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130 Cards in this Set
- Front
- Back
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Primary Prevention
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actions taken to prevent the development of disease among person who don't have the disease
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Secondary prevention
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actions taken among people who have already developed a disease to improve prognosis; early detection/screening
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Tertiary Prevention
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disease management
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What are the purposes of epidemiology?
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study natural history and prognosis of disease
determine extent of disease in a population identify the etiology(causes/risk) of disease evaluate effectiveness provide basis for establishing policy and regulations |
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What is the definition of epidemiology?
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the study of the distribution and determinants of disease frequency in human populations and the application of this study to control problems
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What is the goal of descriptive epidemiology?
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Determines the group who is the most at risk for developing the disease; and ultimately why
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What is a secular trend?
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A change in disease frequency over a long period of time(in years or decades)
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What are cyclic disease changes?
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recurrent alterations in the frequency of disease(often seasonal)
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What are they two types of populations?
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fixed populations
dynamic populations |
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What is a fixed population?
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membership is permanent and defined by an event
-ex: members of Framingham cohort; residents exposed to radiation @ Chernobyl |
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What is dynamic population?
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Membership is transient and defined by being in or out of a "state"
-ex: Residents of Richmond, VA |
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What are the 3 types of frequency measures?
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Ratio
Proportion Rate |
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What is prevalence?
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Quantifies the number of existing causes of disease in a population at a point or during a period of time
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What measure of disease frequency to measure the percentage of freshman girls who become pregnant over the course of their high school years?
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cumulative incidence
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What measure of disease frequency to measure the percentage of senior boys who are fathers at the time of graduation?
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prevalence
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What measure of disease frequency to measure the number of live born babies who die of sudden infant death syndrome during the first year of life per 100, 000 baby-years of follow-up?
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incidence rate
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What measure of disease frequency to measure the number the percentage of infants weighing less than 2500 grams at birth?
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prevalence
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What measure of disease frequency to measures the lifetime risk of breast cancer?
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cumulative incidence
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In 2005, there were 2900 new cases of breast cancer diagnosed among women in Alabama and 200 new cases diagnosed among women in Alaska. Based on these data, is it accurate to say that the incidence rate of breast cancer is higher in alabama than Alaska?
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NO, you need to know the size of the population and the amount of follow up time in each state
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What is a measure of disease severity?
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Case fatality rate
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True or false: to calculate case fatality, you must follow people longitudinally
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True
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The proportion of people with a disease/diagnosis/condition/procedure, who die from it during a specified period of time after symptom onset/diagnosis/ treatment
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case fatality rate
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What do you use to measure infectious disease outbreaks?
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attack rate
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What 3 things must a definition of a case include?
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Person
Place Time |
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What are the steps to an outbreak investigation?
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Establish the existence of an epidemic
Confirm the diagnosis Develop a case definition Identify/count cases to determine who is at risk Describe the cases by person, place and time Develop a hypothesis and evaluate against established facts Plant/conduct and analytic study Implement control and prevention efforts Prepare and disseminate a report |
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What is the ecological fallacy?
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incorrect attribution of a population metric to an individual
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Cross sectional study
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Get point prevalence
“Snapshot”: Looks at prevalence of disease and/or exposure at one time point Begins with a population base and collects individual-level data Does not choose participants based on disease or exposure status Does not follow individuals over time Persons are classified as Diseased or non-diseased, and/or Exposed or unexposed May be either descriptive or analytical, depending on whether the purpose is: To describe the health status of the population (descriptive), or to relate exposure to disease (analytical) |
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Case control study
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Usually retrospective
Stratifying based on disease You either have disease in study or you don’t Measure of association: odds ratio Nested case control Cohort you are prospectively following them within your group Good for rare-diseases |
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Prospective cohort study
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Like lights when they get a disease on a timeline
usually able to collect contemporaneous data specifically for the study More expensive and time consuming Not efficient for diseases with long latent periods Better exposure and confounder data Less vulnerable to selection bias |
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Advantages of cross sectional study
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Relatively quick and cheap
Generalizability (depending on data!) Do not have to know disease/exposure status ahead of time Can collect detailed data exposures, outcomes, and confounders |
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Disadvantages of a cross sectional study
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Time sequence (temporality) between exposure and disease can be difficult to infer
Potential for confounding (selection bias, “Survival” bias or Representativeness of volunteers) |
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Biases of concern in a case control study
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Selection bias
Recall bias Interviewer bias Exposure misclassification |
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Retrospective cohort study
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generally rely heavily on records; this makes them dependent on the completeness and detail in existing records
Usually cheaper and faster to complete Efficient with diseases with long latent period Exposure data may be inadequate |
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True or false: random assignment controls for confounders
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true
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When does selection bias occur?
