In science & esp medicine, risk is a tricky thing to contend with - besides of course being a mathematical one - and involves many considerations in order to have a more fulsome understanding.
In this post @LizMarnik and I attempt to explain these concepts. 1/9
In simple terms, risk is the probability of an event occurring. In statistical terms, the risk of an event occurring is simply defined as its probability.
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Take a fictitious disease - AhCrap. Risk of dying due to this is 2/million & using GoodStuff tx can reduce risk to 1/million.
While relative risk reduction is 50%, only one less person out of 1M w AhCrap are saved by GoodStuff, making absolute risk reduction fairly small.
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Because the risk of dying decreased from two in a million to one in a million, the relative risk decreased by 50%.
However, the absolute risk only changed from 2/1,000,000 to 1/1,000 000, that is, a difference of 0.00005%.
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A few other things to consider, such as:
what the likelihood of the risk occurring is and what the risk-benefit analysis including downstream impacts are.
The examples in this slide demonstrate these points to help put overall risk into context.
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Changing gears, let’s talk about cumulative risk, which is the combined risk from multiple exposures or behaviors over time.
This requires several pieces of information, such as time period, how many exposures, risk assoc w each & how other behaviors impact the likelihood.
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Take this example: risk of TerribleOutcome after the first time one has BadInfection is 2 in 100 or 2%. Risk after each subsequent infection is 1 in 100 or 1%.
Cumulative risk in this example of person having TerribleOutcome over lifetime, i.e. a 15 year period is 3.95%
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So as we can see in this situation, while the individual risk of a subsequent Badinfection may infact be lower than the first infection, the cumulative risk of developing BadOutcome is higher with each additional infection.
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Understanding these can help you make informed decisions.
Putting into context how likely risk is, what impact of the risk is, what overall risk-benefit analysis is & downstream impacts are all important considerations when assessing & evaluating risks + decisions.
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