Impact of Intermittent Hypoxia Related to Obstructive Sleep Apnoea Syndrome on Low-Grade Inflammation in Hypertensive Patients: Potential Implications for Cardiovascular Risk.

There is evidence for a particular relationship between low-grade inflammation (LGI) and intermittent hypoxia (IH) related to obstructive sleep apnoea syndrome (OSAS). However, despite the potential deleterious cardiovascular consequences associated with this LGI in hypertensive patients, few studies have investigated the impact of IH related to OSAS on CRP levels in this subpopulation. In total, 1404 hypertensive patients were selected retrospectively from the Sleep Laboratory database. CRP levels ≥3 mg/L but <10 mg/L were used as cut-offs to identify hypertensive patients with LGI. Logistic regressions were conducted to examine the risk of LGI associated with IH related to OSAS in hypertensive patients. LGI was frequent (33.8%) in hypertensive patients. After adjustment for confounders, multivariate logistic regressions revealed that only moderate to severe OSAS (apnoea-hypopnoea index ≥ 15/h) with high IH (oxygen desaturation index ≥ 15/h) [OR 1.51 (95% CI 1.06-2.14)] was significantly associated with LGI in hypertensive patients (p-value = 0.045). Consistent with our hypothesis, our results demonstrated the existence of a particular subtype of hypertensive patients at high cardiovascular risk characterised by the presence of LGI induced by IH hypoxia related to moderate to severe OSAS, which justifies the establishment of adequate management of this pathology to allow better cardiovascular prevention in this subpopulation.

Cardiovascular Outcome in Patients with Major Depression: Role of Obstructive Sleep Apnea Syndrome, Insomnia Disorder, and COMISA.

In this study, the 10-year cardiovascular risk associated with comorbid sleep disorders (insomnia disorder, obstructive sleep apnea syndrome, and COMISA [comorbid insomnia and sleep apnea]) was investigated for patients with major depression. To enable our analysis, 607 patients with major depression were selected from the data register of the Sleep Unit. High 10-year cardiovascular risk was considered present when the Framingham Risk Score was ≥10%. The 10-year cardiovascular risk associated with comorbid sleep disorders has been assessed using logistic regression analyzes. High 10-year cardiovascular risk is significant (40.4%) in patients with major depression. After successive introduction of the different confounders, multivariate logistic regressions showed that for patients with major depression high 10-year cardiovascular risk was significantly associated with COMISA but was not significantly associated with insomnia disorder or obstructive sleep apnea syndrome alone. Thus, these results highlight the existence of a negative synergistic action between insomnia disorder and obstructive sleep apnea syndrome on the 10-year cardiovascular risk in patients with major depression, which demonstrates the importance of researching and treating COMISA to improve the prognosis of this specific population subgroup characterized by higher cardiovascular morbidity and mortality.

10-Year Risk for Cardiovascular Disease Associated with COMISA (Co-Morbid Insomnia and Sleep Apnea) in Hypertensive Subjects.

Due to the few studies available, this study aimed to investigate the 10-year risk for cardiovascular disease (CVD) associated with COMISA (co-morbid insomnia and sleep apnea) in hypertensive subjects. Clinical data of 1009 hypertensive subjects extracted from the Sleep Laboratory database were analyzed. Framingham Risk Score ≥ 10% was used as a cut-off to identify hypertensive subjects with high 10-year risk for CVD. The association between 10-year risk for CVD and COMISA was investigated using logistic regression analyses. 65.3% of hypertensive subjects from our sample presented a high 10-year risk for CVD. After controlling for major confounding factors, multivariate logistic regression analyses demonstrated that unlike its components present separately, COMISA was significantly associated with high 10-year risk for CVD in hypertensive subjects (OR 1.88, 95% CI 1.01-3.51). In this study, we have demonstrated that the negative synergy between obstructive sleep apnea syndrome and insomnia disorder seems to play a central role in the 10-year risk for CVD in hypertensive subjects, which seems to indicate that the establishment of a systematic research and an adapted treatment of COMISA could open new perspectives to promote a better cardiovascular outcome in this specific subgroup of patients.

