Lecture 5A, part 2

Question 1

What is assessed at the same time in cross-sectional studies?

Answer 1

Exposure and outcome

Question 2

What studies can infer causality?

Answer 2

Experimental

Question 3

In experimental studies, who assigns and exposure and non-exposure?

Answer 3

Investigator

Question 4

Strengths of ecological studies

Answer 4

Quick, easy, and inexpensive
Useful for looking at the impacts of large-scale changes or interventions
Ecologic effects may be of interest/transmission dynamics at the pop level

Question 5

Limitations of ecological studies

Answer 5

May be difficult to detect subtle or complicated relationships
Cannot look at cause and effect in individuals
Ecological fallacy/bias

Question 6

Definition of ecological fallacy/bias

Answer 6

An error in deduction that involves deriving conclusions about individuals solely on the basis of group data analysis
-An association btwn variables on an aggregate level does not necessarily represent the association that exists at the individual level

Question 7

Components of experimental studies

Answer 7

Research question involves a prevention or tx
Small effect expected
Trial is ethical, feasible, and financially possible

Question 8

Components of observational studies

Answer 8

Research question involves a prevention, tx, or causal factor
Moderate or large effect expected
Trial not ethical, not feasible, or too expensive

Question 9

Experimental study definition

Answer 9

Any study in which the investigator actively manipulates the exposure to evaluate the role of that exposure in the prevention or tx of dz

Question 10

What are common types of experimental studies?

Answer 10

Field trials
Community trials
Clinical trials (early phases)
Randomized control trials (considered the “gold standard” of epidemiological research)
Pragmatic trials

Question 11

Strengths of experimental studies

Answer 11

Reduces variation by extraneous factors through 3 strategies: randomization, placebo, blinding
Good info on exposure and dz
Study pop chosen based on eligibility criteria, clearly defined comparison group

Question 12

Limitations of experimental studies

Answer 12

Study pop must be large enough to detect whether there is a true difference between the tx and comparison groups
Ethical issues (cannot study harmful effects)
Non-compliance, f/u
Very expensive, time-consuming

Question 13

Non-experimental studies include ______ and ____ studies

Answer 13

Cohort, case-control

Question 14

What is the goal of non-experimental (observational) studies?

Answer 14

Simulate the results of an experiment had one been possible

Question 15

What is involved in cohort studies?

Answer 15

Follow a group of ppl with a common characteristic or experience (the cohort) over time and measure the occurrence of dz across predetermined exposure or risk categories

Question 16

Selection process in cohort studies

Answer 16

Select ppl without the outcome of interest, categorize them based on their exposure, and follow for the development of dz

Question 17

How are ppl classified in cohort studies?

Answer 17

Based on their initial exposure date

Question 18

How can special cohorts be used in cohort studies?

Answer 18

To study the health defects of rare exposures

Question 19

Timing of cohort studies

Answer 19

Can be either prospective or retrospective

Question 20

Strengths of cohort studies

Answer 20

Clearer temporality
Efficient for investigating rare exposures
Can evaluate a large number of possible health effects of a single exposure

Question 21

Limitations of cohort studies

Answer 21

Data collection- need reliable sources of data for exposures, outcomes, and confounders over time
Time and money
Loss to f/u, not good for dynamic pops

Question 22

What is involved in case-control studies?

Answer 22

Select ppl with the outcome of interest (cases) and ppl without the outcome of interest (controls) and then classify them all according to their exposure status

Question 23

Who are ppl selected in case-control studies?

Answer 23

Based on their outcome status

Question 24

In comparison to cohort studies, how are case-control studies viewed?

Answer 24

Inferior alternative

Question 25

What is the modern view of case-control studies?

Answer 25

They are an efficient way to learn about the relationship between an exposure and a dz