My grandmother had dementia. It developed over many years.; She had various forms of medication and some herbal supplements as well, including the reputed gingko biloba. Her dementia was not constant. There were days she forgot things and other days she remembered them. She could spend days or weeks in a funk and then get better for a little while only to eventually sink again. I imagine it's like that for many people who suffer from it, and alot has to do with nutrition, medication, sleep, sunlight, stress and even things unknown. It's pretty unreasonable to argue over whether JB has it or not. It's been documented many times but there are times he may also regain some of his cognizance temporarily. It's an undulating pattern, like when winter is setting in. Some days are warmer, some are colder...but ultimately the trend is to grow colder.
