PUB 210 Assignment: Analyzing Epidemiology Concepts and Study Designs
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This assignment explores key concepts in epidemiology, examining the impact of medical interventions on disease incidence, prevalence, and duration. It analyzes the effects of new drugs and vaccines on both communicable and non-communicable diseases. The assignment also delves into different epidemiological study designs, including cohort, case-control, cross-sectional, and randomized control trials, providing examples of their application. Furthermore, it examines the calculation and interpretation of prevalence, incidence proportion, and incidence rate, alongside the application of odds ratios and relative risks in assessing disease associations. The document includes calculations, interpretations, and study design justifications, providing a comprehensive understanding of epidemiological principles and their practical application in public health research.
Running Head: EPIDEMIOLOGY CONCEPTS
Epidemiology Concepts
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Institutions and Affiliations:
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Epidemiology Concepts
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Institutions and Affiliations:
Date:
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EPIDEMIOLOGY CONCEPTS
1. (a) The introduction of new drug that cures a previously incurable but non-fatal
non-communicable disease.
Effect on incidence rate: The incidence rate is likely to remain constant or increased
because the drug does not prevent the risk of being infected with the disease thus does not
prevent the rise of new cases. The incidence rate is number of new cases of a disease in a
population of people who are at risk of being infected. Therefore, if the risks for the
disease are not eliminated or reduced, then the chances of new cases still remain the
same.
Effect on prevalence: the prevalence will be reduced as the disease will be cured,
therefore, reducing the total number of cases of the disease. Prevalence is the total
number of cases out of a population at risk of the disease.
Effect on the duration of the disease: the duration will be reduced since the disease will
be cured. When the disease is incurable, the duration is prolonged. The introduction of a
cure manages the symptoms of the disease and cure it therefore, a shorter duration of the
disease in the body.
(b) The introduction of a new drug that prolongs survival but does not cure a fatal
non-communicable disease
Effect on incidence rate: The incidence rate will either be constant or increase. This is
because the drug does not reduce the risk of being infected therefore, new will still be
there.
Effect on prevalence: The prevalence will remain constant or increase since the disease
will not be cured. It could also increase because of the number of survivors with the
disease will be increased since the mortality rate will have reduced.
1. (a) The introduction of new drug that cures a previously incurable but non-fatal
non-communicable disease.
Effect on incidence rate: The incidence rate is likely to remain constant or increased
because the drug does not prevent the risk of being infected with the disease thus does not
prevent the rise of new cases. The incidence rate is number of new cases of a disease in a
population of people who are at risk of being infected. Therefore, if the risks for the
disease are not eliminated or reduced, then the chances of new cases still remain the
same.
Effect on prevalence: the prevalence will be reduced as the disease will be cured,
therefore, reducing the total number of cases of the disease. Prevalence is the total
number of cases out of a population at risk of the disease.
Effect on the duration of the disease: the duration will be reduced since the disease will
be cured. When the disease is incurable, the duration is prolonged. The introduction of a
cure manages the symptoms of the disease and cure it therefore, a shorter duration of the
disease in the body.
(b) The introduction of a new drug that prolongs survival but does not cure a fatal
non-communicable disease
Effect on incidence rate: The incidence rate will either be constant or increase. This is
because the drug does not reduce the risk of being infected therefore, new will still be
there.
Effect on prevalence: The prevalence will remain constant or increase since the disease
will not be cured. It could also increase because of the number of survivors with the
disease will be increased since the mortality rate will have reduced.
EPIDEMIOLOGY CONCEPTS
Effect on the duration of the disease: The duration will be increased since the drug will
ensure survival but not cure. One will likely have the disease for a longer time since the
drug will help prolong life therefore, prolonging the duration of the disease too.
(c) The introduction of new vaccine that prevents most people from developing a
disease. Vaccinated people who still develop the disease recover more quickly than
unvaccinated people.
Effect on incidence rate: The incidence rate will be lowered due to prevention of new
cases of the disease. Therefore, the occurrence of the new cases will be reduced by the
vaccine.
