Critical Review: Sleep, Breast Cancer, and Epidemiological Study

This report presents a critical review of a case-control study that investigated the relationship between self-reported sleep duration, sleep quality, and breast cancer risk in Western Australian women. The review assesses the study's methodology, including the use of questionnaires to gather data on sl...Read More

Running head: CRITICAL REVIEW
CRITICAL REVIEW
Name of the Student
Name of the University
Author’s Note

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Table of Contents
1. Study Description.....................................................................................................................2
2. Article Critique.........................................................................................................................2
2.1 Title and Abstract..................................................................................................................2
2.2 Introduction............................................................................................................................3
2.3 Materials and Methods..........................................................................................................3
2.4 Results....................................................................................................................................5
2.5 Discussion and Conclusion...............................................................................................5
2.6 References..............................................................................................................................6
2.7. Acknowledgements and funding..........................................................................................8
3. Over Assessment and Conclusions of the Article Critique......................................................9

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1. Study Description
In this, article the study is based on evaluation of the risk factors that are associated with
breast-cancer and its relation with sleep-duration and sleep-quality in western Australian women.
There are evidences of women suffering from cancer due to the improper sleep patterns. This
study is conducted through secondary data, which is done from population control based studies
in 2009-2011 in which the participants were give questionnaires about their sleep patterns.
Misclassification bias and selection analysis for potential selection is also conducted in this
study.
2. Article Critique
The major critique found in this article are the results which does not conclude to the
topic in question, the participants are not eligible as data for 5% of the sample were missing,
estrogen receptor testing were not detected in 169 women suffering from breast cancer. The basis
of the result of this study were not acceptable due to the inappropriate results achieved in the end
of the study. The contradiction in this article due to selective biases and misclassifications can be
an obstruction for it to be regarded as a concrete study on the subject matter of breast-cancer and
its association with the sleep pattern as well as sleep quality.
2.1 Title and Abstract
The research article titled-‘Self-reported Sleep Duration, Sleep Quality, and Breast
Cancer Risk in a Population-based Case-Control Study’ has been critiqued and analyzed in this
paper. The title mentions what is the research based on and the type of study is conducted. Case
control study is retrospective in nature, they compare the group who is suffering from the

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diseaseand the group who is not suffering from the disease.It shows an amount of significant risk
factors in the disease (Girschik, Heyworth and Fritschi, 2013).
2.2 Introduction
The critical review of this article will be donewith the help of STROBE guidelines as it
gives an efficient result in medical researches and literature. The experts and researchers
frequently use it for epidemiological studies. Readers need to what was planned, what was done,
what is found and what it all means. This ensures an accurate result in medical literature if
STROBE guidelines is used (Equator-network.org, 2019).
Breast cancer is a prevalent disease amongst the female population all around the world,
be it Australia or globally. Some factors which increase the chances of breast cancer is primary
genetic mutation, weight gain, lifestyle, radiation, carcinogenic food, alcohol addiction,
reproductive health complication and now there are some studies which also shows that the
quality of sleep and duration can impact the health of women (Cancer.org, 2019).
There has been a case of irregular sleep pattern in developed countries according to
international and Australian studies. Some studies also show that there is a reduction of around
13-36 minutes in the habitual sleep pattern. Although, results of shorter duration of sleep shows
signs of weakness, tiredness and lethargy and less links have been found to prove that it causes
breast cancer (Wang et al, 2015).
2.3 Materials and Methods
The ‘Breast Cancer Environment and Employment Study’ is based on a controlled trial,
done in Western Australia of the occupational and environmental risk factors. The sample-size
comprises of 1,000 cases and 2,000 age match control samples. The study was based upon the

