Dementia is a general term that describes a group of symptoms related to the loss of multiple intellectual functions—such as loss of memory, judgment, language and complex motor skills—that interferes with daily living. Dementia is a common disorder in people aged 65 and older (10 percent), and very common in those 85+ (47 percent). It is not a normal part of aging.Alzheimer’s disease is the most common form of dementia for individuals age 65 and older. Someone who has Alzheimer’s disease will progressively develop many problems in thinking, memory, personality, mood, behavior, and functioning. Clinicians diagnose "probable" Alzheimer's disease by taking a complete medical history and conducting lab tests, a physical exam, brain scans and neuropsychological tests that gauge memory, attention, language skills and problem-solving abilities. Proper diagnosis of Alzheimer's disease is critical since there are dozens of other causes of dementia that could exhibit the same symptoms. Some of these dementias, such as those caused by vitamin deficiency, thyroid problems and depression, are reversible; of those that are irreversible, Alzheimer's disease is the most common.