question

Define : association:

answer

statistical dependence between 2 or more events, characteristics of other variables

question

Define/title of following image:

answer

web of causation

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What is a graphic, or representation of complex sets of events or conditions caused by an array of activities connected to a common core or common experience or event:

answer

web of causation

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What is something that increases the chances of getting a disease?

answer

risk factor

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What is a behaviour that puts you at risk for a bad consequence?

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at risk behaviour

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What is a conclusion about the presence of a health-related state or event and reason for its existence:

answer

causal inference

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What are factors or conditions already present that produce a susceptibility or disposition in a host to a disease or condition without really causing it:

answer

predisposing factors

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(T/F) No way to prove causal associations for most chronic disease and conditions

answer

True

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(T/F) Causal inference is a simple process:

answer

False

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Define Biologic gradient:

answer

evidence of dose-response relationship; an increased amount of exposure leads to increased risk of developing disease

question

Biologic gradient in relation to exposure is related to what?

answer

the evidence of a does-response relationship

question

What is the significance of Temporal Sequence?

answer

- exposure must precede disease - in diseases with latency periods, exposures must precede the latent period - in chronic diseases, often need long-term exposure for disease induction

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Cite the difference between Positive reinforcing factors and Negative reinforcing factors:

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- Positive: support, enhance, and improve the control and prevention of the causation of the disease - Negative: factors that help aggravate and perpetuate disease, conditions, disability or death

question

Cite the difference between Direct and Indirect causal associations with an example for each:

answer

1. Direct causal association: no intermediate factor and is more obvious; eliminating the exposure will remove adverse health outcomes. (ex: exposure to staphy. pathogens result in illness) 2. Indirect causal association: involves 1 or more intevening factors; often much more complicated. (ex: high fat diet is associated with polyps, and polyps are associated with colon cancer)

question

Members of households of a person with TB don't uniformly acquire the disease from the index case. Cite 3 factors which could affect the occurrence of infection:

answer

- immune status - genetic susceptibility - exposure dose

question

Why is it important for us to be able to distinguish between an association due to a causal relationship and an association due to confounding (non-causal)?

answer

Answer: it makes a tremendous difference from both clinical and public health standpoints. If the relationship is causal: will succeed in reducing the risk of CHD if we lower cholesterol levels If relationship is due to confounding: then the increased risk of CHD is caused by factor X. Therefore, changes in the level of serum cholesterol will have no effect on the risk of CHD

question

Comment on the following graph and cite 3 possible findings (% of distribution by birth weight of infants of mothers who did not smoke during pregnancy vs. those that did)

answer

- entire weight distribution curve is shifte left in babies born to smokers - reduction in birth weight is not a result of shorter pregnancies - babies of smokers are smaller than those of non-smoker at each gestation age

question

Cite the types of causal associations:

answer

1. Direct causal associations: no intermediate factor and is more obvious ; eliminating the exposure will eliminate the adverse outcome 2. Indirect causal associations: involves 1 or more intervening factors ; often much more complicated; many risk factors

question

Cite the difference between necessary and sufficient causes:

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1. necessary = an exposure that is required for a certain outcome to happen ; is always associated with that outcome 2. sufficient = exposure that by itself will produce a particular outcome, but it may not be the only cause of outcome. So, the outcome may occur without the exposure if it is also caused by other exposures

question

Define: Necessary AND sufficient cause:

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a factor is both necessary and sufficient for producing the disease ex: lead exposure = lead poisoning

question

Define: necessary but not sufficient cause:

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each factor is necessary but not, in itself, sufficient to cause the disease; multiple factors are needed ex: alcoholism

question

Define: sufficient but not necessary causes:

answer

factor is not required to produce a specified outcome BUT when present, is able to cause the outcome by itself. Means that there are other causes of outcome ex: exposure X = outcome Y exposure Z ALSO = outcome Y

question

Define: neither sufficient nor necessary causes:

answer

a cause that isn't required to produce the outcome and when present is not able to cause the outcome by itself; hence there are other causes of the specified disease

question

How can we measure the strength of an association?

answer

- odds ratio - risk ratio

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(T/F) epidemiology determines the cause of a disease in a given individual:

answer

False

question

(T/F) epidemiology determines the relationship or association between a given exposure and frequency of disease in populations

answer

True

question

Cite the difference between causal inference and statistical inference:

answer

1. Causal inference: provides scientific basis for medical and public health action; not a simple process; needs judgement and interpretation 2. Statistical inference: use of info from a sample to draw conclusions about the population from which sample was taken

question

John Stuart formed 3 methods of hypothesis formulation in disease etiology. What are they:

answer

- method of difference - method of agreement - method of concomitant variation

question

Define Temporality:

answer

exposure must precede disease

question

Importance of temporality with an example (asbestos and lung CA)

