Does command substitution within arithmetic substitution get word split?

I seem to recall from comments on this site that the contents of arithmetic expansion **may** be word split, but I can't find the comment again. Consider the following code: printf '%d\n' "$(($(sed -n '/my regex/{=;q;}' myfile)-1))" If the sed command outputs a multi-digit number and $IFS contains digits, will the command substitution get word split before the arithmetic occurs? (I've already tested using extra double quotes: printf '%d\n' "$(("$(sed -n '/my regex/{=;q;}' myfile)"-1))" and this doesn't work.) ----- Incidentally the example code above is a reduced-to-simplest-form alteration of [this function](https://stackoverflow.com/a/35882480/5419599) that I just posted on Stack Overflow.