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Annexes 201IntroductionIn spite of a vast literature on the subject, the effect of gender and education on the evolutionof cognitive performances with age remains controversial. Longitudinal studies of randomlyselected population-based samples of subjects is so far the best way to study theserelationships by the collection of repeated measures of psychometric tests over time [21, 30].This method allows to analyse both the baseline level and the evolution with age of thecognitive performances. However, even in these studies, multiple methodological problemsinterfere with the statistical analysis and disturb the associations. The use of psychometrictests as surrogate markers of performances in several cognitive functions implies twodifficulties. First whatever the battery of psychometric tests used, each test only measuressome domains of cognition even when considered as a global test like the Mini Mental StateExamination (MMSE) [5], a composite score derived from a limited number of cognitiveoperations. Second, several studies have reported that the ability to perform the tests wasstrongly related to gender and education. Females tended to have better performances thanmales on tests involving an important verbal component such as verbal memory tests whilemales were generally better than females on tests requiring visuospatial informationprocessing [3, 15, 23, 29]. High educated subjects tended to perform better on a wide range oftests including the MMSE [14, 17, 27] and community-based studies strengthened this resultby showing that the effects of education on numerous tests scores remained significant afteradjusting for confounding factors such as age [4, 7, 18]. However, when considering testscores it is important to keep in mind their artificial nature and arbitrary meaning. Forinstance, education may influence test-taking behaviour, lower educated subjects having moredifficulty to deal with general as well as specific testing conditions. So, one could argue thatthe degradation of cognitive performances with age related to a low level of education ismediated by the differential ability in developing test-taking skills between high and low3