question

Define epidemiology

answer

study of the distribution and determinants of disease frequency in human populations and the application of this study to control health problems

question

The two parts of "study" are _____ & ______

answer

surveillance and epidemiologic research

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Goal of surveillance

answer

monitor aspects of disease occurrence and spread that are pertinent to effective control

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Goal of epidemiologic research

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harvest valid and precise information about the causes, preventions, and treatments for disease

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What are some of the terms that disease encompasses?

answer

diseases, injuries, disabilities, and death

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Which design would you use when investigating the role of some factor or agent in the prevention or treatment of a disease?

answer

experimental

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What is the most commonly used research design within epidemiology?

answer

observational

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What is one of the pros to conducting observational research?

answer

considered to be "natural" experiments; not limited to preventions and treatments; do not suffer from the ethical and feasibility issues of experimental design

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Describe a cohort study

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typically examines multiple health effects of an exposure; subjects are defined according to their exposure levels and followed for disease occurrence

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Describe a case-control study

answer

typically examines multiple exposures in relation to a disease; subjects are defined as cases and controls, and exposure histories are compared

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Describe a cross-sectional study

answer

typically examines relationship between exposure and disease prevalence in a defined population at a single point in time

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What is the key difference in ecological studies?

answer

examines the relationship between exposure and disease at the POPULATION-level rather than individual

question

Define confounding

answer

reflects the fact that the epidemiologic research is conducted among free-living humans with unevenly distributed characteristics; studies are susceptible to the disturbing influences of extraneous factors

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What is the difference between preventative and therapeutic trials?

answer

preventative - agents are studied to determine if they are effective in preventing or delaying the onset of disease among healthy individuals therapeutic - treatments are tested among individuals who already have a disease

question

What are some common reasons for noncompliance?

answer

toxic reactions to tx, waning interest, desire to seek other therapies

question

What is the major issue with noncompliance?

answer

results in a smaller difference between the tx and comparison groups than truly exists; dilutes the real impact of tx

question

What is the purpose of conducting a run-in period?

answer

ascertain which potential participants are able to comply with the study regimen

question

Name and describe two typical types of analysis in experimental design

answer

intent-to-treat : gives info on the effectiveness of a tx under everyday practice conditions efficacy : determines the tx effects under ideal conditions

question

Explain the difference between fixed, closed, and open population cohorts

answer

fixed: individual's exposure does not change over time (an individual undergoing a medical procedure) closed: a fixed cohort with no losses to follow up open population: exposures that can change over time (i.e. cigarette smoking)

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Name the three timing descriptives of cohort studies

answer

prospective retrospective ambidirectional

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Name & describe the three sources for comparison groups in cohort studies

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-internal : unexposed members of the same cohort **should be used whenever possible -general population: used if unable to find a comparable internal group; based on preexisting population data on disease incidence and mortality -comparison: consists of members of another cohort **least desirable - difficult to interpret results

question

Name some typical sources of information for cohort studies

answer

medical and employment records, interviews, direct physical examinations, laboratory tests, biological specimens, environmental monitoring

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What's in a name: case-control studies

answer

case - those who have a disease control - those who do not have a disease

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What are the components of a case definition?

answer

combination of s/s, physical and pathological examinations, results of diagnostic tests

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Why should prevalent cases be approached with caution?

answer

It is impossible to determine if the exposure is related to the inception of the disease, its duration, or a combination of the two

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Describe the would criterion

answer

controls must be a sample of the population that produced the cases; a member of the control group who gets the disease under the study would end up as a case in the study

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Three disadvantages of population controls in case-control studies

answer

1)time consuming & expensive 2)low level of interest in participating 3)recall may be less accurate than that of cases

question

Two general principles for inclusion in case-control studies

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1) illnesses in the control group should be unrelated to the exposure under study 2)control's illness should have the same referral pattern to the health care facility as the case's illness

question

Name & describe the three methods for sampling controls in case-control study

answer

survivor sampling - select controls from the "non-cases" at the end of the case diagnosis and accrual period case-base or case-cohort sampling - select controls from the population at risk at the beginning of the case diagnosis and accrual period risk-set sampling - controls are selected from the population at risk as the cases are diagnosed

question

Typical analysis used in case-control studies

answer

odds ratio: odds of being exposed compared to the odds of being a case among the non-exposed

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What are some typical uses of observational studies?

answer

-provide information to explain the causes of disease incidence and determinants of disease progression -predict the future health care needs of a population -control disease by studying ways to prevent disease and prolong life with disease

question

When do you use case-control or cohort studies?

answer

little is known about exposure

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When do you use case-control over cohort studies?

answer

to evaluate many exposures the disease is rare disease has a long induction and latent period exposure data is expensive underlying population is dynamic

question

When do you use cohort studies over case-control studies?

answer

to evaluate many effects of an exposure exposure is rare underlying population is fixed

question

When do you use retrospective cohort study design?

answer

disease has a long induction and latent period historical exposure want to save time and money

question

When do you use prospective cohort study design?

answer

disease has short induction and latent period current exposure want high-quality data

question

Name the limitations of cross-sectional study design

answer

cannot infer temporal sequence between exposure and disease if exposure is a changeable characteristic -preponderance of prevalent cases of long duration and healthy worker survivor effect

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Name some advantages of cross-sectional study design

answer

generalizability and low cost

question

What are the population-level factors in ecological study design?

answer

summaries of individual population members, environmental measures, global measures

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What is the typical criteria for study groups in ecological studies?

