a1 Department of Mental Health Sciences, University College London, U.K.
Background: According to the cognitive reserve model, higher levels of education compensate for the neuropathology of Alzheimer's disease (AD), delaying its clinical manifestations. This model suggests that for any level of cognitive impairment, people with more education have worse neuropathology than those with less education and will therefore have shorter survival post-diagnosis. This is the first systematic review of the relationship between more education and decreased survival in people with AD.
Methods: We reviewed the literature systematically, searching electronic databases and reference lists of included studies. We used Centre for Evidence Based Medicine criteria for inclusion and rating of the validity of cohort studies that reported the relationship of education to survival in people with AD.
Results: 22 studies met inclusion criteria. We found Grade A evidence (highest evidence level) that more education was not associated with decreased survival post-diagnosis in AD. Only one of 11 studies rated 1b (highest level of quality) supported our hypothesis that more education predicted reduced survival after adjusting for age, gender and dementia severity; it comprised African-Caribbean participants, who had on average more severe cognitive impairment than other studies' participants.
Conclusions: Education delays the onset of the dementia syndrome in AD, but does not lead to earlier death after diagnosis.
(Received March 28 2008)
(Revised June 04 2008)
(Revised July 23 2008)
(Accepted July 24 2008)
(Online publication November 25 2008)
c1 Correspondence should be addressed to: Matt Paradise, Department of Mental Health Sciences, University College London, Holborn Union Building, Archway Campus, Highgate Hill, London, N19 5LW, U.K. Phone: +44 (0) 207 2885931 Email: [email protected].