I suspect that most people omit to declare conditions on the medical forms, particularly on holiday dives. You would have to have had an incredibly fortunate life not to have had at least a few of the conditions and several of them if some time ago have no bearing on diving. What I have done is seen a GP (who has diving knowledge) at my local practice and had a thorough examination including blood tests. All this cost nothing for a verbal "OK to dive" but if I had wanted him to fill in the PADI form it wold have cost £70.
An interesting point about the unlikely situation of someone being able to truthfully answer No to every single question. Don't recall that point being brought up before on these threads. I honestly can't recall if I fudged a bit or not when filling in all "No"s. It was too long ago.
So, I googled the present form (which appears to be exactly the same ones I filled out (2005-2009).
I "lied" on 3 things--(well, I must have since I at least don't recall getting a letter from my Dr.).
--Currently smoke (a pipe, and infrequently).
--Take prescription medications (I take others now, but back then I took one only and it couldn't possibly cause any problems while diving--a bladder problem).
--hernia operation-- 1990. Some kind of "Hiatal" or Abdominal thing. Dr. knew about it and said diving was irrelevant.
Of course, I'd never list these if I were still a working DM. To be honest, I never gave these things a thought during those 4 years either. But I always talked to my Dr. about my diving and he to me about his swimming. I guess he would've said something all those years if he thought I was at risk at all.
Now, of course I could've answered Yes on these 3 and getting a Dr.'s release would've been no problem. Except that the Dr. was a 50 mile round trip away from home and the shop a 100 mile round trip in the opposite direction. Just saved that little hassle.