foregoing salaah

Q: My father is 92 years old and suffered a stroke about a year ago. The stroke left him weak on one side, he is now not able to control his urine and hence he messes himself. So he now wears diapers. My father had been living with my sister and brother in-law until last month. He now lives with me in Cape Town. I have just learnt that my father hasn’t performed any Salaah for the past year. He says he can’t perform any Salaah because he is always in the state of impurity because he messes himself and he has to wear a diaper. What is the Islamic ruling in regard to this matter?