Survival Analysis Using SAS®: A Practical Guide

The Accelerated Failure Time Model

The class of regression models estimated by PROC LIFEREG is known as the accelerated failure time (AFT) model. In its most general form, the AFT model describes a relationship between the survivor functions of any two individuals. If S_i(t) is the survivor function for individual i, then for any other individual j, the AFT model holds that

Equation 4.1

where ø_ij is a constant that is specific to the pair (i, j). This model says, in effect, that what makes one individual different from another is the rate at which they age. A good example is the conventional wisdom that a year for a dog is equivalent to seven ...