centenarian vs older adult

centenarian

noun
  • One who or that which is at least 100 years old. 

adj
  • Aged 100 years or more; extremely old. 

  • Of or relating to centenarians or a centenary celebration. 

older adult

noun
  • An old person. 

  • Used other than figuratively or idiomatically: see older, adult. 

How often have the words centenarian and older adult occurred in a corpus of books? (source: Google Ngram Viewer )