Alzheimer's disease and Old age

Alzheimer's disease noun - A progressive form of presenile dementia that is similar to senile dementia except that it usually starts in the 40s or 50s; first symptoms are impaired memory which is followed by impaired thought and speech and finally complete helplessness.

Old age and Alzheimer's disease are semantically related. In some cases you can use "Old age" instead a noun phrase "Alzheimer's disease".

Old age noun - A late time of life.

Alzheimer's disease and old age are semantically related. You can use "Alzheimer's disease" instead a noun phrase "Old age".