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Re: st: calculating SMRs, examples?


From   "Svend Juul" <SJ@SOCI.AU.DK>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: calculating SMRs, examples?
Date   Tue, 13 Sep 2005 21:17:23 +0200

Raoul asked:
Are there any good websites or books out there that explain in detail how to calculate a standardized mortality ratio (SMR) with poisson regression using external rates? I find that the STATA manuals do not contain a lot of information regarding this topic, any suggestions?
----

I don't know how much you know, so this may be too basic:

Indirect standardization to obtain SMRs may be performed by Stata in several ways, among others:
-istdize- (see [R] dstdize)
-strate-  (see [ST] strate)
-poisson- (see [R] poisson)

I found -istdize- somewhat complex to work with; it requires quite a bit of date preparation, and some of the requirements don't seem very logical to me.

I found -strate- friendlier and more logical. It requires that you:
1. -stset-
2. -stsplit- the observations in age bands corresponding to the age groups in your reference dataset (reference population mortality rates)
3. -merge- the dataset and the reference file by age group.

Now, each observation represents a person-ageband with time at risk (pyrs = _t - _t0),  death (_d), and reference mortality rate (e.g. mrate):
    . strate , smr(mrate)

You may proceed from here to -poisson-; it requires the expected number of deaths:
   . gen edeaths = pyrs*mrate
   . poisson _d exposure(edeaths) , irr

Was this what you needed?

Svend

________________________________________________________

Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000 Aarhus C,  Denmark
Phone, work:  +45 8942 6090
Phone, home:  +45 8693 7796
Fax:          +45 8613 1580
E-mail:       sj@soci.au.dk
_________________________________________________________

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