The BioClock Studio Winter 2019 presents: The Effects of Sleep Deprivation on Attention and mood.
Meet Taylor. Taylor is a first-year student at the University of California San Diego
studying Human Biology. He's a little overwhelmed by his new college
life, but Taylor believes that he can sacrifice a few hours of sleep each night to best accomplish
studying, volunteering, socializing, and research.
Say hello to Kim! Kim is a third-year student
and for her, sleep is a priority. She believes that she functions best with
a well-rested mind and body and prioritizes getting around 8 hours of sleep a night, even
if it means that she has to finish up some studying in the morning.
Do Kim and Taylor’s differences in sleep schedule affect their performance and well-being?
Before we address this question, let’s first define what sleep is and why we do it.
Simply put - sleep is complicated. While we still do not fully understand the
purpose and effect of sleep, it is hypothesized to serve a role in energy conservation and
restorative functions for the brain and body. It is also possible that sleep aids in the
storage and formation of long-term memory, toxin removal from the brain, emotional regulation,
and more. So, sleep is important. But how much sleep
do we need? Let's look at a research study on the effects
of sleep deprivation and sleep restriction on cognitive function to find out.
48 healthy adults were divided into 4 groups. One group was sleep deprived and had to stay
awake constantly for 72 hours (a situation called total sleep deprivation).
The other three groups were allowed to spend 8 hours, 6 hours or 4 hours in bed each night for
14 days. When they were awake, cognitive performance
for all participants was assessed every 2 hours for every day of the study. This means that
they were asked to perform simple tasks that determined their levels of alertness and attention,
and their ability to process information in working memory.
At the end of the 14 day period, researchers found that participants who slept only 4 hours
a night made significantly more mistakes in performing their assigned tasks than those
who slept longer, implying lower levels of alertness and information retention -- about
equivalent to the level of participants who had gone two full nights without sleep!
Increased lapses in attention were evident after only 4 days of sleep restriction!
Participants who slept 6 hours a night also performed increasingly worse in their assigned
tasks as the 14 day period went on. At the end of the two week study, this group
showed impairment that was as bad as participants who had undergone one night of total sleep loss.
In summary, this study determined that consistently
sleeping less than the recommended 7-9 hours of sleep a night results in a continuous decline
in working memory, attention, and alertness. What does this mean for Taylor and Kim?
This study found that the effects of sleep restriction are cumulative, meaning that over
a couple of days, Taylor will be increasingly less alert and less attentive to stimuli if
he keeps sacrificing sleep. Prolonged sleep restriction can result in
detrimental effects on attention that are just as bad as, or potentially worse over
time than, going a whole night without sleep. Like his classmates, Taylor is cramming classes,
extracurricular activities, and social obligations into his schedule.
Sometimes it seems like there just isn't enough time in the day to achieve all of his goals
and catch the recommended 7 to 9 hours of sleep.
Not only does he sleep for less than the recommended amount per night, but Taylor often pulls "all-nighters"
going a full 24 hours without sleep in hopes of earning a higher grade.
That’s some dedication! But will his strategy actually improve his capacity to learn and
store information? Unfortunately for Taylor, sleep deprivation
is frequently associated with poor academic performance and decreased learning capacity.
Several studies have determined that students going without sleep the night before a test
perform significantly worse than their well-rested peers, sometimes by two full letter grades.
Another study found that on average, the overall GPA of students who get less than 6 hours
of sleep is about half a GPA point lower than that of students who sleep the recommended
amount. This means that Taylor’s chronic sleep restriction
and occasional all-nighters are actually conspiring to damage his grades.
Why does sleep deprivation affect learning? Sleep deprivation can have detrimental effects
on our retention of knowledge, such as the storage and formation of long term memory.
When a person learns new information, a region of the brain called the hippocampus is involved
in processing that information and sometimes facilitating its long-term storage in a process
called consolidation. Research has shown that after a full night's
sleep, this consolidation process improves certain types of learned performance during
later testing, even without any additional studying!
Sleep deprivation, on the other hand, disrupts the ability of the hippocampus to consolidate
short term memory into long term memory. This means that if Taylor stays up all night
studying for a test, not only will he find it harder to study because he is sleepy, but
he may also be less likely to retain the information he went over while he was cramming.
So in a nutshell, we’ve outlined that Taylor’s sleep habits could decrease his GPA. Now,
let’s take a closer look at what happens in his brain to find out why attention and
learning capacity decline in a sleep-deprived state.
Just one night of total sleep deprivation reduces blood flow and neural activity in
the parts of the brain called the prefrontal cortex and the thalamus.
The prefrontal cortex is like the judge of the brain. A normally functioning prefrontal
cortex is needed to carry out executive functions, such as working memory and cognitive flexibility,
both of which are required to maintain sustained attention and focus.
The thalamus is important for activation of the cortex and communication between different
cortical regions, kind of like an excitatory relay station.
