0:00:00.026,0:00:03.487
We're now becoming aware[br]of a significant relationship

0:00:03.511,0:00:06.236
between sleep and Alzheimer's disease.

0:00:06.785,0:00:09.066
[Sleeping with Science]

0:00:11.418,0:00:15.253
Now, Alzheimer's disease[br]is a form of dementia

0:00:15.277,0:00:19.483
typified usually by memory loss[br]and memory decline.

0:00:19.507,0:00:21.443
And what we've started to understand

0:00:21.467,0:00:24.435
is that there are several[br]different proteins

0:00:24.459,0:00:27.625
that seem to go awry[br]in Alzheimer's disease.

0:00:27.649,0:00:30.980
One of those proteins[br]is a sticky, toxic substance

0:00:31.004,0:00:34.325
called beta-amyloid[br]that builds up in the brain.

0:00:34.349,0:00:37.220
The other is something called tau protein.

0:00:37.244,0:00:40.251
How are these things related to sleep?

0:00:40.275,0:00:44.716
Well first, if we look at a large-scale[br]epidemiological level,

0:00:44.740,0:00:46.598
what we know is that individuals

0:00:46.622,0:00:50.516
who report sleeping typically[br]less than six hours a night,

0:00:50.540,0:00:52.645
have a significantly higher risk

0:00:52.669,0:00:55.113
of going on to develop high amounts

0:00:55.137,0:00:58.398
of that beta-amyloid[br]in their brain later in life.

0:00:58.422,0:01:01.725
We also know that two sleep disorders,

0:01:01.749,0:01:06.117
including insomnia and sleep apnea,[br]or heavy snoring,

0:01:06.141,0:01:09.212
are associated with[br]a significantly higher risk

0:01:09.236,0:01:12.186
of Alzheimer's disease in late life.

0:01:12.210,0:01:15.979
Those are, of course,[br]simply associational studies.

0:01:16.003,0:01:17.781
They don't prove causality.

0:01:17.805,0:01:19.209
But more recently,

0:01:19.233,0:01:23.376
we actually have identified[br]that causal evidence.

0:01:23.755,0:01:26.574
In fact, if you take a healthy human being

0:01:26.598,0:01:29.555
and you deprive them[br]of sleep for just one night,

0:01:29.579,0:01:33.285
and the next day,[br]we see an immediate increase

0:01:33.309,0:01:34.928
in that beta-amyloid,

0:01:34.952,0:01:37.167
both circulating in their bloodstream,

0:01:37.191,0:01:40.945
circulating in what we call[br]the cerebrospinal fluid,

0:01:40.969,0:01:43.794
and most recently,[br]after just one night of sleep,

0:01:43.818,0:01:46.545
using special brain-imaging technology,

0:01:46.569,0:01:49.767
scientists have found[br]that there is an immediate increase

0:01:49.791,0:01:53.299
in beta-amyloid[br]directly in the brain itself.

0:01:53.323,0:01:55.734
So that's the causal evidence.

0:01:55.758,0:01:57.856
What is it then about sleep

0:01:57.880,0:02:00.261
that seems to provide a mechanism

0:02:00.285,0:02:02.626
that prevents the escalation

0:02:02.650,0:02:05.395
of these Alzheimer's-related proteins?

0:02:05.730,0:02:07.363
Well, several years ago,

0:02:07.387,0:02:10.069
a scientist called Maiken Nedergaard

0:02:10.093,0:02:12.553
made a remarkable discovery.

0:02:12.577,0:02:17.348
What she identified[br]was a cleansing system in the brain.

0:02:17.678,0:02:18.854
Now, before that,

0:02:18.878,0:02:21.657
we knew that the body[br]had a cleansing system

0:02:21.681,0:02:23.956
and many of you may be familiar with this.

0:02:23.980,0:02:26.034
It's called the lymphatic system.

0:02:26.058,0:02:29.915
But we didn't think that the brain[br]had its own cleansing system.

