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Stata 4, Survival

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

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  1. Stata 4, Survival Hein Stigum Presentation, data and programs at: http://folk.uio.no/heins/ H.S.

  2. Agenda • Kaplan-Meier plots • Cox regression • Example • Age at first intercourse H.S.

  3. Survival data Outcome: • Unajusted analysis • Kaplan-Meier • Regression method • Cox-regression H.S.

  4. 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.

  5. 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.

  6. Mathematical functions • Standard distribution functions Time to event T Density f(t) Cumulative density F(t) • Survival functions H.S.

  7. Some relationships H.S.

  8. 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.

  9. 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.

  10. 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.

  11. Hazards sts graph, hazard by(gender) width(2) H.S.

  12. 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.

  13. Full model stcox gender cohab partfrq H.S.

  14. Proportion hazard test Save residuals: stcox gender cohab partfrq, schoenfeld(sc*) scaledsch(ssc*) Test: estat phtest, detail H.S.

  15. Smoothed Schoenfeld residuals estat phtest, plot(cohab) H.S.

  16. 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.

  17. Predicted survival stcurve, survival at1(gender=1 cohab=1 partfrq=0) at2(gender=2 cohab=1 partfrq=0) H.S.

  18. If proptional hazard fails • Stratified Cox regression • Separate analysis on time intervals • Time dependent covariats • Additive model H.S.

  19. 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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