Questions tagged [cox-model]

Cox proportional hazards regression is a semi-parametric method for survival analysis. No distributional form needs to be assumed, only that the effect of one-unit increase in a covariate is a constant multiple.

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Schoenfeld test (cox.zph) shows no covariate violates PH assumption but global test suggests whole model does (p<0.001). What to do?

Using cox.zph (part of the survival package), I find that no covariate violates the PH assumption in a Cox regression model (p > ...
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Adjust for confounder in calculating explained variability in cox-regression

My question is closely related to this one. I am interested in the proportion of variability which is explained by a certain covariate X in a cox-model. So I have the cox-model “outcome ~ X”, for ...
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Set new reference level for hazard ratios

I run a Cox Regression and afterwards, I predicted the Hazard Ratio (HR) for the predictor values 1 to 10. My data looks something like this: ...
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time-varying coefficients (Cox regression) - interaction terms

I'm fitting a cox regression model that violates the proportionality assumption by breaking the data into three intervals as suggested by Therneau et al. p. 17~ (https://cran.r-project.org/web/...
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Cox regression with numerous interaction terms

I am fitting a Cox regression model using the coxph() function of the survival package in R. I have 15 predictors. One of the predictors is treatment (given / not given). The treatment is a well-...
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Survival Analysis - Describing Results from KM to Cox

I am familiar with the basics of survival analysis although I am stuck in organizing my figures for presentation. I constructed an adjusted KM curve and stratified my covariate of interest by the ...
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How to Illustrate Results from Cox model with Covariates

I have a data set for which I have fit a Cox proportional hazards model. For publication, I'd like to plot a graphical representation (perhaps a cumulative incidence) curve. My variable of interest is ...
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Results of a survival analysis change when converting the data to counting process format

Consider the following simple example: ...
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Is it appropriate to adjust a Cox regression model for the baseline year when using data from open cohorts?

I was wondering whether it is correct to include baseline year as additional covariate in a Cox regression model when using data from an open cohort. I will try to give an example to make this clearer:...
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Cox Proportional Hazard calibration with same it's meant to predict

I want to model time to churn with a Cox Proportional Hazard model and use it to predict people likely to churn. The question I have is how valid is to calibrate the model with the same people I want ...
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p trend for Hazard Ratios of a categorical independent variable

I ran an analysis using a Proportional Hazards Cox regression model. My variable of interest is exposure to pesticides (kg of pesticides applied within 500m of home). We do not expect a linear ...
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Death-cases only in Cox PH?

I am using a dataset with 1078 patients who received an ankle replacement. In ca 100 patients (Event=2) the implant had to be exchanged after an interval of 3-12 years. There are 7 possible reasons ...
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Conducting a subgroup analysis with regression modeling

I'm conducting a survival analysis using Cox Proportional Hazards regression to identify prognostic factors for cancer patients. My covariates include information such as age, sex, tumor location etc. ...
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Adjusted Survival Curves Index of Variability

I am implementing the ggadjustedcurves() function in survminerpackage to create adjusted survival curves as presented in this ...
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Prediction of survival time using cox regression in R

I'm aware that we can get survival function and probability in R but is there a way to predict survival time given it is Cox regression
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Cox proportional hazards model understanding

Assuming that we perform a Cox regression as presented in the example here. I am wondering what we should expect in the output of the Cox regression if, for example, we perform the fit again but this ...
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how to cut/group variables in Cox model

Considering that for a logistic regression one approach is to cut the numeric variables (or group the categorical ones) with some algorithm before running the logistic model (to allow the algorithm to ...
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Number of Covariates in Cox PH Model and Overfitting

I have a small time to event dataset (N=20) where patients are given one of two drugs (drug) at varying doses (...
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Cox regression: Estimate the value of covariate which gives a survival probability of 50 % at a specific time point

I have a data set of 150 individuals where 30 experience the event, all at different time points. I've fitted a cox regression model using step-wise backward selection and the model came out with one ...
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Recurrent Survival Analysis with Time Dependent Covariates

I am analyzing the time (since 2000) of a policy adoption using R. These policies can be updated and so I think a recurrent Prentice Williams Peterson (PWP) model is appropriate. The challenge is that ...
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How is a survival model with constant baseline hazard and time varying covariates called?

The data situation: Supose in different forests data have been collected. These data include the temperature at different time points, the hours of rain, the type of forest and whether the event (a ...
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Time and events in a Cox model

I am going to perform survival analysis using the Cox model, but I have some doubts about the input data. The data have the following structure: ...
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power calculation for cox proportional hazard regression

I am trying to perform a statistical power calculation for cox regression. we want to investigate the association of composition (that has 4 variables) and sickness absence events in the future. for ...
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Creating a risk score from Cox Regression

I have two datasets with palliative cancer patients including 106 and 60 patients, respectively. I have biomarkers of inflammation and coagulation, as well as clinical characteristics for all patients....
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Cox regression with lasso regression

Is it possible to perform lasso regression (glmnet with "cox") for variable selection and then conduct Cox regression using ...
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Interaction not significant in Cox regression model?

