Now, let's talk about advanced sleep-wake phase disorder.
Here, we're looking at that
same sleep pattern over the course of the week and we see
that sleep onset is
earlier than desired. Patients are going to bed earlier than
they would like to.
Again, the awakening time is also earlier than desired and
importantly the sleep
quality and duration are preserved. So these are people that
are going to bed and
sleeping earlier than they would want. Risk factors include
older age. As we age,
our sleep time becomes earlier and earlier in the day. There
is also an autosomal
dominant familial variant as a result of missed sense
mutations that result in a
shorter circadian period. The typical presentation is a
patient who just can't stay
awake during the evening. These are our early birds. Now
let's talk about irregular
sleep-wake rhythm disorder. Here, you can see that same
typical pattern of sleep
over the course of the week and now sleep is significantly
disrupted and erratic.
There are periods of wakefulness and sleep that are not
consolidated leading to
significant fragmentation of sleep episodes over the course
of 24 hours. There is
no clear circadian rhythm, no standard sleep time or awake
time in these patients.
dysfunction of the suprachiasmatic nucleus likely plays a
critical role. The brain
doesn't know when to wake up and there is not a consistent
trigger for the brain to
wake. Risk factors include neurodegenerative disorders and
we can see this
fragmentation of a regular sleep-wake rhythm in patients
with advanced dementia.
Patients will report more than 3 bouts of sleep with each
one lasting 1-4 hours.
Now, let's talk about non-24-hour sleep-wake rhythm
disorder. So normally, the
circadian rhythm is around 24 hours and patients with this
disorder will have a
circadian sleep-wake cycle that begins greater than or less
than that 24-hour period.
And we can call this a free running disorder. So you see
here on Monday night the
patient goes to bed around 11 and that normal circadian
rhythm would have the
patient go into bed at 11 every time of the week. But here,
we see that pushed out.
So it's a progressive free running and lengthening of the
circadian rhythm in this
patient. The sleep duration is still the same and the
quality of the sleep can be
maintained but over time progressive dysfunction and
excessive daytime sleepiness
can occur. In terms of risk factors, blindness can
contribute to a loss of the normal
sleep-wake cycle and circadian rhythm. Traumatic brain
injury can get the brain
out of its normal circadian rhythm and we can see
alterations in non-24-hour
circadian rhythms. And developmental delay can be associated
circadian rhythms. In general, we see insomnia at night in
these patients, difficulty
with morning arousals, increased daytime sleepiness, and at
times patients will
have sleep-wake timing that is aligned with the environment.