Effect on prevalence: The prevalence will be reduced because the number of new cases
will have reduced therefore; the total number of cases will definitely be reduced.
Effect on the duration: The duration will remain constant for those not vaccinated and
those vaccinated but developed the disease, the duration will reduce because they will
recover more quickly as compared to the unvaccinated group.
2. (a) Prevalence of overweight and obesity in the men in:-
January 2006: 3400
6500 x 100=52.3 %
Therefore, the prevalence in 2006 was 52.3%
January 2016: 3400 - 200= 3200
3200 + 1000 = 4200
1000
6500 x 100=64.6 %
Effect on the duration of the disease: The duration will be increased since the drug will
ensure survival but not cure. One will likely have the disease for a longer time since the
drug will help prolong life therefore, prolonging the duration of the disease too.
(c) The introduction of new vaccine that prevents most people from developing a
disease. Vaccinated people who still develop the disease recover more quickly than
unvaccinated people.
Effect on incidence rate: The incidence rate will be lowered due to prevention of new
cases of the disease. Therefore, the occurrence of the new cases will be reduced by the
vaccine.
Effect on prevalence: The prevalence will be reduced because the number of new cases
will have reduced therefore; the total number of cases will definitely be reduced.
Effect on the duration: The duration will remain constant for those not vaccinated and
those vaccinated but developed the disease, the duration will reduce because they will
recover more quickly as compared to the unvaccinated group.
2. (a) Prevalence of overweight and obesity in the men in:-
January 2006: 3400
6500 x 100=52.3 %
Therefore, the prevalence in 2006 was 52.3%
January 2016: 3400 - 200= 3200
3200 + 1000 = 4200
1000
6500 x 100=64.6 %
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EPIDEMIOLOGY CONCEPTS
The prevalence is 64.6%
(b) Incidence proportion: 3400
6500 x 100=15.3 %
(c) Incidence of becoming healthy weight: 200
3400 x 100=0.59 %
3. The conclusion was appropriate. This is because the incidence per 100,000 people is 10,
therefore among 300,000 it would definitely be 30.
If in 100,000 there are 10
Then in 300,000 there will be 300,000
100,000 x 10=30
4. Graph
5. (a) Cohort study design because the study will focus on a group of smokers and follow
them up to observe if they will catch influenza or common cold. Cohort study is whereby
a group of people with a given characteristics are studied and followed up to determine
the occurrence if a disease or mortality from a given condition. The cohort group should
not have the infection at the beginning of the study. This study would prefer prospective
style so as to collect new data in study the cohort group. It allows for accurate collection
of exposure information.
(b) Case control study. This will involve having the case group of smokers and a control
group of non-smokers then collect information on their experience with common cold in
terms of duration. This design helps to determine an association between an exposure and
an outcome. The exposure in this case is smoking while the outcome is common cold.
This study is faster and cheaper. This design is important in studying rare conditions. The
The prevalence is 64.6%
(b) Incidence proportion: 3400
6500 x 100=15.3 %
(c) Incidence of becoming healthy weight: 200
3400 x 100=0.59 %
3. The conclusion was appropriate. This is because the incidence per 100,000 people is 10,
therefore among 300,000 it would definitely be 30.
If in 100,000 there are 10
Then in 300,000 there will be 300,000
100,000 x 10=30
4. Graph
5. (a) Cohort study design because the study will focus on a group of smokers and follow
them up to observe if they will catch influenza or common cold. Cohort study is whereby
a group of people with a given characteristics are studied and followed up to determine
the occurrence if a disease or mortality from a given condition. The cohort group should
not have the infection at the beginning of the study. This study would prefer prospective
style so as to collect new data in study the cohort group. It allows for accurate collection
of exposure information.
(b) Case control study. This will involve having the case group of smokers and a control
group of non-smokers then collect information on their experience with common cold in
terms of duration. This design helps to determine an association between an exposure and
an outcome. The exposure in this case is smoking while the outcome is common cold.
This study is faster and cheaper. This design is important in studying rare conditions. The
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EPIDEMIOLOGY CONCEPTS
association between smoking and common cold is a rare condition, therefore, this design
proves more appropriate. It also allows one to study multiple risk factors since there
could be other factors that are contributing to the development of common cold other
than smoking.
