Alzheimer’ s disease is the most common type of dementia. Current estimates are that about 5.8 million people in the United States have Alzheimer’s disease and related dementias, including 5.6 million aged 65 and older and about 200,000 under age 65 with younger-onset Alzheimer’s. We begin the series on Dementia with an overview, featuring voices of family members and leading experts in the field.