The objective of this course is to give students the most up-to-date information on the biological, personal, and societal relevance of sleep. Personal relevance is emphasized by the fact that the single best predictor of daytime performance is the quality of the previous night's sleep. The brain actively generates sleep, and the first section of the course is an overview of the neurobiological basis of sleep control. The course provides cellular-level understanding of how sleep deprivation, jet lag, and substances such as alcohol, ,caffeine, and nicotine alter sleep and wakefulness. The second section of the course covers sleep-dependent changes in physiology and sleep disorders medicine. Particular emphasis will be placed on disorders of excessive sleepiness, insomnia, and sleep-dependent changes in autonomic control. Chronic sleep deprivation impairs immune function and may promote obesity. Deaths due to all causes are most frequent between 4:00 and 6:00 a.m., and this second section of the class highlights the relevance of sleep for preventive medicine. The societal relevance of sleep will be considered in the final section of the class. In an increasingly complex and technologically oriented society, operator-error by one individual can have a disastrous negative impact on public health and safety. Fatigue-related performance decrements are known to have contributed as causal factors to nuclear power plant failures, transportation disasters, and medical errors.
12.04 - What are the Causes of Daytime Sleepiness?
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From the course by University of Michigan
Sleep: Neurobiology, Medicine, and Society
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Unit 12 - Society: Daytime Sleepiness and Sleep Need - Thomas Roth, Ph.D. (Standard Track)
Unit 12 wraps up the final section of the course and the Society section of the content with a lecture on Daytime Sleepiness and Sleep Need by Thomas Roth, Ph.D.
Meet the Instructors
Ralph Lydic, Ph.D.Professor Emeritus, Molecular and Integrative Physiology, Professor Emeritus, Anesthesiology
University of Michigan Medical School
Helen Baghdoyan, Ph.D.Professor Emeritus, Anesthesiology, Professor Emeritus, Pharmacology, Professor of Psychiatry
University of Michigan Medical School
Let's turn now to discuss what are the causes of daytime sleepiness.
Remember, all those things people made up.
We talked about the fact people think like boring lectures, driving a car.
Well, let me tell you there are only four things in the world which make us sleepy.
It's not complicated.
Sleep at night makes us sleepy,
both in terms of how long we sleep and how continuous is our sleep.
We'll talk about that.
Circadian time. We talked about that.
There are some times of the day where we're more sleepy than others.
CNS acting drugs.
We talked about caffeine,
but the converse is also true.
An area of alcohol makes you sleepy,
caffeine makes you alert.
Finally, from a clinical point of view,
lots of different central nervous system diseases make you sleepy.
Now, how much sleep do we need?
Before we can talk about sleep, how much sleep do we need?
This is a slide from Howard Zeplin.
It shows you sleep need in a variety of species from giraffes to brown bats.
What's interesting is, biological sleep ranges from 2 hours - 20 hours.
The single biggest predictor of this, choroid,
what the biggest choroid is, is metabolic rate.
So organisms with very low metabolic rates,
sleep very little, spend a lot of time to eat,
as organism with very high metabolic rates spend a tremendous amount of time sleeping.
Man is always said to be around 8.0.
Now, one of the things that's very important to understand,
We talked about the fact that there's differences both within individual, between them.
One of the things that's very, very interesting,
one of the biggest indicators of not getting enough sleep is,
this is data from the National Sleep Foundation,
the average workday sleep time 6 hours and 40 minutes.
Although more many studies show less than that,
but very importantly on weekends these people sleep about an hour longer.
So very clearly, if you sleep longer on weekends than weekdays,
or days off than days on,
it's one of the good indicators that you're not getting enough sleep.
Now, this is some data which shows that
there's not only changes within ourselves across the week,
but these are changes across time.
This is Terman, 1910.
People were getting their eight hours, 2003.
This is our data we're now sleeping,
and the several studies have shown this, 6.9 hours.
The average American sleep 6.9 hours on average which is significantly decrease.
So, how much sleep do we need?
This is a magnificent study which is done
by Dr. Tom Wehr at the National Institute of Mental Health.
He was actually interested in studying hormones,
but we'll use it to study sleep deprivation.
He took a group of normal healthy people and very much like we pointed out,
the average person gets about 6.9 hours of sleep.
So put them in the laboratory for 6.9 hours and then he was interested in hormones.
So what he did, I remember epidemiologically had a 6.9.
What he did then is he put them in bed for 14 hours.
For the next several weeks,
all these people could do was either stay awake or go to sleep,
but they couldn't read, they could do nothing,
they could just lie in bed.
What's very interesting is the average person actually the first day slept 12 hours.
And then about 10 hours,
11 hours, and then about 10 hours.
