Introduction
In England, free triennial mammographic breast screening is routinely offered at ages about 50-70 to all women, and any treatment arising from this is also free. The advantages and disadvantages of starting mammographic screening at a somewhat earlier age are uncertain. Likewise, there is uncertainty about the advantages and disadvantages of continuing for some years beyond age 70.
AgeX addresses these questions by randomly comparing different age ranges for routine triennial screening invitations in most of England, monitoring any effects on treatments and on outcomes through government statistics.