Relationship between Sleep Quality and Visual Short-Term Memory
in Young Adults
Haoyue Li
University of California, San Diego, La Jolla, California, 92093, U.S.A.
Keywords: Sleep Quality, Visual Short-Term Memory, Young Adults.
Abstract: Modern studies have indicated an active role of sleeping in memory consolidation. To further explore the
relationship between them, the present study tested the relationship between sleep quality and visual short-
term memory (VSTM) function. The study was conducted via online surveys and targeted at people aged 18
to 30 years old. The survey contained three main sections, basic information, sleep quality questionnaire, and
VSTM tests. There are three questions asking age, gender, and education level of the basic information
section. The Pittsburgh sleep quality index (PSQI) questionnaire was utilized to assess sleep quality, and
global PSQI score was calculated according to the given PSQI calculation model. VSTM tests contain
questions with pictures showing squares of different colors and randomly ask the color of a specific square.
A total of 82 responses were used for data analysis. Most participants included are college students. A few of
them are grad students. The results implicate that no association between sleep quality and VSTM function in
younger adults was found in the present study. After comparison between good and poor sleepers, no
significant difference in VSTM performance was discovered. Furthermore, after comparing the VSTM
performance between females and males, no significant difference was found in the present study. The results
from the present study might offer new insight for the relationship between sleep quality and short-term
memory and thus suggests new direction for clinical treatment to certain mental diseases.
1 INTRODUCTION
Sleeping plays an important role in many aspects. It
is believed that sleeping allows our body and mind to
recharge, helping us to stay healthy. Studies have
shown that sleep deprivation could cause enormous
problems in human healthy. From basic level, sleep
deprivation could increase response time, slowing
down the reaction speed. Regarding to higher level
cognition function, such as memory, perception, and
executive functions, even though there are
disagreements on how sleep loss could affect them,
emerging evidence have suggested that sleep loss
would impair certain functions, including learning,
memory, and especially cognitive systems that rely on
emotions (Killgore 2010). In human bodies, we have
a circadian rhythm, an internal 24-hour clock that
regulates our sleep cycle. For young adults, it’s
recommended to have 7 to 9 hours for sleep.
According to National Sleep Foundation, sleep
quality is defined as the measurement of how well
you are sleeping. There are several factors used to
determine sleep quality, including sleep latency, sleep
waking, wakefulness, and sleep efficiency. In the
present study, the Pittsburgh sleep quality index
(PSQI) used to assess sleep quality contains all
factors mentioned above.
Memory is the ability to both preserve and recover
what we have learned and experienced. There are
three general steps of memory: encoding, storage, and
retrieval. There are two main kinds of memory, short-
term memory which lasts seconds to hours and long-
term memory which could last for years. The present
study mainly focuses on short-term memory,
especially VSTM. Short-term memory (STM) could
be considered as a temporary storage system which
usually lasts about 20 seconds and only holds a small
amount of information. It’s commonly believed that
for human, the STM capacity is 7±2. VSTM is
defined as the memory system that stores visual
information for seconds. Previous studies have
suggested that the capacity of VSTM is 4 items, but
newer findings have indicated that the capacity could
be set by both the information contained and the
number of objects (Alvarez, Cavanagh 2004). In the
present study, pictures with 8 squares of different
484
Li, H.
Relationship between Sleep Quality and Visual Short-Term Memory in Young Adults.
DOI: 10.5220/0011372600003438
In Proceedings of the 1st International Conference on Health Big Data and Intelligent Healthcare (ICHIH 2022), pages 484-489
ISBN: 978-989-758-596-8
Copyright
c
2022 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
colors were presented for a few seconds as visual
stimulus, and a random square will be asked about its
original color to test VSTM function.
The relationship between sleeping and memory
has been studied for a long time. Early studies believe
sleeping functions as a passive role in memory
consolidation by protecting them from external
stimulus, modern studies have shown sleeping plays
an active role since memory undergoes processes for
consolidation (Rasch, Born, 2013). Previous study
has suggested that sleep deprivation could impair
short-term memory of normal objects (Li, Wu, Shao,
Liu 1991).
