Questions tagged [proportional-hazards]

Proportional hazards is an assumption of the Cox proportional hazards model of survival analysis and some other models as well. The assumption is that a linear increase in the predictor will have a uniform multiplicative relationship with the hazard.

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1answer
41 views

Efficient influence function in proportional hazards model

I was hoping someone could help me with this problem in the cox proportional hazards model. I am given the following setup. T is a non-negative random variable with continous distribution and hazard ...
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Cox PH non-proportionality: time-dependent variable?

I am performing Cox regression modelling, searching for predictors for various clinical outcomes. Now, based on Schoenfeld residuals test, some of my binary predictors have p-value <0.05 with ...
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Would you used prediction from Cox or stratified KM for drawing survival curves and testing them?

Let's assume I have an experiment, where I track some event. I want to analyse the time to this event between two levels of a group G: g1 and g2 I want to do the comparative analysis in sub groups, ...
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Why do my survival curves generated by the Cox differ from Kaplan-Meier for the simplest model?

I was told, that the Cox with a single categorical covariate is equal to the Kaplan-Meier stratified by the levels of this covariate. But the two graphs below don't support it. I also use strata() in ...
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1answer
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Is doing Kaplan-Meier for 2 curves equivalent to ajdusting for a covarite or stratyfing in Cox? I want the HR for my KM curves

Using the R terminology (but this is software independent statistical problem), is survfit(surv_object ~ rx, data = ovarian) returning 2 Kaplan-Meier curves the ...
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Survival Analysis - Hazard Ratios of One - Interpretation and Model Fit

I am using Cox Proportional Hazards for a set of data. I continue to find variables with hazard ratios equal to one. I understand that these variables are not hazardous/protective to the life of the ...
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Assessing proportional hazards assumption: p-value from coxzph() vs. visual inspection of plot of scaled Schoenfeld residuals with time

The coxzph() function in the R package Survival shows a significant p-value for violation of the proportional hazards assumption ...
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2answers
55 views

Can it be said, that in case of non-proportional hazards, Cox returns average hazard ratio over the entire period?

I have read two opposite statements about the hazard ratios obtained from the Cox procedure in presence of non-proportional hazards. One is that the HR for a certain covariate, that fails this ...
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Which method of handling non-proportional hazards (here: crossed KM curves in 2+ points) would you prefer?

I have an experiment, where I compare two groups over time in frames of the time to event analysis. The Kaplan-Meier curves cross 3 times. It means, that the hazards ratios switch to the opposite side ...
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35 views

Why is there a linear and non-linear component of a pspline?

I am trying to fit a cox proportional hazards model with several categorical and one continuous covariate. The plot of martingale's residuals from the null model against the continuous term suggests ...
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1answer
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Sampling data from a Cox proportional hazard model [duplicate]

Is it possible to simulate event time T from a distribution that depends on two variables A and Z but the hazard function conditioning on A only follows a proportional hazards model?
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1answer
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All p-values rendered non-significant in Cox model after initializing coefficients from glmnet

I have a set of 200 genes that are split into numerical high and low, encoded as (1/2). I have set this variable this way for linearity of the model. Also, stratified by cancer and normal cases. I ...
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1answer
29 views

How to model competing risks with frailties in R

I am trying to figure out if (a) a competing risks model with frailty-terms is the right method for my data and (b) how to estimate such models in R. My data consists of N ~ 150 individuals with a ...
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1answer
44 views

flexsurvreg - shape and scale proportional hazard model

Please see below codes and plot for fitted curves to Kaplan-Meier data (weibull in this example) using the ovarian data. Based on the estimates, the shape and scale of the fitted Weibull distribution ...
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2answers
222 views

hazard ratio: are they normally distributed?

I am looking at forest plots (in the context of meta-analyses of clinical trials). I see values for hazard ratios, together with 95% confidence interval. My question: to compute this confidence ...
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1answer
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Cox PH hypothesis and time-dependent covariates

The dataset I am working with is of this form: ...
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1answer
81 views

Is the proportional hazards assumption violated (interpreting Schoenfeld residuals)? What is my best option if so?

