NR 503- CHAPTERS 9-15 REVIEW QUESTIONS &
ANSWERS
Question 1
A study is planned to investigate the relationship of factors associated with maternal
hypertension and the risk of congenital birth defects in children born to these women. Which of
the following would be a reason for using a cohort study design?
The need to obtain data on the incidence of early fetal losses due to congenital birth
defects
The low rate of congenital birth defects
The development of pregnancy-related hypertension in asymptomatic women
The consistency of recall of risk factors among women having children with and without
congenital birth defects and those having children
Testing hypotheses about several different risk factors for congenital birth defects such as
maternal age, diabetes, and previous miscarriage history
The cohort design is best for observing the incidence of a disease in persons who do not have the
outcome at baseline. In this study, the researchers will start with women planning on becoming
pregnant and stratify them by presence of hypertension. Since all women will be followed over
time, the occurrence of fetal loss can be tracked by the investigators during the study.
Question 2
A researcher is interested in the etiology of myocardial infarction (MI) among men between 18
and 40 years of age. Her hypothesis concerns the influence of diets high in fat and subsequent
development of MI. What is the best study approach to address this hypothesis?
Case-control study with cases of MI identified post-event and controls sampled from
healthy men in the population, then have both groups complete dietary surveys
Case-report study describing the dietary habits in 100 men having an MI
Ecologic study with the rates of MI compared between cities with higher than average
dietary fat intakes and cities with lower than average dietary fat intakes
Retrospective cohort study with medical records used to collect information on diet
among men with and without an MI
Prospective cohort study identifying a population of men in this age group,
administering a dietary survey and classifying men by high and low fat diet, then
following both groups for the development of an MI
,The choice of a prospective cohort study allows the researcher to select the population of interest
(men ages 18 to 40 years), classify the exposure after an initial assessment, and then follow all
men in the study for incident outcomes. This approach is best described as a cohort study.
Question 3
Which of the following is an advantage to the conduct of a cohort study?
The study population is the same with regard to the risk factors for disease
The disease under study occurs rarely in the population
The incidence of the disease is high in the non-exposed group
The incidence of the disease is high in the exposed group
The study population includes a high number of undiagnosed, asymptomatic individuals
with the disease
A cohort study entails classification of the study population by exposure to the risk factor of
interest. The subsequent incidence of disease occurs during the follow-up time of observation of
the study population. A high incidence of disease in the exposed group provides the researcher
with a large number of outcomes and provides an initial association with the risk factor if the
disease occurs in the exposed group.
Question 4
A cohort study is planned to investigate the potential adverse health effects of daily alcohol
consumption. In assessing the risk of liver cancer related to alcoholism, which of the following is
not an important methodologic consideration?
The need to study a large number of persons for a rare disease outcome
The difficulty of finding enough persons with liver cancer at the beginning of the
study in whom alcohol consumption could be determined
The possible bias associated with persons describing alcohol usage
The likelihood that doctors would monitor alcoholics more closely for liver cancers
The possibility that persons would change their alcohol consumption practices during the
study period
A cohort study must take into account methodologic issues related to rare disease occurrences,
classification of exposure throughout the study conduct, and potential biases related to
identifying outcome events. Ideally, a cohort study would start with non-diseased individuals
who are followed over time, thus finding persons with liver cancer at the beginning of the study
would not be a consideration for a cohort study design.
,Question 5
Which of the following is not an advantage of a retrospective cohort study?
Allows for the study of many disease outcomes resulting from an exposure
Incidence rates can be calculated
Possible bias due to selection of the cohort is eliminated
Potential recall bias can be minimized
Requires less follow-up time than a prospective cohort study
Retrospective cohort studies depend on the ability of researchers to identify eligible cohort
members, describe their past exposure using historical records, and to follow the cohort until the
disease develops. Relying on past records to select persons for entry into the cohort study could
be compromised by biases regarding the investigator’s theorized association of the exposure and
disease.
Question 6
In a study of the adverse effects of x-rays among children, a retrospective cohort study was done
using records from several large children’s hospitals for the period of 1980 to 1985. 10,000
children were selected as a representative population of ill children seen at the hospitals during
that time. Subjects were classified according to whether or not they received an x-ray during
their stay in the hospital and were followed from their hospital stay through 2005 for the
development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263
children who had received an x-ray, and 47 incident cancers occurred in the 6,737 children who
had not received an x-ray during their hospitalization. In this retrospective study, which of the
following groups are eligible for selection into the study?
