Racial Group Differences in NREM Sleep Physiology Contribute to Memory Vulnerability

OBJECTIVE: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.