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I have a dataset with a number of records. For any record $i$, I have:

$(T_i, X_i^{fixed}, X_i^{vary})$

representing an event time $T_i$, a set of features $X_i^{fixed}$ that are time-invariant and a set of features $X_i^{vary}$ that are time-series, reported every minute for every record. Note that I do not have any censoring in the data, every single record has a known event time.

I want to model the event time, conditioned on the features I have. Accelerated failure time models are the most popular in my application, and reading up on these, the authors typically use a set of fixed features to model the log of the event times. That is:

$log(T) = \mu + \beta'X^{fixed} + \epsilon$.

They choose some distribution for $\epsilon$ and then fit the model via optimizing the log-likelihood function.

My question is, are there known methods to incorporate the time-varying features into this framework? I see a lot of discussion of time-varying covariates for cox-models, but not so for accelerated failure time models. The simplest thing I can think to do is just treat this as a standard regression problem (due to no censoring) and at some time $t$, given $X_i^{fixed}$ and the time-series $X_i^{vary}$ up-to $t$, try to predict the remaining time until $T_i$. But, this means each event is present multiple times in the data, so I am unsure if independence among observations is then true.

Any pointers on how to address time-varying AFT models, or other helpful advise on this situation is greatly appreciated.

kjetil b halvorsen
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Kieran108
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  • Does this answer your question? [Weibull Survival Model with Time Varying Covariates in R](https://stats.stackexchange.com/questions/206024/weibull-survival-model-with-time-varying-covariates-in-r) The answers on that page show 2 or 3 different ways to handle time-varying covariates in an AFT model. (Weibull as in the title of that question is both PH and AFT, the answers are more general.) – EdM Aug 19 '20 at 20:12
  • Thanks for this, reading the documentation for one of the answers gave an idea of how to actually formulate the problem. – Kieran108 Aug 20 '20 at 13:08

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