Multiscale cortical morphometry reveals pronounced regional and scale-dependent variations across the lifespan.

Characterizing changes in cortical morphology across the lifespan is fundamental for both research and clinical applications. Most studies report a monotonic decrease in commonly used morphometrics, such as cortical thickness and volume, with only subtle regional variations in the rate of decline. However, these findings are limited to a single length scale. Here, we delineate changes across the lifespan in multiscale morphometrics. We applied multiscale morphometric analysis to structural MRI from subjects aged 6 to 88 years from Nathan Kline Institute Rockland Sample (n = 833) and Cambridge Centre for Ageing and Neuroscience (n = 641), and derived population-level lifespan trajectories at multiple length scales. Lifespan trajectories show diverging and even opposing trends at different spatial scales. Larger scales (1.86 mm) displayed the strongest changes across the lifespan (up to 60%) when considering entire cortical hemispheres. Lobal variations also became more pronounced in scales over 0.7 mm. In a proof-of-principle brain age prediction context, multiscale morphometrics provided additional predictive value, boosting the adjusted $R^{2}$ of the model from 0.35 to 0.7. Our study provides a comprehensive multiscale description of cortical morphology across the lifespan, forming foundations for normative models to identify multiscale morphological abnormalities. Our results reveal the complementary information contained in different spatial scales, suggesting that morphometrics should be considered at multiple length scales.