longevity
This is not a piece of advice to you I'm talking to myself for my practice of writing skills. healthy life expectancy is an indicator which WHO advocated and the period when person can live in healthy and active during the average life expectancy. this means the remaining which from the average length of life deducted the nursing care period such as weakening/illness/dementia. the average length of life means the average life expectancy at one's 0 age. in the definition of the word "dementia" on the weblio dictionary there'd be a hint. Since the 2004 decision by the Ministry of Health, Labor and Welfare in the fields of government and medical/nursing -care, the word "dementia" is on the process of replacing to "cognitive decline". in Japan the replacement has been already done then some parts of expression might be different from the original expressions.
https://www.weblio.jp/content/健康寿命.
https://www.weblio.jp/content/平均寿命.
https://ejje.weblio.jp/content/dementia.
回答
Japanese expression of the word "dementia" changed from "痴呆" to "認知症". this expression change comes from the feeling to be disrespectful because of Japanese kanji are ideograms. so I've searched the English words match to these Japanese words, but I couldn't have found. then I'd assume that there'd be no change in English words concerning this Japanese word change. Dementia In 2004, the study group on terms of the Ministry of Health, Labor and Welfare expressed the view that "cognitive decline" is more appropriate than "痴呆" as a general or administrative term.
https://www.weblio.jp/content/痴呆.
paraphrase of dementia "痴呆" and "cognitive decline". In December 2004, the Ministry of Health, Labor and Welfare submitted a report stating that "痴呆" was meant to be disrespectful, and the term was changed.
https://www.weblio.jp/content/認知症.