Epidemiology Study Designs and Critical Appraisal: PUBH6005 Report

This report delves into the field of epidemiology, providing a comprehensive analysis of various study designs, including Randomized Controlled Trials (RCT), cohort studies, and case-control studies. It begins with an introduction to epidemiology, defining its scope and importance in public health. The report then classifies different types of epidemiological studies, such as observational and experimental studies, and provides detailed explanations of each type, including their advantages and disadvantages. The core of the report involves a critical appraisal of three research articles, each employing a different study design, focusing on hypertension, coffee consumption during pregnancy, and ovarian cancer. The appraisal includes the application of critical appraisal checklists to evaluate the methodologies, results, and conclusions of each study. Furthermore, the report explores the concepts of association and causation, statistical and public health significance, and the potential for bias, confounding, and chance errors in epidemiological studies. The report concludes with a discussion of the implications of the findings and their relevance to public health practice.

Running head: Epidemiology 0
19
Title: Epidemiology

Epidemiology 1
Table of Contents
Research Articles.........................................................................................................................................1
Classification of Epidemiology Study:......................................................................................................22
Difference between Association and Causations:......................................................................................26
Statistical and Public Health Significance.................................................................................................31
Statistical Analysis and Peer Review.........................................................................................................32
Reporting on Studies: Some Helpful factors:.............................................................................................32
Conclusion:...............................................................................................................................................33
References.................................................................................................................................................34

Epidemiology 2
Research Articles
Article 1- RCT (Randomized Controlled Trial)
Discussion- A random trial was performed on African American population as most of the old age people
of that place were infected or can say suffering from Hypertension. It was single-blind trial for 3 months.
At that place almost 213 people were kept under investigation including men and women out of which
127 person were found with diastolic pressure of 90-110mm Hg. The secondary observation was
performed for the blood pressure or the fluctuation in the blood pressure. Two techniques of
Transcendental Meditation were performed on the people of African American and the obtained results
were much better than muscle relaxation. This process helps those people and there was a lot of change in
their suffering of hypertension the main role of discussion was about the trail performed on mental and
physical techniques to reduce hypertension. It was a short time process to identify the problem of
hypertension in people.
Image Source: (RCT case study , 2019)

Epidemiology 3
This paper discussed several key points of RCT with specific importance of results. There are lots of
errors found but most of them are due to bias, confounding and chance linked with the health services
research.
Critical Appraisal Skills Program checklist for RCT:-
Question1. Did the practice results the exact concern?
Yes
No
Cannot be answered
Question2. Was the assignment of infected to randomized?
Yes
No
Cannot be answered
Question.3 Were all of the patients who entered the trial properly accounted for at its conclusion?
Yes
` No
Cannot be answered

Epidemiology 4
Question4. Were patients, health workers and study personnel ‘blind’ to treatment?
Yes
No
Cannot be answered
Question5. Were the groups similar at the start of the trial?
Yes
No
Cannot be answered
Question6. Aside from the experimental intervention, were the groups treated equally?
Yes
No
Cannot be answered

Epidemiology 5
Question7. How large was the treatment effect?
Comments: Treatment was small. It was neither statically nor clinically notable.
Question8. How precise was the estimate of the treatment effect?
Comments: The estimation of treatment was not precise.
Question9. Can the results be applied to the local population, or in your context?
Yes
No
Cannot be answered
Question10. Were all clinically important outcomes considered?

Epidemiology 6
Yes
No
Cannot be answered
Question11. Are the benefits worth the harms and costs?
Yes
No
Cannot be answered
Article 2- Cohort Studies
A research was conducted on the consumption of coffee by any pregnant individual associated with the
spontaneous death or abortion. A group of pregnant women were kept under treatment or surveillance for
a specific time period and they were consuming coffee for that time period. The result of that analysis is
still in records of National Hospital discharge register. A huge number of spontaneous deaths were
observed due to consumption of huge amount of coffee. Reverse causation due to unidentified
spontaneous deaths may explain the association between coffee intake and risk of fetal death prior to 20
completed weeks' gestation but not the association with fetal loss following 20 completed weeks'
gestation. Coffee drinking is very obvious and normal, and in many countries it is considered as
harmless habit, it is proved that caffeine has powerful effects on a wide range of organ systems
(cohort article , 2019).