answer

identified by place or time, or a combination of the two

question

Name the limitations of ecological studies

answer

ecological fallacy (an association observed between variables on an aggregate level does not necessarily represent the association that exists at the individual level) lack of information on important variables

question

Name some advantages of ecological studies

answer

low cost wide range of exposure levels ability to examine contextual effects on health

question

Which observational study design is best in each of the following scenarios: A. Identifying the causes of a rare disease B. Identifying the long term effects of a rare exposure C. Studying the health effects of an exposure for which information is difficult and expensive to obtain D. Identifying the causes of new disease about which little is known E. Identifying the short-term health effects of a new exposure about which little is known F. Identifying the causes of a disease with a long latent period

answer

A. Case-control B. Retrospective C. Case-control D. Case-control E. Prospective F. Case-control

question

Which type of study is being described below: A study that examines the death rates from cervical cancer in each of the 50 states in relation to the avg % of women in each state undergoing annual PAP smear screening

answer

Ecologic

question

Which type of study is being described below: A study that compares the prevalence of back pain among current members of the plumbers and pipe fitters union with that of current members of the bakers and confectionary union.

answer

Cross-sectional

question

Which type of study is being described below: A study that evaluates the relationship between breast cancer and a women's history of breastfeeding. The investigator selects women with breast cancer and an age-matched sample of women who live in the same neighborhoods as women with breast cancer. Study subjects are interviewed to determine if they breastfed any of their children.

answer

Case-Control

question

Which type of study is being described below: A study that evaluates two treatments for breast cancer. Women with stage 1 breast cancer are randomized to receive either lumpectomy alone or lumpectomy with breast radiation. Women are followed for five years to determine if there are any differences in breast cancer recurrence and survival.

answer

Experimental

question

Which type of study is being described below: A study of the relationship between exposure to chest irradiation and subsequent risk of breast cancer that was begun in 2005. in this study, women who received radiation therapy for postpartum mastitis in the 1940s were compared to women who received a non radiation therapy for postpartum mastitis in the 1940s. The women were followed for 50-60 years to determine the incidence rates of breast cancer in each group.

answer

Retrospective cohort study

question

T or F: Observational studies of preventions and treatments are often conducted when experimental studies are unethical or infeasible.

answer

True

question

T or F: The main limitation of observational studies is the investigator's inability to have complete control of extraneous factors called cofounders.

answer

True

question

T or F: A cross-sectional study of the relationship between blood type and the risk of cataracts will produce misleading results because you cannot tell the correct temporal relationship between the exposure (blood type) and disease (cataracts).

answer

False

question

T or F: An ecological study was done to determine the relationship between per capita soft drink consumption and mortality rates from diabetes in ten states in the US. The investigators found a strong association between soft drink consumption and diabetes mortality. Based on this study we can conclude that the individuals who consumed soft drinks were the ones who died from diabetes.

answer

False

question

Name the two ways to compare measures of disease frequency

answer

1) absolute comparisons such as risk or rate differences; describe the public health impact of an exposure 2)relative comparisons such as risk ratio, rate ratios, and odds ratios; describe the strength of the casual relationship between an exposure and a disease

question

Describe selection bias

answer

an error due to systematic differences in characteristics between this who take part in a study and those who do not *more likely in case-control and retrospective cohort studies

question

Name some common sources of selection bias

answer

-inappropriate selection of control groups in case-control studies -nonresponse -agreement to participate that is related to the exposure and disease -loss to follow-up r/t the exposure and disease -healthy worker effect

question

Describe observation bias

answer

a flaw in measuring exposure or outcome data that results in different quality of information between comparison groups

question

Key features of observation bias:

answer

1)occurs after the subjects have entered the study 2)pertains to how the data are collected 3)often results in incorrect classification of participants as either exposed or unexposed or as diseased or not diseased

question

Name the different types of observation bias

answer

recall bias interviewer bias differential and non differential misclassification

question

Describe recall bias

answer

occurs when there is a differential level of accuracy in the information provided by compared groups

question

When does recall bias typically occur?

answer

Case-control studies if cases are more or less likely than controls to recall and report prior exposures (birth defects in infants example) Cohort studies if exposed subjects are more or less likely than unexposed subjects to recall and report subsequent diseases

question

Describe interviewer bias

answer

systematic difference in soliciting, recording, or interpreting information that occurs in studies using in-person or telephone interviews *can occur in all types of study design

question

Typical sources of interviewer bias

answer

Case-control: interviewers are aware of the disease status of a subject and questions cases and controls differently about exposures Cohort & Experimental: interviewers are aware of the exposure or tx status of a subject and query exposed and unexposed subjects differently about their diseases

question

Ways to avoid interviewer bias

answer

-mask interviewers to the subject's disease or exposure status -design standardized questionnaires consisting of closed-ended, easy-to-understand questions with appropriate response options -instruct interviewers on appropriate questioning techniques

question

Describe misclassification bias

answer

(measurement error) error in the classification of the exposure or the disease *most common form of bias

question

Typical sources of misclassification bias

answer

Case-control & retrospective: relevant exposures may have occurred many years before data collection making it difficult for subjects to recall exposure accurately; broad measure definitions used

question

Explain the difference between non differential and differential misclassification

answer

differential - refers to errors on one axis (exposure or disease) that are related to the other axis; the error occurs more often in either the case or control group; biases the results either toward or away from the null nondifferential - refers to errors on one axis that are unrelated to the other axis; if there is an error, it occurs with equal likelihood among diseased and non diseased individuals; dichotomous; biases towards the null

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