Jeroen van der Grond

Ageing is associated with functional reorganization that is mainly characterized by declining functional connectivity due to general neurodegeneration and increasing incidence of disease. Functional connectivity has been studied across the lifespan; however, there is a paucity of research within the older groups (≥75 years) where neurodegeneration and disease prevalence are at its highest. In this cross-sectional study, we investigated associations between age and functional connectivity and the influence of cerebral small vessel disease (CSVD)—a common age-related morbidity—in 167 community-dwelling older adults aged 75–91 years (mean = 80.3 ± 3.8). Resting-state functional MRI was used to determine functional connectivity within ten standard networks and calculate the whole-brain graph theoretical measures global efficiency and clustering coefficient. CSVD features included white matter hyperintensities, lacunar infarcts, cerebral microbleeds, and atrophy that were assessed in each individual and a composite score was calculated. Both main and interaction effects (age*CSVD features) on functional connectivity were studied. We found stable levels of functional connectivity across the age range. CSVD was not associated with functional connectivity measures. To conclude, our data show that the functional architecture of the brain is relatively unchanged after 75 years of age and not differentially affected by individual levels of vascular pathology.

Background Decreased cerebrovascular reactivity, measured as changes in blood‐oxygen‐level‐dependent (BOLD) signal, is a potential new cerebral amyloid angiopathy (CAA) severity marker. Before clinical application, the effect of aging on BOLD parameters, and reproducibility and test–retest reliability of these parameters should be assessed. Purpose Assess the effect of healthy aging on cerebrovascular reactivity (BOLD amplitude, time to peak, and time to baseline). And determine reproducibility and test–retest reliability of these parameters. Study Type Prospective‐observational. Population Eighty‐six healthy adults (mean age 56 years, 55% female), 10 presymptomatic D‐CAA mutation carriers (mean age 34 years, 70% female), and 10 symptomatic D‐CAA mutation carriers (mean age 54 years, 70% female). Field Strength/Sequence 3‐T, three‐dimensional (3D) T1‐weighted MRI and gradient echo BOLD fMRI. Assessment To assess test–retest reliability of BOLD parameters, i.e. BOLD amplitude, time to peak, and time to baseline, BOLD fMRI scans were repeated three times immediately after each other, in both controls and mutation carriers. To assess reproducibility, BOLD fMRI scans were repeated with a 3‐week interval for each subject. Statistical Tests Linear regression analyses and two‐way mixed absolute agreement intra‐class correlation approach. Results Healthy aging was associated with decreased BOLD amplitude ( β = −0.711) and prolonged time to baseline ( β = 0.236) in the visual cortex after visual stimulation Reproducibility of BOLD amplitude was excellent (ICC 0.940) in the subgroup of healthy adults. Test–retest reliability for BOLD amplitude was excellent in healthy adults (ICC 0.856–0.910) and presymptomatic D‐CAA mutation carriers (ICC 0.959–0.981). In symptomatic D‐CAA mutation carriers, test–retest reliability was poor for all parameters (ICCs < 0.5). Data Conclusion Healthy aging is associated with decreased cerebrovascular reactivity, measured by changes in BOLD response to visual stimulation. The BOLD amplitude appears to be a robust measurement in healthy adults and presymptomatic D‐CAA mutation carriers, but not in symptomatic D‐CAA mutation carriers.