Differential Effects of Insulin Resistance on Frontal Lobe Related Cognitive Function in Adolescents and Adults

The aim of this study was to determine whether effects of insulin resistance (IR) on frontal lobe mediated abilities differ between adolescents and middle-aged adults. These analyses included 118 adolescents aged 16-21 and 118 adults aged 45-60. IR was defined as having a homeostasis model assessment of insulin resistance (HOMA-IR) > 3.99. These analyses focused on higher-order frontal lobe-mediated function and assessed the differential effects of IR by age group on eight targeted cognitive/functional measures. There were significant differences between adolescents who were insulin sensitive (IS) and those with IR on the Stroop interference score (Cohen’s d = 0.61) and Frontal Systems Behavior Scale (FrSBe) executive dysfunction (Cohen’s d = -1.00). Adults with and without IR did not differ on any of the selected measures. There were significant interactions between age group and IR status for the Stroop interference score (partial eta2 = 0.029) and FrSBe executive dysfunction scale (partial eta2 = 0.045). Compared to their IS peers, adolescents with IR performed significantly worse on 2/8 indices of frontal lobe function, while no frontal lobe related cognitive differences existed in the adult population. As anticipated, there was a significant age group by IR status interaction for these higher-order frontal abilities. Poor performance in these measures indicates difficulties in planning, organization and self-regulation, skills that are crucial for life-long learning and achievement of future goals. These data suggest that the still-developing brains of adolescents may render them more vulnerable to the negative effects of metabolic dysregulation than do equivalent metabolic abnormalities in adults