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expected incidence rate of exposure and rate of incidence of cancer patients present within
Western Australia. The ethical approval was obtained by the Human Research Ethics Committee
of the Western Australian Department of Health and The University of Western Australia. The
considered participants were women who belonged to the age group of 18-80 years with first
reporting episode of breast cancer. Pathologists, hematologists and radiation oncologists do the
diagnosis of cancer. Cases were not included where breast cancer was reported non-invasive, or
if the diagnosis was done 6 months before the participants notified or if participants were not
fluent in English to complete the questionnaire given to them to obtain accurate results. A total
of 2,089 breast-cancer cases were considered, wherein; 1,205 were women, approx. (58%) who
consented to participate in the research study and 334 (16%) were eligible participants who did
not participate. Also, 545 (26%) of the participants did not respond to the survey-questionanire,
and 5 participants died due to the illness. The younger participants never responded and the elder
group refused to participate. The control sample comprised of women of the age-group 18 to 80
years that resided within Western Australia in between May 2009 to July 2011. The participants
were randomly selected by the authors from the electoral- roll. They matched the frequency and
were distributed in five year age group. As they were residents of Western Australia, it was
obvious that they were fluent in English and could appropriately fill up the questionnaire.
Therefore a total of 4,358 eligible controls were recruited out of which, 1,789 (41%) agreed to
participate. Also, 939 (22%) were eligible controls who did not participate and 1,628 (37%) did
not respond to the questionnaire and 2 of them had died. No difference was detected in terms of
residential isolation or socioeconomic-strata between the control participants and those who did
not participate in the research article. The data was collected through the questionnaire that had
multiple questions on parameters such as demographic, lifestyle factors and reproductive health

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as well as sleep pattern. Questions about sleep examined factors such as normal period of sleep
taking place within workdays, normal length of sleep taking place within weekends and general
sleep quality. The questions comprised the following: “Ignoring the last year, how many hours
of sleep on [non-work/work] days do they usually get?”, “Ignoring the last year, do they
generally consider themselves to be a good sleeper; that meant that do they fall asleep easily
and soundly?” These questions were framed in such a way that they had words like “Ignoring
the last year”. This was done to shun recent sleep-patterns that could be related with accessory
diseases on such instances. Odds ratios and 95% (CI) confidence intervals was considered using
the method of unconditional logistic-regression, with the matched-frequency variable age
included across all models. Variables were linked with the consequence and the disclosure, that
was considered “probable confounders”, and this was encompassed in multivariable-models
without the regard of any relation with the expected consequence.
2.4 Results
The result is determined by selection bias and miscalculated bias. Selection bias was
investigated by recalculating the age of the sample size and the result they gave, ratios were
obtained after making 2 expectations about the sleep duration and sleep quality in non-
participants. The first assumption established that the non-participants had a better duration of
sleep pattern than the participants did and the second assumptive factor was established that the
people who disagreed to participate in the study had a worse quality of sleeping pattern, which
was less than 6 hours a day (Phipps et al., 2016).The misclassification bias is caused by self-
reported data, as the variables were categorical so even the random misclassification can result to
biases. The 5% of the data were missing from the total participants, leaving half of them for
sleep duration and half for the sleep quality. When the distribution of sleep durations was gone

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for reviewing, lesser than 5% of the participants were pulled into the first as well as last
categories and therefore the consequences were segregated into four categories for the section of
data analysis. The categories were more than 6 hours, 6–7 hours, 7–8 hours, and more than 8
hours of sleep duration.
2.5 Discussion and Conclusion
To discuss the results, it can be said that the data showed that there exists no significant
link in between sleep-duration and sleep pattern in relation to the prevalence of breast cancer.
The polygamous nature of the analysis examined different risk factors for breast-cancer by
means of the estrogen-receptor status and menopause and cases showed there was no connection
between quality and sleep duration in relation to risk of breast cancer. In addition, the
classification of the physiological 24-hour cycle of humans showed no relation between sleep-
duration and breast- cancer (Khan et al., 2018). It also indicated a weaker evidence for a
probable connection between the condition of breast-cancer and sleep-duration within women.
Other studies also showed similarities with this study and it said that sleep pattern or duration has
no link with breast cancer. One of them mentioned that long or short hour duration of sleep has
nothing to do with breast-cancer prevalence (Qin et al., 2013). Contrastingly, a study mentioned
that distorted sleep pattern could cause chances of breast cancer in women
(Hopkinsmedicine.org, 2019).

