title: Cognitive reserve and mortality in dementia: the role of cognition, functional ability and depression.
abstract: OBJECTIVE
  This study examined whether dementia patients with greater cognitive reserve had increased mortality rates, and whether this association was different across strata of cognition, functional ability and depression.
  
  
  METHODS
  In the community-based Amsterdam Study of the Elderly, 261 non-institutionalized dementia patients, identified using the Geriatric Mental State Schedule (GMS), were followed for an average of 55.5 months after which mortality data were obtained. Cognitive reserve was indicated by years of education and pre-morbid intelligence (measured using the Dutch Adult Reading Test). Cognition, functional ability and depression were indicated by Mini-Mental State scores, ADL and IADL measurements and GMS depressive syndrome, respectively.
  
  
  RESULTS
  During the follow-up 146 persons (55.9%) died. Cox regression analyses showed that more highly educated dementia patients had higher mortality rates, only if they had low MMSE scores or if they had a concurrent depression. Pre-morbid intelligence was associated with a higher mortality rate, independent of cognition, but this association was much stronger among patients with depression. The positive association between education or intelligence and mortality was not modified by functional disabilities.
  
  
  CONCLUSIONS
  The results suggest that dementia patients with greater cognitive reserve have increased mortality rates, only if the disease has progressed to such an extent that clinical symptoms are more severe. In this respect, the reserve hypothesis needs a modification. Depression in dementia patients with greater cognitive reserve may reflect a subgroup of patients with poor prognosis.
authors.affiliation: Institute for Research in Extramural Medicine (EMGO Institute), and Department of Psychiatry, Vrije Universiteit, The Netherlands.
authors.forename: M I
authors.initials: MI
authors.lastname: Geerlings
authors.forename: D J
authors.initials: DJ
authors.lastname: Deeg
authors.forename: B W
authors.initials: BW
authors.lastname: Penninx
authors.forename: B
authors.initials: B
authors.lastname: Schmand
authors.forename: C
authors.initials: C
authors.lastname: Jonker
authors.forename: L M
authors.initials: LM
authors.lastname: Bouter
authors.forename: W
authors.initials: W
authors.lastname: van Tilburg
mesh_terms: D000368:Aged; D003071:Cognition / Q000145:classification*; D003704:Dementia / Q000401:mortality* / Q000523:psychology; D003866:Depressive Disorder / Q000150:complications*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011379:Prognosis; D012307:Risk Factors