In all dementias there is a loss of intellectual ability. This means losing the ability to use information once known or learned, as well as basic abilities to think and to understand. There are also memory deficits or losses with recent memory being the first area affected. Dementia disorders share common symptoms, but they can have different causes. The most common form of dementia in older adults is Alzheimer's disease.
AD is a progressive, irreversible brain disease that affects the central nervous system.
It is caused by factors that are largely unknown and results in a slow, gradual decline of intellectual functioning, memory, and judgment. It can occur as early as 40 years of age or as late as 100 years of age. Other types of dementia are caused by Parkinson's disease and Huntington's disease. Individuals with Parkinson's disease develop severe problems of movement and balance, and other problems, including dementia. Huntington's disease is a hereditary disease usually appearing when the individual approaches 40 years of age.