Association Between Trajectory of Socioeconomic Position and Regional Brain Volumes Related to Dementia: Results From the NEIGE Study.

BACKGROUND:Low socioeconomic position (SEP) has been linked to an increased risk of dementia. However, little is known about the association between SEP trajectory and regional brain volumes related to dementia. METHODS:A random sample of community-dwelling older adults (n = 428, age = 73.1 ± 5.5) living in Tokamachi City (Niigata Prefecture, Japan) without medical histories of dementia, Parkinson's disease, and depression who underwent automated assessment of brain volumes on magnetic resonance imaging and responded to a self-administered questionnaire survey in 2017. We measured SEP in childhood (household SEP at age 15), young adulthood (education), mid-adulthood (the longest occupation), and late adulthood (current wealth), and further performed group-based trajectory analysis to identify lifetime trajectory patterns on SEP. Multivariate regression models were employed to investigate the association between SEP trajectories and 4 regional brain volumes related to the development of Alzheimer's disease (ie, entorhinal cortex, hippocampus, amygdala, and the parahippocampus), the most common type of dementia. RESULTS:We found 3 distinct SEP trajectories (stable middle class [68%], downward [23%], and upward [9%]). Compared to those who experienced stable middle class, older adults who experienced the upward SEP mobility had significantly larger hippocampus (β: 213.2, 95% confidence interval: 14.7, 411.8). On the other hand, older adults who experienced downward SEP mobility showed no significant differences in any of the 4 brain structural volumes. CONCLUSIONS:Our findings indicate that upward life-course SEP mobility is associated with larger volumes of hippocampus in old age. SEP trajectory may offer us a useful lens to enhance our understanding of the etiology of dementia.