I am using an extension of the Cox model in the counting process format (Andersen-Gill model), with time-dependent covariates. The analysis is investigating the effect of an intervention on hospital ...
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Point estimate for exponential of two variables

a proportional hazard model has two binary covariates. X1 for treatment (placebo and active drug) and X2 for gender. X1=1 for active drug and X2=1 for male. The estimated parameters are β1=0.4 and β2=-...
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2answers
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How to model survival analysis when proportional hazards assumption is not met and stratification and time-varying are not possible?

I am modelling a survival analysis over a rather long follow-up period (10 years). My exposure is time-invariant and clearly violates the proportional hazards assumptions so Cox Proportional Hazards ...
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1answer
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Is it possible and how to predict individual survival curve after Cox regression?

Taking the veteran dataset of a two-treatment, randomized trial for lung cancer in the R package survival as an example, where <...
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Simulating Proportional Hazards Weibull model with 2 binary variables, incorrect estimation?

I am simulating survival times from a Weibull(5,3), and I also simulate 2 spurious binary covariates. When I fit a proportional hazards model with Weibull baseline, ...
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1answer
79 views

Which function of time to use in a Cox Regression for time-varying coefficients?

I have a Cox regression model where the outcome is a non-recurring event. Within the model, two categorical variables violate proportional hazards, and I have currently extended it to account for time-...
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1answer
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Doing Cox univariate analyses followed by multivariable analysis on significant variables?

I have collected a dataset on a group of patients with a rare disease where not much is known. These patients can have an outcome, X, which has been seen in 50 of the 300 patients. I want to find out ...
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Baseline hazard and survival curves in Cox regression [duplicate]

The idea behind Cox regression in survival analysis is that it does not require knowing the baseline hazard rate, $\lambda_0(t)$. Yet, one often needs this rate, and many software packages do estimate ...
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1answer
35 views

Relation between hazard and survival functions

I have recently began using pysurvival package, for standard Cox regression. Their CoxPHModel predicts both the survival and the hazard functions, which I would ...
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1answer
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Cox proportional hazard (non-inferiority hypothesis testing) in R

I have researched this question for hours. Any help is appreciated. I am using the "survival package" in R with coxph function. I will illustrate with this example ...
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1answer
66 views

Understanding Cox regression

I have to work with Cox regression but I'm not getting fully how it works. So I created a very basic fake data sample, and tried to fit a Python Lifelines ...
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1answer
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Unbiased coefficients in Cox Model if proportionality violated?

If a Cox PH Model is specified we should always check the Proportionality assumption. It's obvious that, if it is violated the coefficient for the covariate this is the case for is not the efficient ...
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Test linear trend for hazard ratio

I used Cox proportional hazard models in R to calculate the hazard ratio (HR) of smoking for cardiovascular disease (CVD) in a population. Then I made subgroup analysis by age (20-30,30-40,40-50,50-60,...
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Is the interpretation of hazard ratio on continuous scale (without information on each increment increase) same with each increment increase?

fellow statisticians. I know that my question seems so general, and may be similar to previous questions. However, I did not find any previous questions explicitly asking/answering my question. I am ...
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1answer
49 views

Cox proportional hazards with multiclass dependent variable

Is it possible to perform a multiclass Cox proportional hazards model? I'm interested in finding the probability of self cure on consumer loans, or just study how self-curing clients behave so as to ...
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1answer
101 views

Obtain period-specific hazard ratios in a (piecewise) Cox regression

I am a performing Cox regression. The output of such regression is a hazard ratio. In my case, the HR changes over time, so I want period-specific HRs in specific time intervals. I am unsure how to ...
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1answer
192 views

What does the output of flexsurvreg, for a Gompertz proportional hazards model, mean?

