RR (Relative risk)

RR (Relative risk)

1. 1. To test the existence and strength of the risk of the occurrence of the disease among the exposed group compared to the unexposed group

2. 2. Mainly on data from RCTs and cohort studies.

3. 3. Aka RISK RATIO

   • of the condition of interest (e.g. disease) in the treatment (or exposed) group, to the risk in the control group (in RCTs).
   • Cohort Studies
     • calculated where it is defined as the ratio or the risk of a given disease, in the exposed or at-risk group,
     • compared to the risk of the disease in unexposed group.
     • incidence of the disease is used to describe the disease patterns and then the RR is calculated in further analysis.

4. Interpretation

   • size of the RR is an effective index of the strength of a relationship between the exposure and the disease being investigated
   • Rules
     • RR =1, NO RISK
     • RR>1 , INCREASED RISK
     • RR <1, PROTECTIVE or positive in terms of the disease and the exposure

5. next step in the analysis of the study data is to ask if the RR is a statistically significant1 result.

   • could this result have happened by chance, or is it a “real” (or statistically significant) effect

6. confidence intervals (CI) TO TELL US REAL

   • examine the statistical significance
     • tell us whether the results might be a chance effect or not
       • but also illustrate how small or how large the true effect size might be.

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