Risk of Cardiovascular Disease in Apnoeic Individuals: Role of Comorbid Insomnia Disorder.

Given the limited data available, the aim of this study was to examine the 10-year cardiovascular disease (CVD) risk associated with comorbid insomnia disorder and its specific subtypes in apnoeic individuals. Data from 1104 apnoeic individuals recruited from the database of the Erasme Hospital Sleep Laboratory were analysed. Only apnoeic individuals with a Framingham Risk Score ≥10% were included in the group at moderate-to-high 10-year CVD risk. Logistic regression analyses were conducted to examine the risk of 10-year CVD risk associated with comorbid insomnia disorder and its specific subtypes in apnoeic individuals. Moderate-to-high 10-year CVD risk was present in 59.6% of the apnoeic individuals in our sample. After adjustment for the main confounding factors, multivariate logistic regression analyses revealed that comorbid insomnia disorder and, more particularly, its subtype with short sleep duration were significantly associated with moderate-to-high 10-year CVD risk in apnoeic individuals. In this study, we demonstrate that comorbid insomnia disorder and, more specifically, its subtype with short sleep duration appear to have a negative cumulative effect on 10-year CVD risk in apnoeic individuals, which justifies more systematic research and adequate therapeutic management of this disorder to allow for better cardiovascular disease prevention in this particular subpopulation.

Cardiovascular risk associated with co-morbid insomnia and sleep apnoea (COMISA) in type 2 diabetics.

Objective: In the general population, co-morbid insomnia and sleep apnoea (COMISA) is associated with higher risk of cardiovascular diseases (CVD). However, despite a high prevalence of COMISA in type 2 diabetics, no study has investigated its potential implication in the negative cardiovascular outcome of this particular subpopulation. The aim of this study was therefore to examine the risk of CVD associated with COMISA in type 2 diabetics. Methods: Data from 471 type 2 diabetics recruited from the clinical database of the Erasme Hospital sleep laboratory were analysed. Only type 2 diabetics with SCORE index ≥5% were included in the group at high risk of CVD. Logistic regression analyses were conducted to examine the risk of CVD associated with COMISA in type 2 diabetics. Results: A high risk of CVD was present in 32.9% of type 2 diabetics. After adjustment for the main confounding factors associated with cardiovascular risk, multivariate logistic regression analysis revealed that unlike obstructive sleep apnoea syndrome or insomnia alone, only COMISA was associated with higher risk of CVD in type 2 diabetics. Discussion: In our study, we have demonstrated that unlike its components alone, only COMISA was associated with higher risk of CVD in type 2 diabetics, which highlights the importance of the central role played by the negative synergistic effect of COMISA on the cardiovascular outcome in this particular subpopulation. Thus, given these elements, more systematic research and adequate therapeutic management of COMISA seem to be necessary to allow better cardiovascular prevention in type 2 diabetics.

Risk of Excessive Daytime Sleepiness Associated to Major Depression in Adolescents.

Given the limited data currently available in the literature, the aim of this study was to investigate the risk of excessive daytime sleepiness (EDS) associated with major depression in a large sample of adolescents. The clinical and polysomnographic data of 105 adolescents recruited from the database of the Erasme Hospital sleep laboratory were analysed. A score > 10 on the Epworth Sleepiness Scale was used as cut-off for the diagnosis of EDS. The status (remitted or current) and the severity (mild to moderate or severe) of major depressive episodes were determined based on the diagnostic criteria of the DSM-IV-TR during a systematic psychiatric assessment. Logistic regression analyses were performed to determine the risk of EDS associated with major depression in adolescents. The prevalence of EDS was 34.3% in our sample of adolescents. After adjusting for the main confounding factors associated with EDS, multivariate logistic regression analysis demonstrated that unlike mild to moderate major depression, remitted major depression and severe major depression were risk factors for EDS in adolescents. In our study, we have highlighted that in adolescents, the EDS could be both residual symptom and severity marker of major depression, which seems to justify a systematic psychiatric assessment in adolescents with EDS complaints in order to allow better management of this problem in this particular subpopulation.

