Circadian Rhythm Guide for Night Shift Workers
Your circadian rhythm affects nearly everything—from your energy levels to your sleep quality and long-term health. In this video, Logan Pendergrast, Ph.D., explains what your circadian rhythm is, how it gets disrupted when you’re awake at night and sleeping during the day, and what night shift workers and night owls can do to support their body clock and feel more stable.
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hello everyone and welcome to lesson two
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of our night aling education series My
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name is Logan and I hold a PhD in
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medical science from the Karolinska
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Institute in Stockholm Sweden where my
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PhD work was on circadian rhythms So I
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will be leading us through today's
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lesson circadian rhythm essentials as an
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overview for what we'll be talking about
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today in this lesson We'll start with
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understanding our circadian rhythm what
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the word circadian even means and how we
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can really manage our body's function
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over the course of a day We'll next move
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into an important factor for our
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circadian rhythm which is light and how
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light and timing influence our circadian
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rhythm Next we'll move into various
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hormones what time of day those hormones
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are released and what they do for our
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body And then we'll finish up with
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strategies that we can utilize to help
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us align our circadian rhythms to our
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external environment so that we can
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function more
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effectively So our first question may be
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what is a circadian rhythm and what does
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that word mean well the word circadian
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comes from two Latin words The first
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Latin word being circa which means
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around and the next Latin word being dm
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which means day So we can think of our
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circadian rhythms as the rhythmic
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function of our body around a day Now
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the circadian rhythm is a biological
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clock which is sensitive to our
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environment So our circadian rhythms
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operate by our perception of light which
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is transmitted through our eyes into our
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brain and then that transmission into
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our brain coordinates to the rest of our
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body And the area of our brain that
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receives this stimulus from our eyes is
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called the superismatic nucleus and that
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transmits information to another part of
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our brain called the hypothalamus which
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releases hormones that act on our body
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in various ways which we will talk about
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later in the lesson Now our circadian
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rhythm functions to help us regulate not
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just our sleep but also our hormones
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such as insulin which is a hormone that
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helps us get rid of sugar from our blood
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and our general hunger as well as our
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body temperature and then other
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functions such as our mood And likewise
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our circadian rhythm is sensitive to our
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external environment through other
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factors than light such as what food
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that we eat what temperature it is
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outside and even the social interactions
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that we engage in
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So our next question may be how can we
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understand circadian rhythms in the
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context of our own health well
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disruptions in our circadian rhythm
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don't just lead to issues such as sleep
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disorders We can also see that disrupted
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circadian rhythms can influence our
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health through increasing risk of
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metabolic disease and also increasing
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the risk of issues such as mood
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disorders And so this was shown in a
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study that was published with 91,000
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participants where the individuals with
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irregular 24-hour sleep wake cycles had
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an elevated level of mood disorders a
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lower overall level of happiness and
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even increased levels of feelings of
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loneliness So this really shows that
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there there's a strong interaction
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between how our body's rhythm is working
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and our general mental well-being Now
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although our circadian rhythms operate
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in a similar fashion over a 24-hour
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period it is the case that they are
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flexible to changes in our environment
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And an example of this could be jet lag
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So a jet lag change of just flying from
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a time zone that is maybe one or two
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hours or even two to four hours away can
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lead to elevated levels of feeling
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fatigued which is quite obvious to those
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of us who have experienced it but also a
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decrease in concentration and just a
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general discomfort And this is likely
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the clearest real world example of how a
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small change in our circadian rhythms
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can really influence our health So next
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here we will talk about light And light
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is important because light is the most
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essential regulator of our body's
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circadian rhythms And the way that this
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works is is light from the outside
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environment let's say the sun for
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instance is perceived by the retinas in
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our eyes And that information is then
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relayed via a nerve to the brain
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specifically the superchismatic nucleus
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which then tells the hypothalamus
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another region of our brain that
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releases hormones what time of day it is
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And this release of hormones from the
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hypothalamus then communicates this
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information to the rest of the body Now
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exposure to light in the early part of
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our waking time is not just important
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for our general feelings of energy but
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it's also important for the next time
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that we go to sleep And this has been
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shown in individuals who are shift
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workers where shift workers who are
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exposed to artificial or natural forms
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of light upon waking show a 30%
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reduction in the disturbances of sleep
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the next time that they choose to go to
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sleep And so it's not just the case that
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light is helping us feel awake It's also
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the case that exposure to light early
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upon waking is helping us sleep the next
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time that we go to sleep Now on the flip
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side of this coin it's also the case
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that exposure to light too close to
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going to sleep can influence our ability
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to sleep And the reason that this
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happens is this artificial light let's
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say from our screens or from our
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televisions is perceived by the eyes and
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the superchismatic nucleus as being
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daytime And what this causes is a
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reduction in the release of a hormone
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called melatonin which is responsible
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for a drop in body temperature and a
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general preparedness for sleep And this
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reduction in melatonin will make us feel
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less sleepy and as a result can
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influence our ability to fall asleep So
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it's quite important to manage our
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exposure to light for our general
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circadian rhythms and our well-being
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And so to continue on a bit with how
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important timing is for managing our
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circadian rhythm it's important to
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remember that our circadian clock
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controls these key functions such as our
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hormone release and our metabolism and
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that we can modulate specific external
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factors so that we can optimize our
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general rhythms Now it's known in the
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scientific data that people who work
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shift work are more prone to issues such
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as circadian disruption and also risk of
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cardiovascular disease and diabetes And
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there are fundamental reasons for this
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One of those fundamental reasons is that
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individuals who work shift work often
