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M. Kalfas

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Open access Jul 2026

The association between sleep spindles and cognitive performance in euthymic bipolar disorder

Many people with bipolar disorder (BD) experience persistent cognitive deficits. Sleep spindles have been linked to cognitive ability in healthy populations and psychotic disorders. While there is preliminary evidence for altered spindle activity in BD, research directly examining the association between sleep spindle parameters and cognitive performance in this population is lacking. Therefore, our primary objective was to examine the association between fast spindle density and episodic memory performance in euthymic individuals with BD. As exploratory analyses, we looked at associations between fast and slow spindle density and subjective sleep quality with other cognitive domains. We also conducted a sensitivity analysis, separating all analyses by lithium intake. Thirty-four euthymic participants with BD underwent comprehensive cognitive assessments and were assessed for three consecutive nights using mobile sleep-EEG headbands. Sleep spindles were detected using validated, adapted algorithms and characterised by fast and slow spindle density. Fast spindle density was not associated with episodic memory performance (r = −0.004, p = 0.491, 95% CI [−0.353, 0.499]) but did show a significant positive association with working memory (r = 0.423, p = 0.014, 95% CI (bootstrapped) [−0.167, 0.722]). When removing participants taking lithium, several positive associations emerged between fast spindle density and cognitive performance. These findings suggest domain-specific relationships between sleep spindle activity and cognition in BD, with fast spindles potentially being associated with working memory. Preliminary evidence for lithium-related modulation highlights the importance of considering pharmacological factors. However, the analyses were underpowered, and large-scale studies are needed to deepen our understanding of sleep spindle-cognition relationships in BD.

Anna Tröger, Jules Schneider, D. Tsapekos et al. · Translational Psychiatry · 0 citations

Open access Aug 2026

Transdiagnostic Domain-specific Cognitive Impairment in Inter-episode Mood Disorders and its Relationship with Rest-Activity Phenotypes

Introduction: Cognitive impairment and disturbed rest-activity patterns often persist between episodes of major depressive disorder (MDD) and bipolar disorder (BD). Whether these deficits are disorder-specific or transdiagnostic remains unclear, as does the existence of a link between rest-activity phenotypes and cognitive performance. Methods: Using the All of Us Research Program, we derived normative deviation scores across four cognitive domains (sustained attention, inhibitory control, reward-based impulsivity, social cognition) from non-clinical controls (NCC), then compared deviations in MDD and BD. MDD was adequately powered to regress deviation scores on four 90-day Fitbit-derived phenotypes (step count, sleep duration, wakefulness after sleep onset, sleep timing variability); the same analysis was run on NCC as a sensitivity check. Results: Samples were substantially larger than prior works (MDD 5,087-6,536; BD 545-739; NCC 40,589-51,491). Relative to NCC, MDD and BD exhibited worse sustained attention (Delta Glass = -0.081 vs. -0.187) and higher impulsivity (Delta Glass = 0.092 vs. 0.240), with deficits more pronounced in BD. No wearable phenotype was significantly associated with cognitive performance in MDD (R2< 0.01); NCC associations, though significant, were of negligible magnitude (R2 <= 1.2%). Discussion: Inter-episode cognitive impairment was domain-selective rather than global, with a gradient BD > MDD. Despite adequate power, wearable rest-activity phenotypes were not associated with cognition in MDD. Whether this extends to BD, where deficits were largest, could not be tested due to limited power. Community-dwelling samples likely underestimate impairment relative to clinical cohorts.

F. Corponi, M. Kalfas, M. Reami et al. · medRxiv · 0 citations