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Occurs when controls or cases are more or less likely to be included in the study sample if they have been exposed
inclusion in the study is not independent of exposure |
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What is observation bias?
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An error that arises from systemativ difference in the way information on exposure of disease is obtained from the study groups
May lead to differential or non differential misclassification |
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What is differential misclassification?
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toward or away from the null
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What is nondifferential misclassification
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away from the null
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What is confounding?
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some exposure leads to an outcome
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What is an effect modifier?
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The effect of an exposure on an outcome differs depending on whether another variable (the effect modifier) is present
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What is sensitivity?
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If I have the disease, what is the likelihood that I’ll test positive
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What is specificity?
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If I don’t have the disease, what is the likelihood that I will test negative
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What does predictive value positive mean?
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If I test positive, what is the likelihood that I have the disease
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What does Predictive value negative mean?
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If I test negative, what is the likelihood that I don’ t have the disease
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An appropriate indicator of the virulence of an infectious agent in a population is?
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case fatality rate
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A 46-year old man who experienced jaundice and fever after coronary artery bypass surgery 15 years earlier is found to be Hepatitis B surface antigen positive. He is most appropriately characterized as?
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chronic carrier
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rate or ratio to describe death occurs in 10 percent of cases of meningococcal meningitis
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case fatality
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rate or ratio to describe approximately 9 people die each year in the United States for every 1,000 persons estimated to be alive
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crude mortality rate
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rate or ratio to describe lung cancer deaths in men ages 60-69 expressed as a proportion of all men ages 60-69
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age specific mortality rate
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rate or ratio to describe the number of deaths due to cardiovascular disease expressed as a proportion of all causes of death
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proportionate mortality ratio
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rate or ratio to describe eighty percent of children in the third grade exposed to the measles virus will develop clinical disease
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attack rate
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In a descriptive epidemiologic study a bell-shaped (rapid rise, rapid fall) epidemic curve most commonly depicts:
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point source outbreak of disease
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When a new treatment is developed that prevents death but does not produce recovery from a disease, the following will occur
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prevalence will increase, assuming incidence remains constant
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Which measure is used as a denominator to calculate the incidence rate of a disease?
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person-years of observation
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Disease prevalence rates measure
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The probability of having a disease at a particular time
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Which epidemiologic rate provides the best indication of disease severity?
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case fatality rate
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Which rate is most useful in determining the extent of an outbreak of disease
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incidence rate(risk of developing the disease)
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Age-adjusted death rates are used to
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Eliminate the effects of differences in the age distributions of populations in comparing death rates
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The incidence rate of a disease is five times greater in women than in men, but the prevalence rates show no sex differences. The best explanation is that
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the case fatality rates are higher for women. This results in the decreased duration of disease, of setting the increased incidence among women.
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In a cross-sectional study of peptic ulcer in a community, people meeting the symptomatic criteria for peptic ulcer were found in 80 per 100,000 men aged 35 to 49 and 90 per 100,000 women aged 35 to 49. The inference that in this age group, women are at greater risk of developing peptic ulcer is
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Incorrect due to failure to distinguish between incidence and prevalence
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True or false: Incidence rates can be calculated from case control studies
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false
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In a double blind, randomized trial of the effectiveness of a drug in the treatment of herpes simplex II, patients were randomly assigned to either an active drug or a placebo group. Each person was followed up to six weeks and evaluated as showing: 1) significant improvement; or 2) no significant improvement. The purpose of the double blinded aspect of the study design was to
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Minimize the likelihood of assessment or observer bias.
