Nevertheless, potential causal factors include environmental variables (e.g., negative experiences in class, teacher characteristics), intellectual variables (e.g., the degree of abstract or logical thinking) and personality variables (e.g., self-esteem, learning style, attitude and confidence [ 5, 6]).
Because of the absence of interaction terms with the intellectual lifestyle variables, the only effect of intellectual lifestyle variables on cognition was to shift the baseline cognitive performance up or down (intercept on the y-axis).
The initial model included baseline age (years), sex, APOE carrier status, time from baseline (years), the intellectual enrichment variables, baseline visit number, all two-way interactions of these variables, a three-way interaction of the intellectual enrichment variables with time, and a three-way interaction of Alzheimer's disease pathophysiology and cerebrovascular disease with time.
The demographics, clinical, intellectual enrichment variables, and imaging biomarkers of the subjects included in this analysis are shown in Table 1.
To illustrate the effect of intellectual lifestyle variables, we separated the plots in Fig. 2 by high (75th percentile) versus low (25th percentile) values of education/occupation scores in Fig. 3.
We included all 393 healthy elderly participants in the MCSA who had a baseline 3 T FLAIR-MRI assessment, Amyloid PET scan, intellectual enrichment variables, complete neuropsychological assessments, and at least one additional clinical follow-up with complete neuropsychological assessments.
The primary intellectual activity variables of interest, assessed at baseline, included: (i) education, job-level score based on the primary occupation throughout life; and (ii) current weekly cognitive activity over the last 12 months and mid-life weekly cognitive activity (ages 50 65) (Geda et al., 2011).
Our interest in the intellectual youth variable stems from its utility as in input into a sensible identification strategy.
However, in all the Heckit estimates, the intellectual youth variable was negatively correlated with each measure of having earned a baccalaureate degree.
In this study, results below the 50th percentile on the special scale and below the 10th percentile on the general scale were considered to have intelectual déficit and were excluded from the sample to keep the variable "intellectual level" as homogeneous as possible.
Advancing the studies of this Brazilian adaptation of the LNNB, the present study aimed to obtain validity evidences for TLN-C by investigation of its relations with external criteria (age) and external variable (intellectual quotient IQ), investigation of its predictive capabilities regarding IQ and verification of its reliability by internal consistency analysis.
