Structural brain markers are differentially associated with neurocognitive profiles in socially marginalized people with multimorbid illness.

Abstract

Homeless and marginally housed individuals constitute a socially impoverished population characterized by high rates of multimorbid illness that includes polysubstance use, viral infection, and psychiatric illness. Their extensive exposure to risk factors is associated with numerous poor outcomes, yet little is known about structural brain integrity and its association with neurocognition in this population. In Study 1, we conducted a cluster analysis to re-construct three previously derived subgroups with distinct neurocognitive profiles in a large sample of socially marginalized persons (N = 299). Cluster 1 (n = 87) was characterized as highest functioning overall, whereas Cluster 3 (n = 103) was the lowest functioning neurocognitively, with a relative strength in decision-making. Cluster 2 (n = 109) fell intermediate to the other subgroups, with a relative weakness in decision-making. Next, we examined the association between complementary fronto-temporal cortical brain measures (gyrification, cortical thickness) and neurocognitive profiles using multinomial logistic regression. Chi-square tests and ANOVAs differentiated subgroups on proxy measures of neurodevelopment and acquired brain insult/risk exposure. We found that greater frontal and temporal gyrification and more proxies of aberrant neurodevelopment were associated with Cluster 3 (lowest functioning subgroup). Further, age moderated the association between orbitofrontal cortical thickness and neurocognition, with positive associations in older adults, and negative associations in younger adults. Finally, greater acquired brain insult/risk exposure was associated with the cluster characterized by selective decisionmaking impairment (Cluster 2), and the higher functioning cluster (Cluster 1). In Study 2, we examined the association between white matter integrity and neurocognitive profiles using multinomial logistic regression and Tract-based Spatial Statistics. We found significantly lower fractional anisotropy (FA), with corresponding increased axial and radial diffusivity (AD, RD) in widespread and bilateral brain regions of Cluster 3.Differences in RD were more prominent compared to AD. Altogether, our findings highlight the unique pathways to neurocognitive impairment in a heterogeneous population and help to clarify the vulnerabilities confronted by different subgroups.

Diffusion tensor imaging of neurocognitive profiles in a community cohort living in marginal housing

“…Living in marginal housing, such as single‐room occupancy (SRO) hotels is associated with serious consequences for health, well‐being, and psychosocial functioning (Vila‐Rodriguez et al, ). Co‐occurring polysubstance use, infectious diseases, and severe psychiatric illnesses are commonplace (Krausz et al, ; Vila‐Rodriguez et al, ) and entail significant costs, such as neurocognitive impairments (Gicas et al, ). These impairments may be central to the psychosocial dysfunction of marginalized persons.…”

“…Previously we characterized extensive neurocognitive impairment of marginalized persons living in SRO hotels by grouping participants across multiple neurocognitive domains (attention, memory, executive functioning). Three subgroups with unique profiles of neurocognitive impairments were differentiated by cortical gyrification and thickness (Gicas et al, ). Our prior findings suggested that the poorest performing subgroup showed evidence of greater neurodevelopmental brain aberrations, whereas greater environmental risk exposures characterized persons in the other two subgroups.…”

“…The aim of this study is to ascertain the extent to which white matter DTI variations differentiate previously derived and well validated neurocognitive subgroups (Gicas et al, ) in a sample of vulnerable persons primarily dwelling in unstable housing, such as SRO hotels. We used cluster analysis to subgroup individuals on the basis of similar profiles of neurocognitive strengths and weaknesses (Allen & Goldstein, ).…”

“…This approach is highly suitable for a clinically heterogeneous population in which diffuse white matter abnormalities are likely to be prevalent and has the additional advantage of deriving mean DTI metrics from the center of white matter tracts, overcoming limits of the standard atlas‐based regional approach (Smith et al, ). We hypothesized that patterns of lower FA, with corresponding decreased AD and increased RD would be associated with the neurocognitive subgroup that exhibits the lowest functioning and greatest burden of physical and psychiatric illness (Gicas et al, ).…”

“…To better understand the nature and putative etiologies of hypothesized white matter differences, we examined associations between select major white matter tracts and cortical gray matter regions of interest (ROIs) previously found to differentiate the neurocognitive clusters (Gicas et al, ). Correspondence between white matter and gray matter alterations have been previously identified in schizophrenia patients, suggesting a possible common underlying pathophysiological mechanism (Liu et al, ).…”