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Two scientists want to investigate a new screening test that identifies undiagnosed, early-stage prostate cancer. Both screening tests will be used on the same population of males over 50 years of age. Dr. A uses the standard screening test, which has a sensitivity of 99% and a specificity of 96%. Dr. B uses the new test which is 90% sensitive and 99% specific. If 1000 men undergo screening for prostate cancer with both tests, which of the following is correct?
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Dr. A will correctly identify more people with prostate cancer than Dr. B
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An investigator is trying to determine whether a medical screening program using chest x-rays to detect undiagnosed lung cancer improves the survival time of the persons screened. She looked at the most recent year’s data in the Connecticut Tumor Registry and discovered that the median survival time following the diagnosis of lung cancer is 6 months. She then performed a chest x-ray screening program in shopping centers and bowling alleys. She found that in persons screened by this program, the median time from diagnosis to death is 9 months for the 95 cases of lung cancer discovered. The survival time difference is statistically significant. The investigator concluded that the screening program and subsequent treatment are adding an average of 3 months to the lives of lung cancer patients. You disagree on the basis of
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lead time bias(the amount of time the disease diagnosis is advanced by screening
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What is the relationship of the tuberculosis bacillus to clinical tuberculosis?
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necessary cause
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What is an example of synergy?
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two factors work in concert to produce more disease than one would expect
nitrite use, unproductive anal intercourse and HIV |
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Among elderly subjects who are fit, vigorous exercise reduces the risk of heart disease. Among elderly subjects who are unfit, the initiation of vigorous exercise might precipitate a myocardial infarction (heart attack). Fitness may be considered
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An effect modifier
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Cases and controls were enrolled into a study of end-stage renal disease. Participants were interviewed about their lifetime consumption of Ibuprofin and other medications. All participants tended to have difficulty correctly estimating their lifetime medication use, and cases and controls provide about the same quality of data. This situation would lead to:
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non-differential information bias
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Investigators were interested in was occupational lead exposure. The controls tended to underestimate the number of years worked in lead-exposed jobs, while the cases tended to report this data fairly accurately. This would lead the investigators to:
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overestimate the odds ratio due to differential information bias
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Which of the populations below would not be appropriate as the population base for a retrospective-cohort study?
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all children newly diagnosed with cancer in the State of New York in 1999
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An interview study was carried out to evaluate risk factors for migraine headaches. Interviewers went door-to-door and surveyed a random sample of individuals in a rural community. Participants were asked if they had ever been diagnosed with migraine. They were also identified by age, gender, and race, and asked about a number of exposures, including dietary patterns, psychological factors, sleep patterns, medication use, alcohol consumption, and exposures to electromagnetic fields (EMF). What measure of association would you use to describe the relationship between migraines and EMF?
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prevalence odds ratio
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We are concerned that selection bias may have influenced the results of this study. Which one of the scenarios below is indicative of selection bias?
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individuals with migraine who had substantial EMF exposure were the subgroup with the highest participation rate
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After completing the above study, the investigator looked at the data and found that interview data on obesity did not always agree with medical records data on obesity. She made some calculations, assuming that the medical record was correct. She found that for about 15% of cases and controls, the interview gave a different result than the medical record. This is an example of:
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non-differential misclassification of exposure
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Ionizing radiation, benzene, and certain viruses can each individually cause leukemia without the other two exposures, but only if the exposed individual has a certain genetic deficiency. This genetic deficiency by itself does not cause leukemia, but the disease never occurs in the absence of this genetic factor. The genetic deficiency is:
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A necessary but not sufficient cause
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Ionizing radiation, benzene, and certain viruses can each individually cause leukemia without the other two exposures, but only if the exposed individual has a certain genetic deficiency. This genetic deficiency by itself does not cause leukemia, but the disease never occurs in the absence of this genetic factor. Ionizing radiation exposure is:
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Neither necessary nor sufficient
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A study reported on 100 cases admitted to the hospital for diagnosis and treatment of thyroid cancer and 200 controls admitted to the same hospital during the same time period for treatment of hernias. Only the cases were interviewed and 55 of the cases were found to have been exposed to x-ray therapy in the past, based on the interviews and medical records. The controls were not interviewed, but a review of their hospital records when they were admitted for hernia surgery revealed that only 10 controls had been exposed to x-ray therapy in the past. Based on the description given above, what source of bias is most likely to be present in this study?
