I know that they were often the first to be murdered when they arrived at camps, but surely a few healthier 65+-year-olds made it through? One thing that most of the Holocaust narratives that I've read don't tend to feature is personal experience of the long-term ramp-up to the Holocaust. Were there any survivors who also recounted hearing about the Dreyfuss or Beilis Affairs, or similar incidents well before the Holocaust? I've also read that Jewish emigration to the US spiked in the early decades of the 1900s; is that indicative of a strong upswell of anti-Semitism at the same time? Did older Holocaust survivors feel like they "saw it coming," at least in some way?
One noteworthy example from an older victim is Victor Klemperer's work. He is in his 50's, and redditor 'keloyd' is not far behind, so I am stretching a point to answer your question about the elderly specifically. Some relevant books - I Shall Bear Witness 1933-1941, To The Bitter End 1942-1945, The Lesser Evil 1945-1959, The Language of the Third Reich
I've read the first 2, started #3, and heard good things about #4, partly from the author himself discussing in his earlier books the notes and analysis that may become a future book.
Long story short, Klemperer is a professor of Romance languages in his 50's when Nazis come to power. (An amusing detail - he is a cousin of the actor who played Colonel Klink in Hogan's Heros.) He was not in a concentration camp himself but documented Nazi mistreatment in thorough detail and knew many victims who were sent to the ghettos and murdered. The 1933 Law for The Restoration[!] of The Professional Civil Service forced him into retirement with a partial pension, that eventually went into a locked bank account that they could only withdraw a very small amount from each month for basic necessities. He was ethnically Jewish but had some characteristics that worked in his favor in an unwieldy, bureaucratic, legalistic government. He converted to Christianity in 1903 (and maybe again in 1912.) He was a decorated veteran of WW1. His wife was Aryan German. They had no children - an advantage in that he was not defiling the precious bodily fluids of the Aryan race by siring mischling children.
The first 3 books are his diaries - partly personal and partly written with an eye to future publication. It is an interesting quirk of these books to see petty details about a 50-something couple griping about minor health issues as one expects in a personal diary...right next to thoughtful and deep analysis of sociological trends...right next to strategic planning for how to avoid being murdered by the Gestapo when your Jew-stamped ration card is spent at a store for (partly rotten, but you cannot complain) potatoes, but the clerk gives you change (smaller denoted ration cards) not stamped with a "J".
Klemperer is one of a small number, likely in the low 100's, of Jewish Germans who avoided murder, sometimes just barely, because of bureaucratic scrupulosity of small niggling points combined with supportive Aryan in-law relatives who also suffered a great deal. His wife was pressured to divorce him by the Gestapo - repeatedly and with a level of enthusiasm that I will leave to your imagination. Some little bureaucrat at his old university kept paying his pension through the war. No one can put a name to whoever made this decision, but in my own career, I am a sort of government bureaucrat whose work has an accounting aspect to it; I hope to have the backbone to do the thankless right thing if something like this lands on my desk in future decades.
The books are not pleasant reading, but he writes well. He had some journalism work at some point, so he is more clear and concise than what one may expect from academics.
Lengthy discussions appear in his diary on (1) should we have seen this coming? (2) what is next? (3) What part of "Germanness" caused all this evil? They are in the middle of the thing but manage very good hashing out of these ideas without our 8 decades of hindsight.