(c) Cross-sectional study. This is because random samples are collected systematically
and observed at the fruit serving to determine the association. A cross-sectional study
design determines a relationship between a condition and given variables in a defined
population at a given time, usually over a short period of time. This study is also
preferred because the data is collected only once, provides descriptive analyses and can
also be used to generate hypotheses. It also allows the study of multiple outcomes and
exposure. In this study, the factors associated with fruit serving in the university and the
group that goes for more fruit serving can be studied
(d) Randomized control trials. It is used in testing new treatments. It is study in
participants are allocated at random to either a group receive the new intervention or the
one receiving the standard intervention as a control. The groups will help compare the
effects of the interventions and therefore, it will be used to determine which method is
more effective during vaccination. This study is considered the best in clinical trials.
6. (a) Cross-sectional study. It is good in determining the prevalence and the cause of a
disease by collecting random samples of children systematically who have been infected
and the information on their health status. This will determine the relationship between
the disease and other variables.
association between smoking and common cold is a rare condition, therefore, this design
proves more appropriate. It also allows one to study multiple risk factors since there
could be other factors that are contributing to the development of common cold other
than smoking.
(c) Cross-sectional study. This is because random samples are collected systematically
and observed at the fruit serving to determine the association. A cross-sectional study
design determines a relationship between a condition and given variables in a defined
population at a given time, usually over a short period of time. This study is also
preferred because the data is collected only once, provides descriptive analyses and can
also be used to generate hypotheses. It also allows the study of multiple outcomes and
exposure. In this study, the factors associated with fruit serving in the university and the
group that goes for more fruit serving can be studied
(d) Randomized control trials. It is used in testing new treatments. It is study in
participants are allocated at random to either a group receive the new intervention or the
one receiving the standard intervention as a control. The groups will help compare the
effects of the interventions and therefore, it will be used to determine which method is
more effective during vaccination. This study is considered the best in clinical trials.
6. (a) Cross-sectional study. It is good in determining the prevalence and the cause of a
disease by collecting random samples of children systematically who have been infected
and the information on their health status. This will determine the relationship between
the disease and other variables.
EPIDEMIOLOGY CONCEPTS
(b) The target population would be the children, the parents and the health care providers.
The children will be studied in terms of their health information because they are the
affected group while the parents will be able to give background information of the
children since they are the caregivers of the children at home and the health providers,
who are the ones who diagnose and have the medical information, will be able to give the
symptoms and prognosis of the disease.
(c) The study should have a representative sample in order to capture the whole
population. This would include every child that is infected from every residence and
economical class; helps in determining the factors that contribute to the occurrence of the
disease. The sample size should be large enough to be able to precisely determine the
prevalence of the condition. The larger the sample size the more precise the results. The
data should include interviews, questionnaires and medical examinations to be able to
collect data on exposures and outcomes. It is also important to determine the inclusion
and exclusion criteria at the design stage.
7. (a) 183-61= 122 (66.7%) people who are at risk of having melanoma do not have
freckles. Therefore, one who does not have freckles is more likely to have melanoma as
compared to someone who has freckles. Out of the 183 cases, 122 did not have freckles
but had melanoma.
(b) 61
183 x 100=33 %Chances of having freckles and melanoma. This is because out of
183 cases, there were 61 who had freckles. This means that the 61 also have melanoma.
8. Yes, it is correct to conclude that incidence rate ratio of 10 is high risk for any given disease
among the exposed people in the population. This because the incidence rate ratio is obtained by
dividing the incidence rate in exposed by the incidence rate in unexposed.
(b) The target population would be the children, the parents and the health care providers.
The children will be studied in terms of their health information because they are the
affected group while the parents will be able to give background information of the
children since they are the caregivers of the children at home and the health providers,
who are the ones who diagnose and have the medical information, will be able to give the
symptoms and prognosis of the disease.
