It is important to note this line "due to a gradual decoupling of thirst from hydration status"

older people gradually lose their ability to sense thirst.

So, if you're older, you can be dehydrated but not feel thirsty.

I suspect the practical solution to this is to drink more all the time.

But I also think there's probably a market for some way of letting older people monitor their hydration status, maybe through a watch or other sensor.