All Questions
Tagged with cox-model proportional-hazards
227 questions
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Cox-like model: weighted sum of proportional hazards
We are trying to do inference on vaccine effectiveness (VE) during an epidemic in a risk-stratified population.
Models:
Consider the Cox model:
$$ \lambda_{ik}(t) = \lambda_0(t) \exp [\beta X_{ik}] $$
...
- 217
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1
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33
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Setting a reference in Cox regression with splines and interaction
I run a Cox regression with a continuous variable age and a categorical variable sex. The model includes splines for the continuous variable and an interaction between both. I want to choose the ...
- 343
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1
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39
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`pspline()` terms and checking proportional hazards
I have fit a Cox model with pspline() terms for the continuous covariates. I am trying to better understand how pspline() terms ...
- 209
2
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1
answer
365
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Dealing with non-proportional hazards in a Cox model with many variables and a large dataset
Summary: I am trying deal with non-proportional hazards in a Cox model on a large dataset. My question is whether the proportional hazards assumption really does not hold? If no, is the second model ...
- 209
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1
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59
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Hazard Ratio from two cox models
I am working on a dataset from a clinical trial where patients received either treatment $A$ or treatment $B$. My goal is to develop two separate Cox proportional hazards (PH) models: one for patients ...
- 11
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47
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Time related categorical variable for cox regression
I am trying to fit a Cox regression model to my time-to event data and besides other subject specific variables, I have two specific calendar dates that I want to analyze the effect of. For these two ...
- 57
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1
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75
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Dropping a level of a categorical variable with small number of subjects on cox regression
I am trying to fit a Cox regression model to my time-to event data and have a categorical variable with 5 different levels. I leave one level out as the 'reference'. I also have 2 levels with small ...
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86
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Dealing with categorical variables on cox regression
I am trying to fit a Cox regression model to my time-to event data and have a categorical variable with 5 different levels. If I don't leave one of the levels out, then I will have multicollinearity, ...
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34
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Dealing with Low variance categorical variables on cox regression
I am fitting a time varying cox model to my survival data, and I remove one arbitrary level from each categories, to create the baseline hazard. I have some low variance categorical variables. If I ...
- 57
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15
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Merging Different Groups for Cox Regression
I have time to event data for subjects from different groups, and I use group features as covariates for cox regression. For example, I have 100 subjects from group A, and 200 subjects from group B, ...
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2
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83
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Interpretation of hazard ratios - impact on time to event?
say I use Cox proportional hazards model where I explain time to some event with a number covariates. In the result, for each covariate I get the proportional hazard ratios (HR). A HR lower than 1 ...
- 65
5
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261
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Interpretation of R output for stratified cox-ph model
For the following model:
model <- coxph(formula = Surv(time, status) ~ treatment * sex + strata(sex), data = data)
this is (part of) the model summary in R:
...
- 61
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29
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Multi State Survival Analysis Transition Between States Triggered By different events
I have a state diagram for multistate survival analysis, and between 2 specific states, I have 2 types of transitions triggered by different types of events, i.e, from state 1 to state 2, the ...
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1
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209
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Lifelines-CoxTimeVaryingFitter for Multistate Survival Analysis
I am new to survival analysis and cox regression, and have limited statistical background. I have time-to event data for a multistate survival model and I want to fit a cox model for each transition ...
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47
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In which cases should the time be transformed when plotting the smoothed scaled Schoenfeld residual plot?
I previously asked this question but didn't get any answers, so I'm reposting it now.
I aim to address the argument transform = '' in R, particularly concerning the ...
- 333
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1
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65
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Changes in Schoenfeld Residuals Dependent on Follow-Up Time
It's my understanding that the proportional hazards assumption means that the effect of a covariate on the hazard rate (or the instantaneous risk of an event) remains constant over time. In practice, ...
- 97
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96
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Time-to-event analysis with left-truncation and right-censoring depending on the exposure
I have a couple of questions regarding the best unbiased approaches regarding analyzing time-to-event/age-of-onset for left-truncated with right-censoring data.
To my understanding, when one is ...
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1
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80
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Should the curve be around zero when assessing the smoothed scaled Schoenfeld residual plot for proportional hazard assumption?
I'm using the smoothed scaled Schoenfeld residual plot to assess the proportional hazard assumption. I have a decent understanding of what a smoothed scaled Schoenfeld residual plot shows, but I'm ...
- 333
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48
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Does it make sense to convert the Y-axis by exp() on the smooth scaled schoenfeld residual plot?
I posted a question on Stack Overflow. But the question got closed as the person who closed it wrote that it should belong here in Stack Exchange. I'm not sure why but here is the link for the post. I'...
- 333
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1
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121
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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 ...
- 333
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1
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144
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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 = ...
- 333
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1
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75
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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 ...
- 219
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72
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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, ...
- 649
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32
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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 ...
- 219
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1
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279
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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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4
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1
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183
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smooth scaled Schoenfeld residual plot - how to interpret the plot which is based on a stratified cox model?
I understand what a Smoothed scaled Schoenfeld residual plot is, and what it shows.
Before I go into details with my question, I will provide an example.
I use R to code.
Here is a cox model:
...
- 333
3
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1
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118
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smooth scaled Schoenfeld residual plot - covariates with levels
I'm working with cox proportional hazard (cox-PH) in R. I'm using the smoothed scaled Schoenfeld residual plot to assess the PH assumption.
Suppose I have this model in R, disease as outcome and ...
