How to stratify an additive hazards model?


I am trying to conduct a stratified additive hazards model (Aalen’s additive model).
I am using Stata 12.1.

The stata syntax for the Aalen’s additive hazards model is stlh.

I have pooled a number of cohorts and would like to calculate the coefficients for risk factors for the outcome and let the intercept vary by sex and cohort.

However, nowhere in previous literature can I find information on how to stratify this model, ie, running the model with a function corresponding to the ”strata” command in the stcox.

Has anyone considered this; methodological issues and possible ways of doing it in Stata or R?

I would be very thankful for any type of input.