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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875 views

Estimate the cumulative baseline hazard function from a Cox model coefficients

CoxPh model described as $h(t|X)=h_{0}(t)e^{\beta X}$ where $h_{0}(t)$ is the baseline hazard function and is non-parametric. If you have the following model, ...
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1answer
76 views

How to calculate HR using attained age? [closed]

I want to calculate the hazard ratio for death by comparing individuals with a disease versus others without the disease, but I don't know if the calculation that I'm doing is correct. Participants ...
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1answer
348 views

Should I correct the p-value when testing Proportionnal Hazard assumption with cox.zph()?

When testing the Proportionnal Hazard assumption in a cox model in R, you usually use the survival::cox.zph() function. Output is something like this: ...
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1answer
25 views

Survival analysis of a population - Proportional hazards

first time here :) here's my problem. I developed an agent-based model (ABM) that I used to generate some data that I would like to analyze, but I couldn’t find a methodology that I can be confident ...
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37 views

Can I force the direction of hazards ratio?

I am doing a survival analysis using Cox's proportional hazards model with several predictive variables. Some of the estimated hazards ratio goes in an implausible direction, which contradicts what we ...
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1answer
215 views

Significant but very small beta coefficients in Cox proportional hazards calculation (survival analysis)

I'm analyzing TCGA data to investigate the effects of lncRNAs on survival. Among other things, I wanted to calculate a univariate CoxPH model for each gene to find genes whose expression levels have a ...
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88 views

interpretation of cox HR under non-proportional hazard

When the true hazard ratio $\lambda(t)$ is time varying as shown below, I used a standard cox regression to get a hazard ratio. If the hazard ratio of $\lambda=0.78$, how can this value be interpreted?...
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70 views

Frailty or median values in my cox proportional hazards model?

I am analysing data of woodpecker-made holes and I am interested in seeing what covariates and to what degree affect the survival of these holes (otherwise known as cavities). However, I encounter the ...
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1answer
520 views

Use median survival time to calculate CPH c-statistic?

I'm interested in calculating the concordance ($c$-statistic) of a proportional hazards model. For reference, the c-statistic is detailed in Stat Med. 1996 Feb 28;15(4):361-87. The relevant quote ...
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167 views

Cox Regression in Propensity Score Matched cohort after multiple imputation

I have a follow-up question on the question of this thread: Manipulating data for propensity score matching following multiple imputation with mice package In aforementioned topic we can see the ...
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1answer
627 views

Hazard Ratio Meta-Analysis

I've being reading around the forum and couldn't find exactly what I wanted. I am trying to do an meta-analysis where the HR of each study and the 95% CI were available. I understand variance can be ...
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1answer
666 views

Formatting data for Cox PH with time-dependent covariates

I was hoping for some guidance on the appropriateness of my modeling approach to the following problem. Problem: I'd like to know whether the days receiving nutrition support (cumulative days on ...
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2answers
106 views

What is the meaning of “t” in Cox hazard proportional model?

I'm learning survival analysis and currently have questions about the Cox proportional hazards model. The following figure wants to show that for a certain smoking subject, the hazard of a 10-year ...
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1answer
2k views

How can one invert hazard ratios and their confidence intervals?

Imagine that when we compare treatment A to treatment B there is an associated hazard ratio of 0.56 (95% CI: 0.36 to 0.87). Let's say that instead of this, I want the hazard ratio associated with ...
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157 views

Is the supremum test of cumulative martingales residuals OK to assess proportional hazards of both groups and covariates?

Is the supremum test of cumulative martingales residuals (as implemented by assess in SAS PROC PHREG, and other software) OK for testing PH of both continuous ...
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61 views

Proportional Hazards, Competing Risks, or something else?