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Bias due to the use of different methods of ascertainment of exposure in the case and controls
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Community A and Community B each have crude mortality rates for coronary heart disease (CHD) of 5 per 1000 per year. The age-adjusted CHD mortality rate for Community A is 8 per 1000 per year and for Community B is 3 per 1000 per year. One may conclude that
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Community A has a younger population than community B
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The primary reason(s) that lead(s) to new outbreaks or epidemics of disease include
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changes in host susceptibility
introduction of new susceptibles into the population introduction of new pathogens into a susceptible population |
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The term antigenic or genetic shift refers to
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Major cyclic alterations of the influenza virus mediated by a number of progressive changes in the surface of the virus and by reassortment resulting in a new viral sub-type
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Which of the following are potential indications of the virulence of an infectious agent for a particular population:
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A high case fatality rate
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Investigations of epidemics of salmonella gastroenteritis often find that persons who no longer have acute symptoms of disease may remain infectious to others due to continuous shedding of the organism weeks after clinical symptoms have resolved. This situation characterizes what type of carrier state?
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A convalescent carrier state
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The single risk behavior category that accounted for the greatest proportion of HIV/AIDS cases diagnosed in 2010 among U.S. Males is:
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Male-to-Male Sexual Contact (MSM)
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When comparing mortality rates between different countries, one possible reason that differences exist is not a true biological, environmental, behavioral, or genetic reason but is due to artifacts in the data that makes up the rates. The sources of these artifacts can include all of the following except:
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Changes in the age composition of the population
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The primary steps that you, as the state epidemiologist, would take in the early and middle stages of an investigation of an outbreak of community-acquired staphylococcus aureus, would be all of the following except:
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Evaluate the impact of control measures to see if they have prevented further spread of the disease
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A study was designed to evaluate whether the risk of having an acute myocardial infarction (AMI or heart attack) is triggered by physical exertion and is affected by ambient temperature and whether it takes place indoors or outdoors. The study population consisted of hospitalized 24-hour survivors of an AMI who were 25-74 years of age. Data on symptoms in connection with the AMI as well as socio-demographic characteristics, medical history and smoking status were routinely collected for all participants. Patients were interviewed about their activities on the day of their AMI and the preceding 3 days using a standardized questionnaire. Activities during the hazard period (immediately preceding the AMI) were compared with activities occurring in 2 control periods, 24 and 48 hours earlier.
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case cross over study
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A study was designed to determine the role that senior citizen centers play in decreasing depression in community-dwelling older persons. A non-probability sample of older adults who live in Sebastian County, Arkansas and who attend one of the nine senior centers was selected for study. A questionnaire was administered to 257 participants asking questions about age, living arrangements, gender, and social networks. A Geriatric Depression Scale (GDS-15) was also administered to measure clinically significant depressive symptoms.
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cross sectional study
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To describe the relationship between the location of Pediatric Intensive Care Units (PICU) facilities and county level child death from trauma in the United States, U. S. mortality rates for children from 0-14 years of age dying from injuries in 1996-1998 for each U. S. county (derived from NCHS data), were linked to 1997 county-level data on the availability of PICU facilities, derived from the 1997 American Hospital Association annual survey on hospital facilities.
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ecological study
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Between 1991 and 1994, a community randomized trial was conducted in 12 rural communities in Tanzania to measure the impact of improved STI treatment services delivered through government health-care units. At baseline and follow-up surveys, samples of venous blood were obtained from consenting subjects and tested for HIV antibodies. After the final survey in 1994, cases (defined as persons who became HIV-positive) and HIV-negative controls were selected for further study from among the participants in the randomized community trial. Questionnaires were administered to both groups to ascertain sociodemographic characteristics and detailed information on sexual behavior.
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nested-case control study
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A study was conducted beginning in 2005 of the potential association between occupational exposure to microwave emissions from radars and mortality from cancer. The exposed population consisted of Belgian male military personnel who served in 2 radar battalions in Germany and were ever exposed to Hawk radar systems from 1963 to 1994. An unexposed comparison group consisting of male military personnel who served in artillery battalions located in the same area of Germany and during the same time period as the exposed group was identified. Deaths from cancer and other causes occurring between 1968 through 2004 were identified in both groups.
