Clinical commentary The effect of schooling on reported age of onset of cognitive decline: A collaborative study T.A. Treves a,⇑ , Y. Parmet b , S. Klimovitzky a , A.D. Korczyn c a Department of Neurology, Rabin Medical Center, Beilinson Campus, Petach Tikva 49100, Israel b Department of Engineering, Bengurion University, Beer Sheva, Israel c Department of Neurology, Tel Aviv Medical Center, Tel Aviv, Israel article info Article history: Received 17 April 2016 Accepted 8 May 2016 Available online xxxx Keywords: Alzheimer’s disease Dementia Mild cognitive impairment Risk factors abstract 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; there- fore, 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 6 months among patients with MCI (t = 6.18, p < .001) and by 3 months 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. Ó 2016 Published by Elsevier Ltd. 1. Introduction The age of onset of cognitive decline among patients with Alz- heimer’s disease (AD) is spread widely. Even disregarding subjects with presenile onset, among whom genetic factors might have a larger effect, the heterogeneity is quite impressive [1]. Several fac- tors might be involved, including environmental risk factors and comorbidities. Recently the concept of cognitive reserve was intro- duced, according to which some individuals may be relatively pro- tected against dementia in spite of having significant pathology because of certain preexisting environmental factors. One such fac- tor could be education. In prevalence studies, higher education was thought to be ‘‘protective” against AD, since the prevalence of dementia was higher among less educated people [2–4], with odds ratios exceeding 4 among illiterates [5–7] and meta-analysis of their results leads to a statistically significant effect (p = 0.008) [8]. In incidence data, the effect of schooling on risk of dementia is less clear: Bickel and Cooper (1994) [9], Cobb et al. (1995) [10] as well as Bowler et al. (1998) [11] did not find higher rates among people with lower educational level while Stern et al. (1994) [12], as well as Geerlings et al. (1999) [13] or Launer et al. (1999) [14] did observe it. Studies from memory clinics have been more vari- able (Launer et al. [1999]; Filley et al. [1985]; Moritz et al. [1993]; Nitrini et al. [1995]; Del Ser et al. [1999]; Bowirrat et al. [2001]) [6,14–18], however, inverse effect was not reported and the resultant p of a metaanalysis corroborates a protective effect (p = 0.005 and p = 0.01, respectively [8]). It is unlikely that factors such as education would provide abso- lute protection against dementia, but rather are more likely to affect the relation between pathology (senile plaques) and cogni- tive level [19]. It is likely that the effect of education would be expressed as a delayed onset of cognitive decline. The strength of the protector could thus be expressed by the number of years by which the onset of dementia is delayed [20]. In order to test this hypothesis, we examined whether there was a correlation between the number of years of formal education and reported age at onset of cognitive decline in patients attending memory disorders clinics. http://dx.doi.org/10.1016/j.jocn.2016.05.013 0967-5868/Ó 2016 Published by Elsevier Ltd. ⇑ Corresponding author. Tel.: +972 506963369. E-mail address: thereset@gmail.com (T.A. Treves). Journal of Clinical Neuroscience xxx (2016) xxx–xxx Contents lists available at ScienceDirect Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn Please cite this article in press as: Treves TA et al. The effect of schooling on reported age of onset of cognitive decline: A collaborative study. J Clin Neurosci (2016), http://dx.doi.org/10.1016/j.jocn.2016.05.013