Modifiers of Individual Differences and Within‐person Changes in the Aging White Matter

Abstract

AbstractMy talk will focus on: 1) longitudinal changes and plasticity, and 2) lifestyle and health modifiers of white matter (WM) health in aging.First, individual differences in changes in WM microstructure may be key for identifying preclinical stages of dementia, opening new opportunities for early interventions. I will present the outcomes from a meta‐analysis and systematic review (Colmenares et al., in preparation) based on 28 diffusion tensor imaging (DTI) studies in healthy adults from the past 10 years, addressing the following questions: Over what time periods can decline in WM microstructure be detected using MRI? Do within‐person changes accelerate with age and vary by brain region? What are the modifiers of within‐person changes in WM? Also, for decades, adult WM has been perceived as a “passive” (i.e., only relaying electrical signals) and “static” (i.e., not capable of or involved in neuroplasticity). Despite emerging evidence in rodents on short‐term structural WM changes, evidence for such experience‐induced plasticity in adult humans remains inconclusive. Thus, I summarize evidence from clinical studies to discuss whether the adult WM microstructure is malleable with experience, and what interventions may be the most promising in inducing a change. I will also present our findings on exercise‐induced WM plasticity in older age, using DTI and T1/T2 ratio imaging (Colmenares et al., 2021, Burzynska et al., 2017).Second, lack of physical activity (PA) and sedentary lifestyles are independently associated with increased risk of metabolic and cardiovascular diseases, mortality, and ADRD. Regular PA decreases inflammation and improves vascular function and perfusion. In contrast, insufficient PA and/or excessive sedentary behaviors is known to upregulate markers of metabolic stress and inflammation. I will briefly review our past work relating sensor‐measured PA with WM health, measured with DTI. Then, I will present our ongoing work using quantitative MRI, such as Myelin Water Imaging and Neurite Orientation Dispersion and Density Imaging. For example, I will present associations between systemic health (i.e., BMI, waist circumference, blood pressure, blood glucose and cholesterol), sensor‐measured physical activity (i.e., time spend sedentary and in light, moderate or vigorous physical activity), and myelin and axonal content in healthy adults.