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retrospective cohort study
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A state of genuine uncertainty about the benefits or harms that may result from each of two interventions
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Equipoise
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An experimental study that allows one to examine simultaneously the effects of multiple independent variables and their degree of interaction.
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Factorial design
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After randomization, all patients allocated to each arm in a experimental trial are analyzed together as representing that treatment or intervention group, whether or not they completed or were compliant with the intervention.
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intention to treat
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In a case-control study of computer display exposure and glaucoma, cases and controls were also asked about television viewing habits. Errors in recall of exposure to video screens occurred with equal frequency among cases and controls. What is the most likely effect of this bias on the measure of association reported by this study?
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Underestimated the true relationship
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In a case-control study of computer display exposure and glaucoma, cases and controls were also asked about television viewing habits. Errors in recall of exposure to video screens occurred with equal frequency among cases and controls. Which one of the following biases likely occurred?
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non-differential misclassification
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In a case-control study of obesity and adult-onset asthma, controls are matched to asthma cases on the basis of race and gender. This approach to selection is intended to decreases the influence of which type of bias?
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confounding
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In a case-control study of maternal cigarette smoking as a risk factor for low birth weight, the investigators concluded that mothers of children with low birth weight were more likely to report smoking during pregnancy relative to mothers of children with normal birth weight. The reporting error most likely caused the odds ratio to:
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increase above the true value
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A matched case-control study of sunscreen use during childhood and melanoma results in an Odds Ratio of 1.0. Cases of melanoma were matched by sex and race to controls that were identified by random digit dialing. What is the most likely explanation for the study’s null finding?
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Confounding by age
Information bias concerning past sunscreen use Lack of a true association between childhood sunscreen use inadequate sample size |
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If a subjects’ willingness to participate is related to both their exposure status and disease status, the resulting bias is known as:
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Self-selection bias
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7. A case-control study was performed to determine whether head injury was associated with an increased risk of brain tumors in children. 200 cases with brain cancer were identified from the state cancer registry and 200 controls were recruited from the same neighborhoods where the cases lived. The mothers of the children completed a questionnaire that asked them to describe their child’s past history of head injury. The investigators found that the mothers of the children with brain tumors reported a past head injury for 70 of the cases while a past history of head injury was reported in 30 of the controls. What type of bias was likely to have influenced the findings of this study?
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recall bias
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Loss to follow-up bias is an important concern in which type of epidemiologic study?
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both cohort and experimental
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9. In a case-control study of the possible association between coffee drinking and coronary heart disease (CHD), investigators observed that a third factor, cigarette smoking, occurred more frequently among persons who were heavy coffee drinkers and also occurred more frequently among cases in general, whether or not they drank coffee. The crude Odds Ratio between coffee drinking and CHD was 2.5 The investigators concluded that there is a strong association between coffee drinking and CHD. This interpretation is:
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Incorrect, because the effect of a confounding factor, cigarette smoking, was not accounted for in the analysis
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10. Cases and controls were enrolled into a study of end-stage renal disease. Participants were interviewed about their lifetime consumption of Ibuprofin and other medications. All participants tended to have difficulty correctly estimating their lifetime medication use, and cases and controls provide about the same quality of data. This situation would lead to:
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Non-differential information bias
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the rate or ratio that best describes death occurs in 10 percent of cases of meningococcal meningitis is?
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case fatality rate
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the rate or ratio that best describes approximately 9 people die each year in the United States for every 1,000 persons estimated to be alive is?
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crude mortality rate
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the rate or ratio that best describes lung cancer deaths in men ages 60-69 expressed as a proportion of all men ages 60-69 is?
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age specific mortality rate
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the rate or ratio that best describes the number of deaths due to cardiovascular disease expressed as a proportion of all causes of death is?
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proportionate mortality ratio
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the rate or ratio that best describes eighty percent of children in the third grade exposed to the measles virus will develop clinical disease is?
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attack rate
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Age-adjusted death rates are used to:
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Eliminate the effects of differences in the age distributions of populations in comparing death rates
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Persons harboring an infectious agent who do not develop clinical symptoms but are important epidemiologically because they are capable of infecting other persons are called:
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Inapparent infections
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the 2009-2010 H1N1 strain of influenza was first identified in Mexico, then rapidly spread to the United States, Europe, Asia, and South America is an example of what?
