The use of rejuvenating drugs, usually referred to as "rejuvenat" treatments, is commonplace amongst the middle and upper classes of all technologically advanced Imperial worlds. With regular use they can slow or even reverse human aging dramatically for centuries by repairing damaged DNA strands with specific enzymes and regularly cleansing the build-up of cellular and metabolic toxins from the human body. But sooner or later even the most expensive chemical treatments fail to hide the ravages of age. At that point the subject becomes more vulnerable to infections and organ failure. After 400 standard years of life few human beings within the Imperium can survive without mechanical assistance.