Racial Group Differences in NREM Sleep Physiology Contribute to Memory Vulnerability

Racial sleep disparities may lead to long-term cognitive health consequences, with a specific impact on memory formation and maintenance. Few studies have examined the physiological sleep features, including non-rapid eye movement (NREM) Stage 2 and 3 sleep and the corresponding electroencephalographic activity indicative of these stages (i.e., delta oscillations 0.5-4Hz), that are sensitive to racial stress and result in memory vulnerability, which is the goal of this investigation.

We assessed self-report and polysomnographic indices of sleep, psychosocial outcomes, and memory performance in a sample of young, Black (n=63) and White (n=77) adults living in the U.S.

Black participants self-reported more experiences of discrimination, lower incomes, perceived social status, and educational attainment, as well as worse subjective sleep quality. Racial group membership was associated with differential pre-sleep memory profiles for both neutral and negatively-valenced word pairs; however, memory disparities were attenuated after accounting for sociodemographic and psychosocial factors. Overnight sleep architectural differences emerged, with Black participants spending more time in Stage 2 sleep, less time in Stage 3 sleep, and having reduced NREM delta power when compared to White participants. NREM delta activity was a significant mediator of racial group membership and post-sleep memory performance, especially for negative valenced word pairs.

These findings suggest that known racial sleep disparities likely lead to daily, measurable deficits in memory for Black Americans and that NREM delta activity may be a uniquely sensitive biopsychosocial factor that can support cognitive resilience for those experiencing racialized contexts.