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Stata 4, Survival. Hein Stigum Presentation, data and programs at: http://folk.uio.no/heins/. Agenda. Kaplan-Meier plots Cox regression Example Age at first intercourse. Survival data. Outcome:. Unajusted analysis Kaplan-Meier Regression method Cox-regression. Survival data setup.

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Stata 4 survival

Stata 4, Survival

Hein Stigum

Presentation, data and programs at:

http://folk.uio.no/heins/

H.S.


Agenda
Agenda

  • Kaplan-Meier plots

  • Cox regression

  • Example

    • Age at first intercourse

H.S.


Survival data
Survival data

Outcome:

  • Unajusted analysis

    • Kaplan-Meier

  • Regression method

    • Cox-regression

H.S.


Survival data setup
Survival data setup

  • Status and time

    generate status=!missing(DebutAge)

    generate time=DebutAge

    replace time=Age if status==0

    generate time2=time+uniform() avoid ties

  • Set and describe

    stset time, failure(status==1) Set data

    stdes Describe

H.S.


Setting the timescale
Setting the timescale

Time = time since diagnosis in years:

stset dateexit, failure(dead==1) origin(datediag) scale(365.25)

Time = age in years:

stset dateexit, failure(dead==1) origin(datebth) enter(datediag) scale(365.25)

H.S.


Mathematical functions
Mathematical functions

  • Standard distribution functions

    Time to event T

    Density f(t)

    Cumulative density F(t)

  • Survival functions

H.S.



Kaplan meier
Kaplan-Meier

  • Survival function

  • Syntax

    sts graph, by(sex) KM survival plot

    sts test sex log-rank test

    stci, p(50) by(sex) time to 50% failure

    sts list, at(5 10 30) survival at time 5,…

H.S.


Kaplan meier all
Kaplan-Meier, all

sts graph, fail gwood tmin(8) tmax(30) noorigin

Age at 50% failure:

stci, p(50)

18.4 (18.1,18.8)

H.S.


Kaplan meier by sex
Kaplan-Meier, by sex

sts graph, fail by(gender) tmin(8) tmax(30) noorigin

Age at 50% failure: :

stci, p(50) by (gender)

Males: 18.6 (18.3,19.0)

Females: 18.1(17.8,18.9)

Log-rank test:

sts test gender

p-value=0.3

H.S.


Hazards
Hazards

sts graph, hazard by(gender) width(2)

H.S.


Cox regression

hazard

baseline

RR

Cox regression

  • Model

  • Syntax

    • stcox x1 x2

  • Proportional hazard test

    • stcox x1 x2, schoenfeld(sc*) scaledsch(ssc*)

    • estat phtest, detail

    • estat phtest, plot(x1)

H.S.


Full model
Full model

stcox gender cohab partfrq

H.S.


Proportion hazard test
Proportion hazard test

Save residuals:

stcox gender cohab partfrq, schoenfeld(sc*) scaledsch(ssc*)

Test:

estat phtest, detail

H.S.


Smoothed schoenfeld residuals
Smoothed Schoenfeld residuals

estat phtest, plot(cohab)

H.S.


Baseline hazard
Baseline hazard

stcox gender cohab partfrq, basesurv(bsurv) basehc(bhaz)

stcurve, hazard at(gender=1 cohab=1 partfrq=0) range(8 30) width(1)

H.S.


Predicted survival
Predicted survival

stcurve, survival at1(gender=1 cohab=1 partfrq=0)

at2(gender=2 cohab=1 partfrq=0)

H.S.


If proptional hazard fails
If proptional hazard fails

  • Stratified Cox regression

  • Separate analysis on time intervals

  • Time dependent covariats

  • Additive model

H.S.


Some cox options
Some Cox options

stcox drug age, strata(sex) Stratified

stcox drug age, shared(family) Frailty

stcox drug age, tvc(varlist) Timevar cov

H.S.


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