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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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Recurrent event model - time to multiple medication discontinuations

I am using the following recurrent event model (counting process style input) to plot cumulative mean frequency of multiple medication initiations. Just like patients in the study can initiate ...
Chris's user avatar
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Prediction model for dataset whose variables are on two different levels (patient- and lesion-level)

I want to create a cox regression model for predicting follow-up outcomes (eg death) using my dataset. The issue is that my dataset has some variables that are patient-level (eg demographics) and some ...
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How to assess the goodness-of-fit of an extended Cox model?

I'm trying to build an extended Cox hazard model on a dataset with time-varying covariates, using Python's Lifeline package. However, I've a hard time trying to find out how I can assess the goodness-...
wanderingcatto's user avatar
5 votes
3 answers
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Cox model - unsure of time unit of analysis

I am running a survival analysis (Cox model) on time to event in cancer patients. The start of followup is end of treatment. Tests for the event (recurrence) are performed every 6 months from cancer ...
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How to handle time to event data when there is a competing risk with very low incidence rate

I'm analysing time to event data. The primary outcome is time to discharge, and there is a competing risk of death. A competing risk model seems appropriate, but I was wondering if this still applies ...
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Cubic splines for Cox models

I have a question about cubic splines. I want to be sure that I understood correctly. When I perform a Cox model with proportional hazards, if I insert continous variables in the model I have to check ...
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Survival anlysis [closed]

I carried out univariate Cox and log rank tests and I take the covariates with p-value less than 0.25, then which comes first checking Cox regression assumptions or Multivariable Cox regression?
Efrem Shushay's user avatar
13 votes
4 answers
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Cubic splines in Cox model

I have a question about the cubic splines used in the Cox model to test the linearity for the continuous variables. I read that usually the knots chosen are the quantiles. Can you find different ...
user99751's user avatar
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Constructing nomogram from approximate model in Regression Modelling Strategies

In section 19.5 in Regression Modelling Strategies by Frank Harrell we make an approximate model using linear regression with ols. Since this is an ols object we have to calculate survival quantities ...
ScapeProf's user avatar
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Interpreting the result of post hoc power calculation with powerCT.default for proportinal hazards model

I have 2 samples of data both with over 800000 instances. . In both samples, ~ 75% of people have the exposure. In the first sample 0.3 % of people have an outcome and in the second 5% have an outcome....
Milo's user avatar
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Linearity preservation after PCA covariate transformation

thank you for this interesting discussion about linearity of PCA. enter link description here I have a question, which I do not know if it's trivial or not, but I do need to clarify it. I want to fit ...
sinectica's user avatar
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Why would independences tests show significant correlation between variables while VIF shows no multicollinearity?

When conducting independence tests among the variables, some exhibit significant correlations, yet the VIF analysis indicates no multicollinearity. Is this common, and what implications does it hold ...
Jake S's user avatar
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Number of doses as a predictor in a Cox model

I have some data where time to having a relapse of a particular disease state is the outcome of interest. We are interested in assessing the 'effect' of a particular treatment on relapse risk - ...
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Fitting a Discrete-time survival analysis

I am trying to fit a discrete-time survival analysis using R. My overall goal is to check if the variable pain impacts smoking. Every time I include the variable ...
Gabriel Costa's user avatar
2 votes
1 answer
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Shrinkage of covariates in the Cox model

In a regression model (e.g Cox model) when there are too few events to support modeling all desired covariates / confounders, a possible solution is to apply shrinkage / penalise all but the exposure(...
user167591's user avatar
3 votes
1 answer
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Discrete vs. Continuous Survival regression - for business case / subscription churn

I'm trying apply a survival analysis to a churn problem - customer subscriptions. There's nothing particularly unusual about these subscription - customers either pay, or leave, monthly, or annually, ...
user45867's user avatar
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How should I be interpreting martingale residuals and zph?

I'm new to survival analysis and am practicing on the AIDS Clinical Trials Group Study 175 Data from the UCI Machine Learning Repository. After using R to fit the Cox PH model, I made a plot to look ...
Jake S's user avatar
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Smooth scaled Schoenfeld residuals plot for inspection of cox-ph assumption: What should the time on the X-axis represent?

