Why does my 1 year old baby has suddenly started waking up every hour at night who used to sleep long before?

A. The sleep pattern changes from time to time maybe your child is hungry or your child is not sufficiently full with the food that you given and that is why your child wakes up to have milk every one hour so if you’re still breastfeeding the child I would advise you to replace your breastfeeding with another milk specially and only for the night