Dementia is the medical term used for what historically was called senility - deterioration of intellectual capacity, commonly, but not necessarily, seen in older persons. It is more than just memory loss - it involves loss of memory, reasoning, judgment, calculation, speech and comprehension. Many older persons have temporary lapses in memory, without suffering true memory loss. This can be normal. This is normal.
Older people take longer to commit something to memory, and longer to retrieve things from memory.
This is normal. Dementia exists when a person experiences difficulty carrying out normal tasks as a result of deterioration in overall intellectual capacity. Dementia is not a result of normal aging. The causes of dementia are many, including Alzheimer's disease, a series of small strokes, longstanding hardening of the small arteries of the brain, brain infections such as encephalitis or AIDS, head injury, deficiencies, poisonings, alcohol, medications, Dementia with Lewy Bodies, and so-called Frontotemporal Dementia. In terms of likelihood, two-thirds of all dementias in the United States are caused by Alzheimer's Disease, a specific medical condition resulting from the abnormal deposition of amyloid and other chemicals in the hippocampus of the brain, resulting in a profound decrease in the production of acetylcholine and certain other neurotransmitting chemicals.