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Annexes 204(iii) the recognition form of the Benton Visual Retention Test (BVRT) [2] evaluatesimmediate visual memory. After the presentation for 10 seconds of a stimulus card displayinggeometric figures, subjects are asked to choose the initial figure among four possibilities.Fifteen figures are successively presented. The score ranges from 0 to 15.(iv) the Digit Symbol Substitution Test (DSST) [28] explores attention and psychomotorspeed. Given a code table displaying the correspondence between pairs of digits (from 1 to 9)and symbols, the subjects have to fill in blank squares with the symbol which is paired to thedigit displayed above the square. The subjects have to fill in as many squares as possible in 90seconds. The score, representing the number of correct symbols, ranges from 0 to 76 in thePAQUID sample.Statistical modelThe response dependent variables are the scores at repeated measures of the fourpsychometric tests. The statistical model assumes that the correlation between the four tests isinduced by a latent common cognitive process. The model is thus divided into two parts: (i)the longitudinal model for the latent cognitive process which describes the evolution of thelatent cognitive factor and evaluates the effects of covariates on the latent cognitive evolution,and (ii) the test-specific models which link the measures of the psychometric tests with thelatent cognitive process, taking into account test-specific associations with covariates.The evolution of the common factor was modelled using a linear mixed model [16] whichaims at evaluating changes over time of a repeated outcome (here the latent cognitive level)accounting for correlation between the repeated measures on each subject. The linear mixedmodel included random intercept, age and age squared in accordance with other longitudinalstudies [1, 9] which showed quadratic cognitive evolutions with age. This quadratic trend6