Decreased <scp>BOLD</scp> Signal Variability in Middle‐Aged and Older Adults on the Autism Spectrum

Autism spectrum disorder (ASD) is a lifelong neurodevelopmental disorder. Preliminary evidence suggests an increased risk for early-onset cognitive and neurological decline in ASD. While brain development in children, adolescents, and young adults with ASD diverges from neurotypical (NT) peers, it remains unclear in older adults with ASD. Understanding age-related changes of brain function in ASD is crucial to establish best practices for cognitive and health screenings and develop interventions that might reduce the risk of accelerated decline. Decreases in blood-oxygenation-level-dependent (BOLD) signal variability (BSV) in typical aging have been shown across multiple studies and are associated with poorer cognitive performance. We hypothesized that adults with ASD would show reduced BSV compared to the NT group, with steeper negative age associations in the ASD than NT group. The study assessed BSV during resting state fMRI in adults (40-70 years), 28 with ASD and 39 age-matched NT. General linear models tested diagnostic group, age, and group-by-age interactions, controlling for motion. Significant group-by-age interactions were observed for the right insular, left temporal occipital fusiform, right frontal orbital, and right inferior lateral occipital cortex, with BSV showing strong negative associations with age in the ASD but not NT adults. These findings suggest that BSV decreases may occur earlier in adults with ASD compared to their NT peers. This would be consistent with accelerated aging; however, additional longitudinal analyses are necessary to determine if the results presented truly reflect accelerated aging or arise from lifelong persistent differences in brain function.