Interesting question. I have wondered also. What is this forgetfulness caused from? I tried to Google this question and received:

Dementia is a broader term referring to a decline in cognitive abilities, while Alzheimer's disease is a specific type of dementia. Alzheimer's disease is the most common cause of dementia. Essentially, Alzheimer's is a disease that causes dementia.
Here's a more detailed breakdown:
Dementia:
This is an umbrella term for a group of symptoms, including memory loss, impaired thinking, and behavioral changes, that interfere with daily life.
Alzheimer's Disease:
This is a specific disease that causes dementia. It's characterized by the progressive destruction of brain cells, leading to cognitive decline.
Other Types of Dementia:
While Alzheimer's is the most common, other types of dementia include vascular dementia, Lewy body dementia, and frontotemporal dementia.
Progression:
Alzheimer's disease is a progressive condition, meaning that symptoms worsen over time.
Causes:
Alzheimer's disease is caused by the build-up of proteins (amyloid plaques and neurofibrillary tangles) in the brain, which disrupts brain cell function.
Symptoms:
Common early symptoms of Alzheimer's include memory loss, particularly for recent events, and difficulty with language and abstract thinking.
No Cure:
Currently, there is no cure for either dementia or Alzheimer's disease, but treatments can help manage symptoms and improve quality of life.