Polysomnographic markers of suicidal ideation in untreated unipolar major depressed individuals.

Given the major role played by sleep in the particular relationship between suicidality and major depression, the aim of this study was to empirically identify polysomnographic markers specific to suicidal ideation in major depressed individuals in order to allow better suicide prevention in this high-risk subpopulation. Demographic and polysomnographic data from 190 individuals (34 healthy controls and 156 untreated unipolar major depressed individuals) recruited from the sleep laboratory database were analysed. Suicidal ideation were considered present if the score in item G of the Beck Depression Inventory was ≥1 and/or if they were highlighted during the systematic psychiatric assessment conducted on admission to the sleep laboratory. Independently of depression severity, major depressed individuals with suicidal ideation present a decrease in deep NREM sleep (slow-wave sleep) and an increase in light NREM sleep (stage 1 + stage 2) compared to those without suicidal ideation. There are no significant differences for the other polysomnographic parameters. In our study, we highlighted the existence of potential polysomnographic markers of suicidal ideation in untreated unipolar major depressed individuals, which seems to open up new perspectives for the identification and management of individuals at high-risk of suicide in this particular subpopulation.

Alterations of neural network organization during REM sleep in women: implication for sex differences in vulnerability to mood disorders.

BACKGROUND: Sleep plays an important role in vulnerability to mood disorders. However, despite the existence of sex differences in vulnerability to mood disorders, no study has yet investigated the sex effect on sleep network organization and its potential involvement in vulnerability to mood disorders. The aim of our study was to empirically investigate the sex effect on network organization during REM and slow-wave sleep using the effective connectivity measured by Granger causality. METHODS: Polysomnographic data from 44 healthy individuals (28 men and 16 women) recruited prospectively were analysed. To obtain the 19 × 19 connectivity matrix of all possible pairwise combinations of electrodes by Granger causality method from our EEG data, we used the Toolbox MVGC multivariate Granger causality. The computation of the network measures was realized by importing these connectivity matrices into EEGNET Toolbox. RESULTS: In men and women, all small-world coefficients obtained are compatible with a small-world network organization during REM and slow-wave sleep. However, compared to men, women present greater small-world coefficients during REM sleep as well as for all EEG bands during this sleep stage, which indicates the presence of a small-world network organization less marked during REM sleep as well as for all EEG bands during this sleep stage in women. In addition, in women, these small-world coefficients during REM sleep as well as for all EEG bands during this sleep stage are positively correlated with the presence of subclinical symptoms of depression. CONCLUSIONS: Thus, the highlighting of these sex differences in network organization during REM sleep indicates the presence of differences in the global and local processing of information during sleep between women and men. In addition, this small-world network organization less marked during REM sleep appears to be a marker of vulnerability to mood disorders specific to women, which opens up new perspectives in understanding sex differences in the occurrence of mood disorders.

Impact of number of sleep ultradian cycles on polysomnographic parameters related to REM sleep in major depression: Implications for future sleep research in psychiatry.

Given the contradictory data on REMS alterations in major depression, the aim of this study was to empirically demonstrate that based on the number of sleep ultradian cycles, it was possible to highlight different subtypes of major depression characterized by specific patterns of REMS alterations. Demographic and polysomnographic data from 211 individuals (30 healthy controls and 181 untreated major depressed individuals) recruited from the sleep laboratory database were analyzed. Major depressed individuals with sleep ultradian cycles <4 showed alterations consistent with REMS deficiency (non-shortened REM latency as well as decrease in REMS percentage, REMS duration and REMS/NREMS ratio) whereas major depressed individuals with sleep ultradian cycles >4 showed alterations consistent with REMS disinhibition (shortened REM latency as well as increase in REMS percentage, REMS duration and REMS/NREMS ratio). Regarding major depressed individuals with 4 sleep ultradian cycles, their REMS alterations were intermediate to those present in major depressed individuals with sleep ultradian cycles <4 and >4. Thus, in major depressed individuals, the highlighting of this heterogeneity of REMS alterations based on the number of sleep ultradian cycles seems to suggest the involvement of distinct pathophysiological mechanisms and could open new perspectives for future sleep research in psychiatry.

