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.
11.04 - Changes in Sleep Rhythms Across the Lifespan (Part 2)
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Sleep: Neurobiology, Medicine, and Society
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From the lesson
Unit 11 - Society: Circadian Rhythms, Sleep, and Health - (Standard Track)
Unit 11 kicks off the Society section of the course with a lecture on Circadian Rhythms, Sleep, and Health from Theresa Lee, 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
So coming back to this problem of
the interaction between sleep and what happens with school,
and why adolescents are so chronically sleep deprived.
So we look at the pre-adolescent, the typical day,
they wake up at say 7 O'clock in the morning,
they start their school day at 8:00.
This is pretty typical in the United States.
They're awake through the day.
They go to bed at around 8 O'clock at night.
And so they're getting depending on the child, nine, 10,
11 hours of sleep at night,
all through elementary school.
They wake up, they're bright eyed,
bushy tailed for the most part.
Go off to school happily,
and they're good learners.
Right? This is how we think about kids who have a healthy, happy, normal life.
And on average elementary school kids are sleeping 10 hours a night.
And parents are pretty good,
we understand that kids should be going to bed at a regular hour and we enforce it.
Then puberty comes, adolescence strikes and two things happen.
First of all, the melatonin rhythm is phase delayed,
the need to sleep is phase delayed.
And so the child, the first complaint you hear from children is,
I can't get to sleep at night.
I'm tired. I know I need to go to sleep,
but I'm not sleepy now.
I should be sleepy,
but I'm not sleepy.
My own son, my daughter was less severe of a problem, which is again typical,
but my son, he would just be beside himself and he would make himself get to sleep,
but then he would sleep walk around the house.
So he was asleep, but he wasn't asleep and
these problems are particularly bad at the onset of
puberty for the kids just not being able to
get themselves to sleep and recognizing how tired they are.
Then the schools change the time of day for schools to start.
And we are beginning to see a shift in a different direction in this country.
In Europe, kids often in some countries start school later anyways,
so the problem of sleep deprivation is less for them,
but in the United States it is still the case that most schools have the kids start
about an hour earlier as
middle and or high school students than they did when they were in elementary school.
So first I can't get to sleep,
then I have to get up an hour earlier to get to school on time.
And the result is often within a few months,
I go from getting 10 hours of sleep at
night to getting only seven and a half hours of sleep.
This is at the very time when children go through their last big growth spurt.
Remember how much the babies were sleeping
during the fastest rate of growth in their lives?
Well you're now at the second fastest rate of growth,
particularly for boys and they're not getting enough sleep.
They really need more.
If anything they need more sleep than they were
getting as pre-adolescence and now they're getting less.
So they're sleep deprived,
they're having a hard time having circadian regulation of
their sleep and they need more sleep than they used to.
So it's not very surprising that when kids get to college,
they graduate from high school,
they make it through high school.
They get to college, if they're going to get there and they find that
they are able to regulate the time of
their classes and students don't want to go to 8:00 a.m. classes,
they tend to want to go to 10:00 a.m. or after and they're much happier having
evening courses than the teachers are typically to teach them.
Okay, so young adults and sleepiness,
what are some of the problems we see?
Well, 36 percent of 18 to 29 year olds report difficulty getting up and going to
work as compared to
the next age bracket which is 20 percent and those over 65, nine percent.
So again, this relates to this fact that as we're getting older,
(a) we need less sleep,
(b) we tend to be moving into a more morning type of pattern that
is feels good to us and so the young adult is in a particularly difficult position.
22 percent of young adults are occasionally or frequently late to work
because they're too sleepy to get up in the morning as compared to older folks.
And 40 percent of younger adults are sleepy
during the workday at least two days a week or more.
So again, one can imagine if you're sleepy at work,
how well are you able to focus on your job?
How often do you forget things you need to do?
How often do you make errors that you don't want to make?
And depending on the kind of job you have those can be very serious mistakes.
The aging effect on sleep pattern then could also be found,
that is the difference between your slow wave sleep and REM across the life span pattern.
And in this way, this actually benefits young people.
