Aulus Gellius, Attic Nights
15.7.1-2 (tr. J.C. Rolfe):
It has been observed during a long period of human recollection, and found to be true, that for almost all old men the sixty-third year of their age is attended with danger, and with some disaster involving either serious bodily illness, or loss of life, or mental suffering. Therefore those who are engaged in the study of matters and terms of that kind call that period of life the climacteric.
observatum in multa hominum memoria expertumque est, senioribus plerisque omnibus sexagesimum tertium vitae annum cum periculo et clade aliqua venire aut corporis morbique gravioris aut vitae interitus aut animi aegritudinis. propterea, qui rerum verborumque istiusmodi studio tenentur eum aetatis annum appellant κλιμακτηρικόν.