A reduction of blood flow in these regions of the brain, associated with decreased activity
of the prefrontal cortex and thalamus, may explain why a sleep-deprived person has difficulty
sustaining attention on one task for an extended period of time.
Perhaps one of the most important everyday tasks requiring sustained focus and attention
is driving. So let’s say after a long night of studying,
Taylor decides to drive out to the store to grab some snacks to refuel. How will sleep
deprivation affect his driving performance? Although many experienced drivers view driving
as a passive task that requires little thinking, driving is actually a highly complex, divided-attention
skill. Lapses in attention from sleep deprivation can result in devastating consequences such
as crashes, injury and death. This is bad news for our sleep-deprived Taylor.
The prefrontal cortex is particularly vulnerable to sleep deprivation and is important for
attention and decision making. So, impairments in the functioning of this
region of the brain can severely compromise driving performance, which requires sustained
attention on the road. As a result, young drivers comprise one in
five fatal crashes in developed countries. Both decreased sleep and ongoing maturation
of the prefrontal cortex are factors hypothesized to contribute to accidents in this population.
Driving while sleep deprived has been compared to the impairment in performance that is seen
from drinking alcohol. One study showed that in adults, 17-19 hours
without sleep -- just 1 to 3 hours longer than an “ideal” 16-hour awake period -- has a
negative effect on cognitive and motor performance that is as great as having a blood alcohol
content of point oh-five percent. Going 24 hours without sleep produces effects
equivalent to having a blood alcohol content of point one percent, which is above the legal
level for intoxication in the US and most countries worldwide.
That means that if Taylor pulls an all-nighter, his driving could be as dangerous as if he
had 2 to 3 alcoholic drinks beforehand.
So, in order to preserve his own health and watch out for the safety of others,
we’d recommend Taylor get some sleep before he gets behind the wheel.
We have focused on Taylor’s poor sleep habits
and how they affect his ability to pay attention and perform tasks such as driving and studying.
Now let’s see how sleep deprivation affects one’s mood and subsequently, mental health.
Sleep has been shown to affect how accurately a person can assess the emotions and intentions
of others. Sleep-deprived individuals are more likely
to mistake a neutral social interaction for a more negative interaction.
For example, if Taylor is severely sleep deprived, during a social interaction he is more likely
to believe that the people he is interacting with harbor negative feelings towards him.
In Taylor’s mind, the neutral expressions of his friends or acquaintances are more likely
to be wrongly perceived as angry, apathetic, or irritated. This can result in Taylor feeling
depressed or anxious after social interaction. Why does this happen? Sleep deprivation can
make it more difficult to distinguish between different emotional cues, by increasing your
perception of negative images. This decrease in discrimination of emotional
stimuli after sleep deprivation is linked to increased activity of the amygdala, a structure
in your brain involved in processing possible threats and in regulating anger, fear, and stress.
In addition, the sleep-deprived brain is subject
to alterations in the interactions between the amygdala and the prefrontal cortex, resulting
in changes in emotional regulation. In addition to affecting perception of emotion
in others, sleep deprivation has been shown to deteriorate one’s mood - making a person
more susceptible to feeling stressed, angry, and sad.
Research has shown that the relationship between sleep deprivation and psychiatric disorders
is bi-directional, meaning that sleep deprivation affects the onset of psychiatric disorders,
and psychiatric disorders affect one’s sleep. This vicious cycle is seen in psychiatric ilnesses,
including depression and anxiety disorder.
While we’ve discussed a whole host of negative effects as a result of Taylor’s sleep deprivation,
such as lower academic performance, impaired focus and attention, and unhealthy mood tendencies,
Taylor still has time to build healthier sleep habits and avoid these consequences!
All said and done, it comes down to this - sleep is important for a normal, productive wakefulness period.
So, what can Taylor do to be more like Kim
and get the sleep he needs? Well, let’s walk through a day in Kim’s life.
8:00am: Kim tries to wake up at around the same time every day.
1:00pm: Even if she is swamped with work, she takes the time to enjoy some sunshine
outdoors during the day. Natural sunlight is typically much brighter
than the light we maintain inside buildings, and helps reinforce her healthy circadian rhythm.
She avoids taking naps during the day - but
if she absolutely has to, she prefers to do so as early in the day as possible so she
can go to sleep at her normal time.
6:00 pm: She exercises in some form every day,
and loves weightlifting and swimming! She uses software on her laptop and phone
that shifts the screen colors after dusk, so she won’t be exposed to blue light when
it’s time to be winding down the day. This allows her brain to avoid
the type of light exposure that increases arousal.
Lastly, Kim makes her bedroom dark, quiet, and cool,
by using curtains, eyemasks, and even earplugs if it is too noisy outside.
This pre-sleep ritual allows her to relax and fall asleep around midnight.
Inspired by Kim, Taylor is also taking steps towards prioritizing his sleep. He has improved his grades,
has developed stronger bonds with his friends, and is benefitting from a more positive mood.
If Taylor can do it, you can do it too!