It's after midnight in my time zone, but I know that there's quite a literature (academic) developing addressing the topic of older people still having ongoing trauma issues (just do a Google Scholar search), including some showing signs of trauma in people who have started developing dementia (Browne & Shlosberg, 2006 DOI:10.1080/13607860500312118). I'll continue to follow this topic, in "normal hours", to see what people come up with, especially as I'm interested in seeing if anyone's developed interventions to help the older age person still suffering from symptoms of trauma.
Suffice to say I currently have one client, age 72, who spent his school years, from age 8 onwards boarding away from his parents, who is a real challenge to try to help (PTSD, maybe even CPTSD), due to his having huge problems "connecting" with others AND due to his avoidant attachment style as a result of his experiences during those formative years. People with such styles very often drop out of treatment "unexpectedly" after only a few sessions, despite how much they truly want "connection", so "forewarned is fore armed" -- therapists need to prepare themselves and their clients for dealing with these difficulties as early as possible in their relationships with clients presenting with these issues.