I'm sorry your dad is going senile, I know how worrying it is for you and the family. My mom told me one time, that when she came back from her shopping, my dad was on his way down the stairs in his slippers - when she asked "where are you going" he replied "off to work". This was a few years after he stopped working. Luckily she got him back up.

Apart from the advice you have been given, I can only add this: make sure he has a pice of paper in his pockets with a tel. no and address on, in case he does wander off. Oh and keep an extra eye on him if it's cold outside!

I hope he'll be better and you don't have to worry.