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Knowledge Base » Mental Health » Non-24-Hour Sleep-Wake Disorder

Non-24-Hour Sleep-Wake Disorder

According to the National Organization for Rare Disorders, non-24-hour sleep-wake disorder (Non-24) occurs in 55-70% of completely blind people, but also occurs in an unknown number of sighted people. According to the NHS, in the UK, more than 2 million people are living with sight loss. Of these, around 340,000 are registered as blind or partially sighted.

Many people may be suffering from Non-24 without realising it. Raising awareness helps people to recognise the symptoms and seek appropriate diagnosis and treatment. Non-24 can significantly impact a person’s quality of life. By increasing awareness, affected people can seek help and potentially improve their quality of life.

What is Non-24-Hour Sleep-Wake Disorder (Non-24)?

Non-24-hour sleep-wake disorder (Non-24) is a circadian rhythm sleep disorder where your internal body clock, or circadian rhythm, is not aligned with the 24-hour day. This means that sleep times gradually shift later and later each day. Eventually, the person’s sleep schedule moves through all hours of the day and night over several weeks or months.

As the sleep cycle shifts, people may struggle to stay awake during the day or find it difficult to fall asleep at night, depending on the phase of their cycle. Sleep quality and duration can vary widely, with periods of insomnia or excessive sleepiness.

Sleep is a fundamental biological process that supports nearly every system in the body and is essential for maintaining overall health and well-being.

  • Sleep is crucial for the repair of cells and tissues. During deep sleep, the body releases growth hormones that aid in healing and muscle repair.
  • Adequate sleep strengthens the immune system, helping the body to fend off infections and illnesses. Chronic sleep deprivation can weaken immune defences.
  • Good sleep habits contribute to heart health by maintaining blood pressure and reducing the risk of cardiovascular diseases.
  • Sleep plays a critical role in cognitive processes such as learning, memory, problem-solving and decision-making. During sleep, the brain consolidates and organises information.
  • Proper sleep helps regulate emotions and mood. Lack of sleep is associated with increased stress, anxiety and depression.
  • Sleep enhances focus, attention and reaction times, which are essential for daily tasks and productivity.
  • Quality sleep promotes creativity and the ability to solve complex problems by allowing the brain to form new connections and insights.
  • Sleep deprivation is a significant factor in accidents and injuries. It impairs judgement, coordination and reaction times, increasing the likelihood of mistakes and accidents.
  • Sleep helps regulate hormones that control appetite, metabolism and stress. Poor sleep can disrupt these hormones, leading to weight gain, increased appetite and stress-related disorders.
  • Persistent sleep deprivation is linked to various chronic conditions, including obesity, diabetes, hypertension, and certain types of cancer. Good sleep habits are an essential component of a healthy lifestyle.

Prevalence and Demographics

Non-24 is most commonly observed in people who are totally blind. Without light perception, their circadian rhythm cannot synchronise with the natural light-dark cycle, leading to a free-running circadian rhythm.

Though it is less common, sighted individuals can also develop Non-24 due to other factors affecting the circadian system, such as irregular exposure to light, lifestyle factors or certain medical conditions.

Circadian Rhythms and the Biological Clock

Circadian rhythms are natural, internal processes that regulate the sleep-wake cycle and repeat roughly every 24 hours. These rhythms are influenced by external cues like light and temperature, but they are fundamentally driven by the body’s internal biological clock.

The biological clock refers to the internal mechanism that controls the circadian rhythms. It is composed of a group of nerve cells in the brain known as the suprachiasmatic nucleus (SCN), located in the hypothalamus. The SCN receives information about light exposure directly from the eyes and uses this information to coordinate the timing of various physiological processes, such as the sleep-wake cycle, the most well-known circadian rhythm, regulating when we feel alert and when we feel sleepy.

Hormones like melatonin and cortisol follow a circadian pattern. Melatonin, which promotes sleep, is typically produced at night, while cortisol, which promotes wakefulness, is produced in the early morning.

