Early-Onset Dementia: Frequency and Causes Compared to Late-Onset Dementia

Background: Research on the epidemiology of dementia has focused on the elderly. Few investigations have studied differences in etiologic frequencies between early-onset dementia (EOD), with onset at an age of less than 65 years old, and the more common late-onset disorder. Objectives: To determine relative frequencies and characteristics of EOD versus late-onset dementia (LOD; age of onset ≧65 years) diagnosed in a large memory disorders program over a 4-year period. Methods: We reviewed medical records, including an extensive neurobehavioral and neurological evaluation, of all patients seen at a large Veteran’s Affairs Medical Center Memory Disorders clinic between 2001 and 2004 and assessed demographic variables, final diagnoses, presence of dementia, and differential diagnosis of dementing illnesses. Results: Among 1,683 patients presenting for evaluation of an acquired decline in memory or cognition, 948 (56%) met established clinical criteria for a dementing illness. About 30% (n = 278) of these had an age of onset of