The odds reduction expresses, for odds, what relative risk reduction expresses for risks. Just as the relative risk reduction is (1 – relative risk) the odds reduction is (1 – relative odds) (the relative odds and odds ratio being synonymous). Thus, if a treatment results in an odds ratio of 0.6 for a particular outcome, the treatment reduces the odds for that outcome by 0.4.
The proportional increase in frequency of harmful outcomes between experimental and control participants. It is calculated by dividing the frequency or risk of harmful outcome in the experimental group minus the frequency or risk of harmful outcome in the control group by the frequency or risk of harmful outcome in the control group. If an adverse outcome occurs in 15% of the exposed and 10% of the unexposed the relative risk increase is 50%. Typically used with a harmful exposure.