Dementia can be reversed only if it is caught early. There are different factors that may affect the vital functions of the brain. If the dementia is caused by the lack of vitamins, the intake of drugs, and other alcohol, living a healthier lifestyle can help prevent dementia from taking place.
In fact, dementia will be reversed. If the dementia is caused by trauma or it is really a degenerative disease, this cannot be reversed anymore. The best thing to do is to understand the person who is suffering from dementia. The more that you care for the person, the more at ease you will feel because you know that the person is in safe hands.
Sadly, no. It can be managed and perhaps delayed to an extent but once a person shows clear signs of dementia they are not going to return to a state where dementia is never evident again. However, in the case of Alzeimers' disease, where dementia is present, removing much of the sugar and carbs from the diet can halt and possibly reverse some memory loss.
In Alzeimers' the cause is eating too many carbs and sugar and not enough fat and the adverse effects include pre-dementia, probably ten years before Alzeimers' is diagnosed.