Inspired by all these information, the current study
wants to further examine the association the effect of
sleep quality on visual short-term memory (VSTM).
The hypothesis is that there is association between
sleep quality and VSTM function, and poor sleep
quality would result in worse VSTM performance.
The current study uses Pittsburgh sleep quality index
(PSQI) questionnaire to test sleep quality and 12
questions containing squares of different colors to test
VSTM function among around 80 Chinese young
adults. It’s hoped that by studying the relationship
between sleep quality and VSTM, this study could
help better answer the question that if sleep could
improve STM. In addition, from clinical aspect, this
study might have potential for developing more
effective treatment to mental diseases. Sleeping
disturbances are more common among patients with
mental diseases that have symptoms of memory
disorder than in general population. One such disease
is schizophrenia, as data has shown that about 50-
80% patients reported sleep problems while in
general population, the number is approximately 30%
(Cohrs 2012). Currently, many treatments of
schizophrenia thus usually tend to increase total sleep
time and sleep efficiency (Cohrs 2012). The result of
the present study might provide new insight into
clinical treatment.
2 METHODS
In this study, I conducted online survey designed
through Qualtrics to test the sleep quality and VSTM
function. The online survey contained three main
parts: basic information, sleep quality questionnaire,
and VSTM tests. The whole survey is anonymous.
For the basic information part, participants were
asked three questions: age, gender, and education
level. The PSQI questionnaire is used to test the sleep
quality. The Pittsburgh sleep quality index (PSQI)
questionnaire is a self-rated questionnaire that covers
a 1-month time interval (Buysse, Reynolds, Monk,
Berman, Kupfer 2002). The final global PSQI score
was calculated based on the given PSQI calculation
model. A lower global PSQI score indicates a better
sleep quality. The last part of the online survey is the
VSTM function tests. There is a total of 12 questions
in each survey. For each question, there will first be a
picture with 8 squares at different positions with
different colors. This colorful picture would appear
for 5 seconds. After the 5 seconds, the picture would
automatically disappear according to the design of the
survey, and another picture will be shown with a
multiple-choice question to the participants. The
second picture has the same 8 squares at the same
positions but with no color. An arrow points at a
random square in the second picture, and the
participants will be asked to choose the color of the
indicated square. All positions and color of the
squares and the indicated square in each question are
random. Details of those pictures are shown below
(Figure 1). Each question is counted as 1 point for the
final performance score. For example, if a participant
gets 4 questions right, his or her performance score
will be 4 out of 12 points.
Figure 1: A sample of the pictures used in the VSTM test. The first picture (on the left) will first appear for 5 seconds. After
this short time, the second picture (on the right) will appear with the question asking about the original color of the pointed
square.
Relationship between Sleep Quality and Visual Short-Term Memory in Young Adults
485
The link to this survey was published online
through social media. In order to better control the
noises of other factors that could potentially influence
the short-term memory function, only people aged
between 18 and 30 years old were allowed to
complete the survey. In the end, this survey got a total
of 86 responses. But for the final data analysis, only
82 responses were used. This is because some
responses had very ambiguous answers so that their
global PSQI score could not be accurately
determined. Some responses were incomplete. There
was also one response that has 0 scores for the
performance score, and it is doubted that this person
didn’t seriously take the survey. Therefore, to make
the research more powerful, only 82 responses were
utilized in the analysis.
In terms of the data analysis, descriptive data,
mean and standard deviation, were calculated for the
age, PSQI score, and performance score. Shapiro test
was used to test the distribution of the PSQI score and
performance score. Spearman correlation test was
used to determine if there’s a significant association
between sleep quality and VSTM function. To better
determine if certain parameter could affect the VSTM
function, a two-sided Mann-Whitney test was used to
test the significance of difference in the VSTM
performance. The threshold is set at p = 0.05 for the
significance. All these tests were performed using R.
3 RESULTS
The survey finally got 82 complete responses. Based
on their answers to the question of their education
level, most participants are undergraduate students.
Several of them are grad students. One participant is
currently working. For all responses, mean and
standard deviation of the age, the global PSQI score,
and the performance score were calculated. The
results are shown in the below table (Table 1).