Body temperature fluctuates over a 24-hour period, typically peaking in the late afternoon and reaching its lowest point in the early morning hours. Appetite and digestion are influenced by circadian rhythms, affecting when we feel hungry and how our body processes food.

Circadian rhythms help ensure that we get restful sleep by promoting sleepiness at night and wakefulness during the day. Disruptions to circadian rhythms, such as those caused by shift work, jet lag, exposure to artificial light at night, and having Non-24 can lead to various health problems, including sleep disorders, obesity, diabetes, depression and cardiovascular diseases.

Cognitive functions like memory, attention and problem-solving ability can be optimised when activities are aligned with the body’s natural circadian rhythms.

Light is the primary cue for resetting the biological clock. Exposure to natural light during the day and minimising artificial light exposure at night helps maintain healthy circadian rhythms. Fluctuations in ambient temperature can also signal the biological clock, influencing sleep patterns.

Daily routines and behaviours, such as mealtimes, exercise and social interactions, play a role in reinforcing circadian rhythms, therefore being mindful of these can help in people with Non-24.

Symptoms and Experiences

The condition is especially common among blind individuals but can also occur in sighted people. The most common symptoms include:

  • Irregular sleep patterns – people with Non-24 experience a cycle where their sleep time gradually shifts later each day. This can lead to a progressive delay in sleep onset and waking times.
  • Insomnia – difficulty falling asleep or staying asleep at conventional times is common.
  • Daytime sleepiness – due to the misalignment with the 24-hour day, people with the condition can often feel excessively sleepy during the day.
  • Night-time wakefulness – people with the condition might find themselves awake and alert during the night when they would typically be expected to sleep.
  • Fatigue – chronic tiredness and a lack of energy are frequent due to the irregular sleep patterns.
  • Difficulty with managing daily activities – the sleep can interfere with social, occupational and educational activities, as the person’s active hours may not coincide with typical daytime schedules.
  • Mood disturbances – there can be symptoms of depression or irritability due to the constant struggle with sleep patterns.
  • Cognitive impairment – problems with concentration, memory and overall cognitive function might occur because of the inconsistent sleep schedule.

Causes and Triggers

The causes and triggers of Non-24 can vary and are typically divided into intrinsic and extrinsic factors.

Intrinsic causes include:

  • Blindness – the most common cause of Non-24 is total blindness. People who are totally blind lack the light perception necessary for synchronising their internal circadian clock with the external environment. The absence of light signals prevents the brain from resetting the circadian rhythm, leading to a free-running sleep-wake cycle.
  • Genetic factors – genetic predisposition can play a role in Non-24. Mutations or variations in genes that control the circadian rhythm can disrupt the normal functioning of the biological clock.
  • Neurological conditions – certain neurological disorders or brain injuries that affect the hypothalamus, the brain region responsible for regulating circadian rhythms, can lead to Non-24. Conditions like brain tumours, strokes or neurodegenerative diseases might interfere with the normal function of the circadian system.

Extrinsic triggers include:

  • Environmental factors – lack of exposure to natural light or irregular light-dark cycles can contribute to the development of Non-24. People who spend extended periods in environments without regular light cues, for example submarines, space stations or darkened rooms, may experience disruptions in their circadian rhythms.
  • Behavioural factors – irregular sleep schedules, such as those caused by shift work, frequent travel across time zones, or other lifestyle factors, can disrupt the alignment of the circadian clock with the 24-hour day, potentially triggering Non-24 in people who are susceptible.
  • Medical conditions – certain medical conditions, such as chronic fatigue syndrome, depression or other mood disorders, can disrupt sleep patterns and contribute to the development of Non-24.
  • Pharmacological agents – the use of certain medications or substances that affect the central nervous system can also disrupt circadian rhythms. Drugs such as melatonin receptor agonists, benzodiazepines or stimulants might alter the normal sleep-wake cycle, potentially leading to Non-24 in some people.

