Dementia is a gradual decline of mental ability that affects your intellectual and social skills to the point where daily life becomes difficult. Dementia can affect your memory and your decision-making ability, can impair your judgment and make you feel disoriented, and it may also affect your personality.
Alzheimer's disease is the most common form of dementia and affects about 5% of people over age 65. It occurs more often with advancing age, affecting 20% to 25% of people over the age of 80. About 5% to 10% of dementia is vascular dementia, also known as dementia caused by stroke. At least 10% of cases of dementia are due to a combination of Alzheimer's disease and multiple strokes.
Dementia isn't an acute condition that suddenly appears, and it usually does not require emergency treatment.