Epidemiology 7
Image Source: (Analysis of Chohort study , 201)
Critical Appraisal Skills Program checklist for Cohort Study:-
Question1.Did the study addresses a clearly focused issue?
Yes
No
Cannot be answered

Epidemiology 8
Question2. Was the cohort recruited in an acceptable way?
Yes
No
Cannot be answered
Question3. Was the exposure accurately measured to minimize bias ?
Yes
No
Cannot be answere
Question4. Was the Outcome accurately measured to minimize bias ?
Yes
No
Cannot be answered
Question5.(a) Have the authors identified all important confounding factors?

Epidemiology 9
Yes
No
Cannot be answered
(b) Have they take account of the confounding factors in the design and/or analysis
Yes
\No
Cannot be answered
Question6. Was the follow up of subjects complete enough?
Yes
No
Cannot be answered
Question7. What are the results of this study?

Epidemiology 10
Question8. Do you believe the results?
Yes
No
Cannot be answered
Question9. Can the results be applied to the local population?
Yes
No
Cannot be answered
Question10. Do the results of this study fit with other available evidence?
No
Comments: Small increase in BMI Z-score for every serving of sugar-sweetened beverages per day
during second trimester.

Epidemiology 11
Cannot answered
Question11. What are the implications of this study for practice?
Article-3
Case control Study
A data was collected of 3 years of a specific place where almost 442 cases of ovarian cancer were
examined. Those women which were infected with the disorder were compared with lowest quartile of
cholesterol intake, those in the second, third, and fourth quartiles had a multivariate adjusted odds ratio. In the
observed data it was described that consumption of egg in high amount is also a reason for ovarian
cancer. It was evaluated risks of ovarian cancer was because of different levels of various dietary factors. The
population-based case-control study found that women with higher who were consuming of dietary
cholesterol and eggs were at their risk of ovarian cancer get increased. It also obtained in study that higher
intakes of total vegetables and cruciferous vegetables as well as vitamin E and β-carotene
supplementation were reason with reduced ovarian cancer risk. The protective effect of B-complex
vitamin supplementation needs further study to confirm.
Critical Appraisal Skills Program checklist for case control study:
Question1. Did the study address a clearly focused issue?
Yes
Comments: This study points to a potential prevention strategy for childhood adiposity, but effect size
were small.

Epidemiology 12
No
Cannot be answered
Question2. Did the authors use an appropriate method to answer their question?
Yes
No
Cannot be answered
Question3. Were the cases recruited in an acceptable way?
Yes
No
Cannot be answered
Question4. Were the controls selected in an acceptable way?

Epidemiology 13
Yes
No
Cannot be answered
Question5. Was the exposure accurately measured to minimize bias?
Yes
No
Cannot be answered
Question6. Aside from the experimental intervention, were the groups treated equally?
Question7. How large was the treatment effect?
Comments:
Comments: The treatment was conducted in large number and they were significant

Epidemiology 14
Question8. How precise was the estimate of the treatment effect?
Question9. Do you believe the results?
Yes
No
Cannot be answered
Question10. Can the results be applied to the local population?
Yes
No
Cannot be answered
Question11. Do the results of this study fit with other available evidence?
Comments: The treatment was precise. Although the results were varying.

Epidemiology 15
Yes
No
Cannot be answered
Introduction
In this project the detailed information is provided about the epidemiology. The types of
Epidemiology study is discussed including the disadvantage and disadvantages.
Epidemiology:
The branch of science in medicine that over looking over with the reason of any diseases or disorders and
the number of people affected is known as Epidemiology. This study helps us to know about the
population infected with any disease or disorder and how this affects our community and wealth. The
information which is obtained by the study of epidemiology is use to make strategy for remedy of
disorders affecting community.
The term epidemiology is derived from the Greek word ‘epi’ and ‘demos’ and ‘logos’ where word epi
stands for “on or upon”, demos stands for “people” and logos stands for the “study”. Epidemiologists are
the one who takes the responsibility to find out the reason of the particular disorder. They start to
calculation the data or the collected information of infected area and people. They collect samples by
travelling to different places if there is any requirement for field work. Epidemiologists usually work in
the laboratory by analyzing the reports or the samples (Introduction of Epidemiology , 2019).
Classification of Epidemiology Study:
Epidemiology is categorized in following types as mentioned below (Classification of Epidemioogy
study, 2013):
i. Observational Studies
ii. Experimental Studies
The observation studies have two categories which are described below:

Epidemiology 16
I. Descriptive Study
II. Analytical Study
Descriptive Study- This study is simple to perform than analytical and experimental studies. This study
provides a base to analytical studies (Descriptive Study , 2013).
 Advantage- Large number of results is obtained as no any other subgroups are studied.
 Disadvantage- There is no any way to recover the results or information as the investigation is not
done by experiment
a. Case-coherent Study
b. Cohort Studies
c. Intervention study
Image Source: (Types of Epidemiology Studies , 2013)

