Download Epidemiology Study Questions

Shannon Mikrut
Week 4 Assignment - Study Questions
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Chapter 6
5. To perform a case control study researchers need to consider two groups of study, one in which everyone
has the disease (cases), and the other in which everyone does not have the disease (controls). Collection of
data about past exposure is necessary to see what may have contributed to the disease. I would start by
accessing databases to look at past childhood leukemia cases and see if there was a trend. If a trend was
found I would focus my study there and would do additional research to see if there were any known
environmental toxins in this area. An example would be if an environmental toxin were found to be more
prevalent in industrialized city. My cases for the study would be pregnant women who lived within the
boundaries of the designated area. My controls would be woman who are pregnant with a similar
socioeconomic status and lived in a similar demographic area, but the area had no known environmental
toxins. Using both primary and secondary sources will be necessary for this study example. Parents will
need to provide information about the while the baby was in utero, about the pregnancy, breastfeeding, and
occurrences that have taken place throughout the child’s life. I would examine exposure levels and
following the children’s health status up until a certain age would be a way to see if there was any
correlation between exposure and childhood leukemia.
In an ecologic study, similar techniques would be used; however, instead of individuals being
studied, the group of people living in the industrialized communities where exposure was found versus the
group living communities where no know environmental exposure was found would be studied. The
summary would be based on the two different groups, rather than individuals. Researchers would then look
at the data as a group, rather than individual to individual. This would help form a hypothesis for then
developing a case-control study.
7. OR= 2.74
8. OR= .37
9. OR= 1.60
10. My controls in the study would be everyone in a desired population, for example, 300 people who drive
vehicles. I could obtain this information from the Department of Motor Vehicle database. For example, my
cases would be 100 individuals who had been in a motor vehicle accident. I would then administer
questionnaires, to both the cases and controls in the study. The questionnaire would include questions that
asked about driving behaviors, including talking on a cell phone while driving. Information obtained from
the survey about the frequency of cell phone use while driving would allow me to calculate the odds ratio
of talking while driving and the risk of automobile accident.
One of the challenges with this study example is that the study design being used is a case-control
study. This type of study is most commonly used by epidemiologists for infectious disease outbreak. This
study is a lot more observational and etiologic in nature. As a result, I would suggest using an etiologic
study, due to it being more group based.
11. If women could not develop the disease, they should be excluded as controls because they have no
potential in developing the disease being studied. If a control has no ability to develop the disease studied,
the control is null and does not aid in the research of the disease.
12.
a. The results indicate that eating a low-fat diet would result in lower risk of colon cancer.
b. Results indicate that aerobic exercise does not impact the risk of dental caries.
c. Results indicate that higher exposure to side-stream cigarette smoke increases the risk for lung cancer.
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d. Results indicate that there is three times higher risk of having an ectopic pregnancy when a women has
an infectious disease of the pelvis.
Chapter 7
5. RR= 5
6. A retrospective cohort study is different from a case-control study because it begins with the exposure,
even if the exposure was in the past. Additionally, a case-control study begins with subjects on the basis of
disease status. Data in case-control studies is collected about exposure that occurred prior to onset of the
disease and this is only one point of observation. Retrospective cohort studies incorporate an entire group
of study subjects, and the data collecting includes looking back at exposure throughout the time they have
the onset of disease.
Some of the key criteria of a retrospective cohort study that I would consider would include the
information and data I could obtain in a short period of time. Prospective cohort studies can take several
years until finding significant data, so by using a retrospective cohort study you could decrease time and
money spent. This type of study would be an option for looking at risk of disease over a larger population.
If a smaller population was being studied, I would consider a case-control. The same would be true for a
rare disease versus a more prevalent disease.
7. A relative risk of 2.0 and 0.5 are the same strength in association because they are inverted in their
impact on disease risk.
8. No, I would not advocate for a cohort study due to the strong association of 28.0 to 49.0. There would be
no need to conduct a larger study; the case-control studies would provide enough significant evidence that
exposure leads to the disease.
10. Options for follow-up when a central disease database is not available is to conduct an active follow-up.
In active follow-up, the researcher will have contact with the cohort by using methods such as follow-up
mailings, invitations, and/or phone calls to collect necessary information. This can be very labor intensive
and expensive; however, it is the only option if database information is not available.
11.
Ecological:
Strengths:
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Uses a group as an analysis, which benefits in generating hypotheses
Can be cost effective because they can make use of secondary data
Uses the same community, country, or other unit as the study group, which requires less work in
finding new groups to study
Weaknesses:
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Ecologic fallacy, meaning that there can be bias that occurs because an association that was
observed between variables collected as a whole that does not accurately represent the association
existing at an individual level.
Cross-Sectional:
Strengths:
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Descriptive in nature allowing researchers to collect data based on one observation point.
Taking a sample of a population and drawing inferences is appealing because it takes less time and
money to derive reasonable explanations of a health problem’s severity.
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
Can help interpret the magnitude and distribution of a health problem in a given location.
Weaknesses:
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Lack of utility for studies of disease etiology
Difficult to sort out factors associated with risk of disease
Difficult to study rare or low-frequency diseases
Challenging to decipher temporality issues (whether the disease or exposure came first)
Cross-Sectional:
Strengths:
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Small in size, allowing for efficient and effective results
Likelihood that the study will be repeated.
Helpful for etiology of rare diseases
Can provide a clear cause to effect analysis
Weaknesses:
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Difficult to determine who will represent the cases and who will represent the controls
If exposure is rare in a population, then this type of study may be inefficient
Uncertainty of exposure-disease time relationship
Inability to provide a direct estimate of risk
Cohort Studies:
Strengths:
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Permits direct determination of risk.
Provides stronger evidence of an exposure-disease association because it begins with disease-free
individuals
Can allow for the examination of multiple outcomes.
Provides lag time between exposure and disease development
Weaknesses:
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Can take a lot of time and effort to conduct.
Can be costly because of longer time frame and higher number of subjects participating.
Lose follow-up
12. For a nested case-control study, I would have a larger cohort of all teenage females with both lower and
higher socioeconomic statuses. I would then select all the women who have given birth in the last two years
and evaluate how many of them were from higher socioeconomic status and those from lower
socioeconomic status.
13. The statement that cohort studies overcome the problem of temporality, which is not addressed by other
types of observational studies, means that cohorts do not focus only on a specific time period. Cohort
studies collect data over periods of time, which helps to allow for more in-depth analysis of exposure and
disease.
14. One issue that influences the design of a cohort study is the larger the population size, the greater the
opportunity to collect data in a timely manner. For a cohort to be successful there has to be effective and
efficient data collection methods. If few people are doing the research, it can take a lot of time, energy, and
ultimately be very demanding of the researchers. This can result in burnout and/or premature ending of the
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study. Cohort study protocols require data-management systems that monitor the status of different
components of a study; these systems are often expensive and complex to use. With a large population
being studied, the information being measured may come from multiple sources; this could potentially lead
to misinformation and/or misclassification of results. Researchers need to make sure there is scientific
rationale behind the cohort study for it to be carried out. Before the research begins, the researchers must
also evaluate if there will be an active or passive follow-up stage. The follow-up phase of the study takes
time, effort, and resources, such as money. Lastly, Because of the time, money, and energy it takes to do
such a study, the cohort should be warranted in other scientific research studies.
15. Possible outcomes of cohort studies include incidence of disease, mortality, health status, and specific
biological parameters. Some discrete events would be events that are biological parameters, like increases
in blood pressure or increases in weight, which would be a result of exposure to risk. Disease markers
would be things such as mortality or onset of disease; things that are relatively easily to identify.
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