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# Stata 4, Survival PowerPoint PPT Presentation

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.

Stata 4, Survival

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## Stata 4, Survival

Hein Stigum

Presentation, data and programs at:

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

H.S.

### Agenda

• Kaplan-Meier plots

• Cox regression

• Example

• Age at first intercourse

H.S.

### Survival data

Outcome:

• Unajusted analysis

• Kaplan-Meier

• Regression method

• Cox-regression

H.S.

### 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

stdesDescribe

H.S.

### 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

• Standard distribution functions

Time to eventT

Densityf(t)

Cumulative densityF(t)

• Survival functions

H.S.

H.S.

### Kaplan-Meier

• Survival function

• Syntax

sts graph, by(sex)KM survival plot

sts test sexlog-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

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

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

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

H.S.

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

stcox gender cohab partfrq

H.S.

### Proportion hazard test

Save residuals:

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

Test:

estat phtest, detail

H.S.

### Smoothed Schoenfeld residuals

estat phtest, plot(cohab)

H.S.

### 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

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

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

H.S.

### If proptional hazard fails

• Stratified Cox regression

• Separate analysis on time intervals

• Time dependent covariats