Topographic and sex-related differences in sleep spindles in major depressive disorder: a high-density EEG investigation

Abstract

Background: Sleep spindles are believed to mediate several sleep-related functions including maintaining disconnection from the external environment during sleep, cortical development, and sleep-dependent memory consolidation. Prior studies that have examined sleep spindles in major depressive disorder (MDD) have not demonstrated consistent differences relative to control subjects, which may be due to sex-related variation and limited spatial resolution of spindle detection. Thus, this study sought to characterize sleep spindles in MDD using high-density electroencephalography (hdEEG) to examine the topography of sleep spindles across the cortex in MDD, as well as sex-related variation in spindle topography in the disorder.

Methods: All-night hdEEG recordings were collected in 30 unipolar MDD participants (19 women) and 30 age and sex-matched controls. Topography of sleep spindle density, amplitude, duration, and integrated spindle activity (ISA) were assessed to determine group differences. Spindle parameters were compared between MDD and controls, including analysis stratified by sex.

Results: As a group, MDD subjects demonstrated significant increases in frontal and parietal spindle density and ISA compared to controls. When stratified by sex, MDD women demonstrated increases in frontal and parietal spindle density, amplitude, duration, and ISA; whereas MDD men demonstrated either no differences or decreases in spindle parameters.

Limitations: Given the number of male subjects, this study may be underpowered to detect differences in spindle parameters in male MDD participants.

Conclusions: This study demonstrates topographic and sex-related differences in sleep spindles in MDD. Further research is warranted to investigate the role of sleep spindles and sex in the pathophysiology of MDD.

Fig. 1

Topographic whole range (11–15 Hz) spindle parameters in MDD subjects versus healthy controls, both unstratified and stratified by sex. T-values plotted for the comparisons between groups (2-tailed, unpaired t-test) at each channel with red and blue corresponding to respective increase or decrease (p≤0.1) for a given parameter. Green dots denote channels with significant between group differences following statistical non-parametric mapping with suprathreshold cluster test to correct for multiple comparisons. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Topographic all-night slow (11–13 Hz) spindle parameters in MDD subjects versus healthy controls, both unstratified and stratified by sex. T-values plotted for the comparisons between groups (2-tailed, unpaired t-test) at each channel with red and blue corresponding to respective increase or decrease (p<0.1) in a given parameter. Green dots denote channels with significant between group differences following statistical non-parametric mapping with suprathreshold cluster test to correct for multiple comparisons. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Topographic all-night fast (13–15 Hz) spindle parameters in MDD subjects versus healthy controls, both unstratified and stratified by sex. T-values plotted for the comparisons between groups (2-tailed, unpaired t-test) at each channel with red and blue corresponding to respective increase or decrease (p≤0.1) in a given parameter. Green dots denote channels with significant between group differences following statistical non-parametric mapping with suprathreshold cluster test to correct for multiple comparisons. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)