Transcriber: Leonardo Silva
Reviewer: Reiko Bovee I'd just like a little bit
of a show of hands here to find out how many people here feel that they've gotten an adequate
amount of sleep over the past month. (Laughter) Do I see any hands? A couple of hands. Well, like most Americans, the people here are simply
not getting enough sleep. I'd like to ask one other question. How many people have never driven
a car when you were drowsy? Two people, OK. Yeah. Well, that's reflective
of all of our lives these days. The question that I'm going to pose is: Why are we not sleeping as much? Ten times as many people today are sleeping less than six hours a night than, for example, when I was growing up. If we look at kids of all ages, five-year-olds are getting
two hours of sleep less at night than they did in earlier times. Ten-year-olds, fifteen-year-olds,
twenty-year-olds, we're all sleeping
a couple of hours less per night than we did in the past. So, the question is:
Why are we sleeping less? And I think one of the key issues is actually the light to which
we are exposed, artificial light. And that may seem surprising, but electricity and the ability
to turn it on whenever we wish, along with caffeine and other aspects
of our technological lives, are actually reducing
the amount of sleep that we have. And paradoxically,
in order to understand this, we have to understand
how sleep is organized within the usual day. And we have two
major regulatory processes that affect how alert we are
at any given moment. One of them is related
to how many hours that we've slept and how long we've been awake, and the second
is an internal clock in the brain that times sleep and times
our tendency to feel alert and our tendency to feel sleepy. And paradoxically,
that internal clock in the brain sends out a stronger and stronger drive for waking as the day wears on and it opposes what would, otherwise, be an increasing drive for sleep, the longer that we're awake. And this reaches a real apex near the end of our waking day, and we just have
this internal clock sending out this strong "ahhh" signal
to keep us awake, and that's when we get this second wind near the evening part of our day. What turns off this orchestrated
increasing energy and alertness is the release of the
sleep-promoting hormone, melatonin. And that hormone is typically
released an hour or two before we go to bed at night. But that release of the hormone can be suppressed by light and it can also be shifted by light. So light exposure in the evening can not only suppress
the release of that hormone today, but make it occur later
on subsequent days. And I first learned
what a profound effect this was having when we made the discovery,
a few years ago, that some blind people,
who have no conscious light perception -- that their internal circadian clock can be shifted by light
that they can't see. And that's because just in the same way that the ear has two functions -- one is for hearing
and the other is for balance -- also the eye has two functions: one is for seeing each other and the other is for
circadian photoreception or resetting this internal clock. And so, in this individual, even with his eyes covered -- he has no ability to sense the light and also no response, hormonally, to his being exposed to light. But when his eyes are exposed, even though he is completely blind
and unable to see the light, it immediately suppresses the release of the sleep-promoting hormone, melatonin. But the amazing thing was, when he lived with sighted people, we realized that the timing of this hormone was beginning to be released -- the secretion of this hormone
was being released at 11 or 12 o'clock at night. Whereas when he became an upperclassman at Boston College and got his own room, suddenly you notice that he was beginning
to release this hormone in the afternoon, and it was actually reaching its peak at midnight. And it made me reflect on the fact that midnight is called midnight because it's actually
the middle of the night, if you were to look at the timing
of the Sun rising and setting. But, of course, many people today are just beginning to check
their e-mail at midnight, start their homework,
begin writing that novel and taking on all sets
of other challenges and not even beginning
to think about going to sleep. And so I actually went to an area, where there's not electricity. It's about five hours
outside of Curitiba, Brazil, where I managed to find a home, where there were no electric lights. And I went to visit
the parents of that family, and there were seven children. One of the things I was curious about was, you know, how they managed when it got dark,
at six o'clock in the evening. The mother then said,
"Well, typically we go to bed." So, I said, "What do you do
if a child wakes up?" Because they're in this one room, with a dirt floor, and all nine of them
are sleeping in this room. And I'm thinking, you know,
"If we had to sleep with our kids, what a chaos, pandemonium..." And so I said, "What do you do when it's dark and the kids
wake up during the night?" And the translator,
back and forth, Dr. Louzada, asking over and over again
my question in different ways. And finally, the woman understood
the question and she said, "We never wake up during the night. The children... You know,
