Multimodal neuroimaging insights into the neurobiology of healthy aging across the lifespan.

Abstract

The purpose of this study was to advance our understanding of the neurobiology of healthy aging, which is crucial for improving quality of life and preventing age-related diseases. Despite its importance, a comprehensive investigation of this process has yet to be fully characterized. We used a hybrid PET/MRI scanner to assess neurophysiological parameters in 80 healthy individuals aged 20-78. Cerebral amyloid-beta (Aβ) deposition and glucose metabolism were assessed using PET scans, while participants underwent simultaneous MRI scans. We found a positive correlation between Aβ-deposition and aging, and a negative correlation between glucose metabolism and aging. The insula showed the strongest negative correlation between glucose metabolism and age (Spearman's r = -0.683, 95% CI [-0.79, -0.54], p < 0.0001), while the posterior cingulate cortex had the strongest positive correlation between Aβ-deposition and age (Spearman's r = 0.479, 95% CI [0.28, 0.64], p < 0.0001). These results suggest a spatially dependent link between Aβ-deposition and metabolism in healthy older adults, indicating a compensatory mechanism in early Alzheimer's. Additionally, Aβ-deposition was linked to changes in interregional neural communication. Our study confirms previous findings on aging and offers new insights, particularly on the role of Aβ-deposition in healthy aging. We observed a linear increase in Aβ-deposition, alongside decreases in white matter integrity, cerebral blood flow, and glucose metabolism. Additionally, we identified a complex regional relationship between Aβ-deposition, glucose metabolism, and neural communication, possibly reflecting compensatory mechanisms.