Thinning faster? Age-related cortical thickness differences in adults with autism spectrum disorder

Background: Over the course of the last 30 years, autism spectrum disorder (ASD) diagnoses have increased, thus identifying a large group of aging individuals with ASD. Currently, little is known regarding how aging will affect these individual's neuroanatomy, compared to the neurotypical (NT) population. Because of the anatomical overlap of ASD-related cortical pathology and age-related cortical thinning, both following an anterior-to-posterior severity gradient, we hypothesize adults with ASD will show larger age-related cortical thinning than NT adults. Methods: We analyzed cortical measurements using available data from the multi-site Autism Brain Imaging Data Exchange I (ABIDE I; n = 282) and our own cohort of middle-age to older adults with and without ASD (n = 47) mostly available in ABIDE II (n = 35). We compared correlations between cortical measures and age in right-handed adults with ASD (n = 157) and similar NT adults (n = 172), controlling for IQ and site. Participants were 18–64 years of age (mean = 29.8 years; median = 26 years). Results: We found significant differences between diagnosis groups in the relationship between age and cortical thickness for areas of left frontal lobe (pars opercularis), temporal lobe (inferior gyrus, middle gyrus, banks of the superior temporal sulcus, and entorhinal cortex), parietal lobe (inferior gyrus), and lateral occipital lobe. For all areas, adults with ASD showed a greater negative correlation between age and cortical thickness than NT adults. Conclusion: As hypothesized, adults with ASD demonstrated exacerbated age-related cortical thinning, compared to NT adults. These differences were the largest and most extensive in the left temporal lobe. Future longitudinal work is warranted to investigate whether differences in brain age trajectories will translate to unique behavioral needs in older adults with ASD.