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We're now becoming aware
of a significant relationship
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between sleep and Alzheimer's disease.
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[Sleeping With Science]
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Now, Alzheimer's disease
is a form of dementia
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typified usually by memory loss
and memory decline.
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And what we've started to understand
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is that there are several
different proteins
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that seem to go awry
in Alzheimer's disease.
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One of those proteins
is a sticky, toxic substance
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called beta-amyloid
that builds up in the brain.
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The other is something called tau protein.
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How are these things related to sleep?
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Well first, if we look at a large-scale
epidemiological level,
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what we know is that individuals
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who report sleeping typically
less than six hours a night,
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have a significantly higher risk
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of going on to develop high amounts
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of that beta-amyloid
in their brain later in life.
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We also know that two sleep disorders,
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including insomnia and sleep apnea,
or heavy snoring,
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are associated with
a significantly higher risk
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of Alzheimer's disease in late life.
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Those are, of course,
simply associational studies.
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They don't prove causality.
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But more recently,
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we actually have identified
that causal evidence.
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In fact, if you take a healthy human being
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and you deprive them
of sleep for just one night,
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and the next day,
we see an immediate increase
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in that beta-amyloid,
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both circulating in their bloodstream,
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circulating in what we call
the cerebrospinal fluid,
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and most recently,
after just one night of sleep,
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using special brain-imaging technology,
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scientists have found
that there is an immediate increase
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in beta-amyloid
directly in the brain itself.
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So that's the causal evidence.
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What is it then about sleep
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that seems to provide a mechanism
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that prevents the escalation
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of these Alzheimer's-related proteins?
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Well, several years ago,
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a scientist called Maiken Nedergaard
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made a remarkable discovery.
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What she identified
was a cleansing system in the brain.
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Now, before that,
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we knew that the body
had a cleansing system
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and many of you may be familiar with this.
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It's called the lymphatic system.
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But we didn't think that the brain
had its own cleansing system.
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And studying mice,
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she was actually able to identify
a sewage system within the brain
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called the glymphatic system,
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named after the cells that make it up,
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called these glial cells.
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Now, if that wasn't remarkable enough,
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she went on to make
two more incredible discoveries.
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First, what she found is that
that cleansing system in the brain
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is not always switched on
in high-flow volume
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across the 24-hour period.
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Instead, it was when those mice
were actually sleeping,
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particularly when they went
into deep non-REM sleep,
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that that cleansing system
kicked into high gear.
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The third component that she discovered,
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and this is what makes it relevant
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to our discussion on Alzheimer's disease,
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is that one of the metabolic byproducts,
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one of the toxins
that was cleared away during sleep
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was that sticky,
toxic protein, beta-amyloid,
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linked to Alzheimer's disease.
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And just recently,
scientists in Boston have discovered
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a very similar type of pulsing,
cleansing brain-mechanism
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in human beings as well.
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Now, some of this discussion
may sound perhaps a little depressing.
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We know that as we get older in life,
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our sleep seems to typically decline
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and our risk for Alzheimer's
generally increases.
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But I think there's actually
a silver lining here,
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because unlike many of the other factors
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that are associated
with aging and Alzheimer's disease,
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for example, changes
in the physical structure of the brain,
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those are fiendishly difficult to treat
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and medicine doesn't have any good
wholesale approaches right now.
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But that sleep is a missing piece
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in the explanatory puzzle
of aging and Alzheimer's disease
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is exciting because we may be
able to do something about it.
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What if we could actually
augment human sleep
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and try to improve the quality
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of that deep sleep in midlife,
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which is when we start to see
the decline in deep sleep
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beginning to happen.
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What if we could actually shift
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from a model of late-stage
treatment in Alzheimer's disease
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to a model of midlife prevention?
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Could we go from sick care
to actually healthcare?
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And by modifying sleep,
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could we actually bend the arrow
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of Alzheimer's disease risk
down on itself?
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That's something
that I'm incredibly excited about
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and something that we're actively
researching right now.