Systematic review of the effect of education on survival in Alzheimer's disease.

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.