Epidemiology 17
Let’s discuss the each type of epidemiology separately.
a. Studies of Cross-section:
For a particular point of time when the attribute of the people kept under observation then it
comes under the cross-section studies. The results which obtained from this studies informs about
the specific disorder or nature of people. It is not mandatory to examine the whole population,
only a specimen is enough which clarify the situation about the disorders which represent the
complete group of people.
The group of individual can be investigated by different type of method by taking the
measurements of blood pressure, by taking samples of blood etc.
b. Case Control Study:
In the above mentioned study the experts diagnosed the individual who are infected with any
diseases or disorder and then they get compared with the people who are not having any disease
or disorders.
 Advantage:
The most effective advantage of this study is that it allows examining rare infections
without checking large number of people.
 Disadvantage: This study not permits to investigate the broad health issues at a particular
time we may study only one type of infection or disorder.
c. Cohort Study: This study investigate the group of people for a long term of period and those
people examined by their nature and change in their nature with the time. This study is time
consuming and it is expensive in the cost than other study. A chart about the cohort study method
is presented for better understanding.

Epidemiology 18
Image Source: (Cohort Study , 2013)
 Advantage: Some of the disease cannot be determined in short time also they are severe
in nature for example Cancer, as it cannot be examined suddenly. This study helps the
investigators to investigate the infected person for the time period cancer start to develop.
 Disadvantage: This study takes a long time period for the results and it also expensive in
cost.
d. Intervention Study: In this study the group of individuals provided with the particular treatments.
It means the individuals are considered as subjects and they are treated with the possible cure or
prevention and on the basis of result investigators finds the solution of disorder. These tasks or
study are done in labs or research centers with in the suitable surroundings.

Epidemiology 19
Image Source: (Interevention Study, 2019)
There are two categories of Intervention study which are mentioned below:
i. Therapeutic Intervention Study
ii. Preventative Intervention Study
Difference between Association and Causations:
The connection between two unpredictable reason and result for any observation is known as association.
It is categorized as follows:
i. Positive/negative
ii. Casual
iii. Non-casual
iv. Confounded
v. Spurious

Epidemiology 20
i. Positive Association- When an event of higher value of examiner variable is connected with
the event of higher value of other dependent variable is known as positive association.
ii. Negative: When the higher digit of the examiner variable is connected with the lower value of
other dependent variable is known as Negative association.
iii. Casual Association: When there is change in the dependent variable and for that independent
variable is responsible then it is known as Casual association. The precise condition for the
casual association is Time and direction
iv. Non-casual Association- The type of association which is non-directional in nature known as
Non-casual association.
v. Spurious Association: Spurious association defines that connection between any disorder and
infection and individual who is suffering from it may not be real.
Indirect association- The association which deals with statistical relationship between attribute of interest
and a disorder which existed due to other reason, this factor is known as confounding factor.
Direct Association: The association which defined that there is no any third relation or nature exists
between any other two characteristics.
Most essential useful criteria for proving that association is not causal:
Criteria Comment
Temporality Responsible for cause precedes effect
Strength Risk with relatively large
Dose-response Submission linked in high frequency effect
Consistency Regularly observed by the experts in different situations and

Epidemiology 21
place
Biological plausibility By knowledge of Natural history and biological effect the
causal ideas are compatible with causals.
Temporality: The analysis of temporality is significant for the disorders or infection which takes long
time to grow, such as cancer. The change in the rate of growth of cancer is not the same as from where it
begins due to change in environment.
Strength: According to research and examination of scientists groups of strong association are more
causal than weak ones. It is difficult to create a relationship as it is not easy to find out the factors which
are responsible for confounding. To find out statistics of causality experts have to replicate the original
observations with study of other population.
Dose-Response: According to this the biological effect are more on animal or people with greater
exposure to the ones having less exposure. The dose response relationship is due to confounding factor
which varies according with the factor obtained with investigation.
Consistency: An association is more causal if it is observed under various researches at various places.
Associations which get produced by confounding factors are expected to vary between studies.
Biological and plausibility:
The association is very likely to be causal if it is having any logical link with the scientific understanding
of biological disease and health effect which are under investigation.
Causation: When there is any kind of change is observed in any variable due to change in other one then
the term is known as causation. It defines that there is casual connection between two events.
It is not mandatory that there is always an association between health effect and reason of any disorder it
was described with the studies done by scientists.
General processes of the causation are mentioned below:
i. The epidemiological triad

