not as young as one used to be vs septuagenarian

not as young as one used to be

septuagenarian

noun

Synonym of seventysomething: a person between 70 and 79 years old.

adj

Of or related to seventysomethings.

How often have the words not as young as one used to be and septuagenarian occurred in a corpus of books? (source: Google Ngram Viewer )