PHE5EPI Epidemiology Assignment: Stomach Cancer and Study Designs

This epidemiology assignment delves into various aspects of epidemiological studies, focusing on the health effects of a vegetarian diet on stomach cancer. The assignment includes calculations of prevalence, cumulative incidence, and incidence rates, along with interpretations. It explores study designs, including case-control studies and cohort studies, and determines the appropriate measure of association, specifically the odds ratio. The assignment analyzes the relationship between vegetarian diets and stomach cancer, calculating and interpreting the odds ratio to assess the association. Furthermore, it examines the incidence rates among exposed and unexposed employees to paint exposure, and calculates the attributable risk. The assignment also addresses descriptive study designs, their advantages and disadvantages, and the identification of study types based on provided abstracts and figures. Finally, it requires the student to match different study designs to scenarios and identify relevant measures of frequency or association. The assignment covers a range of epidemiological concepts and analytical techniques.

Running head: EPIDEMIOLOGY
Epidemiology
Name of the Student
Name of the University
Author Note

1EPIDEMIOLOGY
1.
a) Prevalence of Stomach cancer=
(Number of stomach cancer)/ (Total number of population)
= (12/ 1800)
= 0.0066
The prevalence of stomach cancer among the sample at age 50 is 0.0066.
b) During the initiation of study, 12 people were at the risk of developing stomach cancer.
c) Cumulative incidence rate of stomach cancer-
(Number of stomach cancer)/ (number of people at risk of stomach cancer)
= 48/ 12
= 40%
The cumulative incidence of stomach cancer among this sample is 40%.
d) Incidence rate of Stomach Cancer =
(Number of people who develop the health event during a specified time)/ (total person –
time at risk during the specified time)
= (48/12)
= 40%
The incidence rate of stomach cancer in this study is 40%.
e) The incidence rate is the preferred measure of frequency because this reflects the rate at
which new cases are being added to the population. Cure or dying in the populations lessens
the prevalence of the stomach cancer.
f) As the researchers recruited the subjects on the basis of the disease. On the other hand, the
cohort study is based on number of new cases of disease at a specific period of time. So,
researchers chose the case- control study.
g) The measure of association that would be most appropriate in this study is odds ratio.
h) The odds ratio =
= (ad/bc)
= (100*155)/ (185*155)
= (15500/28675)
= 0.54
The odds ratio in the measure of association is 0.54.

2EPIDEMIOLOGY
i) As per the odds ratio obtained, the chance of the case group getting stomach
cancer with vegetarian diet is 54% lower than the case group not getting stomach
cancer with vegetarian diet.
j) From the result obtained, it will discourage me to eat a vegetarian diet as it has a positive
correlation between the cause and effect of stomach cancer in the vegetarian diet.
2.
a) i) The incidence rate of the exposed employees is
= (number of people who develop the health event during a specified time)/ (total person –
time at risk during the specified time)
= (24/500)
= 0.05
The incidence rate of the exposed employees is 0.05.
ii) The incidence rate of the unexposed employees is
= (number of people who develop the health event during a specified time)/ (total person –
time at risk during the specified time)
= (31/800)
= 0.04
The incidence rate of the unexposed employees is 0.04.
iii) The incidence rate of all the employees is
= (number of people who develop the health event during a specified time)/ (total person –
time at risk during the specified time)
= (55/1300)
= 0.04
The incidence rate of all the employees is 0.04.
iv) The incidence rate of exposed employees is more than the unexposed employees and all
the employees into consideration. This means that the employees who have been exposed to
paint have sustained bladder cancer.
b) The measure of association is the odds ratio. The odds ratio for the disease is
= (ad/bc)
= (24*769/31*476)
= (18456/14756)
= 1.25

3EPIDEMIOLOGY
The odds ratio obtained is 1.25 for the disease. The chance of the case group suffering from
bladder cancer due to the pain exposure is 125% higher than the case group not suffering
from bladder cancer due to paint exposure.
c) The extra disease in a exposed population is calculated by attributable risk. The
attributable risk is
= (risk in exposed – risk in unexposed)
= (a/a+b) – (c/c+d)
= (24/24+476) – (31/31+769)
= (0.05) – (0.04)
= 0.01
The extra disease that is observed in exposed employees is 10% more than the unexposed
employees.
3.
a) The study design that has been observed in the abstract is descriptive study design. It is
because there is just the description of the characteristics, that is, overweight in low-income
children. It does not provide reasoning as to how and when does this occur.
b) There are three main exposures in this abstract which were found to be children who reside
far away from playgrounds, who reside near fast-food restaurants and the safety of the
neighbourhood. The outcome that was observed was obesity and overweight in children.
c) The key findings that have been observed were that the mean distance from the child’s
home to fast-food joints and playground was 0.70 and 0.31 miles respectively. Out of the
7020 children evaluated, 9.2% were found to be overweight.
d) For the collection of data, there is no bias involved in selecting the children for the study.
There were incorporation of black and white people. This makes the sample size of the study
huge. The students who were involved in the study were not informed about the study and
acted naturally.
e) The main disadvantage of this type of study is that the identification of the cause is not
possible. It is only expected to describe and report the observations for obesity in children.
4.
The type of study which would be appropriate to be conducted to observe the effect of
drinking green tea on the reduction of the risk of cardiovascular diseases is a cohort study. A
particular group of people would be chosen for a given period of time to understand the
effects. The risk factors associated with the drinking of green tea will be determined to
understand whether cardiovascular diseases occur. Cohort studies are not suitable for diseases

4EPIDEMIOLOGY
that have a long latency. Because cardiovascular disease takes a long time to surface, cohort
studies may not be the best fit for the study.
5.
a) The study design that is represented in the figure is ecology study.
b) The main disadvantage of these studies is that it cannot be applicable to an individual. This
is also known as ecological fallacy.
6.
STUDY STUDY TYPE REASON RELEVANT
MEASURE OF
FREQUENCY OR
ASSOCIATION
STUDY 1 Longitudinal Study The study deals with
the effects cannabis
on psychotic
disorders along with
the behaviours an
individual
experiences which
aligns with the
description of the
study,
Incidence Rate
STUDY 2 Analytical Cross-
sectional study
The exposure and
the health outcome
of six-health related
courses have been
observed in the
study.
Not Applicable
STUDY 3 Prospective Cohort
Study
Similar kind of
individuals have
been selected to test
the effect of the
outcome.
Period Prevalence
STUDY 4 Retrospective cohort
study
The risk factors have
been assessed with
previously examined
factors.
Odds ratio
STUDY 5 Cross-sectional
study
The data from the
studies have been
studies to assess the
factors that can
contribute to the
disease.
Odds ratio
STUDY 6 Retrospective A cohort of Period Prevalence

5EPIDEMIOLOGY
Cohort Study individuals that
share the common
exposure to
understand its
effects on a disease
have been observed
in the paper.
STUDY 7 Randomized Control
Trial
The patients were
randomly allocated
with the treatments
to check on the
effects.
Period Prevalence