In the second week,
they still continued to sleep about 8.5 - 9 hours.
By the third week,
it downed to about 8 hours.
By the fourth week,
they leveled off, and it leveled off by 8.1 hours.
So by the end of four weeks,
the average person's sleep need is this 8.1 hours.
This is how much we deficit.
So we go from 6.9 to 8.1.
Now, does that mean there's extreme danger in this?
In some individuals, yes, in some individuals, no.
But very, very clearly biological sleep need is 8.1 hours.
It's very much that we have a basal metabolic rate.
We don't have massive differences in biological sleep need.
We have massive differences in how much sleep we get.
People always like to ask "Well,
can you teach yourself to sleep less?"
I said, "You can teach yourself to sleep less,
but you can't teach yourself to need less sleep."
Sort of like, "Can you teach yourself to eat more?"
Of course, you can teach yourself to eat more, it's called getting fat.
Again, you can teach yourself to sleep less but it's called "sleep deprivation".
You can't change sleep need.
One of the people who I always get told when I give this lecture is,
well, the last people don't sleep much.
The name that always comes is Thomas Edison,
so I searched a literature on these two slides.
This is Mr. Edison sleeping in a laboratory in a suit and tie.
So very clearly this guy doesn't sleep much,
but here he is in a laboratory on a wooden plank sleeping.
This is my favorite. This is Thomas Edison again.
This is the president of United States.
This is Goodrich and Harding.
You can see again,
Thomas Edison, this man doesn't sleep much,
is sleeping in a suit in the middle of [inaudible] in front of the president of the United States.
So very clearly, people may not sleep in bed,
they may sleep in other places,
but we all need eight hours of sleep.
We get it one way or another.
This is a study by Leon Rosenthal.
And acutely, one of the things that's very
important is that it's a one to one relationship.
If you take fully alert people, give them 8 hours,
they have that 11.36 hours mean sleep we talked about,
if you give them zero hours,
it's zero and any sleep time between that is a straight linear function.
As you go from eight, to six,
to four, to zero hours,
you wind up with a sure and greater, and greater sleepiness.
So this is what happens if you restrict sleep across days and this is sleep restriction.
This is normal eight hours.
This is six hours, four hours,
eight hours, six hours, four hours.
And this is subjective sleepiness.
Listen, remember we talked about the fact that after some period of time,
they start thinking they're not sleepy anymore?
Here's an example of that there.
But on the other hand, if you look at the performance on a psycho-motor test,
you can see they get progressively more and
more sleepy across the two weeks of sleep restrictions.
So very clearly, six hours of sleep,
four hours of sleep, performance gets worse across time.
So that's sleep at night.
Let's look at sleep fragmentation.
So this is again from our laboratory,
this is no sleep, sleep deprivation,
no sleep like the slide we showed somewhere between zero and two,
this is normal sleep, and here's 1.5.
This is waking up once every five minutes,
once every three minutes, once every one.
So this is like an apnea index of six.
And you can see even with one night,
by sleep fragmentations exactly the same as sleep deprivation.
So the more fragmented your sleep is,
the more sleepy you get.
This lack of sleep which you showed on the Rosenthal slide is
more typical of normal healthy volunteers of the general population.
If you look at the elderly population and clinical population,
sleep fragmentation is a bigger cause than actual sleep loss per se.
The other thing that's important.
We talked about early on is
the homeostatic process is modulated by the circadian process,
and so circadian rhythm.
This is a multiple sleep latency test from Dr.
Carskadon's laboratory done across the course of 24 hours.
And we said everybody gets sleepy two to four,
but everybody gets sleepy two to six in the morning.
So this is an MSLT not during the day,
but during the day and at night,
and everybody is sleepy two to six in the morning.
Now, if you look at performance errors and this is from Sweden.
These are metering measurements.
This is when you're sleepy during the day.
This is when you're sleepy at night.
You can see there's a lot more errors.
If you look at car accidents.
This is international data on car accidents.
Again, this is sleepy during the day.
This is sleepy at night. You have an increased number of car accidents.
So very clearly, if I measure your circadian physiology like
Dr. Carskadon did and measure your performance,
and/or if I measure your driving crashes two to six in the morning,
two to four in the afternoon, increase sleepiness,
increase rate of car accidents, decrease performance.
Now, CNS drugs are very important.
This is the effect of alcohol.
This is 0.4, 0.6.
This is legal intoxication in most states in United States.
This is probably more typical in Europe.
But you can see with 0.8,
ethanol dose grams per kilogram,
you wind up with an MSLT which is comparable to a patient with pathological sleepiness.
So here's a study which we did which is sort of compares the two.
So this is BrEC.
This is sleeping no hours,
two hours, four hours, six hours.