Children receiving x-rays in 1990
Children receiving x-rays in 1975
Children receiving x-rays for broken bones in 1983
Children in the hospital for cancer treatment in 1985
Children who were treated in private clinics and hospitals in 1981
Children who received an x-ray during the defined study period and did not have a cancer
diagnosis during that time can be included in the study.
, Question 7
In a study of the adverse effects of x-rays among children, a retrospective cohort study was done
using records from several large children’s hospitals for the period of 1980 to 1985. 10,000
children were selected as a representative population of ill children seen at the hospitals during
that time. Subjects were classified according to whether or not they received an x-ray during
their stay in the hospital and were followed from their hospital stay through 2005 for the
development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263
children who had received an x-ray, and 47 incident cancers occurred in the 6,737 children who
had not received an x-ray during their hospitalization. What are the rates of cancer incidence in
each exposure group?
The rate of cancer incidence in the x-ray exposed group is 15 per 1,000 (49 divided by 3,263 multiplied
by 1,000) and 7 per 1,000 in the non-exposed group (47 divided by 6,737 multiplied by 1,000).
Question 8
In a study of the adverse effects of x-rays among children, a retrospective cohort study was done
using records from several large children’s hospitals for the period of 1980 to 1985. 10,000
children were selected as a representative population of ill children seen at the hospitals during
that time. Subjects were classified according to whether or not they received an x-ray during
their stay in the hospital and were followed from their hospital stay through 2005 for the
development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263
children who had received an x-ray, and 47 incident cancers occurred in the 6,737 children who
had not received an x-ray during their hospitalization. What is the attributable risk of cancer due
to x-ray in this study population? What is the interpretation of this estimate?
The attributable risk equals the incidence rate in the exposed group minus the incidence rate in the -
group. In this instance, the attributable risk is 8 per 1,000. This estimate is interpreted to mean that 8 of
the 15 incident cases of cancer occurring in 1,000 children exposed to x-rays are due to the exposure
itself.
ANSWERS
Question 1
A study is planned to investigate the relationship of factors associated with maternal
hypertension and the risk of congenital birth defects in children born to these women. Which of
the following would be a reason for using a cohort study design?
The need to obtain data on the incidence of early fetal losses due to congenital birth
defects
The low rate of congenital birth defects
The development of pregnancy-related hypertension in asymptomatic women
The consistency of recall of risk factors among women having children with and without
congenital birth defects and those having children
Testing hypotheses about several different risk factors for congenital birth defects such as
maternal age, diabetes, and previous miscarriage history
The cohort design is best for observing the incidence of a disease in persons who do not have the
outcome at baseline. In this study, the researchers will start with women planning on becoming
pregnant and stratify them by presence of hypertension. Since all women will be followed over
time, the occurrence of fetal loss can be tracked by the investigators during the study.
Question 2
A researcher is interested in the etiology of myocardial infarction (MI) among men between 18
and 40 years of age. Her hypothesis concerns the influence of diets high in fat and subsequent
development of MI. What is the best study approach to address this hypothesis?
Case-control study with cases of MI identified post-event and controls sampled from
healthy men in the population, then have both groups complete dietary surveys
Case-report study describing the dietary habits in 100 men having an MI
Ecologic study with the rates of MI compared between cities with higher than average
dietary fat intakes and cities with lower than average dietary fat intakes
Retrospective cohort study with medical records used to collect information on diet
among men with and without an MI
Prospective cohort study identifying a population of men in this age group,
administering a dietary survey and classifying men by high and low fat diet, then
following both groups for the development of an MI
,The choice of a prospective cohort study allows the researcher to select the population of interest
(men ages 18 to 40 years), classify the exposure after an initial assessment, and then follow all
men in the study for incident outcomes. This approach is best described as a cohort study.
Question 3
Which of the following is an advantage to the conduct of a cohort study?
