4. Estimating Risk (Relative risk, attributable risk, attributable risk fraction, odds ratio)

Question 1

What is the Relative risk (risk ratio)?

Answer 1

• used in cohort studies.
• The ratio of the risk in the exposed group to the risk in the unexposed group.

Question 2

How do you calculate the Relative risk (risk ratio)?

Answer 2

RR = a/(a + b)
———-
c/(c + d)

Question 3

interpretation of Relative Risk?

Answer 3

RR = 1 No association between exposure and disease
RR > 1 Exposure associated with ↑ disease occurrence (risk factor)
RR < 1 Exposure associated with ↓ disease occurrence (protective factor)

Question 4

what is the Attributable risk?

Answer 4

• it is a measure of the public health impact of a causative factor.
• it is the difference in risk between exposed and unexposed groups.
• The calculation of AR assumes that the occurrence of disease in the unexposed group represents the baseline or expected risk for the disease.

Question 5

How do you calculate the Attributable risk?

Answer 5

AR = a c
——- - ——–
a + b c + d

OR

AR% = (RR-1/RR) X100

Question 6

what is Odds ratio?

Answer 6

• used in case-control studies.
• OR is another measure of association that quantifies the relationship between an exposure with two categories and health outcome.
• Represents the odds of exposure among cases vs odds of exposure among controls.

Question 7

What is Case-Control study?

Answer 7

• a type of observational study in which two existing groups differing in outcome are identified and compared on the basis of some supposed causal attribute.
• Case–control studies are often used to identify factors that may contribute to a medical condition by comparing subjects who have that condition/disease (the “cases”) with patients who do not have the condition/disease but are otherwise similar (the “controls”).