How can the Hadith "Allah has not sent down a disease but that He has also sent down its cure; he who knows it, knows it, and he who does not know it, does not know it" be reconciled with the Hadith "Allah has not sent down a disease but that it has a cure, except for old age (al-haram)"? And is vascular dementia considered a type of old age (al-haram)?

Summary of the Answer:

Prophetic hadiths state that Allah has not sent down a disease except that He has sent down a cure for it, with the exception of "old age" (al-haram) in one narration, and "death" (al-saam) in another. There is no contradiction between these hadiths, as they can be reconciled by considering the exception of old age as a specific qualification to the general hadith, or by considering the exception as disconnected. Old age is likened to death in that it has no cure and leads to annihilation, and it is not an organic disease in the known sense. Old age is the weakness of old age, or it is a natural decay and a path to annihilation, and it has no cure. As for vascular dementia, specialists should be consulted about it.