(c) The study should have a representative sample in order to capture the whole
population. This would include every child that is infected from every residence and
economical class; helps in determining the factors that contribute to the occurrence of the
disease. The sample size should be large enough to be able to precisely determine the
prevalence of the condition. The larger the sample size the more precise the results. The
data should include interviews, questionnaires and medical examinations to be able to
collect data on exposures and outcomes. It is also important to determine the inclusion
and exclusion criteria at the design stage.
7. (a) 183-61= 122 (66.7%) people who are at risk of having melanoma do not have
freckles. Therefore, one who does not have freckles is more likely to have melanoma as
compared to someone who has freckles. Out of the 183 cases, 122 did not have freckles
but had melanoma.
(b) 61
183 x 100=33 %Chances of having freckles and melanoma. This is because out of
183 cases, there were 61 who had freckles. This means that the 61 also have melanoma.
8. Yes, it is correct to conclude that incidence rate ratio of 10 is high risk for any given disease
among the exposed people in the population. This because the incidence rate ratio is obtained by
dividing the incidence rate in exposed by the incidence rate in unexposed.
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EPIDEMIOLOGY CONCEPTS
Example:
In a particular prospective cohort study that was aimed at establishing hormone replacement
therapy (HRT) for the coronary artery disease among women that had past the menopause stage.
The researchers calculated the coronary artery disease incidence rate among these post-
menopausal women that had been put on HRT and then compared this to the then incidence rate
among the post-menopausal women that had not been put on HRT. From the study, the following
findings were established.
Post-menopausal Hormone
Replacement Therapy Use
Found with Coronary Artery
Disease
Disease-free Follow-up
Person-years
Exposed(Yes) 30 54,308.7
Not Exposed(No) 60 51,477.5
The incidence rate among the exposed(women that used HRT) is calculated as below:
a. Incidence rate: (30/54,308.7) = 55.2 per 100,000 Disease-free Follow-up person-years
The incidence rate among the unexposed (women that did not use HRT) is calculated as below:
b. Incidence rate: (60/51,477.5) = 116.6 per 100,000 Disease-free Follow-up person-years
The incidence rate ratio is calculated = (Incidence rate in exposed)/(Incidence rate in unexposed).
=(55.2)/(116.6)
=0.47
The incidence rate ratio is thus=0.47.
This shows that a post-menopausal woman is 0.47 times more likely to acquire coronary artery
disease if exposed to HRT. From the question, an incidence rate ratio of 10 in exposed persons
implies that one is 10 times more likely to acquire a particular condition when exposed to the
agent under study.
Example:
In a particular prospective cohort study that was aimed at establishing hormone replacement
therapy (HRT) for the coronary artery disease among women that had past the menopause stage.
The researchers calculated the coronary artery disease incidence rate among these post-
menopausal women that had been put on HRT and then compared this to the then incidence rate
among the post-menopausal women that had not been put on HRT. From the study, the following
findings were established.
Post-menopausal Hormone
Replacement Therapy Use
Found with Coronary Artery
Disease
Disease-free Follow-up
Person-years
Exposed(Yes) 30 54,308.7
Not Exposed(No) 60 51,477.5
The incidence rate among the exposed(women that used HRT) is calculated as below:
a. Incidence rate: (30/54,308.7) = 55.2 per 100,000 Disease-free Follow-up person-years
The incidence rate among the unexposed (women that did not use HRT) is calculated as below:
b. Incidence rate: (60/51,477.5) = 116.6 per 100,000 Disease-free Follow-up person-years
The incidence rate ratio is calculated = (Incidence rate in exposed)/(Incidence rate in unexposed).
=(55.2)/(116.6)
=0.47
The incidence rate ratio is thus=0.47.
This shows that a post-menopausal woman is 0.47 times more likely to acquire coronary artery
disease if exposed to HRT. From the question, an incidence rate ratio of 10 in exposed persons
implies that one is 10 times more likely to acquire a particular condition when exposed to the
agent under study.
