A Study on TH Concepts of Epidemiology.

Running Head: A STUDY ON TH CONCEPTS OF EPIDEMIOLOGY
A STUDY ON TH CONCEPTS OF EPIDEMIOLOGY
Name of the Student:
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Author Note:

A STUDY ON TH CONCEPTS OF EPIDEMIOLOGY1
Answer 1
a. The prevalence of stomach cancer among the sample at age 50 can be calculated by using
the formula,
Prevalence= Number of people with stomach cancer at age 50
Total number of individuals∈the population at age 50∗103
∴ Prevalence= 12
1800∗103 =6.67 ≈ 7
Therefore, it can be observed that out of 1000 vegetarian people, only 7 people
have this rare type of stomach cancer. In other words, a very small proportion of the
population is exposed to the risk of developing this stomach cancer. Hence, it can be
concluded that vegetarian diet helps to prevent the concerned stomach cancer.
b. All of the 1800 vegetarian people were at the risk of developing stomach cancer at the
start of 5-year period.
c. The cumulative incidence can be obtained as,
Cumulative Incidence= No. of people with stomach cancer ∈the specified period of time
Total no . of perople∈the population at the risk of developing that disease ∗103
¿ 48
1800∗103=26.67 ≈ 27
It shows that, in a 5 year period, 27 vegetarian people will have the risk of
developing that rare type of stomach cancer out of 1000 vegetarian people. Therefore, it
can be concluded that the risk of developing stomach cancer increases among vegetarian
people with increase in their ages.
d. Incidence rate= No . of new cases duringthe period
Total person−time at risk during that period ∗103= 48
8750∗103 =5.5≈ 6
This means that there are 6 cases of stomach cancer per 1000-person years.

A STUDY ON TH CONCEPTS OF EPIDEMIOLOGY2
e. Cumulative incidence does not take into account the fact that some participants were lost
to follow-up and some died whereas incidence rate considers this (Merrill, 2016). Hence,
incidence rate would be better measurement for this study design.
Answer 2
a. From the theory of study design, it can be noted that prospective cohort study is used to
determine the risk factors of the disease and to establish a cause and effect relationship.
However, case-control study is used to study the association between risk factors and a
disease which is very rare (Rothman, Greenland & Lash, 2014). It can be observed form
question 1 that the development of this particular stomach cancer is very rare among
vegetarian people. Hence, case-control study is more appropriate than the prospective
cohort study in this case.
b. The Odds Ratio would be perfect to measure the association between the vegetarian diet
and risk of stomach cancer since it compares the odds of exposure to a disease among
cases with that of controls.
c. The Odds Ratio is formulated as,
Odds Ratio= Odds of exposure among cases
Odds of exposure among controls =
a
c
b
d
Here, a=100 , b=114 , c=185 , d=155∴Odds Ratio= 100/185
114 /155 =0.73
The Odds ratio is less than 1 which implies that the odds of exposure to stomach
cancer among cases in less than the odds of exposure to stomach cancer among controls.