Risk of resistant hypertension associated with restless legs syndrome and periodic limb movements during sleep: a study on 673 treated hypertensive individuals.

OBJECTIVE: Given the limited data available in the literature, the aim of this study was to examine the risk of resistant hypertension (RHT) associated with restless legs syndrome (RLS) and periodic limb movements during sleep (PLMS) in a large sample of treated hypertensive individuals. METHODS: Demographic and polysomnographic (PSG) data from 673 treated hypertensive individuals recruited from the research database of the sleep laboratory of Erasme Hospital were analysed. After exclusion of the main causes of pseudo-resistance and secondary hypertension, RHT status was defined by the presence of an uncontrolled hypertension despite treatment with at least three antihypertensive agents (including a diuretic) from different classes in correct combination and at the highest tolerated doses or by the presence of controlled hypertension requiring the use of at least four antihypertensive agents. Logistic regression analyses were conducted to examine the risk of RHT associated with RLS and PLMS in treated hypertensive individuals. RESULTS: After adjustment for major confounding factors associated with RHT, multivariate logistic regression analysis revealed that frequent RLS (≥2 episodes/week) combined with PLMS index ≥26/h [odds ratio (OR) 2.20; 95% confidence interval (CI) 1.35-3.61, p = 0.021] was a significant risk factor of RHT in treated hypertensive individuals. CONCLUSION: In treated hypertensive individuals, frequent RLS combined with PLMS index ≥26/h is associated with higher risk of RHT which suggests that this pathology may be a secondary cause of RHT (eg, obstructive sleep apnoea syndrome and insomnia with short sleep duration) justifying the establishment of effective treatments in this particular subpopulation.

Alterations of neural network organisation during rapid eye movement sleep and slow-wave sleep in major depression: Implications for diagnosis, classification, and treatment.

The aim of this study was to empirically investigate the network organisation during rapid eye movement sleep (REMS) and slow-wave sleep (SWS) using the effective connectivity measured using the Granger causality to identify new potential biomarkers for the diagnosis, classification, and potential favourable response to treatment in major depression. Polysomnographic data were analysed from 24 healthy individuals and 16 major depressed individuals recruited prospectively. To obtain the 19×19 connectivity matrix of all possible pairwise combinations of electrodes by the Granger causality method from our electroencephalographic data, we used the Toolbox MVGC multivariate Granger causality. The computation of network measures was realised by importing these connectivity matrices into the EEGNET Toolbox. Major depressed individuals (versus healthy individuals) and those with endogenous depression (versus those with neurotic depression) present alterations of small-world network organisation during REMS, whereas major depressed individuals with potential favourable response to electroconvulsive therapy (versus those with potential unfavourable response) have a less efficient small-world network organisation during SWS. Thus, alterations in network organisation during REMS could be biomarkers for the diagnosis and classification of major depressive episodes, whereas alterations of network organisation during SWS could be a biomarker to predict potential favourable response to treatment by electroconvulsive therapy.

Sleep ultradian cycling: Statistical distribution and links with other sleep variables, depression, insomnia and sleepiness-A retrospective study on 2,312 polysomnograms.

