Cognitive Function Derived from Latent Profile Analysis (LPA)

This outcome variable was derived from latent profile analysis of participants’ performances across nine measures of IQ and executive function, described in detail elsewhere [25]. IQ was assessed with the School-Age Differential Ability Scales-II (DAS-II) Verbal and Nonverbal Reasoning scales [26]. Executive function included two subtests from DAS-II, DAS Recall of Digits Backward and Recall of Sequential Order, which measured verbal working memory [26], and five subtests from the NEPSY-II (A Developmental NEuroPSYchological Assessment-II) [27]. The NEPSY-II Auditory Attention and Response Set measured auditory attention, set switching and inhibition, the NEPSY-II Inhibition and Inhibition Switching measured simple inhibition and inhibition in the context of set shifting, respectively, and the NEPSY-II Animal Sorting measured visual concept formation and set shifting. The LPA identified four subgroups of study participants with similar cognitive profiles: normal, low-normal, moderately impaired, and severely impaired.