I'm looking to do a time-to-event analysis. My data set set has a binary response variable representing 2 distinct outcomes, a time variable, and some censoring. I am mainly interested in the time ...
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1answer
125 views

Calculating the Cox Hazard Rate

I want to write a code that calculates the Cox Proportional Hazard rate: $h(t|x_it,e_i)=e^{x_it \beta + \lambda(t) + e_i}$ where $\lambda_t$ is a spline in slopes and $e_i$ is an unobserved term. My ...
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1answer
334 views

What is the dependent variable in a coxph regression in R?

I am trying to build a Cox proportional hazards model using the coxph function in the survival package in R. My function call is: ...
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121 views

What variant of interaction when the PH assumption is violated in a CoxPH Model?

When the assumption of proportional hazards is violated, the suggestion is to interact offending covariates with time (or a function of time). In this blog post, the author suggests to include only ...
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159 views

How to manually calculate concordance for a coxPH model

I am struggling to work out how the concordance statistic of a coxPH model is derived. I have built a coxPH model on a small dataset (4 observations). The resultant model is given below: ...
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29 views

Cox-Hazard Ratio differences in Software suits; Manual calculation

Working in clinical research my task is to calculate the Hazard ratio, better to check the calculations of someone else. This first calculation was based on ARM=(3 different treatments) with only t=(...
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683 views

How to calculate the cumulative baseline hazard function for a CoxPH model

I have read that the following formula is used to estimate the cumulative baseline hazard function: I also know that the basehaz command in R will also calculate an estimate for the cumulative ...
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1answer
1k views

Expected survival time for Weibull proportional hazards model with R's predict.survreg

The predictions for a Weibull proportional hazards model from R's predict.survreg() are not the expected survival times. Please help me understand this behaviour. ...
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1answer
25 views

How to estimate an additive hazards model?

Consider the additive hazards model: $$\lambda(t) = \lambda_0(t) + \beta^T Z.$$ I want to assume that the baseline hazard $\lambda_0(t) $ is Weibull. However, $\lambda(t)$ has to be positive by ...
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1answer
186 views

Cox Proportional-Hazards Regression vs. Regression modeling of competing risk using Fine and Gray

30000 patients all have one diagnosis in common, 3000 of them have been exposed to a potential risk factor before the common diagnosis. 1500 patients develop a malignancy after the common diagnosis. ...
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119 views

How should I smooth / average semi-sparse service usage data used in a time series regression?

I am using time series regression and survival models to predict future user outcomes based on past usage trends. I am dealing with a data set of daily service usage per user which, on a given day ...
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58 views

I multiplied a predictor variable by 10. Why does my univariate cox regression HR and p-value change entirely?

I calculated the waist-to-hip ratio from, well, waist and hip measurements in cm. The ratio's values would come out in the range of 0.8-1.1, for my population. When I performed a univariate cox ...
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1answer
342 views

Do multiple observations per individual imply pseudo-replication in time-varying Cox proportional survival model (coxme in R)?

I’m running a survival analysis using a cox mixed-effect proportional hazard model with time-varying covariates (using package and function coxme in R). My ...
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247 views

Time scale in survival analysis

I am doing a churn analysis of some bank customers with survival analysis. Right now I am using the customers' years in the bank [0;17] as time scale, and then use the customers' entry age as a ...
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1answer
200 views

How does time factor into Cox regression or a Cox proportional hazards model?

The hazard function for the Cox proportional hazard model is written as follows. $$\lambda(t|X_i) = \lambda_0(t)\exp(\beta_1X_{i1} + \cdots + \beta_pX_{ip}) = \lambda_0(t)\exp(X_i \cdot \beta)$$ I ...
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3answers
2k views

Proportional hazards assumption and time-dependent covariates

Is there a way to check that the proportional hazards assumption is correct for a Cox model with time-varying covariates ?
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548 views

Predicting Lifetimes using CoxPH

I have a dataset of about 9k rows and 60 features (columns). I have a binary status column (1 - dead, 0 - alive) and a lifetime column in days which is right censored. I am currently using the cox-PH ...
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Cox proportional hazard - can hazard be treated as instantaneous probability?

