The term “dementia” encompasses over 50 different diseases. Although each develops differently, in the long term they all impair a person’s cognitive abilities and lead to memory loss.
Alzheimer’s disease (see What is the difference between Alzheimer’s and dementia?) has three phases, each associated with different signs of dementia. In the early stages, short-term memory is affected, causing people to become forgetful; they often misplace items and have difficulty concentrating. They may also forget the names of everyday objects, and they find it harder to get their bearings in unfamiliar environments. A sign that the disease is progressing is the onset of long-term memory loss. Memories from past decades fade away and sufferers find it difficult to recognise even close members of their family. In the final stages of the disease, sufferers also begin to deteriorate physically and require constant care.
A less common form is frontotemporal dementia. People with this disease initially experience very different symptoms: their personality changes, they are easily irritated, and they behave unusually. That is because this form of dementia initially affects the regions of the brain controlling social behaviour. Eventually, though, it too leads to memory loss.
Saskia Blank from the Ideas 2020-Team answered this question.