Composite cognitive scores
Participants underwent a detailed neuropsychological examination [The executive function composite score was created from four established measures of executive function: the Digit Span backward (raw score), Trail Making Test part B (response time), Stroop interference index (response time for interference-naming items) and Letter Fluency (number of words beginning with P letter provided in 2 minutes). For each test, z-scores were computed using the total sample’s mean score and standard deviation. Trail Making Test and Stroop scores were reversed so that higher scores always indicate better performance. The executive function composite score corresponds to the unweighted average of these four z-scores.The episodic memory composite score was created from two established measures of episodic memory: The California Verbal Learning Test (CVLT) and the Wechsler Memory Scale IV Logical Memory, Story B (WMS IV) More specifically, the CVLT scores included the sum of trials 1–5, immediate free recall and delayed free recall, while the Logical Memory scores included immediate and delayed free recall. As for the executive composite, each sub-score was standardized using Age-Well baseline sample average score and standard deviation. The episodic memory composite score corresponds to the unweighted average of these five z-scores.Finally, to facilitate data interpretation, the cognitive composite scores were re-standardized (subtracting the average of the total sample and dividing by standard deviation of the total sample). In both cases, higher scores indicated better performance.