Table 1: mean and standard deviation of age, PSQI score,
and performance score for the whole dataset.
mean sd
age 21.57 (yrs) 2.84 (yrs)
PSQI score 5.21 2.96
Performance score 7.59 2.55
Shapiro test was performed on the PSQI score and
the performance score to test the distribution of these
data. The p-values from this test are shown in the
table below (Table 2). Both p-values are smaller than
the threshold, 0.05, therefore the distributions of these
data are not normal. This indicates that spearman test
should be used for the correlation test and Mann-
Whitney test should be used to test the significance of
difference.
Table 2: p-values from the Shapiro test on the PSQI score
and the performance score of the whole dataset.
p-value
PSQI score 5.268E-5
Performance score 0.01192
The main goal of the study is to determine if sleep
quality is related to the VSTM function. Therefore, a
correlation test was performed to examine if there’s
any association between them. Since the Shapiro test
gave p-values smaller than 0.05, indicating that the
distributions of the PSQI score and the performance
score are not normal, the spearman method was used
for the correlation test. The correlation coefficient is
-0.0839, and the p-value is 0.4536. The correlation
coefficient is slightly negative, implicating that a
lower PSQI score might be associated with a better
performance score. This is expected since a lower
PSQI score means a better sleep quality. However, the
p-value is larger than 0.05, indicating a non-
significant correlation between sleep quality and
VSTM performance. A scatterplot of VSTM
performance vs. PSQI score was also drawn (Figure
2). From the scatterplot, we can that the distribution
is relatively random, which could further support the
conclusion from the correlation test.
Figure 2: scatterplot of visual short-term memory
performance score vs. PSQI score. The distribution in this
scatterplot is relatively random.
ICHIH 2022 - International Conference on Health Big Data and Intelligent Healthcare
486
To better determine if sleep quality could affect
VSTM function, I separated the data into two groups
based on the PSQI score. According to Buysse et al.,
a global PSQI score greater than 5 yielded both high
diagnostic sensitivity and specificity (both over 80%)
in distinguishing good and poor sleep quality
(Buysse, Reynolds, Monk, Berman, Kupfer 2002).
Thus, I categorized participants with a PSQI smaller
than 5 into the good sleep quality group and
participants with a PSQI greater than or equal to 5 into
the poor sleep quality group. After categorizing the
data, good sleep quality group has 37 participants,
and the poor sleep quality group has 45 participants.
Then I ran the Shapiro test on the PSQI score and
performance score of both groups. The p-values of the
PSQI score of both groups are smaller than 0.01, way
smaller than the threshold. The p-value of the
performance score of the good sleep quality group is
0.01485, and the p-value of the poor sleep quality
group is 0.5213. Based on the p-values, most data are
not normally distributed, thus the Mann-Whitney test
should be performed to compare the performance
difference between the two groups.
In order to examine the significance of the
difference, mean and standard deviation of the
performance score were first calculated. The good
sleep quality group has a mean of 7.65 with a standard
deviation of 2.93, while the poor sleep quality group
has a mean of 7.53 with a standard deviation of 2.22.
The Mann-Whitney test gave a p = 0.5019, larger than
0.05. Therefore, the difference in the VSTM
performance between the two groups is not
significant.
To test if gender could be a factor affecting the
VSTM function, data were separated into the female
and male groups based on their answers. There are 64
females and 18 males. The mean and standard
deviation of the PSQI score and the performance
score of these two groups were calculated as shown
in the table below (Table 3&4). Since the group sizes
differ greatly, the Mann-Whitney test was performed
to test the significance of the performance difference.
The test gave a p = 0.7052, greater than 0.05.
Therefore, no significant performance difference was
found between the two genders.
Table 3: mean and standard deviation of the PSQI score and
the performance score for the female group.
Female group mean sd
PSQI score 5 3.07
Performance
score
7.67 2.54
Table 4: mean and standard deviation of the PSQI score and
the performance score for the male group.