You can see, sleeping no time at all is basically having twice intoxicated blood levels.
On the other hand, just sleeping four hours puts you at
a breath ethanol concentration which is considered illegal in most states.
So restricting your sleep time to four hours.
The other thing which is very important,
we did a study at University of Michigan here together with ourselves and Henry Ford.
What's interesting is if I combine alcohol and sleep deprivation,
they potentiate each other.
So very, very importantly whether you're talking about driving,
whether you're talking about anything,
lack of sleep will in fact make you worse,
makes you just as bad if not worse than drinking alcohol in terms of driving.
Put them together it makes them better.
Conversely by the way,
one of the things that happens is what should you do?
Just like not getting enough sleep makes alcohol worse, well,
extending your sleep will mitigate the effects of alcohol.
So, here's the effects of alcohol sleep latency; Normal, Drinking alcohol.
If I sleep 10 hours the exact same placebo, a little more alert.
But in fact, if you decrease the level of alcohol.
So if you're going to-- The important to understand that
decreasing sleep time dramatically increases the effects of alcohol.
The converse is that is caffeine.
This is a reaction time task over 40 minutes.
Remember, we talked about if you're doing things for an hour with time it get worse,
if I give you caffeine it makes it better.
This is 75 milligrams of caffeine which is not that high a dose.
But again, these are caffeine naive subjects.
If you drink a lot of caffeine,
these effects go away very quickly.
And this gives you an idea.
So this is 75 milligrams of caffeine which is an average cup of coffee in United States.
But in fact, things like some company brands can have as much a 760.
The coffee Grande at Starbucks has 760. NoDoz, 200.
Some products we don't even know because they don't tell us.
But very clearly, we can be drinking lots amount of caffeine.
Finally, the last cause of sleepiness which is with the clinical arena,
you're going to hear more about these in clinical lectures is CNS disease.
Let's start out with sleep disorders.
There's shift work disorders by 25 percent of the general population,
so within 20 and 25 percent of the general population of shift work.
Of those people, about 20 percent have
shift work disorder where they really can't
sleep during the day and have difficulty staying awake and function [inaudible].
Obstructive sleep apnea has a prevalence depending on where you put the line,
so in-between 3 and 20 percent.
It's much more common in the elderly.
It's much more common in offensive alignments.
It's much more common in valid populations.
Narcolepsy is a dramatical cause of sleepiness,
it's an abnormality of the orexin system.
Restless leg syndrome.
Circadian rhythm disorders.
Shift work is one of them, but also
in young people it sometimes have phase delay syndromes.
In elderly people, we have phase advance syndromes.
Or if you listen to radio lately they talk about non-24-hour rhythms in blind people.
Certain parasomnias can cause sleepiness as well.
Things like periodical movements.
Now, there are a lot of medical diseases which also Parkinson's disease.
We showed a slide on that.
People with Parkinson's disease are just as sleepy as narcolepsy patients.
I've never quite understood why this isn't a sleep disorder while restless legs is.
These people have profoundly cerebrovascular diseases have caused the significant data.
Endocrine. Lots of endocrine diseases,
either directly cause sleepiness or indirectly through sleep apnea.
Pain. We talked about pain conditions.
Things like fibromyalgia, other conditions defragment sleep
which cause sleepiness and residual sleep symptoms associated with medication.
Lots of drugs from centrally acting anti-histamines to most psycho tropic medications,
all produced daytime sleeping.
Some of the beta blockers produce it.
Finally, secondary psychiatric diseases.
Depression can be an effect that could be related to disease or the symptom,
or an effect of the anti-depressant medication,
or the most of the modern anti-depressant medications don't seem to be sedating.
In fact, they tend to be stimulating.
Anxiety disorders can in fact,
lead to sleep disturbance and bipolar disease during the matic phase seem to be very,
very cause of sleepiness as much as more actually not sleeping than access to sleepiness.
In summary, let me leave you with a couple of thoughts.
It's very important to understand that
daytime sleepiness is highly prevalent in many populations,
there are clinical populations,
and you really need to do that.
You need to seek a clinical attention.
Most of these conditions are treatable,
either the disorder per se or symptomatic with medication.
But for many of us,
excessive sleepiness is very much like other behavioral problems.
We have to learn how much sleep we need.
This fantasy we can learn to sleep six hours is just that, a fantasy.
We have to learn how much sleep we need.
Are we drinking a lot of coffee?
Are we taking medications to keep us awake?
Are we taking energy drinks?
Are we sleeping more on weekends?
To the extent that we do those kinds of behaviors,
we're not getting enough sleep or there's something wrong with our sleep.
In any case, we have the opportunity to fix it,
improve our productivity, improve our safety and the safety of those around us.
Thank you very much for your kind attention.
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