The study population is the same with regard to the risk factors for disease
The disease under study occurs rarely in the population
The incidence of the disease is high in the non-exposed group
The incidence of the disease is high in the exposed group
The study population includes a high number of undiagnosed, asymptomatic individuals
with the disease
A cohort study entails classification of the study population by exposure to the risk factor of
interest. The subsequent incidence of disease occurs during the follow-up time of observation of
the study population. A high incidence of disease in the exposed group provides the researcher
with a large number of outcomes and provides an initial association with the risk factor if the
disease occurs in the exposed group.
Question 4
A cohort study is planned to investigate the potential adverse health effects of daily alcohol
consumption. In assessing the risk of liver cancer related to alcoholism, which of the following is
not an important methodologic consideration?
The need to study a large number of persons for a rare disease outcome
The difficulty of finding enough persons with liver cancer at the beginning of the
study in whom alcohol consumption could be determined
The possible bias associated with persons describing alcohol usage
The likelihood that doctors would monitor alcoholics more closely for liver cancers
The possibility that persons would change their alcohol consumption practices during the
study period
A cohort study must take into account methodologic issues related to rare disease occurrences,
classification of exposure throughout the study conduct, and potential biases related to
identifying outcome events. Ideally, a cohort study would start with non-diseased individuals
who are followed over time, thus finding persons with liver cancer at the beginning of the study
would not be a consideration for a cohort study design.
,Question 5
Which of the following is not an advantage of a retrospective cohort study?
Allows for the study of many disease outcomes resulting from an exposure
Incidence rates can be calculated
Possible bias due to selection of the cohort is eliminated
Potential recall bias can be minimized
Requires less follow-up time than a prospective cohort study
Retrospective cohort studies depend on the ability of researchers to identify eligible cohort
members, describe their past exposure using historical records, and to follow the cohort until the
disease develops. Relying on past records to select persons for entry into the cohort study could
be compromised by biases regarding the investigator’s theorized association of the exposure and
disease.
Question 6
In a study of the adverse effects of x-rays among children, a retrospective cohort study was done
using records from several large children’s hospitals for the period of 1980 to 1985. 10,000
children were selected as a representative population of ill children seen at the hospitals during
that time. Subjects were classified according to whether or not they received an x-ray during
their stay in the hospital and were followed from their hospital stay through 2005 for the
development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263
children who had received an x-ray, and 47 incident cancers occurred in the 6,737 children who
had not received an x-ray during their hospitalization. In this retrospective study, which of the
following groups are eligible for selection into the study?
Children receiving x-rays in 1990
Children receiving x-rays in 1975
Children receiving x-rays for broken bones in 1983
Children in the hospital for cancer treatment in 1985
Children who were treated in private clinics and hospitals in 1981
Children who received an x-ray during the defined study period and did not have a cancer
diagnosis during that time can be included in the study.
, Question 7
In a study of the adverse effects of x-rays among children, a retrospective cohort study was done
using records from several large children’s hospitals for the period of 1980 to 1985. 10,000
children were selected as a representative population of ill children seen at the hospitals during
that time. Subjects were classified according to whether or not they received an x-ray during
their stay in the hospital and were followed from their hospital stay through 2005 for the
development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263
children who had received an x-ray, and 47 incident cancers occurred in the 6,737 children who
had not received an x-ray during their hospitalization. What are the rates of cancer incidence in
each exposure group?
The rate of cancer incidence in the x-ray exposed group is 15 per 1,000 (49 divided by 3,263 multiplied
by 1,000) and 7 per 1,000 in the non-exposed group (47 divided by 6,737 multiplied by 1,000).
Question 8
In a study of the adverse effects of x-rays among children, a retrospective cohort study was done
using records from several large children’s hospitals for the period of 1980 to 1985. 10,000
children were selected as a representative population of ill children seen at the hospitals during
that time. Subjects were classified according to whether or not they received an x-ray during
their stay in the hospital and were followed from their hospital stay through 2005 for the
development of cancer. During the follow-up period, 49 incident cancers occurred in 3,263
children who had received an x-ray, and 47 incident cancers occurred in the 6,737 children who
had not received an x-ray during their hospitalization. What is the attributable risk of cancer due
to x-ray in this study population? What is the interpretation of this estimate?
The attributable risk equals the incidence rate in the exposed group minus the incidence rate in the -
group. In this instance, the attributable risk is 8 per 1,000. This estimate is interpreted to mean that 8 of
the 15 incident cases of cancer occurring in 1,000 children exposed to x-rays are due to the exposure
itself.
