Risk

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susumandrai

Junior Member
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Feb 7, 2012
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Suppose your absolute risk of developing a cardiac disease in your lifetime is 73 in 1000. Taking a cholesterol reducing drug, such as simvastatin, reduces the relative risk by 18%.
How many people have to take this drug to expect one person to benefit?

Answer is 77 people but I can't figure how..
Any help will be appreciated.
Thanks
 
susumandrai said:
Suppose your absolute risk of developing a cardiac disease in your lifetime is 73 in 1000. Taking a cholesterol reducing drug, such as simvastatin, reduces the relative risk by 18%.
How many people have to take this drug to expect one person to benefit?

Answer is 77 people but I can't figure how..
Any help will be appreciated.
Thanks
Click to expand...
absolute risk of developing a cardiac disease in your lifetime is 73 in 1000

risk of developing a cardiac disease - after taking the drug - is 18% reduced [math] \to \ \ [/math] ? in 1000
 
If absolute risk decreases by 18%, then 0.073 x 0.82 = 0.05986 = 60 in 1000 approx.
How does this lead to 77?
 
I think I got the answer:
Absolute risk reduction (ASR) = risk with exposure - risk without exposure
ASR = O.073 - 0.060 = 0.013

Number needed to treat = 1 / ASR
= 1 / 0.013
= 77 (approx)

Hope this is correct

Thanks :)
 
I'm not familiar with all the terminology here (absolute vs relative, "ASR"), but I agree with you. The change in probability is 0.072*0.18 = 0.01314, and 1/0.01314 = 76.1. They must round up.
 
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