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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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Check proportional hazards assumption for a Cox model on a large dataset [closed]

I am trying to check whether some variables violate the proportional hazards assumption in a Cox model on a large dataset. The outcome variable is misuse of a given prescription drug and the ...
Thomas's user avatar
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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 ...
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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 ...
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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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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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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 ...
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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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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 ...
chris_chris's user avatar
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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: ...
user412691's user avatar
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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 ...
smgtkn's user avatar
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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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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 ...
Devi Sita's user avatar
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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, ...
Bren's user avatar
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1 answer
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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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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 ...
Devi Sita's user avatar
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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'...
Devi Sita's user avatar
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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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1 answer
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Assessing Proportional Hazards Assumption in Survival Analysis [closed]

I have a question, I am using survival analysis to study the relationship between smoking and lung cancer and the covariates are BP, BMI, and gender. Exposure to smoking satisfies the ph assumption, ...
just one's user avatar
2 votes
1 answer
56 views

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 ...
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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, ...
Bryan Shalloway's user avatar
1 vote
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Survival analysis where the total count of different types of events matter?

I'm currently trying to conduct survival analysis where events are not just the binary variables of 1/0 (i.e., did the event happen or not). However, I'm not quite sure how to proceed in this case. My ...
kay_m43's user avatar
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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 ...
brucezepplin's user avatar
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1 answer
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Restricted mean survival time for rare events

I like the restricted mean survival time (and the difference in RMST between cohorts) in survival analyses. However, it does not really convey the effect of an exposure on rare outcomes. For instance, ...
Max's user avatar
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Can I use a Hazard Ratio to determine the absolute risk of a population?

I am trying to convert the Hazard Ratio from this paper (Risk of Gastrointestinal Adverse Events Associated With Glucagon-Like Peptide-1 Receptor Agonists for Weight Loss) to determine the prevalence ...
David Andrews's user avatar
5 votes
1 answer
259 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 ...
hehe's user avatar
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The AFT and PH model

According to the following - https://dylanspicker.com/courses/STAT437/content/041%20+%20044.%20Lecture%20Notes.pdf the PH and AFT models are equivalent for Weibull distribution. Does this implies the ...
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4 votes
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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: ...
Devi Sita's user avatar
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3 votes
1 answer
101 views

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 ...
Devi Sita's user avatar
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2 votes
1 answer
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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 ...
user167591's user avatar
2 votes
1 answer
84 views

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" ...
user167591's user avatar
3 votes
1 answer
60 views

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 ...
Maverick Meerkat's user avatar
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14 views

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 ...
tchoup's user avatar
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4 votes
2 answers
190 views

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 ...
Eran's user avatar
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4 votes
1 answer
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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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6 votes
2 answers
300 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 ...
braces's user avatar
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3 votes
1 answer
264 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 ...
Isaac Allen's user avatar
1 vote
1 answer
42 views

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 ...
Sebastian's user avatar
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1 answer
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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 ...
J McVittie's user avatar
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0 answers
34 views

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&...
Eran's user avatar
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1 vote
1 answer
77 views

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 ...
elbord77's user avatar
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2 votes
0 answers
75 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 ...
Laura Hill's user avatar
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0 answers
76 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 ...
Laura Hill's user avatar
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0 answers
20 views

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 ...
Royce's user avatar
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0 answers
75 views

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 ...
Kant's user avatar
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1 vote
0 answers
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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 ...
John's user avatar
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0 answers
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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?
Haoqun Cao's user avatar
3 votes
1 answer
291 views

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 ...
Maverick Meerkat's user avatar
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0 answers
19 views

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 ...
NN_Developer's user avatar
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0 answers
13 views

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 ...
user213352's user avatar

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