Introduction to Stata 8 - (GRIPS

Including age in the analysis
stset data with ageout as the time-of-exit variable, agein as the time-of-entry
variable:
. // c:\dokumenter\proj1\gen.st.cancer2.do
. use c:\dokumenter\proj1\cancer1.dta , clear
. stset ageout , enter(time agein) failure(died==1) id(lbnr)
. summarize
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
lbnr | 48 24.5 14 1 48
... |
_st | 48 1 0 1 1
_d | 48 .6458333 .4833211 0 1
_t | 48 57.61966 5.444583 49.87939 68.70284
_t0 | 48 56.328 5.659862 47.97637 67.73915
. save c:\dokumenter\proj1\st.cancer2.dta
The sts and stcox analyses as shown above now must be interpreted as age-adjusted
(delayed entry analysis). Summary of time at risk and age-specific incidence rates:
stptime , at(45(5)70) by(drug) // 5 year age intervals
stsplit
[ST] stsplit
To look at the influence of age at incidence or survival, stsplit the data, expanding each
observation to an observation for each age interval:
. // c:\dokumenter\proj1\gen.stsplit.cancer2.do
. use c:\dokumenter\proj1\st.cancer2.dta , clear
. stsplit agegr , at(45(5)70)
. summarize
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
lbnr | 61 26.37705 14.03586 1 48
drug | 61 1.967213 .8557105 1 3
drug01 | 61 .6229508 .4886694 0 1
agein | 61 55.58628 5.651005 47.09552 67.87458
ageout | 61 56.87054 5.563221 49.01218 68.8737
risktime | 61 1.412568 .8856398 .0833333 3.25
died | 48 .6458333 .4833211 0 1
_st | 61 1 0 1 1
_d | 61 .5081967 .5040817 0 1
_t | 61 56.87054 5.563221 49.01218 68.8737
_t0 | 61 55.85415 5.610502 47.09552 67.87458
agegr | 61 54.01639 5.832357 45 65
. save c:\dokumenter\proj1\stsplit.cancer2.dta
The data now has 61 observations with events and risktime distributed to the proper age
intervals. Describe risktime etc. by:
bysort drug: stsum , by(agegr)
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