Seek the help of a physician. If Alzheimer’s, a type of dementia, is caught in the early stages, there is a lot of preventative care and treatments that physicians may offer your father to maintain, and even increase, quality of life. Make notes of any of the common Alzheimer's signs or symptoms your father might show.
If you find that taking care of your father is becoming too burdensome on you, consider having other family members help or hire outside help. There are in-home health aides, as well as adult day care centers that have staff specially trained for seniors with Dementia or Alzheimer's.