What does absolute risk reduction measure?

Absolute risk reduction measures the difference in risk between treatment and control groups. It quantifies how much the risk of a particular outcome is decreased due to a specific intervention compared to a control treatment. By comparing the event rates in both groups, absolute risk reduction provides a straightforward, intuitive number that represents the impact of the treatment.

For instance, if there are 20% of patients in the control group experiencing an event and 10% experiencing it in the treatment group, the absolute risk reduction is 10%. This figure directly informs clinicians and patients about the effectiveness of a treatment in clear, actionable terms.

The other options do not accurately capture what absolute risk reduction refers to. The total number of events prevented by treatment relates more to the concept of number needed to treat, while the calculation of the number of patients needed to treat derives from absolute risk reduction but is not the measure itself. The percentage of risk in the control group pertains to the baseline risk but does not reflect the comparative impact of the treatment. Hence, understanding absolute risk reduction is essential for interpreting clinical trial results effectively.