Differential age-associated brain atrophy and white matter changes among homeless and precariously housed individuals compared to the general population

ImportanceHomeless or precariously housed individuals live with poor health and experience premature mortality compared to the general population. With an increasing average age among this demographic, syndromes associated with neurogenerative disease are also increasing. Quantitative MRI measures may help define the roles of age and risk factors for poor brain health among these individuals. ObjectiveTo evaluate whether MRI measures of brain structure are differentially associated with age and selected risk factors among individuals who are homeless or precariously housed compared to a general population sample. Design, setting, and participantsCross sectional comparison of baseline data from 312 community-based, precariously housed participants with a publicly available dataset of 382 participants recruited from the general population. Exposure(s)The primary exposure was housing status (precariously housed vs general population). Risk factors in the precariously housed sample included mental illness, substance dependence, intravenous drug use, HIV, and history of traumatic brain injury. Main outcome(s) and measure(s)The main outcomes were MRI measures of whole-brain tissue- to-intracranial volume ratio, fractional anisotropy, and mean diffusivity. Multiple linear regression and piecewise regression were used to evaluate differences in associations between MRI measures and age between the samples, and to explore associations with risk factors in the precariously housed sample. ResultsCompared to the general population sample, older age in the precariously housed sample was associated with more whole-brain atrophy ({beta}=-0.20, p=0.0029), lower whole-brain FA ({beta}=-0.32, p<0.0001), and higher whole-brain MD ({beta}=0.69, p<0.0001). Several MRI measures had non-linear associations with age, with further adverse changes after age 35-40 in the precariously housed sample. Frontal and temporal cortical thickness, corpus callosum volume, and diffusivity in the association tracts, corpus callosum, and thalamic radiations were the regions of interest most differentially affected. History of traumatic brain injury, stimulant dependence, and heroin dependence were associated with more atrophy or alterations in white matter diffusivity in the precariously housed sample. Conclusions and relevanceOlder age is associated with adverse MRI measures of brain structure among homeless and precariously housed individuals compared to the general population. Education, improvements in care provision and policy may help to reduce the health disparities experienced by these individuals.