What Are Circadian Rhythm Disorders?


The human sleep-wake cycle is designed to follow a 24-hour period known as the circadian rhythm (1). Although the exact timing of the circadian rhythm can vary from person to person, most people tend to wake up in the morning and go to sleep at night. Circadian rhythm sleep-wake disorders occur when a person's circadian rhythm falls out of alignment with their school, work, or social obligations and causes significant sleep problems or trouble functioning in day-to-day life.

The prevalence of circadian rhythm sleep disorders is unknown (2). However, factors such as age, genetics, underlying health conditions, gender, and lifestyle factors may elevate the risk (3) of developing one of these disorders. As light is one of the most powerful cues for anchoring the circadian rhythm, circadian rhythm disorders may be exacerbated by light exposure near bedtime or insufficient light exposure during the day.

Types of Circadian Rhythm Disorders

Learning about the different types of circadian rhythm disorders can help you discover how to know if your circadian rhythm is off.

Advanced Sleep-Wake Phase Disorder

People with advanced sleep phase disorder typically become sleepy in the early evening (4), at least two hours earlier than what is considered socially acceptable. Resisting evening sleepiness and staying up later may lead to sleep deprivation, as these individuals have a natural tendency to wake up in the very early morning as well. Advanced sleep phase disorder runs in families and is more common in middle-aged and older adults, affecting approximately 1% of middle-aged adults.

Delayed Sleep-Wake Phase Disorder

Delayed sleep phase disorder is characterized by bedtimes that are significantly later than what is considered socially acceptable. When work, school, or social commitments require them to wake up early, individuals with a delayed circadian rhythm may fall into a cycle of nighttime insomnia and chronic sleep deprivation. Delayed sleep phase disorder is most common in adolescents, affecting between 7% and 16% of teens. The disorder is often accompanied by anxiety and depression and may have a genetic component.

Non-24-Hour Sleep-Wake Rhythm Disorder

People with non-24-hour sleep-wake disorder have a circadian rhythm that is shorter or (usually) longer than 24 hours. Bedtimes drift a little later every day until they eventually complete a full loop of the clock. Diagnosing non-24-hour sleep-wake disorder can be tricky, because insomnia and daytime tiredness symptoms change from week to week and may periodically disappear altogether. Non-24-hour sleep-wake disorder occurs in about 50% of people with total blindness due to the lack of light cues.

Irregular Sleep-Wake Rhythm Disorder

Instead of displaying a consolidated sleep period during the night, individuals with irregular sleep-wake rhythm disorder sleep at shorter random intervals throughout the day and night. Irregular sleep-wake rhythm disorder is more common in children with developmental disabilities and individuals with neurodegenerative disorders, such as Parkinson's disease. The disorder may arise as a consequence of damage to nerves that control the circadian clock, combined with a long-term care home lifestyle that lacks a strong set of day and night cues.

Shift Work Disorder

Those who work night or early-morning shifts or who have irregular work schedules may be unable to sleep when they want to, even if all the conditions for sleep are perfect. Most shift workers are able to adapt to their unusual schedules. However, for approximately 10% to 38% of shift workers, work-related sleep troubles lead to chronic sleep deprivation. Age, work schedule, commute time, and other factors play a role in how easy it is to adapt to a shift work schedule.

Jet Lag Disorder

Jet lag occurs when the internal body clock falls out of alignment with the local day and night as a result of rapid travel across multiple time zones. People with jet lag may feel tired during the day and unable to sleep through the night. Although almost everybody experiences jet lag when flying across multiple time zones, these symptoms tend to resolve after about a week. However, for people who fly frequently, such as flight attendants (5), jet lag may cause chronic sleep and health problems. Jet lag is usually worse when flying east.

How to Manage Your Circadian Rhythm Sleep Disorder

Most people with circadian rhythm sleep disorders find their insomnia and daytime sleepiness symptoms improve when they are able to sleep at their preferred times. The problem is that these internal schedules are often incompatible with social and work schedules. Therefore, treatment for circadian rhythm sleep disorders usually focuses on strengthening sleep-wake cues.

Depending on the disorder, your doctor may recommend timed light exposure, melatonin supplements, carefully scheduled naps, wake- or sleep-promoting agents, sleep hygiene techniques, or chronotherapy that gradually shifts bedtimes later until they fall at the desired hour.

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