Relative risk, Attributable risk, Population attributable risk in cohort study #bcbr #relativerisk
Channel: SPM & Research with Dr Rock Britto
Date: 2023-08-29

The relative risk (RR), also known as the risk ratio, is a statistical measure used in epidemiology and medical research to quantify the strength of the association between an exposure (such as a risk factor or treatment) and an outcome (such as a disease or health condition). It compares the risk of an event occurring in one group (exposed to the factor) to the risk of the same event occurring in another group (unexposed or having a different level of exposure).

The formula for calculating the relative risk is:

Relative Risk (RR)
=
Risk of Event in Exposed Group
Risk of Event in Unexposed Group
Relative Risk (RR)= 
Risk of Event in Unexposed Group
Risk of Event in Exposed Group
​
 

Key points about the relative risk include:

Interpretation:

An RR greater than 1 indicates that the event is more likely to occur in the exposed group compared to the unexposed group. This suggests a positive association between the exposure and the outcome.
An RR less than 1 indicates that the event is less likely to occur in the exposed group, implying a negative association or a protective effect.
Interpretation of RR Values:

RR = 1: No association between exposure and outcome.
RR more than 1: Positive association, higher risk in the exposed group.
RR less than 1: Negative association, lower risk in the exposed group.
Advantages:

The relative risk provides a clear and intuitive measure of the strength of an association.
It's particularly useful for comparing the risk of outcomes between groups in prospective cohort studies and randomized controlled trials.
Limitations:

The relative risk cannot be calculated if the risk of the outcome is zero in either group.
It can overestimate the risk when the outcome is common in the population.
Confidence Intervals:

Like other measures, the relative risk is often reported with a confidence interval (CI) to indicate the level of uncertainty around the estimate.
If the 95% CI includes 1, the result is not statistically significant, suggesting no significant association.
If the 95% CI does not include 1, the result is statistically significant, indicating a significant association.
The relative risk is a fundamental measure for understanding the relationship between exposures and outcomes. Researchers use it to assess the impact of risk factors, interventions, or treatments on the occurrence of specific events. As with any statistical measure, the interpretation of relative risk should consider the study design, potential biases, and the context of the research question.
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