In Nazi Germany, the elderly were not actively deported to concentration camps because the primary focus of the Holocaust was the extermination of Jews. However, many found themselves in concentration camps indirectly if they were classified as politically undesirable or socially deviant, had mental or physical disabilities, or were otherwise deemed disposable by the Nazi regime.
As for the ill, this group faced even grimmer prospects. The "Aktion T4" euthanasia program, which began in 1939, specifically targeted individuals with physical and mental disabilities. Patients were selected for involuntary euthanasia if their condition was deemed a burden on the German healthcare system or society as a whole. They were sent to specialized killing centers, where they were subjected to lethal injection, gassing, or starvation.
The Aktion T4 program laid the foundation for the implementation of the extermination facilities in Nazi concentration camps such as Auschwitz, Sobibor, Belzec, and Treblinka. As the war escalated and the Nazi leadership sought a way to efficiently exterminate large populations of Jews and other minority groups, the methods used in the Aktion T4 program were applied to these extermination centers.
It's important to remember that the extermination process had no regard for age or health condition. While elderly and ill individuals were not prioritized for deportation to concentration camps, those already there or found through selection processes faced the same systematic extermination as able-bodied, Jewish prisoners.