I have tried to determine whether my Cox model violates the proportional hazard assumption by plotting a smoothed scaled Schoenfeld residuals plot in R, as shown below: ...
Devi Sita's user avatar
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2 votes
2 answers
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Multiple Imputation for missing outcomes in Cox regression

Imagine an RCT with a time-to-event outcome which is analyzed using a Cox regression. There are four assessments (T1=before randomization, T2=3 weeks, T3=6 weeks, T4=12 weeks). Under the censoring at ...
Survival's user avatar
2 votes
1 answer
46 views

Individual fixed effects for Cox Proportional Hazard model

I have a panel data set with right censoring. So I have individuals i with several time varying covariates Xit. For some individuals we observe event E (canceling their contract) and others we don't. ...
TiTo's user avatar
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1 answer
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When should the robust error function in R be used in Cox proportional hazard regressions?

Let's consider a scenario where I compute a HR that appears to violate the proportional hazard assumption according to the cox.zph test, but when plotting the ...
Devi Sita's user avatar
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1 answer
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How do I interpret the HRs for each time interval computed by survSplit in R?

I’m testing the association between an exposure and outcome. I have performed a Cox proportional hazard model in R and estimated a HR. Both the exposure and the outcome are binary variables, where 1 = ...
Devi Sita's user avatar
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SNNs with low-moderate data requirements?

I've been looking into utilizing a survival neural network for my dataset, but am having difficulty finding a model that works with my relatively low amount of data. I have ~10 datapoints for ~300 ...
Epic Cabbage's user avatar
1 vote
1 answer
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Estimate number of covariates in Cox regression model

My doubt about overfitting is almost general, but in this particular case is all about survival models. I am working in a case-cohort study, estimating the HR in a cohort where heart attack correspond ...
Javier Hernando's user avatar
2 votes
2 answers
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How to include drug exposure periods in a time to event analysis?

I'm finding it difficult to settle on a method in the literature on how to deal with exposure time of being on a drug(s) (or not) on a future outcome. Let's say my outcome is death and I have ...
brucezepplin's user avatar
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Can Cox or Fine-Gray model include exposure that occurs during observation?

I'm making a Fine-Gray model about pregnancy, but I notice that some pregnancy complications may occur during the observation instead of at the beginning of it because those complications are often ...
黑月盟月's user avatar
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Need help in Censoring for Survival Analysis?

I have data of employees who joined in different months in last 3 years, assume it as a x month and out of those people people left in different months, assume this as y months. I have total 23000 ...
Gopi Shankarappa's user avatar
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Marginal structural model using PROC PHREG

I would like to fit a marginal structural model to account for treatment switching during follow-up. I found a great paper on how to do this in R: https://www.sciencedirect.com/science/article/abs/pii/...
Emma Jean's user avatar
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2 votes
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Cox Regression: handling immediate drop-outs

In an RCT with two groups, I‘m currently analyzing data using cox regression. While I‘m familiar with the concept of censoring, a rather substantial amount of participants (~32% and 35% in the groups) ...
Survival's user avatar
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Is controlling for a time period (during which an economic crisis took place) controlling for fixed effects in a Cox extended model?

I'm using a Cox extended model to measure if job contract durations changed before or after labour reform A and B were passed. So the labour reform variable is time varying (0 if no reform, 1 if ...
Pointed's user avatar
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Reporting of Cox model w/ restr. cubic splines

I'm new in fitting multivariable Cox models w/ restricted cubic splines. This is my code: ...
sjg's user avatar
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2 votes
1 answer
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Is it possible to "adjust" batch effect as random in survival analysis?

My attempt is to define a survival analysis model from a case-cohort study, where a subcohort is initially selected randomly. Later on, all cases from the entire cohort are added non-randomly to the ...
Javier Hernando's user avatar
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27 views

Interpreting hazard ratio in table

This poster has been making headlines lately due to its subject and conclusions. Specifically, I'm interested in understanding how the hazard ratios are being calculated in this table: For example, ...
Bryan Shalloway's user avatar
1 vote
0 answers
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How does the "ZPH" option of PROC PHREG in SAS 9.4 works?

As I saw in SAS 9.4 documentation, the "ZPH" option in PROC PHREG statement requests diagnostics based on the weighted Schoenfeld residuals for checking ...
Calio Xu's user avatar
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How to compare 2 multiply imputed nested Cox proportional hazards models?

