McKiernan, Elizabeth

Abstract Dementia is associated with altered resting-state connectivity, measures of which could aid in its early detection and monitoring. High-density diffuse optical tomography (HD-DOT) is well suited to detect these alterations at scale due to its numerous practical advantages, but it has not yet been applied to dementia. In this study, we investigated resting-state functional connectivity across the prefrontal cortex in individuals with mild cognitive impairment (MCI, n = 22), Alzheimer’s disease (AD, n = 21), and in healthy controls (n = 22). A graph theoretical approach was taken to characterise both global and local patterns of prefrontal connectivity over a 5-minute resting period. We found that individuals with MCI exhibited denser and stronger networks with shorter path lengths, which normalised in AD, accompanied by a redistribution of network hubs that were less stable. These results perhaps reflect the recruitment of additional connections in the early stages of pathology to maintain short-term network stability, which is ultimately associated with less efficient and more fragmented network organisation in later stages. Following the demonstration of HD-DOT’s capacity to detect differences between healthy ageing and AD-type cognitive impairment, this work opens up new possibilities for the use of optical imaging in the study of this clinical population and HD-DOT’s potential for scalable clinical use.

Abstract Background Individuals living in socioeconomically disadvantaged areas are disproportionately affected by dementia. However, the pathway leading from neighbourhood deprivation to cognitive symptoms is not well understood. To test our hypothesis that this relationship is associated with cerebral small vessel disease (SVD), we examined (1) whether neighbourhood deprivation related to midlife SVD burden and cognition, and (2) whether these links can be explained by modifiable lifestyle risk factors. Method In this multi‐centre cross‐sectional study, 514 cognitively healthy midlife participants aged 40‐59 years (median 52 years, 64.6% female) underwent clinical assessment and 3T MRI. Postcode data were used to obtain national indices of neighbourhood deprivation. To quantify SVD, we assessed white matter hyperintensities (WMH), perivascular spaces, cerebral microbleeds, and lacunes. Cognition was assessed using the Computerized Assessment of Information Processing (COGNITO) battery. Lifestyle risk factors were evaluated based on clinical data. Using multivariate statistics like structural equation modelling (SEM) and canonical correlation analysis (CCA), we examined associations between these constructs both globally and at the item‐level (i.e., distinction between domains of cognition/deprivation), to shed light on specific domains that could inform targeted prevention strategies. Result Neighbourhood deprivation related to greater prevalence of lifestyle risk factors ( r = 0.36, p < .001), greater SVD burden (b=0.18, p = .01; Figure 1), and greater cognitive impairment ( r = 0.36, p < .001), independent of educational attainment, sex, and age. These links with neighbourhood deprivation were largely driven by lifestyle factors relating to vascular health (sleep, physical activity, obesity, hypertension) (Figure 2), and cognitive deficits consistent with SVD (processing speed, visuospatial) (Figure 3). Residents of deprived neighbourhoods displayed greater prevalence of lifestyle risk factors, except alcohol consumption. Lower cognitive scores were most closely associated with deprivation domains of Crime and Living Environment (Figure 3). The DEPRIVATION→SVD path was mediated by lifestyle risk factors (z=2.57, p = .010), and the DEPRIVATION→COGNITION path was mediated by SVD (z=‐2.14, p = .032) (global SVD & hypertensive subtype, but not CAA‐SVD). Conclusion The pathway linking neighbourhood disadvantage to cognitive impairment at midlife is influenced by vascular risk factors and cerebrovascular burden. Tailored strategies could promote resilience against dementia by promoting health behaviours aligned with the community's unique needs.

ABSTRACT INTRODUCTION Neighborhood deprivation increases dementia risk, although mechanisms remain unclear. We tested a framework in which modifiable risk factors and cerebral small vessel disease (SVD) mediate the link between neighborhood deprivation and cognition. METHODS In 585 cognitively healthy midlife adults (ages 40–59), neighborhood deprivation was derived from postcodes, cognition was assessed using the COGNITO, lifestyle risk factors were measured using clinical assessments, and SVD (white matter hyperintensities, lacunes, microbleeds, perivascular spaces) was assessed on 3T magnetic resonance imaging. Multivariate analyses examined association pathways among these variables. RESULTS Neighborhood deprivation was associated with poorer cognition ( r = 0.36, p < 0.001), greater prevalence of modifiable risk factors ( r = 0.36, p < 0.001), and greater SVD burden ( β = 0.18, p = 0.008). Serial mediation showed that the effects of deprivation on cognition were indirect, possibly operating via lifestyle risk and SVD, explaining 20% of the total effect, whereas SVD alone explained 28%. DISCUSSION Neighborhood disadvantage relates to poorer cognition, possibly mediated through vascular risk factors and cerebrovascular disease. Highlights Neighborhood deprivation linked to poorer cognition in healthy midlife adults Deprivation linked to small vessel disease (SVD) and modifiable risk factors (chiefly cardiovascular risk) Association between deprivation and cognition mediated by modifiable risk and SVD Mediation was exclusive to hypertensive SVD, but not cerebral amyloid angiopathy (CAA)‐related SVD