Male group mean sd
PSQI score 5.94 2.51
Performance
score
7.28 2.63
4 DISCUSSION
Based on the results from the data analysis, three
conclusions could be reached. First, there’s no
association found in this study between sleep quality
and VSTM function. Second, sleep quality might not
affect VSTM function. Third, gender might not be a
factor that influences VSTM function. Some previous
studies have reached a similar conclusion as the
present study. One study conducted by several
undergraduate students at Georgia college tested 25
individuals for their sleep quality short-term memory
function. Their study also used the PSQI for testing
sleep quality and word recall tasks for the short-term
memory function. They found no correlation between
sleep quality and the number of words recalled and no
significant difference in the number of words recalled
by males and females (Holcomb, Raisin, Gravitt,
Herrick, Mitchell 2016). This could reflect the results
of the present study.
In another study conducted by Xie et al. (2019),
sleep quality, working memory, and depressed mood
were assessed. They used a short-term recall task and
measured both the capacity and the precision of the
working memory. They found that poor sleep quality
could reduce the short-term memory capacity but not
the precision (Xie, Berry, Lustig, Deldin, Zhang
2019). This conclusion could mirror the results in the
present study. In the present study, the performance
score of the VSTM tests is the number of questions
the participant answered correctly. This could be
considered as a measurement of the precision of
short-term memory. In other words, the conclusion of
the present study could be interpreted as no
association found between the sleep quality and the
precision of VSTM and no significant influence in the
VSTM precision by sleep quality found based on the
data, which is the same result as the previous study.
This might also indicate that for future interest, the
relationship between sleep quality and short-term
memory capacity could be studied.
Even though there are some studies indicating that
there might not be association between sleep quality
and short-term memory function, many previous
studies have suggested the opposite. An early study
Relationship between Sleep Quality and Visual Short-Term Memory in Young Adults
487
conducted by Li et al. (1991) examined the sleep
quality and short-term memory with several tasks and
proved the importance of sleep in short-term memory
function. The results from their short-term memory
tests showed that sleep deprivation caused obvious
drops in the score (Li, Wu, Shao, Liu 1991). They
further conducted REM sleep deprivation using rat
model and found the duration of the deprivation is
potentially related to the strength of the impact on the
short-term memory function by sleep deprivation. In
addition, the team assessed the sleep quality and
found that good sleepers had remarkably higher
scores on digit span test than poor sleepers (Li, Wu,
Shao, Liu 1991). However, for digit symbol, cube
figure, and digit cancellation tests, no significant
differences were found between the two groups (Li,
Wu, Shao, Liu 1991). This finding might to some
extent support the results found in the present study.
The VSTM test in the present study only contains
squares, which is similar to the cube figure test. Thus,
it might be reasonable that no significant relationship
between sleep quality and short-term memory was
found. However, it might be worthy for future studies
to investigate the reason why certain tests do not
reveal the relationship.
The current study found no significant difference
in VSTM function between two genders. One early
study about gender difference and short-term memory
function somehow provided similar result. The study
tested on 1279 individuals, 637 males and 642
females, aged from 5 to 19 years old and performed
14 subsets of the Test of Memory and Learning
(TOMAL) on all individuals (Lowe, Mayfield,
Reynolds 2003). With this large sample size, the study
revealed similarities between two genders on the
VSTM tests. Even though a few tests showed minor
differences, there were no consistent pattern found,
and the magnitude of those differences are small,
indicating there might be no gender difference in
VSTM function (Lowe, Mayfield, Reynolds 2003).
However, the study revealed that gender difference
might play a role in other kinds of short-term memory.
The study concluded that females scored higher on
two verbal memory tests while males scored higher
on spatial memory tests. These findings might offer
new future directions in terms of gender effect on
certain short-term memory function.
The main goal of the present study is to determine
the relationship between sleep quality and VSTM
function. The conclusion rejected the original
hypothesis which proposed that worse sleep quality
might be associated with poor VSTM function.