0:02:30.344,0:02:31.906
And studying mice,

0:02:31.930,0:02:37.171
she was actually able to identify[br]a sewage system within the brain

0:02:37.195,0:02:39.546
called the glymphatic system,

0:02:39.570,0:02:42.037
named after the cells that make it up,

0:02:42.061,0:02:43.762
called these glial cells.

0:02:43.786,0:02:45.898
Now, if that wasn't remarkable enough,

0:02:45.922,0:02:49.406
she went on to make[br]two more incredible discoveries.

0:02:49.430,0:02:53.641
First, what she found is that[br]that cleansing system in the brain

0:02:53.665,0:02:58.307
is not always switched on[br]in high-flow volume

0:02:58.331,0:03:00.531
across the 24-hour period.

0:03:00.555,0:03:04.126
Instead, it was when those mice[br]were actually sleeping,

0:03:04.150,0:03:07.189
particularly when they went[br]into deep non-REM sleep,

0:03:07.213,0:03:10.918
that that cleansing system[br]kicked into high gear.

0:03:10.942,0:03:13.816
The third component that she discovered,

0:03:13.840,0:03:15.506
and this is what makes it relevant

0:03:15.530,0:03:18.272
to our discussion on Alzheimer's disease,

0:03:18.296,0:03:21.599
is that one of the metabolic by-products,

0:03:21.623,0:03:25.487
one of the toxins[br]that was cleared away during sleep,

0:03:25.511,0:03:29.424
was that sticky,[br]toxic protein, beta-amyloid,

0:03:29.448,0:03:31.591
linked to Alzheimer's disease.

0:03:31.615,0:03:35.770
And just recently,[br]scientists in Boston have discovered

0:03:35.794,0:03:40.643
a very similar type of pulsing,[br]cleansing brain-mechanism

0:03:40.667,0:03:42.616
in human beings as well.

0:03:42.640,0:03:47.074
Now, some of this discussion[br]may sound perhaps a little depressing.

0:03:47.098,0:03:49.846
We know that as we get older in life,

0:03:49.870,0:03:52.534
our sleep seems to typically decline,

0:03:52.558,0:03:55.546
and our risk for Alzheimer's[br]generally increases.

0:03:55.570,0:03:58.456
But I think there's actually[br]a silver lining here,

0:03:58.480,0:04:00.780
because unlike many of the other factors

0:04:00.804,0:04:04.025
that are associated[br]with aging and Alzheimer's disease,

0:04:04.049,0:04:07.225
for example, changes[br]in the physical structure of the brain,

0:04:07.249,0:04:10.168
those are fiendishly difficult to treat

0:04:10.192,0:04:14.383
and medicine doesn't have any good[br]wholesale approaches right now.

0:04:14.407,0:04:17.746
But that sleep is a missing piece

0:04:17.770,0:04:21.953
in the explanatory puzzle[br]of aging and Alzheimer's disease

0:04:21.977,0:04:25.951
is exciting because we may be[br]able to do something about it.

0:04:25.975,0:04:29.276
What if we could actually[br]augment human sleep

0:04:29.300,0:04:31.614
and try to improve the quality

0:04:31.638,0:04:33.956
of that deep sleep in midlife,

0:04:33.980,0:04:36.749
which is when we start to see[br]the decline in deep sleep

0:04:36.773,0:04:37.962
beginning to happen.

0:04:37.986,0:04:39.996
What if we could actually shift

0:04:40.020,0:04:44.933
from a model of late-stage[br]treatment in Alzheimer's disease

0:04:44.957,0:04:47.750
to a model of midlife prevention?

0:04:47.774,0:04:52.289
Could we go from sick care[br]to actually healthcare?

0:04:52.313,0:04:54.235
And by modifying sleep,

0:04:54.259,0:04:56.700
could we actually bend the arrow

0:04:56.724,0:05:00.128
of Alzheimer's disease risk[br]down on itself?

0:05:00.152,0:05:03.593
That's something[br]that I'm incredibly excited about

0:05:03.617,0:05:07.023
and something that we're actively[br]researching right now.