Circadian health expert and medical scientist Logan Pendergrast, Ph.D., explores how light exposure shapes sleep quality and why it is one of the most powerful environmental factors we can control. He explains how artificial light—whether from devices, lamps, or windows—can interfere with melatonin production and disrupt the body’s ability to wind down.
This segment highlights practical ways to adjust lighting in your environment so that your brain and body get the right signals for rest. By understanding how to minimize disruptive light and create a sleep-friendly atmosphere, you can set the stage for deeper, more restorative sleep.
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I'll move into talking a bit about what
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are some practical tips that we can
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utilize to help maintain our health. So
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one example of a practical tip that you
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can implement is exposure to light. So
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exposure to natural light in particular
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but this could be strong artificial
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light engages the uh optic nerve of the
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brain and stimulates a elevation of
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cortisol which is the wakefulness
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hormone and suppresses melatonin so that
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we can feel a bit more awake as we move
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through our day. But it also sets the
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rhythm so that our body knows when we
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are biologically beginning to wake up
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and when it is time after maybe the
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buildup of adenosine over the course of
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12 to 16 hours then it will know when it
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is time to go to sleep. Another
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practical tip that we could utilize uh
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although some of us do abuse is
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caffeine. So caffeine actually inhibits
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the action of adenosine which is that
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sleep pressure neurotransmitter in our
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brain to help us feel a bit more awake.
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So consumption of 1 to 200 millig of
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caffeine and I believe the calculation
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is actually 1 to 3 mg of caffeine per
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kilogram of body weight can help us
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really avoid this feeling of sleepiness
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if we wake up in the morning with too
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much adenosine. And it can help us
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maintain our energy and our alertness.
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And one caveat to this, which you've
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probably heard people mention quite a
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bit, is that consumption of caffeine
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within about 6 to 8 hours of our time
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that we would go to sleep can interfere
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with the effectiveness of adenosine to
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bring our body to sleep. So adenosine
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isn't necessarily a neurotransmitter
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that we're seeking to avoid at all costs
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because it actually helps us to sleep.
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So avoiding caffeine about 8 hours
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before we reach time to go to sleep is
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likely the most effective option for
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getting the benefits of caffeine but
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also kind of avoiding the issues that
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are associated with consuming caffeine.
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And another example here is our sleep
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related to our sleep environment. And so
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prior to sleeping, sleeping in an
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environment that is cooler, anywhere
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from 60 to 67° F by dropping the air
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conditioning down, let's say, or
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sleeping next to a fan, can help us
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reach a deeper state of sleep.
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Additionally, sleeping in a dark,
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completely dark, quiet room can help us
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maybe avoid the negative effects of
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light on our release of melatonin or
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maybe avoid the effects of sound on our
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levels of cortisol so that we can really
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set up the perfect hormonal environment
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so that we can reach deep levels of
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sleep. And then lastly here related to
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eating meals. So eating meals about an
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hour or two after waking can in initiate
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the release of specific hormones such as
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insulin which can serve as what are
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called zygr or time setters for our
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body's physiology so our body knows that
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it's time to be awake and to move
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around. And then on the inverse of this,
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avoiding these large heavy meals such as
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just a a oversized dinner, maybe uh not
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eating uh a pound of steak before maybe
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2 to 3 hours before it's time to go to
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bed. it. Avoiding these large meals can
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help our body maintain our temperature
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because as we consume a large meal, our
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body temperature has to elevate to um
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use the energy to digest the food which
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can affect our temperature drop which is
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necessary for engaging in deeper sleep.
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And so if we can initiate all of these
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tips as we're in a desynchronized sleep
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environment, we can really counteract
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the negative effects of that.