I am estimating a Gompertz proportional hazards model in R using the package "flexsurvreg", but I'm having a hard time understanding the output of this function. My dataset is collected from ...
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1answer
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Modelling likelihood of failure

My goal is to assign vehicles a “risk” score (perhaps on a scale of 1 to 5) based on their history. I have data on the vehicle’s age, model, mileage, and dates it was repaired. This risk score would ...
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how to prepare time to event value in case of longitudinal data for Survival Analysis

I have longitudinal transaction data of a retail store where each row is a transaction done by an individual. I would like to perform a survival analysis to analyse how long a customer will transact ...
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78 views

Cox regression for non-repeated events with panel data

I have a question with regard to the research design for a research paper I´m writing on. The data comes in the following form: ...
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1answer
83 views

Cox regression assessing joint relationship between baseline groups? JAMA example

I'm a new R user trying to better understand the analytical framework behind an important JAMA paper (doi:10.1001/jama.291.2.210) and how it can be coded in R. It's objective was to evaluate if, in ...
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1answer
413 views

Cox regression. Find 95% confidence interval for comparison of two groups

I am working with pbc dataset in R and would like to build 95% confidence interval for the comparison of two groups: 60-year-old males on DPCA with bilirubin = 1 mg/dL 40-year-old females on placebo ...
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2answers
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Calculate effects on survival time from Cox proportional hazard model?

Novice stats question here: When I run a cox model over daily survival data as a function of 3 covariates, the results: ...
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What could explain radically different HRs and ORs with similar absolute probabilities

This is a weird question that may not have a good answer, but I thought I'd take a shot. In this clinical trial (hereafter, the ACTT-I Trial: https://www.nejm.org/doi/full/10.1056/NEJMoa2007764), it ...
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assumptions of the mixed-effects Cox regression model

In typical Cox proportional hazards models the assumption of proportionality can be tested using the function cox.zph() in R, but I am doing a mixed effect cox model with the coxme function in R. Is ...
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1answer
107 views

Cox proportional hazards model with inverse probability treatment weights: testing the Cox proportional hazards assumption

I have survival data of persons who participated/didn't participate in a health promotion program. To estimate the effect of the health promotion program on the hazard of mortality, I plan to use a ...
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Generating quantile-type predictions from Cox Proportional Hazards model

I am trying to generate quantile-type survival time predictions from a Cox proportional hazards model, similar to those generated from: ...
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1answer
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Limit on number of features in Cox Proportional Hazards model with penalized spline

I am trying to fit a Cox proportional hazards model with penalized splines using the survival R package with the following, but it seems like I am hitting a limit ...
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1answer
53 views

How to interpret HR under non-ph

How do I interpret a HR under non-proportional hazards? Sounds silly, but I couldn't find a clear answer. Allison 2014 calls it a rough average. How is this average rough, and not a real average of ...
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1answer
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Why is cox.zph splitting terms?

I'm using survminer to try to create a survival formula for a phenotype data set. ...
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1answer
60 views

Proportional hazards model with lognormal baseline hazard in R?

I would like to fit a proportional hazards model with log normal baseline hazard in R. I have found several options for the semiparametric Cox proportional hazards, but I have not found a package to ...
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15 views

How to go about interpreting time-varying co-variates in survival analyses?

I'm pretty new to stats.. been working with cox models and getting a little confused. 1) Why do they occur? 2) How might one interpret/clinically translate a time-varying co-variate for cox models? ...
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1answer
54 views

Cox proportional hazards. What does constant over time mean?

I am studying the Cox PH model. But there is one thing I cannot seem to wrap my head around. In the Cox PH model, we want the hazard ratio to be constant over time. But what is time in this case? ...
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23 views

Choosing a distribution for parametric hazard modeling

I have a question concerning determination of the baseline hazard function in a parametric survival regression such as Exponential, Weibull, e.g. Is there a way to determine which one is best? I have ...