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- clarifying the order in which Exposure and disease occur - the length of the interval between the E and D ex: asbestos linked to increased risk of lung cancer BUT latent period between the exposure and appearance of lung can at least 20years

question

Define Biological gradient:

answer

dose-response relationship (increase amount of exposure with increase risk of disease)

question

Cite an example that shows the importance of coherence in difference epidemiologic patterns:

answer

presence of serological ____________ of Hep. B infection is associated with greatly increase rates of liver cancer. Those who have liver cancer have the genome for Hep. B

question

Define Specificity:

answer

an exposure is associated with only one disease, or the disease is associated with only one exposure

question

Match the following letters with numbers: a. attack rate b. person-time rate c. Berkson's bias d. healthy worker effect 1. incidence density 2. results in biases RR 3. results in underestimation of OR 4. cumulative incidence rate

answer

a = 4 b = 1 c = 3 d = 2

question

Which of the following is not a type of selection bias: a. health worker effect b. loss to follow-up c. Neyman bias d. all of the above are types of selection bias in cohort studies

answer

c - neyman bias

question

Which of the following is the most time consuming and costly study design? a. case control b. retrospective cohort c. prospective cohort d. cross-sectional

answer

c - prospective cohort

question

A valid statistical association in any analutical study design requires consideration of confounding. What is confounding?

answer

when an extrinsic factor influcences the disease outcome, and independent of that relationship, also influences the exposure affects both exposure and disease outcome

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(T/F) Establishing a valid statistical association is a necessary part of establishing a cause-effect relationship

answer

True

question

(Chance/Bias/Confounding) A case-control study showed that a strong negative association existed between exercise and heart disease

answer

confounding

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(Chance/Bias/Confounding) A case-control study found a positive association between self-reported alcohol use during pregnancy and fetal alcohol syndrome

answer

bias

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(Chance/Bias/Confounding) A randomized clinical trial measured the association between found that drug A versus placebo did not significantly improve 10 year survival

answer

chance

question

(Chance/Bias/Confounding) A cohort study found no statistical association between smoking and coronary heart disease (RR=1)

answer

chance

question

(Chance/Bias/Confounding) The interviewer in a case-control study assumed that an association existed between alcohol consumption and MI. She was aware of whether individuals in the study had MI or not

answer

bias

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Match the following (letter with numbers): a. blind b. increase sample size c. randomize 1. a way to control for confounding 2. a way to control for bias 3. a way to control for a chance finding

answer

a = 2 b = 3 c = 1

question

A precipitating factor is best defined as what?

answer

factors essential to the development of disease, conditions, injuries, disability and death

question

Match the following (letters with numbers) 1. method of difference 2. method of agreement 3. method of concomitant variation a. increased number of children not immunized against measles causes the incidence rate for measles to go up b. valley fever occurs only in the deserts of the southwestern US c. increasing trends in cigarette smoking is directly associated with increasing trends in lung CA in many diff. places in world

answer

1 = b 2 = c 3 = a

question

Which of the following is the best for establishing temporality? a. cross-sectional b. ecologic c- case-control d. experimental e. none of the above

answer

e. none of the above

question

Define random error:

answer

an error defined as the deviation of the total error from its average value (mean)

question

In contrast to systematic errors, the effect of the random errors may be reduced by ........... ?

answer

repitition of the experiment/observation and averaging the outcomes

question

_________________________________________________ is how close a number of measurements of the same quantity agree with each other, while ________________________________________________________ is how close the measurement is to the true value of the quantity being measured

answer

- the precision of measurement - the accuracy of measurement

question

_____________________________ - a random error appearing to cause an association between an exposure and an outcome

answer

chance

question

chance is caused by ____________________________ and it leads to _________________________

answer

- random error - unprecise results

question

The best way to avoid error due to random variation is ___________________________________________________________

answer

to increase the sample size

question

Avoiding bias at the design stage of a study is paramount because of the difficulty to ________________________________________________________________

answer

identify and account for it there after

question

CIte the types of bias:

answer

- selection bias - observational bias - confounding bias

question

A bias that results from selection of subjects into the sample or their allocation to treatment group producing a sample that is not representative of the population, or treatment groups that are systematically different

answer

selection bias

question

a phenomenon initially observed in studies of occupational diseases: workers usually exhibit lower overall death rates thatn the general populations because severly ill and chronically disabled are ordinarily exclded from employment

answer

healthy workers effect

question

a type of bias that results when cases and/or controls are recruited from hospital patients

answer

Berksonian bias

question

systematic differences in the way subjects remember or report exposures or outcomes

answer

recall bias

question

an interviewer's knowledge may influence the structure of questions and the manner of presentation which may influence responses

answer

interviewer bias

question

Define: loss to follow up:

answer

those that are lost to follow up, or who withdraw from the study may be different from thsoe who are followed for the entire study

question

Define: Hawthorne effect:

answer

an effect first documented at a Hawthorne manufacturing plant; people act differently when they know that they are being watched

question

Controls for confounding may be built into _____________________________ or ___________________________ of a study

answer

- the design - analysis stages

question

What are the aspects of design stage:

answer

- randomization (for experimental studies) - restriction (allow only those into the study who fit into narrow band of a potentially confounding variable) - matching (match cases and controls on the basis of the potential confounding variables - especially age and gender)

question

There are 2 kinds of analysis stage:

answer

1. Stratification: the process of grouping members of the population into relatively homogenous subgroups before sampling 2. Multivariate analysis: a generic term for any statistical technique used to analyze data from more than one variable

question

Cite 2 mechanisms that can produce selection bias:

answer

1. control selection bias 2. differential loss to follow up bias in a cohort study 3. self-selection bias - refusal to participate

question

Recall from participants can be faulty due to:

answer

a. systematic differences int he way subject remembers exposure and outcomes b. amplification of recollections - difficulty of tracking certain behaviours - reluctance to report embarassing moments

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