We think of dementia as an illness of the old. Regan described the senility of her father, King Lear, as “the infirmity of his age.”1 However, dementia can affect younger or middle-aged adults. Approximately 200 000 Americans younger than 65 years have dementia.2 Young-onset dementia (YOD) represents 4% to 10% of all dementia cases.2 By convention, YOD is defined as dementia occurring before age 65 years, although this age criterion is a sociological construct.
Levine DA. Young-Onset DementiaUnanswered Questions and Unmet Needs. JAMA Intern Med. 2013;173(17):1619-1620. doi:10.1001/jamainternmed.2013.8090