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EPIDEMIOLOGY CONCEPTS
8. (a) Overall incidence rate ratio = 8492
1123929 x 100=0.756 %
Low level of screen-time incidence ratio: 1318
280364 x 100=0.47 %
Intermediate level of screen-time incidence ratio: 3070
436372 x 100=0.7 %
Highest level of screen-time incidence ratio: 4104
407193 x 100=1 %
(b) There is an association between the screen time and the incidence but it is not strong
since the average incidence rate ratio is.75%. The association grows stronger with
increase in screen-time as calculated with high level screen-time has a higher incidence
rate ratio. Therefore, increase in screen-time level is directly proportional to incidence
rate ratio of sight problem.
(c) 100% - 0.47%= 99.53% of sight problem would be theoretically prevented if all
children had low levels of average daily screen time.
9. (a) The occurrence of community disadvantage has higher odds in association with
walking on the sunshine coast. This is because the odds ratio is greater than 1. Therefore,
they have high association. The odds ratio shows how an exposure is related to an
outcome. It therefore, represents the odds there will be a given outcome given a particular
exposure compared to the odds of the outcome happening in the absence of the said
exposure.
(b) The relative risk shows that the community is more disadvantaged by walking on the
gold coast. This is because the relative risk is more than 1. Therefore, they are associated.
The relative risk is the ratio of the probability of the occurrence of an event in an exposed
8. (a) Overall incidence rate ratio = 8492
1123929 x 100=0.756 %
Low level of screen-time incidence ratio: 1318
280364 x 100=0.47 %
Intermediate level of screen-time incidence ratio: 3070
436372 x 100=0.7 %
Highest level of screen-time incidence ratio: 4104
407193 x 100=1 %
(b) There is an association between the screen time and the incidence but it is not strong
since the average incidence rate ratio is.75%. The association grows stronger with
increase in screen-time as calculated with high level screen-time has a higher incidence
rate ratio. Therefore, increase in screen-time level is directly proportional to incidence
rate ratio of sight problem.
(c) 100% - 0.47%= 99.53% of sight problem would be theoretically prevented if all
children had low levels of average daily screen time.
9. (a) The occurrence of community disadvantage has higher odds in association with
walking on the sunshine coast. This is because the odds ratio is greater than 1. Therefore,
they have high association. The odds ratio shows how an exposure is related to an
outcome. It therefore, represents the odds there will be a given outcome given a particular
exposure compared to the odds of the outcome happening in the absence of the said
exposure.
(b) The relative risk shows that the community is more disadvantaged by walking on the
gold coast. This is because the relative risk is more than 1. Therefore, they are associated.
The relative risk is the ratio of the probability of the occurrence of an event in an exposed
EPIDEMIOLOGY CONCEPTS
group to the probability of the occurrence of the event in a group that has not been
exposed which will be the comparison group.
(c) There is an association between walking on an average of at least one hour per day.
This is because the odds ratio shows that walking on sunshine coast is associated with the
community disadvantage while according to the risk ratio, the community is at risk of
being disadvantaged when walking for an average of at least one hour.
group to the probability of the occurrence of the event in a group that has not been
exposed which will be the comparison group.
(c) There is an association between walking on an average of at least one hour per day.
This is because the odds ratio shows that walking on sunshine coast is associated with the
community disadvantage while according to the risk ratio, the community is at risk of
being disadvantaged when walking for an average of at least one hour.
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EPIDEMIOLOGY CONCEPTS
References
Gallagher, L. (2012). Session Title: Ethics and Epidemiologic Decision-Making for Population
Benefits. Annals of Epidemiology, 22(9), 680.
Kim, J. (2013). Epidemiology and Causation. Kosin Medical Journal, 28(2), 87.
Li, H. (2013). Systems biology approaches to epidemiological studies of complex diseases.
Wiley Interdisciplinary Reviews: Systems Biology And Medicine, 5(6), 677-686.
References
Gallagher, L. (2012). Session Title: Ethics and Epidemiologic Decision-Making for Population
Benefits. Annals of Epidemiology, 22(9), 680.
Kim, J. (2013). Epidemiology and Causation. Kosin Medical Journal, 28(2), 87.
Li, H. (2013). Systems biology approaches to epidemiological studies of complex diseases.
Wiley Interdisciplinary Reviews: Systems Biology And Medicine, 5(6), 677-686.
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