Diagnosis and Management

A diagnosis of Non-24 usually involves:

  • A detailed sleep history over an extended period of time.
  • Documentation of progressively delayed sleep onset and wake times.
  • Identification of any symptoms of chronic sleep deprivation or irregular sleep patterns.
  • A sleep diary kept by the patient for at least one to two weeks, noting sleep onset and wake times.
  • Wearing a wrist actigraph, a device that tracks movement and provides an objective measure of sleep-wake patterns over several weeks.
  • Polysomnography providing overnight sleep studies to rule out other sleep disorders.
  • Melatonin rhythm measurements through saliva or blood tests to assess the timing of melatonin production.

Management of the condition usually involves:

  • Light therapy – for sighted individuals, exposure to bright light during the morning hours can help to reset the circadian clock.
  • The use of light boxes – these are used as they simulate natural daylight.
  • Melatonin supplements – taking melatonin in the evening before the desired bedtime to advance the circadian phase. The dosage and timings need to be individualised and closely monitored.
  • Chronotherapy – gradually delaying sleep times by 1-2 hours per night until the desired bedtime is achieved. This requires strict adherence to the schedule, making it challenging for many patients.
  • Prioritising sleep hygiene – establishing a consistent bedtime routine and creating a sleep-conducive environment. It is recommended that the room be cool, dark and quiet.
  • Pharmacotherapy – this includes tasimelteon, a melatonin receptor agonist, specifically approved for Non-24 in totally blind people. Other medications such as hypnotics or wakefulness-promoting agents may be used to manage symptoms but should be used with caution and under medical supervision.
  • Behavioural therapy – cognitive behavioural therapy for insomnia (CBT-I) can be used to address any concurrent insomnia or maladaptive sleep behaviours.

There should be regular follow-up appointments in order to assess treatment efficacy and adjust treatment as needed. Continuous monitoring using sleep diaries or actigraphy to ensure the alignment of the sleep-wake cycle with the desired schedule should be used.

Educating patients and their families about the nature of Non-24 and the importance of adhering to treatment plans is important. Providing resources such as support groups or counselling to help cope with the social and occupational challenges posed by the disorder will also be beneficial.

Coping Strategies

If you have been diagnosed with Non-24 there are things you can do to help you cope, including:

  • Strict sleep schedule – try to maintain a consistent sleep and wake time every day, even on weekends. This consistency can help regulate your circadian rhythm.
  • Sleep hygiene – create a relaxing bedtime routine, avoid screens before bedtime, and make sure your sleep environment is conducive to rest.
  • Napping – strategic napping can help manage excessive daytime sleepiness, but avoid napping too late in the day to prevent disrupting night-time sleep.
  • Adjusting your schedules – if possible, adjust work or school schedules to better fit your sleep-wake cycle. Flexible schedules can help accommodate periods when you are most alert and productive.
  • Support groups – joining support groups or talking to others who have Non-24 can provide emotional support and practical tips for managing the condition.
  • Physical activity – engaging in regular physical activity, especially in the morning, can help regulate your sleep patterns. Avoid intense exercise close to bedtime.
  • Healthy eating – eating a healthy, balanced diet – maintain a balanced diet and avoid caffeine and heavy meals close to bedtime. Eating at regular times can also help stabilise your internal clock.

Implementing these strategies can help manage the symptoms of Non-24 and improve overall quality of life. Since Non-24 can vary widely in its impact, a combination of approaches tailored to individual needs is often the most effective way to cope with the disorder. Working with a sleep specialist or a chronobiologist who can provide tailored advice and treatment options based on your specific situation can be beneficial.

The RNIB is the UK’s leading charity for people with vision loss. The RNIB website offers useful information, such as coming to terms with sight loss.

Non-24 is an organisation specifically for people with Non-24. They offer useful information and practical advice about living with the disorder.

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About the author

Claire Vain

Claire Vain

Claire graduated with a degree in Social Work in 2010. She is currently enjoying her career moving in a different direction, working as a professional writer and editor. Outside of work Claire loves to travel, spend time with her family and two dogs and she practices yoga at every opportunity!

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