I'm doing a question on cox proportional hazard models that at the very last step leaps from hazards to probabilities, and I'm not sure how it does this. I've paraphrased it below to keep it simple, ...
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1answer
129 views

Training on censored data with varying sequence length

I have a sequence of daily events, along with times between events. Each such sequence is labeled by $i$ and consists of $n_i$ events. For every $i$, each event $j$ has a list of features $x_{ij}$, ...
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1answer
410 views

Interpretation of hazard rate for multiple failures

I'm trying to run survival analysis of Cox proportional model with panel data that consists of IDs and time variable. Each individuals are allowed to fail more than once in the sample period. My ...
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1answer
988 views

How to manually calculate `survfit` in cox hazard model?

Here is a toy survival model with age only. But I still do not know how the surv numbers in survfit are calculated: $\exp(\beta ...
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2answers
4k views

Recommendations for Non-Proportional Hazards

This is an issue that has plagued me for a long time and I have found no good answers in textbooks, Google, or Stack Exchange. I have data set of >100,000 patients for which four treatments are ...
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1answer
1k views

How can I obtain prediction intervals for survival prediction in the Cox model?

Prediction of survival times in Cox proportional hazard regression model has been discussed here. In R, survfit::survival using ...
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1answer
358 views

Help with a Cox Proportional Hazard Simulation in R

I am trying to follow along with a scientific journal. I am not used to running simulations so I could use a little help in R. Here is the simulation from the paper. For each experiment, we ...
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1answer
1k views

Proportional hazards assumption: trouble interpreting my results for cox.zph() function in R

I am testing my proportional hazards assumption in R using the cox.zph() function: ...
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1answer
474 views

How to cope with non-proportionality?

I run a Cox model with 2 covariates, in addition to the variable of interest. For one covariate, the assumption of proportional hazards is violated. I know different methods developed to cope with non ...
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1answer
437 views

Cox proportional model with multiple failures for same subjects

I have a dataset that I'm trying to model using Cox proportional hazard models. The data include patient IDs and several attributes about the patients (including time till failure). Due to the nature ...
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2answers
891 views

Proportional hazards vs proportional odds for modeling ordinal data

When working with ordinal response data, we can use a proportional odds model to calculate the log odds in favor of one category over another. Often we use a logit link yielding the following model: ...
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1answer
404 views

Hazard ratio curves

Does anyone know of a method to calculate and plot [absolute] hazard ratio curves over a continuous variable? I know of the 'smoothHR' package in R, but it uses an arbitrary reference value and I ...
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Can I calculate the number of patients in experimental and control group based on HR?

I would like to conduct the meta-analysis of randomized clinical trials. In some of them in the subgrup analysis the number of patients in experimental group (Ne) and control group (Nc) are not given, ...
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2answers
666 views

Does the proportional hazards assumption still matter if the covariate is time-dependent?

If I estimate a Cox Proportional Hazards model and my covariate of interest is dependent (continuous or categorical), does the proportional hazards assumption still matter? I recently went to a ...
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1answer
160 views

How can I use a Cox proportional hazards model to obtain probabilities?

I am using a Cox proportional hazards model to estimate the probability of an event (failure of a mechanical device, say) occurring at discrete, finite times: $t = 0, 1, 2, \ldots$. In Cox's original ...
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0answers
126 views

How to interpret insignificance of time-varying coefficient and main effect

I have a survival-time dataset where entities (countries) are measured at discrete intervals (years). I'm interested in examining the effect of some fixed treatments (i.e. ones that occur at the ...
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1answer
398 views

Hazard ratio vs confidence interval

Why or when is the hazard ratio more than the range of the confidence interval? As I understood it, the hazard ratio must fall with in the range of the confidence interval.
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1answer
61 views

How to test in SPSS: categorical with continuous predictor and categorical response?

Edited: I'm a statistics newbie, so please be gentle I'm trying to figure out what test to use to analyze a categorical concurrent with continuous predictor for a categorical response. For example:...