Flexible parametric accelerated failure time models

Accelerated failure time (AFT) models are used widely in medical research, though to a much lesser extent than proportional hazards models. In an AFT model, the effect of covariates act to accelerate or decelerate the time to event of interest, i.e. shorten or extend the time to event. Commonly used parametric AFT models are limited in the underlying shapes that they can capture. In this project, we developed a general parametric AFT model, and in particular concentrate on using restricted cubic splines to model the baseline to provide substantial flexibility, as well as extending to time-dependent acceleration factors.


The latest stable version of staft is available on the Statistical Software Components archive, and can be installed directly in Stata by typing:

ssc install staft


Crowther MJ, Royston P, Clements M. A flexible parametric accelerated failure time model and the extension to time-dependent acceleration factors. Biostatistics 2022; (Accepted – pre-print).