When you're young, when you do go to sleep,
you're going to get plenty of slow wave sleep at the beginning of the night for
most people and the REM will increase across the night the way it's supposed to.
So if you actually get seven or eight hours of sleep during most nights,
you're going to get a nice healthy pattern of sleep that
helps restore the brain and allow the brain to do the things it needs to do.
And when I say older,
I mean over 70 because as long as you are physiologically healthy,
it's unlikely that you're going to have any kind of serious problems
with your sleep until you get into the old, old category.
And many people sleep very well into their 90s even,
but more and more individuals as we get older complain about having fractured sleep.
So here you see an example,
where the person is not staying in slow wave sleep nearly as
long as they used to so the restorative function of that phase is lost.
They have big long bouts of REM earlier in
the night and in fact wake up often multiple times during the night.
So sleep consolidation is difficult.
Now, it turns out that as we age many of us,
not everyone, but many people,
the pineal gland, the source of melatonin begins to
calcify and less and less melatonin is produced.
So, in some cases,
older people could take melatonin and it will
help them go to sleep and help consolidate their sleep.
So one group where studies have shown
a good effect of taking three to five milligrams of melatonin at night,
about a half an hour before you go to bed that can help people sleep, be better.
So, let's summarize that,
what are the kinds of sleep changes that happen with age?
As we become very elderly,
we increase the number and duration of our awakenings,
we have reduced sleep efficiency,
which means when you're going to sleep,
you're not in slow wave and REM in the right pattern.
So, there's decreased slow wave,
often decreased REM if you're having lots of
awakenings or you might have inappropriately timed REM,
the latency to REM goes down,
so you're having REM too early in the night.
There's a phase advance overall as you age in the timing of sleep.
That's not necessarily a bad thing,
you just have to regulate that you get enough sleep.
And there's an increase in the number of shifts between stages,
and that's the fractured amount of sleep.
Sleep disruption can happen at any age.
So the adolescent it's happening because of this phase delay.
In the 30 to 60 year old,
the adult, who has, sort of,
what we classically think of a normal need for seven to nine hours of sleep,
other kinds of things tend to disrupt sleep.
Onset insomnia, about five percent of men,
14 percent of women complain of having trouble getting to sleep at night.
And most commonly, what they describe the problem as is that they
go to bed and they lie there worrying and they're anxious about events of the day,
or thinking about what's going to happen the next day.
So, there are ways to help with that, to make it better.
Interestingly, there is a sex difference in this effect.
Women tend to have onset insomnia more often than men,
and indeed, to be more driven by this worry problem.
And it tends to worsen in later years for all people,
even if worrying and anxiety are not a part of the scene.
Night awakenings are common as well.
Surprisingly, in the 30 to 60 year bracket,
it's more common in women.
70% of the time,
whoever's doing this wakes up because they need to go and urinate.
That's what nocturia is.
As we get past 60 years of age,
we tend to flip, and men tend to be awaken more often for this purpose.
They worsen dramatically for men over the age of 80,
typically because of prostate issues,
and can be so disruptive of sleep that it's as bad as sleep apnea.
We also find that in the even in this age bracket between 30 and 60,
there are individuals who describe having excessive daytime sleepiness during the day,
that is a very difficult time staying awake.
44 percent of men are described particularly as they get towards
the 60 age group as having habitual snoring,
and that can be very severe or not.
And then there's a group that have both snoring and excessive daytime sleepiness,
and this group almost always turns out to be someone who has some degree of apnea,
sleep apnea, which if you haven't already
heard about it taking this course, you will soon.
Apnea is a disorder where you stop breathing or your
diminished breathing and then you have to wake up to get your breathing restarted.
Obesity positively correlates with these breathing disorders but not perfectly.
Thin people can have apnea.
Thin people can have snoring.
There can be other kinds of causes for that.
But there's no question, that being male and overweight is more likely to put you into
this category as you get into your 50s and
60s of snoring and excessive daytime sleepiness,
which will be found to have some sort of breathing disorder or apnea,
which can prevent particularly,
the deep stages of sleep because that's when the breathing stops.
