatic brain injury.

Etiology

•The etiologic origin is likely central degeneration of SCN neurons.

•Decreased exposure to or input of external synchronizing agents (zeitgebers), such as light and activity, results in a weakened central circadian rhythm.

•Sleep is fragmented into a series of at least 3 naps that occur throughout a 24-hour period.

•Total sleep time is usually normal for the patient’s age.

Non–24-Hour Sleep-Wake Disorder

Basics

•This disorder is characterized by fluctuating periods of insomnia and/or excessive sleepiness that occur because the intrinsic circadian pacemaker is not entrained to a 24-hour light-dark cycle.

•Most individuals with this disorder are totally blind, and the failure to entrain circadian rhythms is related to the lack of light input to the SCN.

•Occasionally, the disorder is associated with mental retardation or dementia.

Symptoms

•A person’s day length is longer than 24 hours. Sleep times get progressively later and later, so the person is eventually sleeping during the day until he or she cycles back to a nighttime bedtime.

Differential Diagnosis

•The presence of sleep disorders, including obstructive sleep apnea (OSA), narcolepsy, and restless legs syndrome, among others, needs to be considered.

•In addition to comorbid sleep disorders, psychiatric disorders—particularly depression and anxiety—are common in patients with nearly all types of CRSDs and should be considered in the differential diagnosis.

•Children and adolescents with a delayed sleep phase may experience depression and other psychiatric problems, including behavioral problems, as a result of daytime drowsiness and missing school. Daytime drowsiness can also lead to lowered academic performance from missed school days or tardiness and inattention. Dependency on caffeine, sedatives, or alcohol may also be seen.

Diagnostic Considerations

•The diagnosis of all CRSDs is based on a careful history and review of a sleep diary with actigraphy.

—In addition to the typical symptomatology, diagnosis of irregular sleep phase requires a history of a minimum of 3 irregular sleep-wake cycles in a 24-hour cycle, recorded for 14 days in a sleep diary and/or with actigraphy.

•Polysomnography (PSG) is not routinely indicated to establish the diagnosis. However, PSG is indicated to assess the presence of other comorbid sleep disorders, such as OSA syndrome and narcolepsy.

—Bright-light therapy

▪Exposing the child to bright light for approximately half an hour in the morning helps to reset the body’s internal clock. Reduced exposure to bright light in the evening also helps.

—Taking melatonin about an hour before the desired bedtime may help shift the circadian clock.

•Advanced sleep phase

—Sleep-wake scheduling

▪Time light exposure in the evening and avoid light in early morning hours.

—Melatonin or hypnotics may be beneficial for sleep maintenance insomnia.

•Jet lag

—Melatonin

▪For greatest effectiveness, melatonin should be taken at the target bedtime, optimally starting 3–4 days before departure.

—Light therapy

▪Strategic exposure and avoidance of exposure to light have been used as an effective treatment approach.

—Additional treatment options include maintaining home-based sleep hours for brief travel, short-term use of hypnotics for insomnia, and caffeine to alleviate daytime sleepiness.

Resources for Families

•What Is Delayed Sleep Phase Disorder? (National Sleep Foundation). sleepdisorders.sleepfoundation.org/chapter-5-circadian-rhythm-sleep- disorders