Elderly cat's change of behavior

I've had my cat, Garfield, for 18 years.  He's a very healthy outdoor cat and, despite his age, has remained very spry and can still climb just about anything.  However, as of late, he's adopted a very odd, and sometimes very annoying, behavior in the mornings.

We have always, during nights, confined him to a room downstairs with all his stuff (litter box, bed, dry food, water) since if he was left to himself he would often wake the entire household in the early hours of the morning to be let out.  This had never been a problem before and we would let him out as we were getting ready for work or school in the mornings.  He never seemed to have an issue with it.

Now, we will oftentimes hear him meowing - a loud, persistent howl, almost - as early as 4 a.m. and he does not relent until someone lets him out.  If that was the only thing, it wouldn't be an issue ... what's difficult to deal is that after we let him out: the meowing does not stop.

He will sit in the middle of the kitchen meowing that same howl of a meow.  So we give him wet food, a saucer of skimmed milk or water (sometimes all three) but he isn't interested.  We open the door to let him out but he isn't interested in that either.  He will go around meowing at all the closets or closed doors to be let in but as soon as they're opened, he loses interest.  The ONLY thing that will keep him quiet for some small measure of time is once someone is out of the shower, he will go and lay at the bottom of the tub for a while.

We've tried just keeping him out and about the house all night with everything he needs laid out in the kitchen but that hasn't worked either.  I'm just running out of ideas as to WHAT he WANTS and now I'm beginning to think that he doesn't know himself.

Is there any way to break this strange habit of his?

[FurballsMom]

Maybe the poor cat is getting senile.

[opus88]

your kitty IMO has a UTI (urinary tract infection)...very common with older male kitties, he is howling b/c he is in an extreme amount of pain...I lost one of mine year ago who was acting the very same, by the time I realized something was wrong and got him to a Vet it was to late for treatment....with this UTI he may well have bladder crystals that are blocking his urethra making it impossible to empty his bladder which may burst if left untreated.
PLEASE take this kitty to a Vet for a urinalysis ASAP....he is in a terrific amount of pain...good luck

[Piparskeggr]

At kitty's age, I would caution towards a trip to the vet.  If it's a UTI, it is eminently treatable...having had such (on top of stones), I can well imagine the pain Garfield has.

Plus, older kitties do get lost in the house sometimes and the yowling is a sign of distress from that, too.  Anita's family's cats Fonzie (08/70 - 02/93) and Tiger (11/69 - 10/92), both manifested this behavior when they got elderly.