Cohort Study Design Chapter 9

Question 0

Fill in the blank:

causal and preventative factors can be identified through_______of________ or subgroups of individuals in a population in______________

Answer 0

Systematic investigation

Different populations

Different places or times

Question 1

What are the basic assumptions of epidemiology?

Answer 1

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

Question 2

Hierarchy of research evidence is a pyramid start at the bottom and explain the layers as it goes up

Answer 2

Ideas opinions

Case reports

K-series

Case-control studies

Cohort studies

Randomized controlled studies

Randomized controlled double-blind studies

Question 3

What does analytical epidemiology study

Answer 3

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

Question 4

What does descriptive epidemiology study

Answer 4

Person, place and time

Question 5

What is the most important element of study design for analytical epidemiology

Answer 5

What group you compare is the most Porten element of study design

Question 6

Define Association

(Bolded probably will be on the exam)

Answer 6

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

Question 7

Explain why we assess the validity of association

Answer 7

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

Question 8

Hypothesis formulation

Explain the difference between the null hypothesis and the alternative hypothesis cite examples

Answer 8

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)

Question 9

List the guidelines for developing a hypothesis

Answer 9

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

Question 10

List study designs used by epidemiologist to evaluate hypothesis

Answer 10

Cohort studies- Prospective and retrospective

(randomized trial)

Case-control studies

Question 11

List the steps in a cohort study

Answer 11

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

Question 12

When designing a 2 x 2 for a cohort study what should the titles be for the columns and the rows?

Answer 12

The columns from left to right disease develops, disease does not develop

The rose from top to bottom exposed, not exposed

Question 13

In a 2 x 2 for a cohort study explain what is contained in each of the four boxes ABCD

Answer 13

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)

Question 14

In cohort studies the measure of association between exposure and disease is termed what?

What is the formula?

Answer 14

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)

Question 15

When interpreting relative risk as a measure of association and cohort studies what do the values mean

Answer 15

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

Question 16

How do you epidemiologist express relative risk?

Answer 16

Rate ratio

20.0/17.4 = 1.61

Question 17

How do you public health professionals express relative risk

Answer 17

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

Question 18

What is the formula for expressing relative risk (risk ratios) when the relative risk is > 1

Answer 18

(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

Question 19

Explain how to express relative risk when <1

Answer 19

(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

Question 20

List advantages to cohort studies

Answer 20

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

Question 21

List the disadvantages to cohort studies

Answer 21

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