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pandemic
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everal campers developed cholera after drinking water from a contaminated well is an example of what?
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outbreak
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Rocky Mountain Spotted Fever is the most lethal and most frequently reported rickettsial illness in the United States. Over 800 cases are reported every year throughout the United States is an example of what?
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endemic
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In a double blind, randomized trial of the effectiveness of a drug in the treatment of herpes simplex II, patients were randomly assigned to either an active drug or a placebo group. Each person was followed up to six weeks and evaluated as showing: 1) significant improvement; or 2) no significant improvement. The purpose of the double blinded aspect of the study design was to:
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Minimize the likelihood of assessment or observer bias.
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An interview study was carried out to evaluate risk factors for migraine headaches. Interviewers went door-to-door and surveyed a random sample of individuals in a rural community. Participants were asked if they had ever been diagnosed with migraine headaches. They were also identified by age, gender, and race, and asked about a number of exposures, including dietary patterns, psychological factors, sleep patterns, medication use, alcohol consumption, and exposures to electromagnetic fields (EMF). THis is an example of?
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a cross sectional study
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What measure of association would you use to describe the relationship between migraines and EMF?
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prevalence ratio
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In a cross-sectional study of peptic ulcer in a community, people meeting the symptomatic criteria for peptic ulcer were found in 80 per 100,000 men aged 35 to 49 and 90 per 100,000 women aged 35 to 49. The inference that in this age group, women are at greater risk of developing peptic ulcer is:
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Incorrect due to failure to distinguish between incidence and prevalence
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A random sample of the population of Salina, Kansas, was selected. People in the sample were asked questions about their current health including history of heart disease. Blood pressure and serum cholesterol measurements were made on each person in the sample.
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cross sectional study
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A study was conducted of older adults enrolled in Adult Changes in Thought (ACT) within the membership of the Group Health Cooperative, a large health maintenance organization in Seattle, Washington. Members of ACT who had a fall between July 1998 and June 2000 were compared with a group of matched controls selected from the same group (ACT) on the type of shoes they were wearing at the time of the fall or similar time period among the controls.
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nested case control
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In Cleveland, Ohio, rates of admissions to the emergency room for treatment of childhood asthma for the period from 1 January 2004 to 31 December 2004, were compared with monitoring data for environmental ozone levels in the Cleveland metropolitan area for the same time period to determine if there was a relationship between reported admissions to the ER for asthma and peaks of high ozone levels in the ambient air.
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ecological study
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In Seattle, Washington, parents of children who were admitted to the Harbor View Hospital’s emergency room for treatment of an injury, were interviewed about their child’s sleeping pattern in the 24 hour interval prior to the injury and compared that with the 24-hour sleeping period of the previous day, when the child served as a control.
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case-crossover study
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In order to test the effectiveness of a new intervention for smoking cessation, smoking males between the ages of 20 – 45 were recruited and were randomly assigned to the new smoking cessation intervention group or to the standard smoking cessation intervention. Long-term smoking cessation rates were measured at 6 months and at 1 year after the two groups were randomized.
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experimental study
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A cohort study was conducted to examine cigarette smoking and the risk of oral cancer. The investigators selected exposed and unexposed subjects so that they had the exactly same distribution of race. This method to address confounding by race is called:
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matching
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What types of study designs are MOST prone to selection bias?
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Retrospective cohort study
Case-control study |
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Which of the following methods can be used to minimize recall bias in a case-control study?
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blind subjects to the study hypothesis
blind interviewers to the study hypothesis avoid open-ended interview questions use a control group comprised of diseased individuals |
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Non-differential misclassification tends to bias study results in which direction?
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towards the null
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Selection bias is most likely to occur in which type of study?
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Retrospective cohort studies
Case-control studies |
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The healthy worker effect is a form of what type of bias?
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selection bias
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Information bias occurs
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After the subjects have entered the study
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Which of the following is a method for controlling confounding in the analysis phase only of a study?
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Stratification
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Residual confounding can result from
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Use of broad categories of a confounder in the analysis
Confounders for which no data were collected Inaccurate data on a confounder |