The number of alternations between Non-Rapid Eye Movement (NREM) sleep and Rapid Eye Movement (REM) sleep in humans is usually considered to consist of 4-5 cycles of about 90 minutes duration per night. Previous studies by our group showed a normal distribution on 26 healthy human subjects. The present study retrospectively analyzes the polysomnograms of 2,312 unmedicated patients who were admitted for medical and/or psychiatric reasons in the Erasme University Hospital between 2003 and 2014. The normal distribution of the Number of Cycles and Mean Cycle Duration was confirmed. Q-Q plots were very close to linearity. This distribution allows the use of these variables in parametric comparisons. The Number of Cycles per night and the Mean Cycle Duration showed predominant links with REM sleep-related variables, such as the REM Latency, REM sleep duration, the REM/NREM sleep ratio. None of these variables was associated with the diagnosis of Major Depressive Disorder, nor the intensity of Depression as measured by the Beck Depression Inventory (short version). On the other hand, the diagnosis of Major Depressive Disorder was significantly associated with the Insomnia Severity Index and correlated with the intensity of depressive symptoms (Beck Depression Inventory).

The sleep network organization during slow-wave sleep is more stable with age and has small-world characteristics more marked than during REM sleep in healthy men.

Sleep plays an important role in cognitive functioning. However, few studies have investigated the sleep network organization. The aim of our study was to empirically investigate the presence and the stability with age of a small-world network organization during REM and slow-wave sleep using the effective connectivity measured by the Granger causality. Polysomnographic data from 30 healthy men recruited prospectively were analysed. To obtain the 19 × 19 connectivity matrix of all possible pairwise combinations of electrodes by the Granger causality method from our EEG data, we used the Toolbox MVGC multivariate Granger causality. The computation of the network measures was realised by importing these connectivity matrices into the EEGNET Toolbox. Even if all small-world coefficients obtained are compatible with a small-world network organization during REM and slow-wave sleep, slow-wave sleep seems to have a small-world network organization more marked than REM sleep. Moreover, the sleep network organization is affected greater by age during REM sleep than during slow-wave sleep. In healthy individuals, the highlighting of a sleep network organization during slow-wave sleep more stable with age and with small-world characteristics more marked than during REM sleep may help to better understand the global and local processing of information during sleep.

Prevalence and risk factors of excessive daytime sleepiness in major depression: A study with 703 individuals referred for polysomnography.

BACKGROUND: To date, few studies have investigated the prevalence and risk factors of excessive daytime sleepiness (EDS) in major depression. Thus, the aim of the present study was to examine the prevalence and risk factors of EDS in a large sample of individuals with major depression. METHODS: Data from 703 individuals with major depression were retrospectively collected from the sleep laboratory research database of Erasme Hospital for analysis. A score of > 10 on the Epworth Sleepiness Scale was used as the cut-off for EDS. Logistic regression analyses were conducted to examine the clinical and demographic risk factors of EDS in major depression. RESULTS: The prevalence of EDS in our sample was 50.8%. Multivariate logistic regression analysis revealed that the following were significant risk factors of EDS in major depression: non-use of short to intermediate half-life benzodiazepine receptor agonists, BMI ≥ 25 kg/m², age < 60 years, C-reactive protein > 7 mg/L, Beck Depression Inventory score ≥ 16, atypical depression, apnea-hypopnea index ≥ 15/h, and use of selective serotonin reuptake inhibitors or serotonin-norepinephrine reuptake inhibitors. LIMITATIONS: To evaluate EDS, we used the Epworth Sleepiness Scale, which only allows for a subjective measure of daytime sleepiness. CONCLUSION: EDS is a common symptom in individuals with major depression. In this subpopulation, interventions are possible for most risk factors of EDS, which justifies improved management of this symptom to avoid its negative consequences.

Objective sleep alterations and long-term use of short or intermediate half-life benzodiazepine receptor agonists are risk factors for high blood pressure in individuals with insomnia: a study in 1272 individuals referred for sleep examinations.

