The search of true links between educational level and dementia

Education and dementia show a consistent, cross-cultural relationship which affects the prevalence rate of cases diagnosed with Alzheimer's disease (A D). Different hypotheses are proposed by various authors who try to explain the nature and significance of this correlation. Some authors present this relationship as the evidence of a protective role that education could hav e on the biological changes associated with dementia. Others consider educa tion as a builder of a potential functional reserve, which allows people to benefit of a more redundant functional array of cognitive abilities even w hen some of them could be deteriorated by the ongoing biological process of dementia. This correlation is strongly attenuated when longitudinal studie s are considered which are based mostly on clinical observations. On the co ntrary, the correlation with education is very high when cognitive assessme nt procedures are employed to define the cases with dementia. This specific ity of the relationship with the presence of cognitive measure, points out the critical role that education has in the use of these instruments which are traditionally known as highly correlated with education. Some consider this, as a contamination that education causes on the "pure" cognitive comp onent of the measures, advocating a suppression of such interference. Other s consider it as a natural component of the variance that cognitive measure s present in the population which is sensitive to the differential cognitiv e development that more intensive educational curricula cause in part of th e population and which, as a consequence, is transferred to the relationshi p with the presence of a cognitive decline considered as dementia. Whatever the interpretation, it still remains to be defined if this relationship co nstitutes a real danger for a bias in the diagnostic procedures of dementia cases with an over-representation of positive cases in the undereducated p art of the population and an under-representation of the same cases among t he overeducated part of the same population.