a 2014 study published by the American Academy of Neurology, Poor sleep quality is associated with increased
cortical atrophy in community-dwelling adults, researchers, Sexton et al., performed
a correlational study to explore the relationship between level of sleep quality
and corresponding physical conditions of the body, specifically the brain. Both
correlational and experimental studies compare two variables. However, even
though by correlational design, we can establish whether a relationship exists
between two variables, we cannot determine the cause of that relationship because
this design lacks the processes needed to establish the direction of the
relationship, eliminate possible third variables, or tell which variable comes
first. Also, correlational studies employ grouping variables that are only used
to categorize observations and aid visualization, unlike those of an experiment.
The conductors of this study, Sexton et al., 2014, do not implement manipulation
or random assignment, two distinguished tools of an experimental design, to propose
any causal relationship between one’s standard of sleep quality and the physical
conditions of one’s brain. The researchers in this correlational study speculated
that lower levels of sleep quality were associated with degeneration of size
and function in certain regions of the human brain, such as several structures of
the cortex. To conduct the study, the researchers used the Pittsburg Sleep
Quality Index to measure the sleep quality of community residents, varying in
age and gender, and compared these levels to different features of the cortical
and hippocampal areas of the brain, such as decay and cubic measure, obtained through
MRI scans. They then performed several post hoc tests to analyze whether age
played a role in their findings, as well as to evaluate potential third-party influences
such as body mass index (BMI,) blood pressure, and levels of physical movement.
Only partially supporting the original hypothesis, the research findings displayed
that lower levels of sleep quality were longitudinally correlated with increased
rates of degeneration in cortical functions and decreased cortical cubic measure,
with the exception of the hippocampus. These results were predominantly true of
relationships within the group of participants over the age of sixty, and the
aforementioned third-party variables did not prove to play a role in the
finding. The researchers also reiterate a key note of this study in their
conclusion: “Poor sleep quality may be a cause or consequence of brain atrophy,
and future studies examining the effect of interventions that improve sleep
quality on rates of atrophy may hold key insights into the direction of this
relationship.” By including this statement, the researchers stress that the
design of this particular study did not include the necessary measures for
indicating any causal relationships between the variables that they compared, though
an experimental study could. Their findings strictly indicate association, not

            In her article, “Lack of Sleep May
Shrink Your Brain,” the author, Val Willingham, cites findings from the above
study, Sexton et al., 2014, as well as a few other sources to discuss how sleep
deprivation affects the physical condition of the human brain. Despite the
researchers’ steady assertions that their research cannot evidence a causal relationship
between poor sleep quality and brain volume, the title that Willingham chose
for her article, which utilizes the outcomes of this study for credibility and
evidence, is inappropriate and misleading because the it suggests order and direction
in the relationship. Her title implicates that sleep quality influences brain
size, though the possibility remains that it could be the reverse. Order and
direction of a correlation can only be supported by experimentally-designed
studies, as these studies perform the sufficient measures to eliminate third-variable
problems and to observe the causal power of a certain variable. It continues,
and Willingham begins her article by describing the design and outcome of the 2014
study published by the American Academy of Neurology, specifically noting that those
individuals considered to have lower levels of sleep quality did also happen to
display a greater decline in brain size throughout the study. From here, Willingham
inserts information from other studies, such as sleep deprivation inducing
brain illnesses, to work towards her next statement: “So it stands to reason
that, if a lack of sleep can lead to memory loss, the size of the brain would
also be affected.” Neither studies that the author draws information from directly
support the relationship that the author asserts here. Instead, Willingham pulls
findings from both studies to draw her own conclusion about a causal relationship
between sleep quality and brain volume; this statement is therefore fallacious.
However, as the author continues, she contradicts her statement above and cites
the original, valid conclusions drawn in Sexton et al.,2014: the direction of
the relationship between sleep quality and brain degeneration has yet to be
established, and further research would need to be conducted to decipher which
variable manipulates the other. Although Willingham closes her article with an
accurate report of the final conclusions from the study, she makes several statements
and conclusions throughout that imply a causal relationship, which cannot be
supported by the study.

            After close evaluation of both articles,
I conclude that, overall, Val Willingham does not provide readers with an entirely
accurate report of the 2014 American Academy of Neurology study in her article,
“Lack of sleep may shrink your brain.” In her report, Willingham is guilty of
faulty reasoning; she utilizes information found in several studies to form her
own conclusions about the effects of sleep on brain volume, that are not
necessarily supported by the findings in Sexton et al., 2014. Willingham’s statement
quoted above gives the illusion of credibility, when in fact the only
relationship actually evidenced is merely correlation, not causality. Though she
does accurately relay information regarding the structure design of the study accurately,
when discussing the results, the author’s language suggests causality. As
aforementioned, causal conclusions cannot be drawn from correlational studies
because these types of studies do not involve the additional measures, such as
manipulation of a variable and random assignment, required to establish causational
power and direction. Manipulating or changing a variable allows us to observe
its causal power and it eliminates the question of direction in the
relationship. With random assignment, individual differences are averaged out
between different groups, which dismisses the third-variable problem of not
knowing if an outside variable is influencing the correlation between the two
variables being studied. An example of possible third-variable in the correlation
between level of sleep quality and brain size could be  


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