INTRODUCTION: Given conflicting data in the literature, the aim of this study was to examine the risk of high blood pressure (HBP) associated with sleep alterations, measured during polysomnography, and long-term use of benzodiazepine receptor agonists in a large sample of individuals with insomnia. METHODS: Demographic and polysomnographic data from 1272 individuals with insomnia recruited from the research database of the sleep laboratory of Erasme Hospital were analyzed. HBP status was defined by the presence of one of the following: self-report at interview of either a physician's diagnosis or taking antihypertensive medication; or an average systolic blood pressure ≥140 mm Hg or an average diastolic blood pressure ≥90 mm Hg at the medical examination. Logistic regression analyses were conducted to examine the risk of HBP associated with objective sleep alterations and long-term use of benzodiazepine receptor agonists in individuals with insomnia. RESULTS: The prevalence of HBP in individuals with insomnia is 30.03%. After adjustment for major confounding factors associated with HBP, multivariate logistic regression analysis revealed that short sleep duration (<5 h), severely reduced sleep efficiency (<65%), high sleep fragmentation (sleep fragmentation index ≥18/h), and long-term use of short or intermediate half-life benzodiazepine receptor agonists were significant risk factors for HBP in individuals with insomnia. CONCLUSION: In individuals with insomnia, objective sleep alterations and long-term use of short or intermediate half-life benzodiazepine receptor agonists are associated with higher risk of HBP. Therefore, better management of these reversible risk factors is required to avoid the negative consequences of the co-occurrence of insomnia and HBP.

Risk of high blood pressure associated with objective insomnia and self-reported insomnia complaints in major depression: A study on 703 individuals.

BACKGROUND: Since few studies have investigated the risk of high blood pressure associated with objective insomnia and self-reported insomnia complaints in major depression, the aim of this study was to examine this risk in a large sample of individuals with major depression. METHODS: Data from 703 individuals with major depression recruited from the research database of the sleep laboratory of the Erasme Hospital were analysed. High blood pressure status was defined by the presence of one of the following: self-reports at interview of either a physician-diagnosis or taking antihypertensive medication; or an average systolic blood pressure ≥140 mmHg or an average diastolic blood pressure ≥90 mmHg during at least two medical examinations. Logistic regression analyses were conducted to examine the risk of high blood pressure associated with objective insomnia and self-reported insomnia complaints in major depression. RESULTS: After adjustment for major confounding factors associated with high blood pressure, multivariate logistic regression analysis revealed that severe objective insomnia, low complaints of repeated nighttime awakenings or early morning awakening, and intermediate or low self-reported insomnia complaints were significant risk factors of high blood pressure in major depression. CONCLUSION: In major depression, severe objective insomnia and lower self-reported insomnia complaints are associated with higher risk of high blood pressure, which justifies a better management of objective insomnia and a better assessment of insomnia complaints in this particular subpopulation to avoid the negative consequences related to the co-occurrence of high blood pressure and major depression. Abbreviations: AHI, Apnea-Hypopnea Index; BDI, Beck Depression Inventory; BMI, Body Mass Index; DSM IV-TR, Diagnostic and Statistical Manual of Mental Disorders fourth edition - Text Revision; ESS, Epworth Sleepiness scale; ISI, Insomnia Severity Index; HBP, High Blood Pressure; OSA, Obstructive Sleep Apnea Syndrome; REM, rapid eye movement sleep.

Research into an Association between Anhedonia and Decreased REM Latency in Moderately to Severely Depressed Patients.

Anhedonia stands as a core symptom and potential trait marker of major depressive disorder (MDD). The importance of rapid eye movement sleep latency (REML) as a biological marker of depression has previously and repeatedly been studied. The aim of this paper is to analyse the relationship between anhedonia and REML in moderately to severely depressed patients. The shortened Beck Depression Inventory (BDI-13) was chosen to assess depressive symptoms and, among them, more particularly, anhedonic symptoms. Two-way ANCOVA was used for statistical analyses. A significant association between anhedonic symptoms and REML was found when the number of sleep cycles (NCy) and the severity of depression were added as covariates. Our findings suggest that REML may be a useful variable to differentiate some diagnostic subtypes of depression related to anhedonia.

Prevalence and risk factors of type 2 diabetes in insomnia sufferers: a study on 1311 individuals referred for sleep examinations.

