Question

The ratio of the risk of disease among those exposed to a factor to the risk among those not exposed is defined as:

• A. Relative risk
• B. Odds ratio
• C. Attributable risk
• D. None of the above

Hint:

A ratio (not a difference) of incidence in exposed versus non-exposed.

Answer 1

The Correct Option is A

Step 1: The question asks for the measure that compares the risk in an exposed group to the risk in a non-exposed group. This ratio is the Relative Risk (RR), also called the risk ratio. Step 2: It is calculated as \[RR = \frac{\text{incidence of disease among the exposed}}{\text{incidence of disease among the non-exposed}}.\] An RR of 1 means exposure has no effect on the outcome, RR \(>\) 1 means exposure increases risk, and RR \(<\) 1 means exposure is protective. Step 3: RR is the key measure of association in cohort studies, where incidence can be measured directly. Step 4: The distractors are wrong because the odds ratio is the ratio of odds (used mainly in case-control studies), while attributable risk is the difference (not the ratio) between the two incidences, representing the excess risk due to exposure. Hence the answer is Relative risk.