Relative risk reduction

In this article, we will explore the impact and influence of Relative risk reduction on contemporary society. Since its emergence, Relative risk reduction has captured the attention of millions of people around the world and has gained a prominent place in popular culture. Over the years, Relative risk reduction has demonstrated his ability to shape opinions, inspire movements and challenge established norms. In this sense, it is crucial to carefully examine how Relative risk reduction has contributed to the evolution of society in different aspects, from politics and economics to the artistic sphere and individual expression. This article aims to shed light on the fundamental role Relative risk reduction has played in our daily lives and its influence on the way we perceive the world around us.

Illustration of two groups: one exposed to a treatment, and one unexposed. Exposed group has smaller risk of adverse outcome (RRR = 0.5).
The group exposed to treatment (left) has the risk of an adverse outcome (black) reduced by 50% (RRR = 0.5) compared to the unexposed group (right).

In epidemiology, the relative risk reduction (RRR) or efficacy is the relative decrease in the risk of an adverse event in the exposed group compared to an unexposed group. It is computed as , where is the incidence in the exposed group, and is the incidence in the unexposed group. If the risk of an adverse event is increased by the exposure rather than decreased, the term relative risk increase (RRI) is used, and it is computed as . If the direction of risk change is not assumed, the term relative effect is used, and it is computed in the same way as relative risk increase.

Numerical examples

Risk reduction

Example of risk reduction
Quantity Experimental group (E) Control group (C) Total
Events (E) EE = 15 CE = 100 115
Non-events (N) EN = 135 CN = 150 285
Total subjects (S) ES = EE + EN = 150 CS = CE + CN = 250 400
Event rate (ER) EER = EE / ES = 0.1, or 10% CER = CE / CS = 0.4, or 40% —
Variable Abbr. Formula Value
Absolute risk reduction ARR CER − EER 0.3, or 30%
Number needed to treat NNT 1 / (CER − EER) 3.33
Relative risk (risk ratio) RR EER / CER 0.25
Relative risk reduction RRR (CER − EER) / CER, or 1 − RR 0.75, or 75%
Preventable fraction among the unexposed PFu (CER − EER) / CER 0.75
Odds ratio OR (EE / EN) / (CE / CN) 0.167

Risk increase

Example of risk increase
Quantity Experimental group (E) Control group (C) Total
Events (E) EE = 75 CE = 100 175
Non-events (N) EN = 75 CN = 150 225
Total subjects (S) ES = EE + EN = 150 CS = CE + CN = 250 400
Event rate (ER) EER = EE / ES = 0.5, or 50% CER = CE / CS = 0.4, or 40% —
Variable Abbr. Formula Value
Absolute risk increase ARI EER − CER 0.1, or 10%
Number needed to harm NNH 1 / (EER − CER) 10
Relative risk (risk ratio) RR EER / CER 1.25
Relative risk increase RRI (EER − CER) / CER, or RR − 1 0.25, or 25%
Attributable fraction among the exposed AFe (EER − CER) / EER 0.2
Odds ratio OR (EE / EN) / (CE / CN) 1.5

See also

References

  1. ^ Porta, Miquel, ed. (2014). "A Dictionary of Epidemiology". Dictionary of Epidemiology - Oxford Reference. Oxford University Press. doi:10.1093/acref/9780199976720.001.0001. ISBN 9780199976720. Retrieved 2018-05-09.
  2. ^ Szklo, Moyses; Nieto, F. Javier (2019). Epidemiology : beyond the basics (4th. ed.). Burlington, Massachusetts: Jones & Bartlett Learning. p. 97. ISBN 9781284116595. OCLC 1019839414.
  3. ^ J., Rothman, Kenneth (2012). Epidemiology : an introduction (2nd ed.). New York, NY: Oxford University Press. p. 59. ISBN 9780199754557. OCLC 750986180.{{cite book}}: CS1 maint: multiple names: authors list (link)
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