Temporal Characteristics of Delta Activity During NREM Sleep in Depressed Outpatients and Healthy Adults: Group and Sex Effects

Abstract

A CONSIDERABLE NUMBER OF STUDIES HAVE INDICATED THAT MAJOR DEPRESSIVE DISORDER (MDD) is characterized by difficulties initiating and maintaining sleep, increased stage 1 sleep, an early onset of rapid eye movement (REM) sleep, increased phasic REM activity, and a reduction in slow-wave (stage 3-4) sleep (cf. 1). However, a recent meta-analysis has indicated that no single sleep variable reliably differentiates depressed patients from healthy controls. 2 Moreover, not all studies, particularly more recent work, have shown significant differences between patients and controls. 3-4 Short REM latency (<65 minutes) and/or reduced slow-wave (SW) sleep, for example, are only present in 40%-60% of outpatients with MDD. As suggested recently, it is very likely that confounds such as age and sex have contributed to discrepant outcomes in sleep studies of MDD, most notably with regard to slow-wave sleep and measures of delta EEG activity (cf. 3-5). This issue is a key focus of the present paper.Work on REM and SW sleep abnormalities has led to speculation that sleep regulatory processes are disrupted in MDD. Specifically, the regulatory disturbance has been postulated as one of REM disinhibition, due to an imbalance in cholinergic-aminergic neurotransmitters that leads to both the early onset of REM and increased phasic REM activity. 6 There is fairly strong evidence that MDD is associated with increased cholinergic sensitivity using critical REM induction tests. To date, there is little evidence to refute this theory of sleep disturbance in MDD, although cholinergic sensitivity may not be specific to depression. 4 Others have suggested that the circadian oscillator that controls temperature, neuroendocrine function, and REM sleep is phase-advanced relative to SW sleep. 7-8 More recent evidence indicates that MDD is more likely to be associated with blunted amplitude circadian rhythms, 9Study Objectives: The primary aim was to evaluate group and sex differences in delta activity across non-rapid eye movement (NREM) sleep in depressed patients and healthy controls. Design: Repeated-measures ANOVA contrasted delta power, amplitude and incidence in the first three NREM periods (stages 2,3, and 4) of sleep. The time course of delta activity was evaluated with exponential regressions. Age effects on delta were evaluated with linear regression analysis. Setting: Two consecutive nights were spent in the laboratory, the first of which served as adaptation. Patients or Participants: Twenty-two (9 men, 13 women) symptomatic, but unmedicated, outpatients with major depressive disorder (MDD) and 23 healthy controls (15 men, 8 women) participated in the study. Measurements and Results: Delta power and amplitude showed significant group by sex interactions. Men with MDD showed lower power and amplitude in NREM sleep compared to women with MDD, but did not differ significantly from controls. However, the time course of delta power and amplitude was significantly different in men with MDD, with lower accumulation and slower dissipation ac...

Sleep Macroarchitecture in Depression: Sex Differences~!2009-11-01~!2010-03-01~!2010-04-21~!

“…Men with MDD had significantly less slowwave sleep and more Stage 1 sleep than in MDD women. These findings are in general agreement with previous research [26,27,29]. It should be noted, however, that there are only a handful of studies on sex differences in sleep in depression.…”

“…Among those studies detecting sex differences in MDD, the most robust finding is that men with MDD show lower amplitude slow-wave activity (SWA), also known as delta activity in NREM sleep. The time course of SWA and response to homeostatic sleep challenge is also blunted in men with MDD [29][30][31]. By contrast, women with depression do not show reduced SWA and may be hyperresponsive to sleep challenge [30,31].…”

“…Although there is compelling evidence that depression pathophysiology is different between men and women [24], the literature regarding sex differences in sleep variables remains equivocal and controversial, with several studies finding few differences between males and females with MDD [26,27], while others report robust EEG differences [28][29][30]. Among those studies detecting sex differences in MDD, the most robust finding is that men with MDD show lower amplitude slow-wave activity (SWA), also known as delta activity in NREM sleep.…”

Comparison of Different Methods for the Evaluation of Treatment Effects from the Sleep EEG of Patients with Major Depression

“…Therefore, it may be expected that the patient, after treatment, has an increased delta power during deep sleep states. This, however, is not necessarily the case [13,23]. The increasing values of the delta/beta ratio are essentially caused by reduced beta activity.…”

Sleep Disorders in Shift Workers in the Emergency Department and Efficacy of Melatonin

“…Although antidepressants such as tricyclics and selective serotonin reuptake inhibitors suppress REMS, they increase REMOL (59). Most antidepressants increase the amount of MT1 receptor mRNA in hippocampal regions (60).…”