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Annexes 211By applying a nonlinear latent variable model [22] to the psychometric data of the PAQUIDcohort, we have been able to estimate the evolution with age of a comprehensive indicator ofcognition and to distinguish the impact of education and gender on cognition from theirimpact on four psychometric tests used for measuring cognition. Thus, after adjusting forvascular factors, gender was associated with the latent cognitive factor, women having thesame baseline cognitive level but a deeper decline in older ages than men. This associationsuffered from confusion since without accounting for smoking status, the association wasnon-significant. Indeed, 82% of the smokers are men and smokers tend to have a deepercognitive decline with age. Gender had also a differential effect on the four tests. Especially,we found that men performed better than women to the BVRT which is consistent withprevious studies reporting that men use to be better performers than women in tests involvingvisuospatial skills [23, 29]. In contrast, we found that women performed better than men tothe IST15 which is also in agreement with previous findings reporting that women tend tobetter perform than men on tasks with verbal modality [23, 29].In the same vein, we distinguished the effect of education on the latent cognitive evolutionfrom its specific effect on the psychometric tests. We found that subjects who graduated fromprimary school had in mean a better cognitive level than subjects who did not graduate whichcorroborates previous results about the influence of education on neuropsychologicalperformances [4, 7, 18]. Nonetheless, we also showed that this effect differed significantlyaccording to the psychometric test considered. Thus, the difference between a subject whograduated from primary school and a subject who did not graduate decreased with age whenconsidering the IST15 and DSST while it remained the same whatever the age whenconsidering the MMSE or the BVRT. In contrast with the MMSE or the BVRT, the IST15and DSST include a speed component and it was found previously that the decrease inprocessing speed explained most of age-related differences in cognition [24].13