Circadian Sleep Disorders

Question 1

To cause a phase advance, should bright light be used before or after a temperature nadir (bottom)?

Answer 1

After

Bright light after temperature nadir = phase advance (earlier in day)

Bright light before temperature nadir = phase delay (later in day)

Question 2

What is the normal DLMO?

In DSPD?

In ASPD?

Answer 2

8 to 10 pm is normal

In DSPD it is delayed by hours

In ASPD it is advanced by hours

Question 3

In patients with DSPD do they have a normal ability to compensate for sleep loss?

Answer 3

No. They are not able to compensate as well.

Question 4

What circadian sleep disorder has a strong genetic basis?

Answer 4

ASPD (PER2 gene)

Question 5

In ASPD when should melatonin be taken?

When should light therapy be used?

Answer 5

• Melatonin: Early in the AM (it should be several hours after the temperature nadir). Melatonin pulls the rhythm towards it (thus causing a phase delay).
• Light: Late evening (7 to 9 pm). Light pushes the rhythm away from it (thus causing a phase delay).

Question 6

What has a stronger effect on circadian rhythms, light or melatonin?

Answer 6

Light

Question 7

What is non-24-hour sleep-wake disorder and in what group of people is it most commonly seen?

Answer 7

It is a free running disorder is which there is a daily phase delay (shifing to the right).

It is most commonly seen in blind people

Question 8

Circadian disorders are common in what 3 medical conditions?

Answer 8

1. Hepatic encephalopathy
2. Parkinson’s disease
3. Dementia

Question 9

When does DLMO typically occur?

Answer 9

2 to 3 hours before habitual bedtime

Question 10

Core Body Temperature minimum (CBTm) typcially occurs when?

Answer 10

2 to 3 hours before sleep offset (normal wake time)

Question 11

How can CBTmin be calculated using DLMO?

Answer 11

DLMO + 7 hours

Question 12

What is the best treatment for non-24 hour sleep-wake disorder?

Answer 12

Melatonin 1 hour before desired bedtime

Question 13

What is the best treatment for DSPD?

What is the next best treatment?

Answer 13

Bright light for 30 minutes shortly after CBT min

Melatonin given a few hours prior to desired bedtime

Question 14

How long does it take for the human biological oscillator (known as Tau) to complete one cycle?

Answer 14

24.2 hours

Question 15

How many time zones must be crossed to meet a diagnosis of Jet lag disorder?

Answer 15

2 or more time zones

Question 16

Which requires a phase delay, flying east to west or west to east?

Answer 16

Flying east to west. It requires you to stay awake longer (thus delaying sleep at the new normal time)

Question 17

Which requires a phase advance, flying west to east or east to west?

Answer 17

Flying west to east (since you will be have to be awake earlier to be on the same schedule as those on the east coast - you advanced)

Question 18

Which is easier to adapt to, west to east travel or east to west and why? After how many times zones travelled is the least beneficial?

Answer 18

• East to West. It’s a phase delay. Since our circadian clock is a natural phase delay (24.2 hours) we are naturally able to stay up later than go to bed earlier.
• 8 time zones

Question 19

What happens when a patient with a predisposition to DSPD is exposed to bright light in the evening?

Answer 19

It causes a phase delay as they are hypersensitive to melatonin suppression with bright light exposure

Question 20

How long is the circadian rhythm in ASPD?

Answer 20

Less than 24 hours

Question 21

What is chronotherapy?

What circadian disorder is it used in?

Answer 21

Progressively delaying sleep and wake times by 3 hours every few days until they reach the desired sleep time.

It is used in DSPD

Question 22

Treatment for Non-24-hour sleep-wake disorder (4 things)

Answer 22

1. Bright light in AM
2. B12
3. Rapid release melatonin or tasimelteon (Hetlioz) 20 mg
4. Sleep hygeine

Question 23

What medical condition is delayed sleep phase syndrome seen in 33% of patients?

Answer 23

Chronic liver cirrhosis