Association of quantitative susceptibility mapping signal in gray matter with clinical characteristics and aging-related MRI markers: The Multi-Ethnic Study of Atherosclerosis.

BACKGROUND AND

OBJECTIVES

In neuropathologic studies, iron accumulation in gray matter (GM) is associated with aging and specific neurological diseases, but less is known about its correlates in community-based populations.

METHODS

In the Multi-Ethnic Study of Atherosclerosis, brain MRI was conducted in 2018-2019. To estimate iron content, we derived the median quantitative susceptibility mapping (QSM) signal from four regions: the basal ganglia and cortical GM of the frontal, temporal, and parietal lobes. We examined cross-sectional associations with demographic and clinical characteristics, cognitive test performance, gait speed, and brain MRI measures of atrophy and small vessel disease.

RESULTS

We studied 943 participants (14 % Chinese, 25 % Black, 20 % Hispanic, 41 % White; mean age 74 years; 48 % men). In multivariable models, higher left basal ganglia QSM signal was associated with older age (7.2 ppb per 10 years; 95 %CI 4.6,9.9), smoking (7.1; 3.4,10.9), and diabetes (7.4; 2.5,12.3). Lower QSM signal was associated with Black race (-15.3; -20.6,-10, relative to White) and higher high-density lipoprotein cholesterol (-3.4 per 20 mg/dL; -5.8,-0.9). In cortical GM, QSM signal was associated with greater waist circumference, lifetime alcohol use, and log-transformed white matter hyperintensity (WMH) volume (0.08-0.12 SD units per SD, all p ≤ 0.002), but not with cognitive test performance or gait speed.

DISCUSSION: In cross-sectional analyses in a community-based cohort, older age, White race, smoking, diabetes, and greater WMH volume were associated with higher QSM signal in basal ganglia and/or cortical GM. Longitudinal studies are needed to further explore GM QSM signal in relation to cognition and gait in older individuals.