Abstract
Abstract Background In this proof‐of‐concept study, we examined whether NREM slow wave activity (SWA) is associated with regional in‐vivo tau deposition; and whether race‐specific differences exist in this association, in clinically normal older adults with normal sleep, in the context of Aß. Method This was a cross‐sectional analysis of baseline data from 21 community‐dwelling cognitively normal older‐adults with normal sleep. Participants were matched on age, sex, BMI, and APOE4 carrier status in a 1:3 ratio, blacks: whites. Normal sleep was defined as 6‐9 h of total sleep time and absence of AHI4%>15 and AHI4%>5 with sleepiness. SWA was defined as power between 0.5‐4.0 Hz during NREM with NREM cycles characterized as stages NREM 2‐3 of = 15 min. terminated by rapid eye movement (REM) or wakefulness of = 5 min. Tau burden was assessed using 18F‐PI2620. Linear mixed‐effects models with random intercept and slope were used to assess associations between NREM SWA, and regional in‐vivo tau PET deposition, respectively, controlling for Aß, age, BMI, sex, APOE4‐status, education and other sleep variables. Result Of the 21 participants, 7 (33.3%) were black, 12 (57.1%) were women and 5 (24%) were APOE4 carriers. The mean (SD) age, and education were 69.1 (5.5), and 17.2 (3.8) years respectively. NREM SWA was associated with tau deposition in the entorhinal cortex, inferior and middle temporal ROIs, including gray matter neocortical ROIs i.e., anterior ventral striatum, orbitofrontal, precuneus, superior frontal, lateral temporal and posterior cingulate gyrus cortices (p <.01 for all). Racial differences existed in the entorhinal cortex, and inferior and middle temporal ROIs, including the lateral temporal, parietal, precuneus and posterior cingulate gyrus cortices (p <.02 for all), with black participants having lower tau levels relative to white participants. Divergent NREM SWA and tau associations were observed in the entorhinal cortex, precuneus, and inferior and middle temporal ROIs with NREM SWA negatively correlated with tau‐PET levels in whites and positively correlated in blacks. Conclusion Racial differences in physiological sleep features, uniquely associated with tau levels in the brain, may reflect one mechanism of how sociocultural factors, often through behavioral processes, become physiologically expressed as increased AD‐risk in blacks.