title: Midlife vs late-life depressive symptoms and risk of dementia: differential effects for Alzheimer disease and vascular dementia.
abstract: BACKGROUND
  Depression and dementia are common in older adults and often co-occur, but it is unclear whether depression is an etiologic risk factor for dementia.
  
  
  OBJECTIVE
  To clarify the timing and nature of the association between depression and dementia.
  
  
  METHODS
  We examined depressive symptoms assessed in midlife (1964-1973) and late life (1994-2000) and the risks of dementia, Alzheimer disease (AD), and vascular dementia (VaD) (2003-2009) in a retrospective cohort study. Depressive symptoms were categorized as none, midlife only, late life only, or both. Cox proportional hazards models (age as timescale) adjusted for demographics and medical comorbidities were used to examine depressive symptom category and risk of dementia, AD, or VaD.
  
  
  METHODS
  Kaiser Permanente Medical Care Program of Northern California.
  
  
  METHODS
  Thirteen thousand five hundred thirty-five long-term Kaiser Permanente members.
  
  
  METHODS
  Any medical record diagnosis of dementia or neurology clinic diagnosis of AD or VaD.
  
  
  RESULTS
  Subjects had a mean (SD) age of 81.1 (4.5) years in 2003, 57.9% were women, and 24.2% were nonwhite. Depressive symptoms were present in 14.1% of subjects in midlife only, 9.2% in late life only, and 4.2% in both. During 6 years of follow-up, 22.5% were diagnosed with dementia (5.5% with AD and 2.3% with VaD). The adjusted hazard of dementia was increased by approximately 20% for midlife depressive symptoms only (hazard ratio, 1.19 [95% CI, 1.07-1.32]), 70% for late-life symptoms only (1.72 [1.54-1.92]), and 80% for both (1.77 [1.52-2.06]). When we examined AD and VaD separately, subjects with late-life depressive symptoms only had a 2-fold increase in AD risk (hazard ratio, 2.06 [95% CI, 1.67-2.55]), whereas subjects with midlife and late-life symptoms had more than a 3-fold increase in VaD risk (3.51 [2.44-5.05]).
  
  
  CONCLUSIONS
  Depressive symptoms in midlife or in late life are associated with an increased risk of developing dementia. Depression that begins in late life may be part of the AD prodrome, while recurrent depression may be etiologically associated with increased risk of VaD.
authors.affiliation: Department of Psychiatry, University of California, San Francisco, 4150 Clement St., San Francisco, CA 94121, USA. deborah.barnes@ucsf.edu
authors.forename: Deborah E
authors.initials: DE
authors.lastname: Barnes
authors.forename: Kristine
authors.initials: K
authors.lastname: Yaffe
authors.forename: Amy L
authors.initials: AL
authors.lastname: Byers
authors.forename: Mark
authors.initials: M
authors.lastname: McCormick
authors.forename: Catherine
authors.initials: C
authors.lastname: Schaefer
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Whitmer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000209:etiology*; D015140:Dementia, Vascular / Q000209:etiology*; D003863:Depression / Q000150:complications*; D005260:Female; D015438:Health Behavior; D006304:Health Status; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors