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?
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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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