Changes in this layer start 7 years before death. Cyndi Dale explains:
Many illnesses, like cancer for example, show up in the auric field long before they affect the body and can be seen in this layer of the aura.... most individuals prepare for death during a five- to seven-year time span, meaning that their soul begin to disengage and prepare for the passing about five to seven years before their body dies. This idea, interestingly enough, been confirmed for me through corporate consulting work I have done for an elder residence. Workers there have said that they can often tell when someone is going to die and that the process typically lasts about seven years.
(...) the thickness and whiteness/brilliance of the seventh auric layer change the closer someone is to death. In genral, as the soul prepares to leave, the seventh auric layer thins out. More spiritual energy is therefore directed to and through it, thereby lightening the tone of this layer.