# Questions tagged [time-varying-covariate]

A variable that records something about a study unit in a longitudinal study that changes over the course of the study.

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• 572
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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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### How do I incorporate a patient's current age into a survival model?

I have a dataset with 10,000 patients, and for each patient, I have the following information: Biological sex (male/female) Baseline age (age at the time the patient joined the study) Age at the ...
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### How do I test the Cox proportional hazards assumption if my model already has an interaction term?

If my model already has an interaction term (ex. sexHispanic ethnicity), how do I test the Cox proportional hazards assumption using interaction with time-dependent covariates? Would I enter timesex ...
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1 vote
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### Counting process style survival analysis - do I still need to interact with time?

I'm working in Stata with a Cox model and I have a dataset in counting process style (multiple records per subject). Each observation per subject has covariants that could potentially be different ...
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### Linear Mixed Models for randomized clinical trial

I am working on analyzing data from a randomized clinical trial which is studying the effect of a mesh type on patient-reported pain. The 2 study arms are the 2 different meshes (biologic and ...
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### 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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### 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 ...
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### How to test for effect modification and mediation by time-varying factors in a longitudinal context?

I have longitudinal data with measures of an exposure, outcome, variables that may be mediators or effect modifiers, and confounders at 3 time points. I would like to account for time-invariant and ...
• 471
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### Formatting cox data with time-dependent continuous variables and unequal time intervals

I am planning to do a joint model for longitudinal and survival data, with multiple time-dependent/time-varying continuous variables. However, I am having trouble re-formatting my dataset to be in a ...
139 views

### Time varying coefficients with splines in Cox model

I am wondering whether it is valid to fit spline interactions between time and predictor variables (either categorical or continuous) in a Cox model. I am having difficulties specifying this model, ...
• 859
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### Why can't we use normal Cox ph survival model by incorporating time-varying covariate features into it?

Using the stanford heart transplant dataset, I have seen articles on why time-varying covariates are important as an input for survival analysis models. But can't we incorporate the time at which ...
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1 vote
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### Cox survival model with pre-determined time-dependent covariate

I am working on the Cox survival analysis model with time-dependent covariate, which is a very very common model. However, in most papers and R packages, I noticed they estimate the parameters of ...
1 vote
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### What survival model can handle a different time for each covariate?

I would like to fit something like a Cox model but each covariate on my data could have been measured at a different time, different for each person. Is there any alternative survival model allowing ...
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1 vote
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### How to Conduct and Analyze Time Series Ordinal Logistic Regression using R?

I am working on a project where I have collected ordinal outcome data at three different time points. I am interested in modeling the change over time with these ordinal outcomes. Initially, I ...
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### Latent growth curve model - can I talk about an effect over time if I only have my outcome at the last timepoint?

I have a latent growth curve model with two variables. X (exposure to media) was measured at 5 time points over several years. Y (misinformation proneness) was measured only at the last time point (...
1 vote
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### Time-independent variables in survival analysis

In any non-cross-sectional, prospective (whether it be longitudinal, survival, etc) study there are baseline variables which contain the status of the variable at the beginning of the study, and these ...
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### Time-Varying-Intercept in Logistic Regression

Background I have a panel of binary response data - I have a different cross section of individuals each month, across many months, and the outcome is 0 or 1. When fitting a logistic regression that ...
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### Cox time varying covariates (time dependent)

I have a question about an extended cox regression model. I have reviewed several materials, such as "D.G. Kleinbaum and M.Klein, Survival Analysis: A Self-Learning Text, Third Edition" but ...
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### repeated measures multinomial logit or competing risks?

I need some help/advice for tackling the following problem: interested in exploring the association between various covariates and the reason for termination from a data registry. The hypothesis/...
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 ...
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### Time Dependent Interaction Term in Cox Regression

I am running a cox regression for survival analysis using the coxph() function in R for a very large dataset. My model is set up as: Surv(time,event) ~ age + race + sex +... The study period is 1 year....
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### Do dynamic logistic models require data points to be temporally independent?

despite my searching, I cannot find a clear answer to the question: Do dynamic logistic regression models require data points to be temporally independent? An answer, an hint and/or a reference would ...
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### Generalizing ATT to the time-varying setting

In the case of a point treatment, the average treatment effect among the treated (ATT) is the treatment effect standardized to the subset of the sample that received treatment $A=1$ as an estimate of ...
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