# 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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119 views

### 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. ...
32 views

### Inverse sampling weights in Cox proportional hazard leads to violation of the PH-assumption?

I'm running a cause-specific Cox proportional hazard model to identify the association between potential risk factors and an outcome in a cohort study. I am incorporating time-varying covariates, use ...
77 views

### How do you convert hazard ratios to differences in life expectancy?

How do epidemiologists convert hazard ratios to difference in life expectancy? For example, let's say I find that the hazard ratio of all-cause mortality in City A is 1.25 compared to City B. I want ...
44 views

### 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 ...
1 vote
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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 ...
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### Simulating Time-Dependent Covariate and Applying coxph Function to Estimate Association Parameters

Let $T$ denote a failure time random variable drawn from a proportional hazards model with a time-invariant covariate $X\sim U(2, 7)$ and a time-varying covariate $Z(t) = kt$ for $k > 0$. Assuming ...
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### Coefficient of one independent variable in Cox regression flips when inserting two other independet variables together

I'm running a cox regression to test the effect of different variables on crime. There's one independent variable of interest (X), for which I hypothesize a negative relationship with crime (i.e., HR&...
1 vote
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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 ...
66 views

### 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 ...
47 views

### Cox proportional hazard assumption, different results, which to follow

I was wondering if anyone would be able to help me understand whether the proportional hazard assumption is met or not. For context I have a large dataset with >10 million observations (up to 40 ...
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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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### Using both time dependent covariates and time dependent coefficients in a Cox Model

In the context of a study, I am comparing two surgical interventions and I am interested in the time delay before the occurrence of a specific clinical event after surgery. I have conducted a ...
1 vote
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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 ...
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### How to estimate the baseline cumulative hazard function with ties?

I know that in the proportional hazard model, Breslow estimator is used for estimating baseline cumulative hazard. But what about when the data has some(or many) ties?
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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 ...
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### Log-likelihood function for CoxTimeVaryingFitter

The mathematical formulation of partial log-likelihood function (https://in.mathworks.com/help/stats/cox-proportional-hazard-regression.html) is defined as: The above formulation does not take into ...
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### Assessing Differences in Survival with a Multi-Level Categorical Variable

I would like to check if my overall survival differs be a multi-level categorical variable. I have 300 subjects and 15 levels. Is KM log-rank the most appropriate test? If so, how do I check the PH ...
15 views

### Testing for heterogeneity by a multi-level categorical variable in a cox regression

I am interested to know if there is heterogeneity in a multi-level categorical variable in a survival model. Does Cox make sense given the test of heterogeneity would assume proportional hazards - ...
1 vote
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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 ...
1 vote
101 views

### 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 ...
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### How to handle non-proportional hazards when you have multiple groups and differences in event rate based on study design

I am looking at time-to-event data by a variable with multiple groups (8). When I plot the stratified KM, some curves cross, some are ok, and some diverge. Also, I'm interested in the 30-day event ...
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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 vote
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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 ...
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### Survival analysis - Cox proportional-hazards model problem with output

I have a time to event dataset were I’m looking at the time until individuals perform a specific action. I’m monitoring these individuals for a certain time and if that action is not performed during ...
1 vote
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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 ...
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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 ...
1 vote
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### Logic to caluclate shape and scale parameter in survival analysis

I have the below dataset: ...
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### Can I perform a mixed effects Cox model on population of different size?

I want to test the survival of multiple populations with 2 different treatments and include 2 random effects as well. Hence, I want to perform a mixed effects Cox model. I count how many ants died ...
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### Generate survival data with functional data using R

I am reading this article here and trying to regenerate their simulation study. Here is this scenario here, among others, but if I can figure out one, the rest follow. That is, Simulation set-up we ...
270 views

### 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 ...
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### Study design when exposure more likely to lead to test for outcome

I am doing an observational study looking at the association between a baseline exposure (binary) and the first instance of an abnormal blood test result (binary) among people with serial blood tests. ...
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### Options on modelling a hazard function with a turning point

I have some survival data and need to fit survival models to it and extrapolate. I plotted the log cumulative hazard and empirical hazard plot (using muhaz). There appears to be a change in the hazard ...
1 vote
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### Cox regression: are my covariates time-variant? what with PH assumption violation?

I was wondering if any have advice on what the correct steps/interpretation are with regards to the following questions on Cox regression. As a side note, I am using STATA MP 15.1 to analyse the data ...
120 views

### What is the minimum of 2 Weibull distributions with the same shape parameter

If X and Y are two independent Weibull distributions with the same shape parameter, what distribution is the min(X, Y). I am trying to find out the hazard ratio for the following case. If I model Z=...
1 vote
301 views

### 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 ...
171 views

### 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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### interpreting HR with time dependent covariates cox regression

I did time-dependent covariate analyses with cox regression in R. But I wonder if the interpretation is the same as for a cox model with a fixed covariate? Context: in my analysis the physical ...
294 views

### Using multiple genes building gene signature and survival analysis

This is the paper which is kind of I'm trying to implement based on my set of genes which i have narrowed down from WGCNA analysis. Its a both conceptual and R related question[How to do it in R] my ...
321 views

### Finding partial log-likelihood of survival data

Cox proportional hazards model: $$\lambda_2(t)=\lambda_1(t)e^{\beta}$$ I have survival data for two different groups I would like to find the profile of the partial log-likelihood for the data as a ... 1 vote
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### Cox PH model HR - is it possible to measure against the general average?

Reproducible example: ...
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### Obtain the survival function plot by building an overall survival regression model

I need to build an overall survival regression model that can show the survival plots for id's with multiple rows. I have used the Weibull function to define the baseline hazard function h0(t) and Cox ...
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### hazards model of unemployment

I want to study how holding student debt after college graduation could affect the exit to unemployment and, more specifically, finding a job that requires less than college degree after college ...
1 vote
397 views

### Compare two hazard ratios from two subgroups?

For example, for the smoker group, a cox regression shows that the hazard rate of alcohol use on survival is 1.41. In the non-smoker group, another cox regression shows that the hazard ratio of ...
1 vote
19 views

### Synthesizing hazard ratios that are based on different comparisons (meta-analysis)

I intend to evaluate the effect of an exposure (E), continuous, on my outcome (O), binary. The available cohort studies are based on time-to-event analysis and report hazard ratios (HR). However, ...
1 vote
363 views

### Should the proportional hazards assumption be met for cox model with time dependent covariates? What about recurrent event models?

This question has been asked here before but in each thread I found, there was some disagreement about whether the proportional hazards (PH) assumption needs to be met for cox models with time ...
1 vote
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### Cox Proportional Hazards: Why p < 0.1 in univariate to be included in the multivariate

Recently, I was asked to explain in my peer-review article by the reviewer to elaborate on why I employed variables that showed a trend towards significance (p<0.1) as well as statistical ...
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### How to create a Cox proportional-hazards model with count data and proportions?

Suppose I have data with the following format: ...
421 views

### Flexible parametric survival (Royston-Parmar) model for non-proportional hazards

I am reading more about flexible parametric survival models and their implementation in the flexsurvspline function in the ...