Cohort Study Design Chapter 9 Flashcards
Fill in the blank:
causal and preventative factors can be identified through_______of________ or subgroups of individuals in a population in______________
Systematic investigation
Different populations
Different places or times
What are the basic assumptions of epidemiology?
Human disease does not occur at random; it is deterministic.
If the variables related to the disease could be controlled, or were known, the outcome could be predicted
Causal and vented factors can be identified through systematic investigation of different populations or subgroups of individuals and populations in different places or times
Hierarchy of research evidence is a pyramid start at the bottom and explain the layers as it goes up
Ideas opinions
Case reports
K-series
Case-control studies
Cohort studies
Randomized controlled studies
Randomized controlled double-blind studies
What does analytical epidemiology study
Analytical epidemiology studies the determinants of health (disease)
Variables of interest: exposures (risk factors, protective factors, predictor) and outcomes (disease, event)
Formulate hypothesis-compare the experience of two or more groups of subjects with respect to exposure and I’ll come
Test hypothesis what groups you compare is the most important element of design
What does descriptive epidemiology study
Person, place and time
What is the most important element of study design for analytical epidemiology
What group you compare is the most Porten element of study design
Define Association
(Bolded probably will be on the exam)
The statistical dependence between two variables
The degree to which the rate of disease in persons with a specific exposure is either higher or lower than the rate of disease among those without that exposure
We have to make a judgment of whether a cause-effect relationship between exposure and disease exist
Explain why we assess the validity of association
Does the observed association really exist
Is the association valid
Are there alternative explanations for association? For example could it be explained by chance, bias, confounding
Hypothesis formulation
Explain the difference between the null hypothesis and the alternative hypothesis cite examples
No hypothesis-no association between exposure in disease
Alternative hypothesis-there is an association between exposure in disease beyond random error or chance
One sided association is greater than expected or association is less than expected (example H pylori infection is associated with an increased risk of stomach ulcers)
Two-sided there is an association between (example sarcoidosis is associated with the use of coal stove)
List the guidelines for developing a hypothesis
State the exposure to be measured as specifically as possible
State the health outcomes as specifically as possible
Strive to explain the smallest amount of ignorance
List study designs used by epidemiologist to evaluate hypothesis
Cohort studies- Prospective and retrospective
(randomized trial)
Case-control studies
List the steps in a cohort study
Select two groups of individuals: exposed and not expose
Follow them through time
Determine the incidence of disease in both groups
Compare rates among the exposed to rates in the non-expose
Interpret the data
When designing a 2 x 2 for a cohort study what should the titles be for the columns and the rows?
The columns from left to right disease develops, disease does not develop
The rose from top to bottom exposed, not exposed
In a 2 x 2 for a cohort study explain what is contained in each of the four boxes ABCD
A-number of individuals who are exposed and have the disease
B-number who are exposed and do not have the disease
C-number who are not exposed and have the disease
D -number who are both non-exposed and non-diseased
Incident rates of disease can be determined by the sum of the Rows (exposed VS not exposed)
In cohort studies the measure of association between exposure and disease is termed what?
What is the formula?
Relative risk is the ratio of the two rates
RR = incidents in the exposed/incidents in the non-exposed
(A/A+B)/ (C/C+D)
When interpreting relative risk as a measure of association and cohort studies what do the values mean
If R R = 1
Risk in the exposed equal to the risk in the non-exposed (no Association)
If RR > 1
Risk in the exposed is greater than the risk and then on exposed (positive association)
If RR < 1
Risk in the exposed is less than the risk in the non-exposed (negative association) protective effect
How do you epidemiologist express relative risk?
Rate ratio
20.0/17.4 = 1.61
How do you public health professionals express relative risk
People who consume alcohol or approximately 1.6 times more likely to develop coronary heart disease compared with people who do not drink alcohol
Or
The risk of coronary heart disease is 60% greater and people who drink alcohol compared with people who do not drink alcohol
What is the formula for expressing relative risk (risk ratios) when the relative risk is > 1
(RR-1) X 100 = the percent increased change
Example:
If the relative risk is 1.60 then the ratio is 60 times more likely to develop the disease
Explain how to express relative risk when <1
(1-RR) x 100 = decrease in change
Example:
Vigorous exercisers are 0.5 times less likely to have MI than people who don’t exercise
List advantages to cohort studies
Multiple outcomes can be measured for anyone exposure
Can look at multiple exposures
Exposure is measured before the onset of disease; less potential for recall bias
Good for RARE EXPOSURES
Temporal relationship between exposure in disease
Allows examination of natural course of disease survival
List the disadvantages to cohort studies
Costly and time-consuming
Needs a large sample size
Lost to follow-up (subject move, die, no longer interested) bias
Participants me move between one exposure category
Knowledge of exposure status made by his classification of the outcome
Being in the study may alter participants behavior
Poor choices for the study of RARE DISEASE
Classification of individuals(Exposure outcomes that is) can be affected by changes in diagnostic procedures
