why does my cat cry at night -- party due to old age and other condtions

I had a cat that yowled quite a bit during her final years of life. She was almost 20 when she passed away. She was diagnosed with an overactive thyroid and had been put on medication for that condition. The yowling and crying took place primarily at night. I’d usually find her looking confused so I always thought that she was “lost”. I’d point her in the direction I thought she might have been heading (litterbox or food dish as examples) & most times she’d follow through & then I’d take her off to bed with me.