Aging and sleep lost causes a variety of similar problems.
And so, we're beginning to think that some of the changes that happen with age
may be due to the changes in sleep and having too little sleep.
So, the first two here have to do with changing
the debility to deal with sugar which can lead to people developing diabetes.
So, glucose tolerance is the rate at which you deal with a bolus of glucose,
getting it out of your bloodstream,
and into fat or some other use,
and it requires that your insulin response be appropriate,
go up when this sugar appears and go down quickly thereafter.
Well, if simple sleep loss at any age
decreases your glucose tolerance and insulin sensitivity,
if you have three nights in a row of only four hours of sleep,
your response to sugar looks like somebody in a pre-diabetic stage.
Three nights of four hours of sleep and you're pre-diabetic,
and you just remember that.
That's a really serious effect.
Now, those changes tend to happen as we age as well.
The question is, why? There's a great deal of
variability and whether it happens as we age.
People who are overweight,
it's more likely than people who are not overweight.
People who don't sleep well,
it's more likely that people who don't sleep well.
But obesity, if you're pre-diabetic, you tend to put on weight.
So, we're beginning to see that relationship
between sleep and metabolism and the use of sugar,
the development of diabetes,
as being integrated to each other.
And in fact, there are plenty of folks now,
who in the websites,
will tell you about sleep and that one way to help
reduce your pre-diabetic state is to sleep more.
And indeed, sleeping more reduces,
they will help improve your glucose tolerance and insulin sensitivity.
And whether that really will prevent you from being obese,
I don't know, I don't think anybody really knows,
but it sure won't hurt.
OK. If you have sleep loss,
you also increase your cardiac sympathetic activity,
which means your blood pressure can go up,
your heart rate goes up,
your ability to respond to rapid onset of activity and then recover from it is not good.
Your norepinephrine levels, which help raise
your your physiological alertness and ready for flight-or-fight responses is elevated.
So again, three nights of four hours sleep,
and you're going to have elevated blood pressure,
and elevated reactivity to the environment.
And again, these are things that are commonly seen in people who are aging,
whether they're overweight or not,
but being overweight and sleep deprived clearly makes those problems worse.
In addition, when you are sleep deprived,
your evening cortisol levels go up.
So, our cortisol levels in humans tend to rise in the morning and peak
around mid to late afternoon and then to gradually fall as we go to sleep.
And what we find with people who are sleep deprived is that that rise is maintained
farther into the evening and that interacts with these other variables,
which are related to metabolism,
and can cause ultimately damage in the brain.
Again, these things, this is something that's quite common in the elderly.
Again, it's much more common in people who are overweight.
The hormone leptin and grelin are altered.
Leptin is the hormone which when you've eaten and
your blood fat levels are elevated tells the brain you've got enough,
that you need to stop eating,
that you've got enough calories in your system.
Grelin is a hormone that reacts to the falling of
these things and increases your appetite,
helps drive the motivation to go get food.
So, when you've had four hours of sleep for three nights,
you decrease your ability to correctly read the fact that you've eaten recently,
and you increase the hormone that tells you you need to eat.
The result is, you're hungry.
You feel hungry and you go out and eat,
and there are a number of studies that have shown us that this combination of
events leads to changes in the insulin sensitivity and glucose tolerance and leads to,
again, looking like a pre-diabetic.
And finally, getting away from this idea
about the physiological and metabolic effects of sleep loss,
we have the effects on mood alertness and vigilance that I mentioned before.
Three hours, three nights of four hours of sleep is
enough to make someone incredibly moody, typically depressed,
highly reactive to things in the environment,
your alertness declines, your vigilance declines,
your ability to perform tasks declines.
Again, all of these things are very
rapidly reversible by a couple of good nights of sleep,
and one has to wonder whether many of the effects we see in the very
elderly are the result of sleep loss and the fact that their sleep is not normal.
OK, this is going to be a good moment to take a break,
and we will wind up this lecture by coming back and talking about what one can
do to improve your sleep circadian and durations so that we feel healthy.
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