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Annexes 206Explanatory variablesIn addition to age and age squared, the model included educational level (graduated fromprimary school versus did not graduated) and gender which were included as covariates bothin the linear mixed model for the latent cognitive level and in the models for eachpsychometric test. Thus, we were able to estimate association of covariates with theunderlying global cognitive level, on one hand, and on each test score adjusting on the latentlevel, on the other hand. Moreover, summing these two estimates, we may also compute theglobal association of the covariate with each psychometric test without adjustment on thelatent cognitive level. We examined both the impact of covariates on the mean latentcognitive level and on its evolution (by including interaction between covariates and age orage squared). We also adjusted the latent cognitive level model on vascular factors collectedat the initial visit V0, that is history of stroke, high blood pressure (HBP) (self-reported usualsystolic and diastolic blood pressures respectively higher than 140 and 90 mm Hg or use ofdrug for HBP), diabetes (self-reported history of diabetes, diabetes diet or diabetes drug),hypercholesterolemia (diet or drug against hypercholesterolemia) and smoking status at V0(current or past smoker versus no-smoker), the frequency of some of these factor beingmarkedly different between men and women. Only significant factors (simple effects orinteractions) were kept in the final model except that non significant effects of gender oreducation were maintained in the latent process model when the corresponding differentialassociations in the test-specific models were significant.Sample selectionCognitive measurements at the initial visit (V0) were excluded from the analysis because of afirst passing effect previously described [12]. Indeed a test-retest improvement was observed8