New tweet from Togashi (August 12, 2022)

This comment was posted to reddit on Aug 12, 2022 at 4:56 am and was deleted within 18 hour(s) and 26 minutes.

To add onto this:

Togashi has been insistent on not wanting assistants (other than his wife), as he wants it to be entirely his work (probably because YYH was heavily influenced by what Shonen Jump wanted to do). Comparatively, I know for sure Oda (One Piece) has had a few assistants for a while. Same with other series like One Punch Man.
Togashi has been doing this for a very long time. YYH started 7 years before One Piece for some perspective.
Also, from a more general perspective, once you get hurt, you are way more likely to hurt yourself in that same way. So if Togashi was feeling the pain near the second half of YYH and did nothing about it, he'd be completely fucked by now (which lines up with reality). The back in particular is a really bad muscle to fuck up.
Lastly, losing your mobility, especially at an older age, completely destroys your quality of life. Take the shit/shower story for instance, he literally cannot perform a common bodily function because the pain is unbearable.