7B: Circadian rhythm sleep disorder

What is a circadian rhythm sleep disorder?

A sleep disorder caused by misalignment between the internal sleep–wake cycle and the external environment or schedule.

What are common causes of circadian rhythm sleep disorders?

Shift work, jet lag, daylight saving time, adolescence or aging, environmental light exposure.

What are symptoms of circadian rhythm sleep disorders?

Difficulty initiating/maintaining sleep, excessive daytime sleepiness, impaired functioning, and sleep schedule conflict with daily life.

What is Delayed Sleep Phase Syndrome (DSPS)?

A disorder where sleep onset and wake time are delayed by 2+ hours, making it difficult to fall asleep early enough.

What factors contribute to DSPS?

Hormonal changes (especially in adolescence), longer-than-average circadian period, high sensitivity to evening light, reduced morning light sensitivity.

What is the treatment for DSPS?

Bright light therapy administered in the morning.

How does bright light therapy help DSPS?

It stimulates the SCN to promote cortisol release and suppress melatonin, shifting melatonin release earlier and promoting earlier sleep.

What is Advanced Sleep Phase Disorder (ASPD)?

A disorder where sleep onset and wake time are advanced by 2+ hours, causing early sleepiness and early waking.

What factors contribute to ASPD?

Aging, reduced evening light exposure, low morning light exposure, social/professional disruption of sleep schedule.

What is the treatment for ASPD?

Bright light therapy administered in the evening.

How does bright light therapy help ASPD?

It delays melatonin release and sleep onset, shifting the circadian rhythm later.

What is Shift Work Disorder?

A sleep disorder caused by working night or rotating shifts that disrupt the natural sleep–wake cycle.

Who is commonly affected by shift work disorder?

Workers in healthcare, emergency services, transport, hospitality, security, and manufacturing.

What are the effects of shift work disorder?

Daytime sleep difficulties, night-time fatigue, poor performance, and increased health risks.

What is the treatment for shift work disorder?

Bright light therapy before or during night shifts.

How does bright light therapy help shift work disorder?

It delays melatonin release, increases night-time alertness, and supports sleep after shifts.

When should bright light therapy be used for DSPS?

In the morning at the desired wake time.

When should bright light therapy be used for ASPD?

In the evening to delay sleep onset.

When should bright light therapy be used for shift work disorder?

Before or during a night shift.

How does bright light therapy shift the circadian rhythm?

By stimulating the SCN to adjust melatonin and cortisol release timing.

Why is the timing of light exposure important in therapy?

Timing ensures the therapy is effective for shifting the circadian rhythm in the desired direction.

What is the role of cortisol in sleep–wake cycle adjustment?

It promotes wakefulness; morning release helps align waking with external cues.

Why must the light amount be tailored in therapy?

To match the individual’s needs and prevent side effects like headaches or discomfort.

What are the safety guidelines for bright light therapy?

Do not look directly at the light; keep a safe distance to prevent eye damage.

What effect does morning light exposure have in DSPS?

Promotes earlier wakefulness and shifts melatonin release earlier in the evening.

What effect does evening light exposure have in ASPD?

Delays melatonin release, helping the person stay awake longer and sleep later.

What does bright light therapy aim to treat in shift workers?

Difficulty sleeping during the day and staying awake during night shifts.