we go to bed at dusk, and the children wake up at dawn." And I realized that the artificial light
to which we're exposed is wreaking havoc on our ability
to remain in synch with the 24-hour day. And I began to, then, look at the results
of our laboratory experiments. We had studied hundreds of people in which we defined
the daily rhythm of light sensitivity. And here, you can see
that light exposure in the evening hours, resets our internal clock to a later hour, and light exposure in the morning
is resetting your circadian system to an earlier hour, and that's how we keep
in synch with the 24-hour day. As I mentioned, this second wind is lined up to occur late in the evening, to allow us to stay awake
for this marathon of 16-hour wakefulness that we all experience each day. And then, I was thinking about
what must it have looked like 200 years ago? Or what would it have looked like
in this blind individual, who was living in his own room
and didn't have electric light? We would expect the daily rhythm
of light sensitivity to take this shape,
then melatonin would be released as it was in his case,
at about five o'clock in the afternoon. So, the second wind
would actually be taking place when we were all running
to get a coffee break and so on. The artificial light to which
we're ordinarily exposed has pushed the circadian system
to a later hour and shifted us to the equivalent
of Hawaiian time, shifted our brains westward, placed this second wind
late in the evening and squeezed the timing available
for our biological night, because we're still getting up
with the chickens. In fact, the biggest segment
of the working population, in terms of its temporal distribution, is for jobs starting
between 3:30 and 6:30 in the morning. So, the jobs and the work
are starting earlier, our kids are going to school earlier -- we're making the high school kids start
at sevensomething in the morning, even though 100 years ago
they didn't start till nine. Kids, back then,
didn't even use alarm clocks to get up for school. How many of you never used an alarm clock to get up when you were going to school, like 95% of the kids did at that time? So, we've created this big squeeze. So we have this early wake time, this circadian surge in wake propensity and it's an unintended consequence
of artificial light. And then, when we add in caffeine, many people don't realize
that it has half-life of 6 to 9 hours. So, when we take it after dinner, it's going to interfere
with the restorative value of sleep that we would otherwise get. The function of sleep
is to repair and reorganize the brain. Sleep is critical for learning. In fact, we integrate the knowledge
that we've learned today with our prior experiences and we rehearse places we've been and routes that we've taken and so on. During the night, when we are asleep, it is also the time that we get insight. Now, if we don't get enough sleep -- we're one of the few animals that deprives ourselves of sleep, and most other species, the only time that they're sleep deprived is when they're not getting enough to eat. And so, the two systems are intertwined. So, we want to eat more
if we're not sleeping enough. If we go on a diet
and try to restrict our calories, but we're also restricting our sleep, then 75% of the weight that we lose will be in body mass rather than from fat, because of the changes
in the hormonal environment that occur when we're not
getting enough sleep. If you sleep for four, five hours a night, even for a week, men's testosterone levels
drop to the same degree that they would having aged ten years. So, it has many different effects. It increases distractibility, kids become hyperactive. Paradoxically, they don't become sleepy, but they have difficulty focusing attention. And we all become
a little bit hypomanic. We don't quite become manic, but we get this feeling of euphoria and that may be why sleep loss is associated with burnout, depression and other adverse
mental health consequences. And we're sleep depriving our kids. You know, they're spending
8.5 hours a day on recreational media, if they have a TV in their bedroom. And it turns out that they're spending more time doing that than sleeping. So, it's no wonder
that they're hyperactive. One out of ten twelve-year-old boys is now diagnosed with ADHD. So, what to do? To thrive, you have to decide
if sleep is a priority. Establish a regular bedtime. Establish a regular wake time. Find a cool, dark, quiet place to sleep and make your bedroom
a technology-free zone, because it's going to interfere
with your ability to sleep. Get rid of the caffeine, get rid of the alarm clock and find out how much sleep
you really need and then try to get that. And what could be the benefits? First of all, you're going to be
able to concentrate, so that you can perform better, you can be more accurate. You'll have greater insight, you'll have faster reflexes, reduced risk of injury, you'll optimize your metabolic fitness and your appetite, enhance your immunity, decrease your risk of infection, reduce your risk of diseases
like diabetes, and stroke, and cancer and heart disease. Ben Franklin, famously, in the Poor Richard's Almanack, said, "There will be sleeping
enough in the grave." One thing I can tell
is that you'll get to that grave sooner... (Laughter) ...if you don't sleep enough. If you want to thrive well alive, sleep. Thank you. (Applause)
