Sleep spindle activity in depressed patients is correlated with cognitive performance and predicts treatment outcome

Objective: There is increasing evidence that stage 2 sleep spindles are linked to memory encoding processes and seem to reflect important aspects of efficient cortical-subcortical connectivity. This study investigated if reduced levels of sleep spindle activity are associated with cognitive impairment during depression and if the levels of sleep spindle activity are predictive for treatment outcome. Methods: 12 patients (mean age 50.5±8.6 years) with a major depressive episode were treated with trimipramine 200mg/d over six weeks. Polysomnography was performed after one week of treatment. Visually scored sleep spindles were correlated with depression severity (HDRS) and cognitive-psychomotor performance, as assessed with a comprehensive test battery, after one, two and six weeks of treatment. Results: Higher levels of sleep spindle activity in night 7 were significantly correlated with better psychomotor-cognitive performance on day 7 as well as on days 14 and 42. Higher levels of sleep spindle activity were correlated with treatment response after 6 weeks. Discussion: Our data suggest that sleep spindle activity is important for attention, complex information processing and psychomotor coordination. Moreover, the level of sleep spindle activity during depression may serve as a predictive marker for improvement of cognitive functioning and antidepressive treatment response.