can an older cat be trained to use a litter box

Question
An older 6 year old cat adopted us 5 months ago.  He is used to being outside ...He wants to sleep in during the day and go out at night (he is neutered). He is adorable, loving and we love him.  As he is older, I am concerned he will not be as fast in getting away from predators in the night.  He refuses to use a litter box.  He wants to go outside.  Is there a chance of "training" him so he will stay inside the house?

Thank you so much.  He has been a blessing in our lives and we do not want to see him get hurt.

Answer
Barbara,

Here is some information from Tidy-Cat on getting outdoor cats used to using a litterbox:

Cats are creatures of habit so any change must be gradual. It would be helpful to know the location of Kitty's favored relief station. Maybe it's the loose soil in the flowerbed? The compost or leaves in the back yard? Whatever it is, take your extra-large-size litter box to that very location, and fill it up with the soil, leaves, sand, whatever he's now using. Mix it about 2/3rds of his "known" material with 1/3rd of a commercial cat box filler. When possible, use a litter box scoop to deposit some of his--er, ahem--fresher deposits in this box, as a visual and odiferous reminder. Watch to see if he'll investigate and use the box. Most cats are very curious, and this should intrigue him a bit.

You'll still need to let him out for a bit each day, until he gets the idea--but once he begins using the indoor box, you can start mixing a greater percentage commercial litter compared to the dirt/leaves/sand until eventually he's transferred acceptance. At the same time, reduce the amount of time he's allowed outside, until he's fully accepted his new indoor facilities.

Also, I would keep the litterbox close to the door at first.

I hope this info helps.
Tabbi