However, as stated above, many previous studies
have found such effect on short-term memory
function. One potential reason for this mix might be
age. Many studies have illustrated that age could
affect short-term memory function, and usually the
short-term memory function peaks at young
adulthood. One such study tested on younger children
(10 to 12 years), teenagers (13 to 15 years), younger
adults (20 to 25 years), and older adults (70 to 75
years) and concluded that item-bindings, closely
related to short-term memory function, are
functioning better in teenagers and young adults than
children and older adults (Fandakova, Sander,
Werkle-Bergner, Shing 2014). Some studies also have
shown similar conclusion and proved from
neurobiology aspect. One such early study claimed
that the binding process and the top-down control,
related to posterior and frontal brain regions and their
interactions with the whole neural network,
experience large changes across the lifespan as both
grow mature until young adulthood and decline as age
increases, leading to the peak of short-term memory
function in young adulthood (Sander, Lindenberger,
Werkle-Bergner, 2012). In the present study, most
participants could be considered as young adults.
According to the above findings, the participants
included in the present study might exert ceiling
effect, all performed high short-term memory
function regardless of sleep quality. Therefore, the
effect of sleep quality might be reduced so that no
association was found.
There are certain limitations in the present study
as well. First, all participants are aged 18 to 30 years
old. Most of them are college students. As discussed
above, these participants could exert a ceiling effect
on the study, reducing the power of sleep quality on
short-term memory function. This also constrains the
scope and the application of this study, limiting it to
be only applicable to young adults. This also
introduces the second limitation of the present study.
The survey of this study took place during the
summer break, during which students’ sleep quality
might not strongly influence students’ behavior due to
many other factors. This “summer breaklimitation
can potentially decrease the association between
sleep quality and short-term memory function. To
improve it, future studies could conduct at another
time period to avoid summer break. The third
limitation is due to the accessibility of research tools.
All data of the present study were collected via an
online survey, and no monitor was conducted when
participants finished the survey. Therefore, if
participants cheated, for example, taking pictures
during the VSTM tests to help them remember the
color, researchers could not know the truth. Thus,
their performance score might not reflect their real
ICHIH 2022 - International Conference on Health Big Data and Intelligent Healthcare
488
VSTM function. Improvement could be made by
giving the survey in person to better control
environmental influence. In addition, since the
VSTM tests were designed personally by the
researcher, the professionality might not be fully
guaranteed. For future studies, if possible, more
professional tests should be utilized. Fourth, there
might be response bias in the present study. The link
to the survey was published online through social
media. As a result, only people who have social media
and are interested in the survey would complete the
survey, resulting in response bias. Therefore, the
result of the present study might not be able to apply
generally. Finally, self-response bias might appear in
the present study. The PSQI questionnaire utilized to
assess sleep quality is a self-rated questionnaire. The
global PSQI score is calculated only based on the
response from the participant. Even though the
calculation model usually counts component scores
based on a range of the answer to be more general, the
inaccuracy of responses still could affect the global
PSQI score, thus further affecting the conclusions.
For future study, the relationship between age,
sleep quality, and short-term memory function could
be studied by increasing the age range of the sample.
Researchers could also have several groups of
different ages and make comparisons between them.
In addition, despite the fact that no relationship
between sleep quality and VSTM were found, there
might be relationship between sleep quality and other
kinds of short-term memory. Thus, those
relationships could be studied due to interest by
including various kinds of short-term memory tests,
such as auditory word recall tasks. Finally,
understanding the relationship between sleep quality
and short-term memory function might shed light on
future treatment for mental diseases. As mentioned in
the introduction section, some mental diseases have
symptoms of sleeping disturbances associated with
memory disorder. Thus, future studies could explore
which factor of sleeping is related to the disease in
order to develop clinical treatment.
5 CONCLUSIONS
The present study mainly investigated the
relationship between sleep quality and VSTM
function among young adults and included analysis of
gender effect as well. Three conclusions are reached
in the present study. First, theres no association
found in this study between sleep quality and VSTM
function. Second, sleep quality might not affect
VSTM function. Third, gender might not be a factor
that influences VSTM function. These results might
indicate that further examinations are required to
determine the relationship between sleep quality and
VSTM. Based on findings from previous studies,
future studies could also investigate sleep quality and
other kinds of short-term memory, gender effect, and
effect of different factors of sleep on short-term
memory function to develop clinical treatments for
mental diseases. Since sleep and memory are closely
related to many mental diseases, results from the
present study might suggest new direction in future
effective clinical treatment.
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