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2.6 References
Boyle, T., Vallance, J.K., Buman, M.P. and Lynch, B.M., 2017. Reallocating time to sleep,
sedentary time, or physical activity: associations with waist circumference and body mass
index in breast cancer survivors. Cancer Epidemiology and Prevention Biomarkers,
26(2), pp.254-260.
Cancer.org (2019). What Is Breast Cancer? | Breast Cancer Definition. [online] Cancer.org.
Available at: https://www.cancer.org/cancer/breast-cancer/about/what-is-breast-
cancer.html [Accessed 12 Oct. 2019].
Creative, B. (2019). Good news for sleep deprived - Harry Perkins Institute of Medical Research.
[online] Perkins.org.au. Available at: https://www.perkins.org.au/news/good-news-for-
sleep-deprived [Accessed 12 Oct. 2019].
Davis, M.P. and Goforth, H.W., 2014. Long-term and short-term effects of insomnia in cancer
and effective interventions. The Cancer Journal, 20(5), pp.330-344.
Equator-network.org (2019). The Strengthening the Reporting of Observational Studies in
Epidemiology (STROBE) Statement: guidelines for reporting observational studies | The
EQUATOR Network. [online] Equator-network.org. Available at: http://www.equator-
network.org/reporting-guidelines/strobe/ [Accessed 12 Oct. 2019].
Girschik, J., Heyworth, J. and Fritschi, L. (2013). Self-reported Sleep Duration, Sleep Quality,
and Breast Cancer Risk in a Population-based Case-Control Study. American Journal of
Epidemiology, 177(4), pp.316-327.

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He, C., Anand, S.T., Ebell, M.H., Vena, J.E. and Robb, S.W., 2015. Circadian disrupting
exposures and breast cancer risk: a meta-analysis. International archives of occupational
and environmental health, 88(5), pp.533-547.
Hopkinsmedicine.org (2019). Lack of Sleep and Cancer: Is There a Connection?. [online]
Hopkinsmedicine.org. Available at: https://www.hopkinsmedicine.org/health/wellness-
and-prevention/lack-of-sleep-and-cancer-is-there-a-connection [Accessed 12 Oct. 2019].
Khan, S., Duan, P., Yao, L. and Hou, H., 2018. Shiftwork-mediated disruptions of circadian
rhythms and sleep homeostasis cause serious health problems. International journal of
genomics, 2018.
Mansano-Schlosser, T.C. and Ceolim, M.F., 2017. Association between poor clinical prognosis
and sleep duration among breast cancer patients. Revistalatino-americana de
enfermagem, 25.
Phipps, A.I., Bhatti, P., Neuhouser, M.L., Chen, C., Crane, T.E., Kroenke, C.H., Ochs-Balcom,
H., Rissling, M., Snively, B.M., Stefanick, M.L. and Treggiari, M.M., 2016. Pre-
diagnostic sleep duration and sleep quality in relation to subsequent cancer survival.
Journal of Clinical Sleep Medicine, 12(04), pp.495-503.
Qian, X., Brinton, L.A., Schairer, C. and Matthews, C.E., 2015. Sleep duration and breast cancer
risk in the Breast Cancer Detection Demonstration Project follow-up cohort. British
journal of cancer, 112(3), p.567.
Qin, Y., Zhou, Y., Zhang, X., Wei, X. and He, J. (2013). Sleep duration and breast cancer risk: A
meta-analysis of observational studies. International Journal of Cancer, 134(5), pp.1166-
1173.

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Wang, P., Ren, F.M., Lin, Y., Su, F.X., Jia, W.H., Su, X.F., Tang, L.Y. and Ren, Z.F., 2015.
Night-shift work, sleep duration, daytime napping, and breast cancer risk. Sleep
medicine, 16(4), pp.462-468.
2.7. Acknowledgements and funding
The authors who affiliated where Western Australian Institute for Medical Research, The
University of Western Australia, Nedlands, Western Australia, Australia (Jennifer Girschik, Lin
Fritschi); and School of Population Health, The University of Western Australia, Crawley,
Western Australia, Australia.
The Australian National Health and Medical Research Council, who gave a project grant of
572530, supported this work. The University of Western Australia Hackett PhD Scholarship and
a Cancer Council Western Australia PhD top-up scholarship supported Jennifer Girschik. A
National Health and Medical Research Council Fellowship supported Prof. Lin Fritschi.
3. Over Assessment and Conclusions of the Article Critique
The article critique of this article concludes that there are still no evidences for the link
between sleep duration and quality with breast cancer in the women of Australia. Researchers are
in a contradiction about the result of this study. As this article had many inefficiencies in the
process of this research due to its inaccurate sample and few complications in data collection, it
does not conclude a fixed and true result. The factors the study was based on was not very
appropriate like the oestrogen receptor test and other such inaccuracy.

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