HSH744 Epidemiology Assessment

HSH744 Epidemiology 1 – Assessment task 2 answer sheet
Due Thursday 17th May, 5pm
Please type all of your answers into the spaces provided below.
Student name__________________________________________________________
Student number ________________________________________________________
Question
number
Answer
1 Randomized controlled trial
2 Ecological study
3 Cross-sectional study
4 Retrospective cohort study
5 Cross-sectional study
6 Prospective cohort study
7 Point prevalence
8 Period prevalence
9 Maintaining high rates of follow up can be difficult
10
The disease should be severe, relatively common and perceived as a
public health problem
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HSH744 Epidemiology 1 – Assessment task 2 answer sheet
11
Relatively quick and cheap to conduct
Can investigate a wide range of possible risk factors
Can be used to effectively identify and study cases of rare outcomes
Can employ expensive or time-consuming tests
12 Occurs clearly in excess of the expected numbers
13
They are quick, cheap and easy to do with existing data
They are useful for generating hypotheses for later testing
14
The gender of the study participants
The household annual income of the study participants
15 Daily smoking by study participants
16 Odds ratio
17 True
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HSH744 Epidemiology 1 – Assessment task 2 answer sheet
18
The results should be treated with caution as it could be due to chance
variability in the data. This is because it has an odds ratio of 0.86 with a
95% CI of 0.61-1.26. This means that the true odds ratio of the target
population lies between 0.61-1.26. Therefore, the true population odds
ratio has a possibility of being 1.0. Odd ratio is one if the measure of
association between the cases and the control in case control study or
exposure and the outcome in the cohort study. Odds ratio also measures
the strength of association between the exposure and the outcome. It is
calculated by taking the odds of the disease in the exposed group
divided by the odds of the disease in the unexposed group.
Odds ratio, OR =odds ¿¿
OR =
a
b /c
d
= ad
bc
Interpretation: An odds ratio of 1 is interpreted as there being no
increased or decreased likelihood of a factor (living in rural area)
affecting an outcome (daily smoking). Living in rural is not associated
with more daily smoking. An odds ratio of more than 1 means there is
an increased likelihood of the outcome occurring due to the factor in
question while an odds ratio of less than 1 means there is a decreased
likelihood of the outcome occurring due to the factor in question. It
should be noted that Odds ratio does not totally establish that the
exposure is the contributing factor to the outcome. It could be that the
association is due to a third factor that was not checked in the study.
These factors that are related to both the exposure and outcome are
known as confounding factors.
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HSH744 Epidemiology 1 – Assessment task 2 answer sheet
19
Airborne diseases like influenza flu. This is because the games will
bring together a lot of people together within relatively enclosed spaces.
This is a conducive environment for the transmission of airborne
diseases. Some flu strains are also known to be very contagious. Some
of the flu can also be fatal. This means they pose a big threat and are
therefore a major public health concern.
Sexually transmitted infections. The common wealth games gives an
opportunity for a large number of people to meet at a single place. This
opportunity would increase the level of sexual activity and incidences of
sexually transmitted infections. The games might also be an avenue of
spread of new, more drug resistant strain of sexually transmitted
infections.
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HSH744 Epidemiology 1 – Assessment task 2 answer sheet
20
The health surveillance system was not designed in the best way. They
should have collected more data. A better way was to start the data
collection before the arrival of the teams. This would have enabled
collection of data on determinants of health that would have influenced
the health of the teams and were in place before the teams arrived.
These factors include the level of sanitation, water supply and food
sanitation and safety, accommodation and any pre-existing diseases
among others.
Data collection should also continue past the final day. This is because
some diseases have a longer incubation period. This means that the
clinical symptoms of the disease will manifest several hours or days
after the exposure. Such disease includes most of the sexually
transmitted infections. These diseases might be missed if data collection
is stopped on the final day of the games.
21 Confounding.
22 Loss to follow up
23
The analysis compared people who were randomised to the aspirin
group with those who were not randomised to take aspirin, regardless of
whether or not they actually took the aspirin.
24
Controls who are also hospital patients may be more representative of
hospitalised cases than controls selected from general population
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HSH744 Epidemiology 1 – Assessment task 2 answer sheet
25
Odds Ratio. This is the odds of the disease in the exposed divided by
the odds of the disease in the unexposed.
OR= odds exposed/odds unexposed
=
a
b /c
d
=
59
467 /176
1977
= 1.419
= 1.4
The result means that heavy alcohol drinkers have 1.4 times more
likelihood of developing pancreatic cancer compared to the non-heavy
alcohol drinkers. An odds ratio of 1 signifies that the exposure in this
case heavy drinking has no association with the outcome. An odds ratio
of more than 1 signifies that the exposure increases the risk of having
the outcome by a fold represented by the value of the odds ratio. An
odds ratio of less than 1 signifies that the exposure reduces the risk of
having the outcome in question. It means that the exposure is instead
protective against the outcome in question. However, the odds ratio
does not totally establish the association between the exposure and the
outcome as there might be other confounding factors.
26
The exposed and non-exposed groups under study be as similar as
possible with regard to possible confounding factors
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