Influence of an Early-Onset Age of Type 1 Diabetes on Cerebral Structure and Cognitive Function

Abstract

OBJECTIVE -Children who develop type 1 diabetes before age 7 years (early-onset diabetes; EOD) have comparatively poorer cognitive abilities. Whether this relates to psychosocial consequences of chronic illness or organic factors related to diabetes and its complications remains unresolved. We hypothesized that if differences in neuroradiological structure and cognitive ability coexisted in those who had EOD, then an organic component to their etiology was likely. RESEARCH DESIGN AND METHODS-A cohort of 71 young adults with longduration type 1 diabetes diagnosed during childhood or adolescence participated in a crosssectional evaluation of cognitive ability (neuropsychological test battery) and brain structure (magnetic resonance imaging). Diabetes onset age, preceding severe hypoglycemia exposure, retinopathy status, and diabetes duration were examined as potential correlates of cognitive and neuroradiological differences. No participants had previous neuropsychological pathology.RESULTS -In EOD participants (n ϭ 26), current intellectual ability (Wechsler Adult Intelligence ScaleϪRevised performance IQ; P ϭ 0.03) and information processing ability (Choice Reaction Time; P ϭ 0.006) were comparatively poorer than was observed in those with lateronset diabetes (n ϭ 45). Furthermore, lateral ventricular volumes were 37% greater (P ϭ 0.002) and ventricular atrophy was more prevalent (61 vs. 20%; P ϭ 0.01) in the EOD group than in those who had later-onset type 1 diabetes.CONCLUSIONS -An early childhood onset of type 1 diabetes was associated with mild central brain atrophy and significant differences in intellectual performance in adulthood, implying that neurodevelopment may be adversely affected by EOD. The differences observed in brain structure support an organic contribution to their etiology but do not exclude a coexistent contribution of psychosocial factors. Diabetes Care 28:1431-1437, 2005O ptimal intellectual development may be compromised by early childhood onset type 1 diabetes. The diabetes-related factor most consistently related to later intellectual ability is the onset age of type 1 diabetes; children developing the disorder in early childhood are more likely to score relatively poorly on cognitive tests, independent of diabetes duration. Ack et al.(1) first identified an association between early-onset type 1 diabetes (EOD) and comparatively lower general intelligence test scores; children with diabetes averaged 10 IQ points lower than their siblings. Subsequent studies identified small-tomoderate permanent differences in nonverbal (2-5) and verbal (6) intelligence, information processing (3,7-9), visuospatial ability (3-5), attention (7-11), executive function (7,9,12), and learning and memory ability (2,3,7). Prospective evaluation has confirmed that EOD independently influences verbal and nonverbal intelligence, attention, psychomotor speed, and executive functions (6,9). Some researchers have suggested that the differences in intellectual ability may reflect chronic hyperglycemia, severe hypog...

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