title: Early-onset dementia: frequency and causes compared to late-onset dementia.
abstract: 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.
  
  
  OBJECTIVE
  To determine relative frequencies and characteristics of EOD versus late-onset dementia (LOD; age of onset > or =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 <65 years, compared to 670 with LOD. Patients were predominantly male (98%). Compared to the late-onset group, the EOD patients were less severely impaired on presentation, but they did not differ in gender distribution or educational background. The EOD group had significantly more dementia attributed to traumatic brain injury, alcohol, human immunodeficiency virus (HIV), and frontotemporal lobar degeneration compared to the LOD patients. In contrast, the LOD group had significantly more Alzheimer's disease compared to the EOD group.
  
  
  CONCLUSIONS
  This study, conducted at a Veterans Affairs Hospital, is the largest series to date on EOD, and found a previously unexpectedly large number of patients below the age of 65 with cognitive deficits and impaired functioning consequent to head trauma, alcohol abuse, and HIV. These findings highlight the differential distribution and importance of preventable causes of dementia in the young.
authors.affiliation: Department of Neurology, David Geffen School of Medicine at the University of California at Los Angeles, Los Angeles, CA, USA. amcmurtray@mednet.ucla.edu
authors.forename: Aaron
authors.initials: A
authors.lastname: McMurtray
authors.forename: David G
authors.initials: DG
authors.lastname: Clark
authors.forename: Dianne
authors.initials: D
authors.lastname: Christine
authors.forename: Mario F
authors.initials: MF
authors.lastname: Mendez
mesh_terms: D017668:Age of Onset; D000368:Aged; D000437:Alcoholism / Q000453:epidemiology; D000544:Alzheimer Disease / Q000453:epidemiology* / Q000209:etiology*; D001930:Brain Injuries / Q000453:epidemiology; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology; D015140:Dementia, Vascular / Q000453:epidemiology; D005260:Female; D006801:Humans; D006816:Huntington Disease / Q000453:epidemiology; D015994:Incidence; D020961:Lewy Body Disease / Q000453:epidemiology; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000453:epidemiology; D015995:Prevalence