Epidemiology 22
ii. The web
iii. The wheel
iv. The sufficient cause and components causes models.
i. The epidemiological Triad:
A model which defines the relationship between the host, agent and surroundings in a definite time is
known as epidemiological triad.
Image Source: (Epidemiological triad, 2019)
Agent: The term is used for the microorganism, viruses or bacteria that are capable to cause the infection.
Host: It refers to the individual who get affect by the disease or any infection.
Environment: Sometime agent is not only reason of disease or infection; it can be because of biological
factors.
Causation in web:

Epidemiology 23
In epidemiology this term Causation in web defines when there is a connection between various factors
which have some efforts to cause the disease.
Image Source: (Web of Causation , 2019)
Wheel of Causation:
This study not highlights on the host but it focuses on the surroundings and states that for any disease or
any infection surrounding or environment is responsible.

Epidemiology 24
Image Source: (Wheel of causation , 2019)
Sufficient cause and necessary cause: -
i. Sufficient cause:
The lowest combination required for condition or events which needs for the results are known as
sufficient cause. The factors which are responsible for origination of sufficient cause are known as
components cause.
ii. Necessary cause:
The factor which is responsible or which is mandatory for cause of any infection or disease is known
as necessary cause.
Statistical and Public Health Significance
Statistical Significance-
The trail which conducted randomly with in proper observation and with proper analysis the people
compared or studied with each other. The relation can be concluded between quantify of chance or
quantify of cure. If difference outcomes high in the number then it can be explained that this difference is
because of treatment or cure. The same trail can be conducted for the non-randomly as well. There are
two tools used for the phenomenon which are;

Epidemiology 25
I. Standard Deviation
II. Standard Error
Standard deviation defines the amount of difference between individual and population, whereas standard
error describes about changes in mean from similar seized samples concluded from the individual of same
population. The average distribution leads with a proper and efficient process for handling statistical
significance. It can be identified that standard error is high or where it is low by comparing with size of
treatment.
Significance for Public Health
Now days the statistics related with health are used to keep the society about disease, disorder gets
published in order to maintain their problems and improve their health. Newspapers, journals and articles
update statistic about benefits of diet, exercise about the change in the environment which may affect the
healthy life of any individual. Statistic knowledge is very important for the understanding public health.
Statistical Analysis and Peer Review
Scientist pay a lot of attention to these two factors as these play vital role for the consideration in the
study. Study that use correct method is known to be as statistical significance, are more comfortable than
those that lack or misuse statistical analysis. It is very essential to keep in mind though, that statistical
significance does not understand that an association indicates cause and effect and is not a criterion for
causation.
Before the publishing the peer review is the process of analysis the report. The experts find outs the
mistakes if present in the report it will lead to rejection of that report. It is not completely annoying for
journalists to report on these other types of scientific announcements, but their provisional nature must be
defined.
Reporting on Studies: Some Helpful factors:
 Focus on the study design, not just the conclusions: The experts have to focus on the type of
study to which it was related. It should always remember that which topic have to give more
weightage.

Epidemiology 26
 Ask about possible confounding: The articles or the research which are already present they
might not be suitable for the discussion. Researchers should be triggered to discuss whether there
are possible confounders that may fluctuate the results.
 Scrutinize animal tests with care: There should be knowledge about the statics significant, the
method which was choose was proper or not. To what size, if any, can the results be applied with
human condition?
 Check out the bona fides of a study and its authors: The studies which are published must cover
the high part then the reports which are already available. Studies that consists proper and
accurate statistical analysis of the data should carry much more portion than those that do not.
 Provide context and analysis: New Research must be checked with the context of previous
research especially related to the criteria of consistency and biological plausibility.
 Fight the temptation to fill explanatory vacuums: The human society never supports
unpredictability. It is obvious to hold the explanation or any results.
Conclusion:
Here all the topics related with the epidemiology are covered including the types of study. The
association and causations are covered briefly

Epidemiology 27
References
(201). Analysis of Chohort study . https://academic.oup.com/aje/article/162/10/983/65244.
(2013). Classification of Epidemioogy study.
http://www.cisncancer.org/research/how_cancer_is_studied/epidemiological/study_types.html.
(2013). Cohort Study . http://www.cisncancer.org/research/how_cancer_is_studied/epidemiological/
study_types_02.html.
(2013). Descriptive Study . http://www.cisncancer.org/research/how_cancer_is_studied/epidemiological/
study_types.html.
(2013). Types of Epidemiology Studies .
http://www.cisncancer.org/research/how_cancer_is_studied/epidemiological/study_types.html.
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