I've got 2 nested Cox models, which I fit to 10 imputed datasets. Pooling the regression coefficient estimates and associated p-values I've done already. I'm trying to work out if adding one extra ...
Isaac Allen's user avatar
11 votes
1 answer
509 views

SAS and R produced different results for the same cox ph model on the same data

I have fitted a Cox ph model using both R 4.3.1 and SAS 9.4 with the same data. In SAS, I used Proc phreg, while coxph function ...
Calio Xu's user avatar
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1 answer
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Cox regression with two-way interaction and interaction p value

Hi I am using Cox regression to do some survival analysis. I have one continous predictor variable called "biomarker" and two binary categorical variables sex and diabetes. I want to get the ...
Fabian's user avatar
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3 votes
1 answer
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Which models are available to estimate relative life expectancy (in years, not in hazard ratios)?

I have a well-phenotyped survival dataset (i.e. it has a high number of relevant covariates for a study of mortality) for which I estimate how certain conditions influence life expectancy (LE). It ...
DianaS's user avatar
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2 votes
1 answer
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Why is there a difference in approach between cross-validation and using the test set in ISL's explanation of survival analysis?

The following is from Introduction to Statistical Learning Python edition, page 485, from the survival analysis chapter. They make a distinction between the cross-validation process (to choose a ...
NovicePatience's user avatar
1 vote
1 answer
24 views

Y axis of calibration plot: incidence per X vs percentage at risk

I am considering showing how mis-calibrated a cox proportional hazard model is by plotting the 10th percentiles of risk on the x axis vs the incidence per 100,000. For each bin in x I could plot data ...
brucezepplin's user avatar
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11 views

External Validation of Prediction Models - Cox vs Logistic Regression, pros and cons?

I have made a Cox PH model for prognostication of a favourable outcome (with competing events being death). I now have an independent set of data to do external validation on this model. The primary ...
Hong's user avatar
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1 vote
1 answer
30 views

Interpretation of the Hazard Ratios in Lifeline's Time varying cox regression

I'm trying to understand how to interpret the hazard ratio of time-varying covariates, returned by lifelines.CoxTimeVaryingFitter. Following the example on their page, I have the following data: ...
asere's user avatar
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2 votes
1 answer
40 views

NA results after pooling estimates and coeff of mixed effects cox model from MICE imputation dataset

I need your help with my problem. So, after step of imputation missing data through MICE method, I got multiple imputed dataset. Then, I pooled the estimates and coefficients with mixed effect cox ...
Hoang-Giang Pham's user avatar
2 votes
1 answer
32 views

Can you lag a covariate in a Cox proportional hazards model?

I am using a Cox PH model to study at what point in their lives people decide to move outside of the United States. My sample is 500 people who live in the United States, and the unit of analysis is ...
Rabbit's user avatar
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1 answer
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Cox proportional hazard model ran out of iterations = summary gave significant results with very small p values

I am running a cox proportional hazard model on a data set of 63 instances and 11 variables. When I do univariate analysis, all runs fine and I get non-significant results for all variables When I run ...
has_J's user avatar
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Performing a survival analysis makes sense in this case?

I'm a medical student performing my final degree thesis, so sorry in advance for my little knowledge in stats. I'm performing a retrospective study on the surgical field where I want to evaluate the ...
user406570's user avatar
2 votes
1 answer
155 views

Survival analysis with missing values for some variables

I'm performing a survival analysis. I did the univariant Cox regression model for all my variables (about 40). I even performed the univariant analysis in all those variables that had missing values ...
Arthurr's user avatar
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1 answer
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non-significant p value in a multivariable cox regression following exhaustive model selection

I run an exhaustive model selection for Cox proportional hazard in R using "glmulti" package. I used the best model for creating multivariable Cox regression. In the multivariable Cox hazard,...
Ahmed Elkoumi's user avatar
2 votes
1 answer
53 views

Which variables I should include in the multivariable Cox regression model?

I'm performing a survival analysis and I have some quantitative variables that I categorized (but I also mantained the quantitative variable for the univariate analysis). For example, I have the ...
Arthurr's user avatar
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5 votes
1 answer
248 views

Is the effect in a Cox proportional hazard collapsible if the covariates are normally distributed and the baseline hazard is constant?

Since the Cox PH model is a non-linear model, we would expect the effect to be non-collapsible. i.e., the marginal and conditional effects differ. I did some calculation for a setting where the ...
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