Depressive Symptoms Attenuate the Cognitive Benefits of Slow Wave Sleep in Older Black Americans

TL;DR

Depressive symptoms reduce the cognitive benefits of deep sleep in older Black Americans, highlighting the importance of considering mood in sleep research.

Contribution

This study reveals how depressive symptoms interact with slow wave sleep to affect memory in older Black Americans.

Findings

SWS and depressive symptoms independently affect visual-spatial working memory.

High depressive symptoms negate the cognitive benefits of SWS.

The interaction between SWS and depression is significant in this population.

Abstract

Slow wave sleep (SWS), critical for memory consolidation, has been linked to better visual-spatial working memory (VSWM)—a sensitive early marker of cognitive decline. Depressive symptoms have been shown to modulate memory performance, but their interactive effects with SWS remain underexplored in Black American populations disproportionately impacted by sleep disturbances. This study investigated the interaction between objectively measured SWS and depressive symptoms on VSWM among older Black Americans.

As part of a larger observational study examining longitudinal benefits of sleep in older Black Americans, participants (N = 59; mean age 52.76) completed three consecutive nights of at-home sleep monitoring using the Sleep Profiler, a validated wearable device. VSWM performance was assessed using standardized memory tasks, while depression was assessed using the Geriatric Depression Scale. Moderation analysis was used to examine whether depression moderated the relationship between SWS and VSWM, while controlling for age, gender and marital status.

SWS (B = 0.665, p = 0.006) and depressive symptoms (B = 2.177, p = 0.008) had significant independent effects on VSWM. The moderation analysis revealed a significant interaction (B=-0.1106, p = 0.007) between SWS and depressive symptoms. Further examination of the conditional effects revealed a positive association between SWS and VSWM at low depressive symptom levels (t = 2.8847, p = 0.0057) and a negative association at higher depressive symptom levels (t=-2.7760, p = 0.0076).

These findings suggest that while SWS supports VSWM at low levels of depressive symptoms, the benefit diminishes under high depressive symptoms. Thus, emphasizing the need to investigate sleep–mood interactions when assessing the benefits of sleep among aging Black Americans.