Hello, Unfortunately, there is no good answer to the question of his life expectancy since that is much more dependent upon his overall state of health and other comorbid conditions he may have such as hypertension, diabetes, and renal function (among others). There are no known medications or treatments on the market to reverse the consequences of dementia. My advice is that he obtain a caregiver who can help with his activities of daily living. This will help much more than medication in keeping him safe and improving his chances at a longer life in order to avoid falls and make sure he gets medications, hydration, and meals daily and on time. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr Dariush Saghafi, Neurologist