Sometimes the most difficult illnesses to deal with aren’t physical, but mental. One such cognitive disorder is dementia, which can affect anyone at any age, but is most common after the age of 60. So, what is dementia? It is a general definition for a disease which results in memory loss, lack of focus, and an inability to communicate or use reasoning skills. Alzheimer’s disease, Huntington disease, and Parkinson’s disease are closely related to dementia.