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eat at irregular times They're not
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typically eating the standard breakfast
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that non-shift workers eat when they
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immediately wake up and they're just
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eating less often with other people And
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so one way to counteract this would be
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to eat meals at a specific time every
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day always And so an example of this
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would be perhaps we work a shift from uh
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11:00 p.m until 7 a.m and we let's say
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wake up at something like 5:00 p.m So if
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we wake up at 5:00 p.m and we eat a meal
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at 6:00 p.m and then eat another meal
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three to four hours later and then
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another meal three to four hours later
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We should be doing that consistently
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every day even on days where we're not
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working so that our body can anticipate
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this in terms of their rhythm and we can
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prepare digestive enzymes and all the
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other bodily processes that are
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associated with digesting our food
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Additionally it's important as well to
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go to sleep at the same time every day
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And the reason for this is so that our
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body can anticipate the release of
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specific sleep hormones such as
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melatonin to prepare us for sleep in a
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coordinated way repetitively over time
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And if we can implement these tips of
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consistency in both our eating and our
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sleeping time regimen then this can help
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us coordinate and really overcome any
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sort of challenges that are involved
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with working shift work So now we'll
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move into talking a bit about hormones
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And as I mentioned hormones are
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oscillating over the course of a day in
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ways to help us maintain our function
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and optimize our function during either
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the early part of the day or the later
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part of the day And there are a few
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examples of this One primary example is
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cortisol You may have heard of cortisol
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before This is associated with being the
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stress hormone which we associate with
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being a bad thing typically But actually
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uh cortisol is a hormone that helps us
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feel more awake and alert And it's the
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case in the scientific research that
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individuals who have higher levels of
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morning cortisol perform about 20%
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better on memory and attention tasks So
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this hormone is helping individuals
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retain memory and feel alert Another
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example of a hormone that changes over
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the course of the day is melatonin I'd
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mentioned this in previous slides but
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melatonin helps our body to prepare for
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sleep And part of the way it does this
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is by reducing our body temperature
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which prepares us for deeper phases of
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sleep such as phase three and phase 4
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sleep And speaking of phase three and
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phase four sleep this moves us to growth
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hormone And growth hormone is a hormone
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that is associated with repair of our
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body's tissues such as our muscle And
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it's a recovery hormone that can help us
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recover from exercise or our daily
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activities and it is elevated actually
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during phase three and phase four sleep
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So this is another reason why it's
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important to maintain a steady
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biological rhythm so we can reach these
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deeper stages of sleep which can help us
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recover from our daily
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activities Continuing forward here with
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just a few more hormones Our next
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hormone that we'll talk about is insulin
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So insulin is typically associated with
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diabetes However it is a helpful hormone
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for our general energy metabolism What
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insulin does is is it takes sugar from
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our bloodstream and deposits it into our
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cells to be used for energy And insulin
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is at its most elevated earlier upon
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waking And so if we're consuming foods
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such as breads or cereals those foods
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are more digested and then placed into
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our cells more readily by insulin
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earlier upon
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waking The next hormone here that we'll
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talk about is testosterone So like
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insulin testosterone is elevated in the
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earlier part of our day and it is
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responsible in both males and in females
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for greater levels of energy
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improvements in libido and greater
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muscle strength So we can capitalize
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upon these benefits earlier upon waking
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through
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testosterone And our last hormone here
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is thyroid hormone So thyroid hormone is
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responsible for cellular energy
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metabolism and energy generally in the
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cells in our body And thyroid hormone is
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increased later after waking So as we
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approach sleep thyroid hormone is our
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general means of energy
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production So as a general takeaway here
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after talking about all these hormones
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the circadian rhythms generally help us
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manage these hormones in a tightly
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regulated process so that we can
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function more as we move throughout our
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day So as a final takeaway here we'll
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just move into a summary of what we've
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learned today Our circadian rhythms are
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an integral part of our general
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functioning in our body and they are
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sensitive to light So the perception of
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light in our environment coordinates
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information to our eyes which then
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coordinates to our brain which
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coordinates to the rest of our body so
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that our body knows what time it is And
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what this does is it oscillates our
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release of various hormones that help us
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manage our energy levels Now there are
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tips to help maintain our circadian
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function whether we're night owls or
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early birds One of these tips is to just
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maintain a consistent sleep schedule And
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this can be done by just coordinating
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what time we go to bed and what time we
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wake up every day even on days when
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we're not working And this helps our
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brain to know when to release hormones
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like melatonin so that we can more
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effectively prepare for sleep The next
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tip here is just coordinating and making
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sure that we're eating our meals at
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consistent times every day so that our
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digestive hormones can know when to be
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released to help us more effectively
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deposit the food that we're eating into
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our cells and utilize them for energy
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The next tip here is to get natural
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light exposure as early as possible upon
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waking so that we can get the release of
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those helpful hormones such as cortisol
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to help us feel more alert and to have
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an improvement in our memory and
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cognitive function And then our last tip
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here is to avoid uh exposure to
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artificial light as we reach our time to
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sleep And the reason for this is because
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as we prepare for our time to sleep we
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see the release of melatonin And if our
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eyes are perceiving light then our brain
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thinks that it is daytime and that will
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impair the release of melatonin which
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can impair our ability to sleep And so
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if we can remember these tips we can
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more tightly coordinate our circadian
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rhythms and function better and be more
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energetic as we move throughout our day
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And so that is all I have for today I
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will see you at our next lesson Thank
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you for listening to Night Owl