Similarly, compared with the least well educated group, participants with six to eight years of education had an odds ratio for Alzheimer's disease of 0.49 (95% CI 0.24 to 1.00) and those with nine or more years had an odds ratio of 0.15 (0.05 to 0.40).
In analyses controlling for possible confounders, including demographics and socioeconomic, vascular and lifestyle factors, the authors found that the associations between education and both all-cause dementia and Alzheimer's disease remained, with women and men being equally affected.
In addition, controlling for the presence of the apoliporotein E4 (ApoE4) allele, a known risk factor for early-onset Alzheimer's disease, did not modify the association. However, "among the ApoE4 noncarriers the risk of dementia was 0.44 (95% CI 0.16 to 1.17) for people with medium education, and 0.05 (0.01 to 0.38) for high education compared with that for low education in the model with full adjustments," the authors noted.
"As vascular factors contribute to the risk of dementia and AD, one of our hypotheses was that these factors could at least partly explain the effect of education on dementia," the authors wrote. "However, adjusting for midlife vascular and lifestyle related risk factors did not change the association between education and dementia."