# [R] Relative Risk in logistic regression

John Sorkin JSorkin at grecc.umaryland.edu
Sun Feb 3 15:46:55 CET 2013

```Amin,
It is incorrect to use the relative risk as a measure of association in a logistic regression.  The measure of association in a logistic regression is the odds ratio. The odds ratio is an approximation of the relative risk. The approximation becomes progressively better as the disease becomes progressively rarer. Regardless of whether the disease is rare or not, inferences drawn from a logistic regression are valid. Please do not report a logistic regression using relative risk. It is not correct to do so.
John

John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)>>> aminreza Aamini <amin.r.fan at gmail.com> 2/3/2013 9:15 AM >>>
Dear Coleagues ,
As my friend John  mentined,* the measure of association from a logistic
regression is the odds ratio, not the relative risk*. but the point is in
follow-up studies, it is commonly preferred to estimate a risk ratio rather
than an odds ratio. Thats why im looking for RR in logistic models.
Bytheway thank you all for ur consideration.
Amin

On Sun, Feb 3, 2013 at 1:42 PM, Michael Dewey <info at aghmed.fsnet.co.uk>wrote:

> At 10:49 30/01/2013, aminreza Aamini wrote:
>
>> Hi all,
>> I am very grateful to all those who write to me
>> 1) how i  can  obtain relative risk (risk ratio) in logistic regression
>> in R.
>>
>
> @TECHREPORT{lumley06,
>   author = {Lumley, T and Kronmal, R and Ma, S},
>   year = 2006,
>   title = {Relative risk regression in medical research: models, contrasts,
>           estimators, and algorithms},
>   number = 293,
>   institution = {{UW} Biostatistics Working Paper Series},
>   keywords = {glm, Poisson},
>   url = {http://www.bepress.com/**uwbiostat/paper293<http://www.bepress.com/uwbiostat/paper293>
> }
>
> }
>
>
>  2) how to obtain  the predicted risk for a certain individual using
>> fitted regression model in R.
>>
>>
>> Amin.
>>
>
> Michael Dewey
> info at aghmed.fsnet.co.uk
> http://www.aghmed.fsnet.co.uk/**home.html<http://www.aghmed.fsnet.co.uk/home.html>
>
>

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