BACKGROUND: Several studies have investigated the particular relationship between insomnia and type 2 diabetes. However, few studies have investigated the prevalence and risk factors for type 2 diabetes in insomnia sufferers. The aim of this study was to examine the prevalence and risk factors of type 2 diabetes in a large sample of insomnia sufferers. METHODS: Data from 1311 insomnia sufferers recruited from the research database of the Erasme Hospital sleep laboratory were analyzed. Only individuals with a diagnosis of type 2 diabetes according to the diagnostic criteria of the American Diabetes Association at admission were included in the diabetes group. Logistic regression analyses were conducted to examine clinical and demographic risk factors of type 2 diabetes in insomnia sufferers. RESULTS: The prevalence of type 2 diabetes in insomnia sufferers is 21.13%. Multivariate logistic regression analysis revealed that significant risk factors of type 2 diabetes in insomnia sufferers were as follows: being male, Z-drugs use, high blood pressure, hypertriglyceridemia, alcohol consumption of ≥4 units/day, BMI ≥25 & <30 kg/m2, BMI ≥30 kg/m2, age ≥50 years, C-reactive protein ≥4.5 mg/L, a sleep duration of <6.5 h, apnea-hypopnea index ≥15/hour, periodic limb movements index ≥26/hour, and severe complaints of early morning awakening. CONCLUSION: Type 2 diabetes is a common pathology in insomnia sufferers. In this subpopulation, most of the risk factors for type 2 diabetes are reversible, which justifies better prevention and management of this pathology in order to avoid its negative consequences.

The dichotomy between low frequency and delta waves in human sleep: A reappraisal.

BACKGROUND: We present the results of an analysis of the low frequency (LF) (0.25-1Hz) and delta (1-4Hz) waves during human sleep. Our objective was to investigate whether LF and delta waves should be considered as separate entities. METHODS: The slow-wave electroencephalogram (EEG) activity of 2 sets of 10 young, healthy volunteers was analysed utilising the rarely-used Lomb-Scargle periodogram. This method has advantages over the more commonly-used Fast Fourier Transform analysis. RESULTS: During the night, the frequencies of the most powerful waves are concentrated in the 0.5-2Hz range and show a continuous tendency to shift towards slower frequencies during sleep. COMPARISON WITH EXISTING METHODS: When considering the frequency dynamics of slow-wave activity below 3Hz, the unifying theory of LF and delta waves is more parsimonious than the idea that there is a different origin and regulation for the two sub-bands. CONCLUSIONS: The unifying theory of LF and delta waves is the simplest explanation for the slow-wave activity of the EEG below 3Hz. This finding is important for the clinical use of slow-wave activity.

Prevalence and Risk Factors of Type 2 Diabetes in Major Depression: A Study on 703 Individuals Referred for Sleep Examinations.

BACKGROUND: Several studies have investigated the prevalence and risk factors of depression in individuals with type 2 diabetes. However, few studies have investigated the prevalence and risk factors for type 2 diabetes in major depression. OBJECTIVE: The aim of this study was to examine the prevalence and risk factors of type 2 diabetes in a large sample of individuals with major depression. METHODS: Data from 703 individuals with major depression recruited from the research database of the sleep laboratory of the Erasme Hospital were analysed. Only individuals with a diagnosis of type 2 diabetes according to the diagnostic criteria of the American Diabetes Association were included in the diabetes group. Logistic regression analyses were conducted to examine clinical and demographic risk factors of type 2 diabetes in major depression. RESULTS: The prevalence of type 2 diabetes in major depression is 21.2%. Multivariate logistic regression analysis revealed that male sex, high blood pressure, hypertriglyceridemia, BMI ≥30kg/m², age ≥50 years, sleep duration <6.5 hours, C-reactive protein ≥4.5mg/L, Beck Depression Inventory >12, and apnea-hypopnea index ≥5/h were significant risk factors of type 2 diabetes in major depression. CONCLUSION: Type 2 diabetes is a common condition in major depression. In this subpopulation, most of the risk factors for type 2 diabetes are reversible, which justifies better prevention and management of this disorder to avoid its negative consequences.