Moderating role of physical activity on hippocampal iron deposition and memory outcomes in typically aging older adults.

Physical activity (PA) is linked to better cognitive and brain health, though its mechanisms are unknown. While brain iron is essential for normal function, levels increase with age and, when excessive, can cause detrimental neural effects. We examined how objectively measured PA relates to cerebral iron deposition and memory functioning in normal older adults. Sixty-eight cognitively unimpaired older adults from the UCSF Memory and Aging Center completed neuropsychological testing and brain magnetic resonance imaging, followed by 30-day Fitbit monitoring. Magnetic resonance imaging quantitative susceptibility mapping (QSM) quantified iron deposition. PA was operationalized as average daily steps. Linear regression models examined memory as a function of hippocampal QSM, PA, and their interaction. Higher bilateral hippocampal iron deposition correlated with worse memory but was not strongly related to PA. Covarying for demographics, PA moderated the relationship between bilateral hippocampal iron deposition and memory such that the negative effect of hippocampal QSM on memory performances was no longer significant above 9120 daily steps. PA may mitigate adverse iron-related pathways for memory health.

Data-driven physical actigraphy patterns relate to cognitive and vascular health in older adults.

Health benefits of physical activity (PA) are well known; however, specific PA patterns that relate most strongly to cognitive aging outcomes are poorly understood. We characterized latent profiles of PA among older adults and examined associations with cognition and vascular burden. 124 functionally normal older adults wore a Fitbit™ for 30 days. Daily average step count, sedentary time (0 steps/min), and high-intensity time (≥120 steps/min) were calculated. Participants completed neurocognitive testing assessing cognitive domains of executive functioning and memory; medical history, from which vascular burden (i.e., a count of cardiovascular conditions) was calculated; and brain MRI (n = 44). Subgroups with similar PA patterns were identified via latent profile analysis. Three latent PA classes emerged: Class 1Low PA (n = 49), Class 2Average PA (n = 59), and Class 3High-intensity PA (n = 16). PA class related to executive functioning and vascular burden, driven by better outcomes in Class 3 than Class 1. Sex-stratified analyses revealed these associations were strongest in males. Post hoc analyses showed a positive association between high-intensity PA and white matter integrity among males. High-intensity PA related to better cognitive and vascular health, particularly among males. Findings inform physical activity-specific and person-specific recommendations for optimal cognitive aging.

Regional Vulnerability of the Corpus Callosum in the Context of Cardiovascular Risk.

Many factors outside of cardiovascular health can impact the structure of white matter. Identification of reliable and clinically meaningful biomarkers of the neural effects of systemic and cardiovascular health are needed to refine etiologic predictions. We examined whether the corpus callosum demonstrates regional vulnerability to systemic cardiovascular risk factors. Three hundred and ninety-four older adults without dementia completed brain MRI, neurobehavioral evaluations, and blood draws. A subset (n = 126, n = 128) of individuals had blood plasma analyzed for inflammatory markers of interest (IL-6 and TNF-alpha). Considering diffusion tensor imaging (DTI) is a particularly reliable measure of white matter integrity, we utilized DTI to examine fractional anisotropy (FA) of anterior and posterior regions of the corpus callosum. Using multiple linear regression models, we simultaneously examined FA of the genu and the splenium to compare their associations with systemic and cardiovascular risk factors. Lower FA of the genu but not splenium was associated with greater systemic and cardiovascular risk, including higher systolic blood pressure (ß = -0.17, p = .020), hemoglobin A1C (ß = -0.21, p = .016) and IL-6 (ß = -0.34, p = .005). FA of the genu was uniquely associated with cognitive processing speed (ß = 0.20, p = .0015) and executive functioning (ß = 0.15, p = .012), but not memory performances (ß = 0.05, p = .357). Our results demonstrated differential vulnerability of the corpus callosum, such that frontal regions showed stronger, independent associations with biomarkers of systemic and cardiovascular health in comparison to posterior regions. Posterior white matter integrity may not reflect cardiovascular health. Clinically, these findings support the utility of examining the anterior corpus callosum as an indicator of cerebrovascular health.

Wearable Use in an Observational Study Among Older Adults: Adherence, Feasibility, and Effects of Clinicodemographic Factors.

Introduction: Wearables have great potential to improve monitoring and delivery of physical activity interventions to older adults with downstream benefits to multisystem health and longevity; however, benefits obtained from wearables depend on their uptake and usage. Few studies have examined person-specific factors that relate to wearable adherence. We characterized adherence to using a wearable activity tracker for 30 days and examined associations between adherence and demographics, cognitive functioning, brain volumes, and technology familiarity among community-dwelling older adults. Methods: Participants were 175 older adults enrolled in the UCSF Longitudinal Brain Aging Study who were asked to wear a FitbitTM Flex 2 during waking hours for 30 days. Sixty two of these participants were also asked to sync their devices to the Fitbit smartphone app daily to collect minute-level data. We calculated adherence to wearing the Fitbit daily (i.e., proportion of days with valid activity data) and adherence to daily device syncing (i.e., proportion of days with minute-level activity data). Participants also completed a brain MRI and in-person cognitive testing measuring memory, executive functioning, and processing speed. Spearman correlations, Wilcoxon rank sum tests, and logistic regression tested relationships between wearable adherence and clinicodemographic factors. Results: Participants wore the Fitbits for an average of 95% of study days and were 85% adherent to the daily syncing protocol. Greater adherence to wearing the device was related to female sex. Greater adherence to daily device syncing was related to better memory, independent of demographic factors. Wearable adherence was not significantly related to age, education, executive functioning, processing speed, brain gray matter volumes, or self-reported familiarity with technology. Participants reported little-to-no difficulty using the wearable and all reported willingness to participate in another wearable study in the future. Conclusions: Older adults have overall high adherence to wearable use in the current study protocol. Person-specific factors, however, may represent potential barriers to equitable uptake of wearables for physical activity among older adults, including demographics and cognitive functioning. Future studies and clinical providers utilizing wearable activity trackers with older adults may benefit from implementation of reminders (e.g., texts, calls) for device use, particularly among men and individuals with memory impairment.