Dementia refers to the loss of cognitive functions (thinking, reasoning, the ability to remember) that are severe enough to interfere with a person’s daily functioning. This group of symptoms is not a disease per se, but may accompany certain diseases or conditions. Dementia is irreversible when caused by disease or certain injuries. It may be partially or fully reversible when caused by drugs, alcohol, depression, or imbalances in certain substances, such as hormones or vitamins.
Alzheimer’s disease is a progressive, degenerative disease of the brain, characterized by loss of function and death of nerve cells in several brain areas, leading to loss of recent memories and new learning first, and eventually old memories, too.