- 333
2
votes
1
answer
68
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Cox model: time interaction vs. covariate interactions
In the Cox model, violation of proportional hazards suggests that the effect of an exposure is not constant over time. One way this can be handled is by including time varying coefficients in order to ...
- 923
2
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1
answer
104
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Cox model: extremely high Schoenfeld residuals
I have run fixed in time Cox models (crude and covariate adjusted) for the effect of a binary exposure. Sample size is approx. 200,000 and there are approx. 10,000 events and 4000 "yes" ...
- 923
3
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1
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101
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Why can't Cox-PH handle left or interval censoring?
I've been trying to find a mathematical explanation for this. Note, I'm talking about the "classic" Cox-PH, not the extensions given after to incorporate interval/left censoring.
In this ...
- 3,680
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14
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Disaster exposure as treatment in survival analysis - multiple "treatments" / pre-"treatment" trends (in R)
I am looking at using a cox proportional hazards model to look at migration after disasters. I have two disasters at T1 and T2 (which are two years apart). I created two models looking at the risk of ...
- 399
5
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2
answers
272
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Illustrating the hazard function across values of an independent continuous varable
I'm running a Cox model in which my main interest is the effect of a continuous independent variable on the hazard of committing crime.
I want to illustrate the effect of this variable. For this ...
- 347
4
votes
1
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412
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Testing the proportional hazards assumption with a time varying covariate
One of the cohort studies I have carried out recently involved examining the association between post-diagnostic beta-blocker use and breast cancer outcomes in a cohort of breast cancer patients. ...
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3
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1
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444
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Do I need to care if an adjustment variable violates the proportional hazards assumption?
I'm assessing the effect of an exposure variable on cancer risk. I am not necessarily trying to build the model that best predicts cancer risk, I am instead trying to best isolate the effect on cancer ...
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1
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51
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Cox ph model with icenReg: how to code data without event indicator
I want to analyze my data with the interval-censored cox regression of the icenReg package.
I have 5 time-points (1,2,3,4,5). Events can only happen once. Each person starts with baseline (T1). People ...
- 133
1
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1
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126
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How does length of follow-up affect hazard ratio (prop hazards vs non-prop hazards)
As the title says, I'm trying to figure out how the length of follow-up affects the value of the hazard ratio (e.g. from a Cox model). If proportional hazard holds, then presumably the hazard ratio ...
- 557
2
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0
answers
93
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Proportional hazard assumption: graphical approach vs subsampling
Hopefully someone can guide me on the following.
I have a large dataset (> 151k firms with multiple observations per firm).
My dataset looks at firm failure using counting process style and my ...
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0
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23
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Why such a large difference between Odds Ratios and Hazard Ratios?
I am studying the risk of dementia secondary to hearing loss. I have fashioned a Cox time-dependent model with multiple covariates, all with factor levels, but have also done a logistic model for ...
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0
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59
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Testing Proportional Hazards Assumption in Cure model
I am currently working on estimating a cure survival model where I want to incorporate a Cox proportional hazards (PH) model for the latency part of the model (i.e. the part for the observations that ...
- 363
3
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1
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448
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Cox Proportional Hazard Partial Likelihood rigorous derivation
I'm trying to find a rigorous derivation of the partial likelihood for Cox-PH. I find the hand-wavy explanation of Cox in "Partial Likelihood 1975" unsatisfactory:
There are 2 points which ...
- 3,680
1
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0
answers
14
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Difference ACD and Survival Analysis models
Autoregressive conditional duration (ACD) models are typically used in econometrics for dealing with trade duration (TD) data and it is used to capture the clustering structure.
In other areas of ...
- 363
3
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1
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689
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Choice between Proportional Hazard and Accelerated Failure Time survival models
How can I determine whether to use proportional hazard (PH) or accelerate failure time (AFT) survival models in order to analyze my data?
Are there any established guidelines or common practices that ...
- 363
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27
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Estimates of Cox Proportional Hazards Model
Why do some studies that utilize the Cox Proportional Hazards Model analysis use relative risks, others used odds ratios, and others used hazard ratios?
1
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1
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142
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Survival Analysis model choice
I am trying to investigate the statistical difference between two groups in my population and exploring suitable survival models for analysis. Let me first outline the data I am working with to ...
- 363
1
vote
1
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156
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Capture time variation in survival analysis
I am currently working with intraday time-to-event data, where the time to event typically spans just a few minutes. I want to compare the survival curves of two subpopulations in my sample.
The ...
- 363
2
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1
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545
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DIfference between hazard ratio and partial hazard in survival analysis
The hazard function in survival analysis is represented as (https://in.mathworks.com/help/stats/cox-proportional-hazard-regression.html):
Here the exponential term is termed as hazard ratio as ...
- 151
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1
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63
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3
votes
1
answer
1k
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Schoenfeld residuals for factors with cox.zph
The cox.zph function of the survival package computes the Schoenfeld residuals for each variable and tests the porportionality assumption with a score test, but I ...
2
votes
1
answer
736
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Stratified-Extended Cox regression modeling to deal with survival data with time-varying covariates
I'm working on Cox regression in my PhD research and I would like to know some references about applying the stratified-extended cox regression model on a real life data.
I'm interested about ...
0
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1
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622
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How do I choose correct model (AFT or PH) & distribution when Cox proportional hazards is not appropriate?
I have been tasked with evaluating hospital length of stay (LOS) in two groups of patients using the Cox proportional hazards model. One group of patients received a medication, the other did not. ...
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