Measures of Association

Question 1

Name types of descriptive studies?

Answer 1

1. case reports
2. case series
3. cross sectional
4. ecological

Question 2

Name types of anaytical studies?

Answer 2

1. case control studies
2. cohort studies
3. randomized control tables
4. systematic reviews
5. quasi-interventional studies
6. ecological

Question 3

Between descriptive and analytical which one is experimental?

Answer 3

descriptive studies are never experimental but analytic studies may or may not be experimental

Question 4

Describe cohort studies?

Answer 4

start with exposed and not exposed then follow up for disease or no disease
- are used in studies of etiology
- It enables comparison of populations that have had a certain exposure to those with no exposure

Question 5

Describe case control studies?

Answer 5

start with have the disease (cases) and do not have the disease (controls) then follow up with were exposed and were not exposed
- are also used to address questions of etiology

Question 6

Describe experimental/intervention studies?

Answer 6

from a study population people are randomly assigned either the new treatment or a current treatment and see if improve or do not improve from each treatment

Question 7

What are measures of association?

Answer 7

A measure of association quantifies the relationship between exposure and disease among the two groups

Question 8

What are exposure factors?

Answer 8

refers to any factor that may be associated with an outcome of interest
e.g.
behaviour
genetic
time
person
place
environmental
social

Question 9

What are 2x2 tables in epidmiology?

Answer 9

used to summarize frequencies of disease and exposure and used for calculation of association

Question 10

The measures of association usually used in the design/studies are?

Answer 10

absolute risk difference and relative risk ratios or rates
1. Absolute
- Risk difference exposed - unexposed
2. Relative
Risk ratios
- Odds ratios exposed / unexposed
Note: Odds ratios are also used in cohort studies

Question 11

What is relative risk/risk ratio?

Answer 11

• Relative risk compares the risk of an event among a specific group with the risk in another group.
• The exposed group is the group of primary interest while the comparison group is called unexposed group.
• Demographic factors as sex (e.g., males versus females) and exposure to a suspected risk factor (e.g., did or did not eat potato salad) differentiates the groups.

Question 12

What is the equation for relative risk ratio?

Answer 12

• The ratio of the risk of disease in persons exposed compared to the risk in those unexposed
• Often, a measure of association between incidence of disease and exposure of interest
  RR = incidence rate of disease in exposed/incidence rate of diseases in non-exposed

Question 13

What is odds ratio?

Answer 13

Odds ratio is the ratio of the odds
of an exposure in the case group to the odds
of an exposure in the control group.
- Remember that Odds Ratios are usually higher than Risk ratios

Question 14

Describe the interpretation of relative risk ratio?

Answer 14

If RR = 1, Risk in exposed equal to risk in non-exposed (no association)
If RR > 1, Risk in exposed greater than risk in non-exposed (positive association; possibly causal)
If RR < 1, Risk in exposed less than risk in non-exposed (negative association; possibly protective)

Question 15

What are case control studies?

Answer 15

Studies are designed to determine if an exposure is associated with an outcome.
Note: Case-control studies are always retrospective – starts with an outcome then traces back to investigate exposures.

Question 16

How do you conduct case control studies?

Answer 16

Firstly, you identify the cases (a group known to have the outcome of interest) and the controls (a group known to be free of the outcome). Then, trace back in time to learn which subjects in each group had the exposure(s), comparing the frequency of the exposure in the case group to the control group.

Question 17

What are case control studies used for?

Answer 17

Commonly used to investigate rare diseases and outbreaks
- The researcher uses available data of the disease or outbreak.
- To measure association during data analysis, Odds Ratios are used

Question 18

Who participates in a case control studies?

Answer 18

• Case control studies enroll a group of persons with disease or outcome (“case-patients”) and a comparable group without disease (“controls”).
• The total study participants of interest are determined by the principal investigator. However, the total number of people with the outcome is not usually known.