The effect of schooling on reported age of onset of cognitive decline: A collaborative study

Higher education has been reported to be a protective factor against dementia. We suggest that the strength of a risk factor may be measured by the length of time by which it delays disease onset; therefore, we examined whether people with lower education develop cognitive decline at an earlier age than people with more schooling. The study population was based on patients referred to our Memory Clinics from 1994 to 2004. Analysis of covariance was used to evaluate the effect of schooling on the reported age of memory decline, in patients with mild cognitive impairment (MCI) and in patients diagnosed with Alzheimer's disease (AD). The mean reported age of onset of cognitive decline was unexpectedly lower in patients with higher education than in patients with fewer schooling years, with a relatively small effect size (beta=-0.6), and the effect was more marked in the MCI group. Every year of schooling advanced the reported age of onset by 6months among patients with MCI (t=-6.18, p<.001) and by 3months among patients with AD (t=-2.4, p=0.017). Education may affect the reported age of onset of cognitive decline, but its magnitude is small. It is possible that increased awareness in more educated people leads them to consult earlier; this could explain the paradoxical finding of earlier reported age of onset of cognitive decline in patients with higher education.