I ran a cox model with an interaction between two categorical variables (sex and treatment group) included like: ...
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Coefficients in Cox model

The output of coxph has coefficients vector as follows: ...
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Longitudinal Cox Regression analysis?

So I have a dataset that is currently in wide format and I have multiple waves recording data such as age, death, diagnosis etc. I have done a simple Cox regression analysis: ...
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Cox regression model - testing the proportionality assumption for an interaction term?

I'm interested in testing sex differences in the outcome Y (e.g., mortality), and if there are sex differences in the effect of BMI on mortality. I planned to use a Cox regression model primary<-...
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Is age categorical or quantitative or both?

First off, sorry if this is a simple question. I've been asked to get stuck in with some clinical epidemiology. The internet is my only support group as I am not a student under the supervision of an ...
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Baseline hazard function is the hazard function obtained when all covariates are set to zero

I am trying to learn Cox proportional hazard model but I have hit a wall with the basehaz function. Lets suppose for example I have some data that I want to use ...
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Right censored or right truncation and Cox model?

Suppose, a list of targeted population is invited to participate in a health program. Invitation date could vary for every individual based on eligible criteria (this criterion is the same for all). ...
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Sample size calculation for multivariable Cox regression for treatment comparison

I am trying to calculate the required sample size for a future study. Specifically, the goal is to compare two treatments based on their survival. The Cox model will be used, and along with the ...
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How to choose the best combination of covariates in Cox multiple regression?

I am performing a multivariate Cox regression analysis, and would like to find what combination of those covariates best predict my outcome. Say I have a list of candidate genes whose expressions ...
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Cox regression different results with different combinations of variables

I need help understanding how to use cox hazzard model to calculate risk of death in data from a cohort study. I have a set of data on physical activity and I want to do a cox regression on ...
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How to use Cox PH model for LOS

I would like to use Cox model to predict hospital length of stay. My data is as follows: Patient ID Length of stay Sex Comorbidity 1 Comorbidity 2 Comorbidity 3 Diagnosis Age Ethnic group Blood Test ...
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Test assumption of common baseline - Adersen-Gill Cox regression?

I'm running a Andersen-Gill recurrent (multiple events) cox model and I want to test the assumption of common baseline across events. Is this as simple as entering 'event' into the model and checking ...
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What does 'km' transform in cox.zph function mean?

I'm trying to understand how cox.zph function in r programming language works and I find myself not knowing what km transform ...
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Interpreting a hazard ratio for time-dependent coefficients

I have a cox model with two main effects (x,y) and two interaction terms (xt, yt) where t is time. I am having some trouble interpreting the hazard ratios. Does the hazard ration become more of an ...
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Age as a time-dependent covariate

I have some confusion around time-dependent covariates / coefficients. I'm trying to run a cox regression with age as a time-dependent covariate. Lets say the variable is age-at-first-drivers-license (...
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When using using predictCox, why does cumhaz change while time is constant?

I'm trying to understand how to predict survival probabilities. I found this, which was helpful. However, after trying to practice on my own and compare my results to predictCox I got some confusing ...
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Interpreting hazard ratios in stratified models

I am unsure how to interpret hazard ratios from cox-proportional hazard models that include 1 or more stratified terms. For example, say I run a cox regression with treatment as a covariate and ...
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1answer
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Coefficient test (Wald) vs model test (Wald, LR and Score) in multiple regression cox model

I am aware that, in multiple regression cox model, we test (Wald) each variate to show if it has significant impact on survival. Also, we got the significance of overall model using Wald, LR and Score ...
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contrast in plotHR for spline HR plot

I am using plotHR to plot spline with hazard ratio - I would like to set my reference point using 'cntrst'. In R: plotHR(mfit, term="td_macce30d_map", plot.bty="o", xlim=c(50, 110), xlab="MAP (mm Hg)...
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What do LR / Wald / Score test represent in Cox model?

It said that these three tests represents the global statistical significance. What does this mean? There is a p-value for each variate indicating whether that variate affects survival significantly. ...
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How to code effect modifier in a Cox Regression using R?

The definition of the distinction between the effect modifier and interaction term is: Interaction and effect modification are formally defined within the counterfactual framework. Interaction is ...
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Adapting Cox Regression to Time dependent continuous variables [duplicate]

I am interested in using cox survival regression model when the covariates are not expected to be constant over time and also continuous. I did check a few books and the time dependent Cox Regression ...
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survival probability to proportional hazard ratios in r

I am using Cox proportional hazard regression to determine the association between physical behaviors (physical activity, sedentary behavior, and sleep) and mortality. to elaborate on these results, I ...
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Kaplan Meier Diagnostic Utility

I'm trying to understand a paper that claims to have identified a gene expression signature that can distinguish primary from metastatic tumors. The authors stratify their data into patients with and ...
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Homogeneity test in survival meta-analysis with adjusted HR

I was wondering what was the way to measure heterogeneity in a survival meta-analysis. I have for each study, an hazard ratio calculated with a penalized cox model (...