Old age and Second childhood

Old age noun - A late time of life.

Second childhood and old age are semantically related. in period of being elderly topic. In some cases you can use "Second childhood" instead a noun phrase "Old age".

Second childhood noun - Mental infirmity as a consequence of old age; sometimes shown by foolish infatuations.

Old age and second childhood are semantically related. You can use "Old age" instead a noun phrase "Second childhood".