Insomnia with objective short sleep duration is associated with longer duration of insomnia in the Freiburg Insomnia Cohort compared to insomnia with normal sleep duration, but not with hypertension

Insomnia Subtypes Have Differentiating Deviations in Brain Structural Connectivity

BACKGROUND

Insomnia disorder is the most common sleep disorder. A better understanding of insomnia-related deviations in the brain could inspire better treatment. Insufficiently recognized heterogeneity within the insomnia population could obscure detection of involved brain circuits. In the current study, we investigated whether structural brain connectivity deviations differed between recently discovered and validated insomnia subtypes.

METHODS

Structural and diffusion-weighted 3T magnetic resonance imaging data from 4 independent studies were harmonized. The sample consisted of 73 control participants without sleep complaints and 204 participants with insomnia who were grouped into 5 insomnia subtypes based on their fingerprint of mood and personality traits assessed with the Insomnia Type Questionnaire. Linear regression correcting for age and sex was used to evaluate group differences in structural connectivity strength, indicated by fractional anisotropy, streamline volume density, and mean diffusivity and evaluated within 3 different atlases.

RESULTS

Insomnia subtypes showed differentiating profiles of deviating structural connectivity that were concentrated in different functional networks. Permutation testing against randomly drawn heterogeneous subsamples indicated significant specificity of deviation profiles in 4 of the 5 subtypes: highly distressed, moderately distressed reward sensitive, slightly distressed low reactive, and slightly distressed high reactive. Connectivity deviation profile significance ranged from p = .001 to p = .049 for different resolutions of brain parcellation and connectivity weight.

CONCLUSIONS

Our results provide an initial indication that different insomnia subtypes exhibit distinct profiles of deviations in structural brain connectivity. Subtyping insomnia may be essential for a better understanding of brain mechanisms that contribute to insomnia vulnerability.

Insomnia with objective but not subjective short sleep duration is associated with incident cardiovascular and/or cerebrovascular disease

STUDY OBJECTIVES

Insomnia with objective short sleep duration (ISSD) has been associated with cardiometabolic outcomes (ie, hypertension or diabetes). We examined whether ISSD, based on objective or subjective sleep measures, is associated with more serious health problems, such as incident cardiovascular and/or cerebrovascular disease (CBVD).

METHODS

1,258 men and women from the Penn State Adult Cohort (56.9% women, aged 48.3 ± 12.95 years) without CBVD at baseline were followed up for 9.21 ± 4.08 years. The presence of CBVD was defined as a history of diagnosis or treatment of heart disease and/or stroke. Insomnia was defined as a complaint of insomnia with a duration ≥ 1 year. Poor sleep was defined as a complaint of difficulty falling asleep, staying asleep, nonrestorative sleep, or early morning awakening. Objective short sleep duration was defined as < 6 hours' sleep based on polysomnography. Subjective short sleep duration was based on the median self-reported percentage of sleep time (ie, < 7 hours).

RESULTS

Compared with normal sleepers with normal sleep duration, the highest risk of incident CBVD was in the ISSD group (odds ratio = 2.46, 95% confidence interval = 1.04-5.79), and the second highest was in normal sleepers with short sleep duration (odds ratio = 1.68, 95% confidence interval = 1.11-2.54). The risk of incident CBVD was not significantly increased in poor sleepers or those with insomnia with normal sleep duration. Finally, insomnia with subjective short sleep duration was not associated with increased incident CBVD.

CONCLUSIONS

These data add to the cumulative evidence that ISSD, based on objective but not subjective measures, is the more severe biological phenotype of the disorder associated with incident CBVD.

CITATION

Pejovic S, Vgontzas AN, Fernandez-Mendoza J, et al. Insomnia with objective but not subjective short sleep duration is associated with incident cardiovascular and/or cerebrovascular disease. J Clin Sleep Med. 2024;20(7):1049-1057.

A meta-analysis of the association between insomnia with objective short sleep duration and risk of hypertension

The aim of this meta-analysis was to examine the association between insomnia with objective short sleep duration (ISSD) with prevalent and incident hypertension in cross-sectional and longitudinal studies, respectively. Data were collected from 6 cross-sectional studies with 5914 participants and 2 longitudinal studies with 1963 participants. Odds ratios (ORs) for prevalent and risk ratios (RRs) for incident hypertension were calculated through meta-analyses of adjusted data from individual studies. Compared to normal sleepers with objective normal sleep duration (NNSD), ISSD was significantly associated with higher pooled OR for prevalent hypertension (pooled OR = 2.67, 95%CI = 1.45-4.90) and pooled RR for incident hypertension (pooled RR = 1.95, 95%CI = 1.19-3.20), respectively. Compared to insomnia with objective normal sleep duration, ISSD was associated with significantly higher pooled OR of prevalent hypertension (pooled OR = 1.94, 95%CI = 1.29-2.92) and pooled RR for incident hypertension (pooled RR = 2.07, 95%CI = 1.47-2.90), respectively. Furthermore, normal sleepers with objective short sleep duration were not associated with either prevalent (pooled OR = 1.21, 95%CI = 0.84-1.75) or incident (pooled RR = 0.97, 95%CI = 0.81-1.17) hypertension compared to NNSD. Our findings suggest that ISSD is a more severe phenotype of the disorder associated with a higher risk of hypertension. Objective short sleep duration might be a valid and clinically useful index of insomnia's impact on cardiovascular health.

The first-night effect and the consistency of short sleep in insomnia disorder

The nature and degree of objective sleep impairments in insomnia disorder remain unclear. This issue is complicated further by potential changes in sleep architecture on the first compared with subsequent nights in the laboratory. Evidence regarding differential first-night effects in people with insomnia disorder and controls is mixed. Here, we aimed to further characterize insomnia- and night-related differences in sleep architecture. A comprehensive set of 26 sleep variables was derived from two consecutive nights of polysomnography in 61 age-matched patients with insomnia and 61 good sleeper controls. People with insomnia expressed consistently poorer sleep than controls on several variables during both nights. While poorer sleep during the first night was observed in both groups, there were qualitative differences regarding the specific sleep variables expressing a first-night effect. Short sleep (total sleep time < 6 hr) was more likely during the first night and in insomnia, although approximately 40% of patients with insomnia presenting with short sleep on night 1 no longer met this criterion on night 2, which is important given the notion of short-sleeping insomnia as a robust subtype.

Insomnia nosology: a systematic review and critical appraisal of historical diagnostic categories and current phenotypes

Insomnia nosology has significantly evolved since the Diagnostic and Statistical Manual (DSM)-III-R first distinguished between 'primary' and 'secondary' insomnia. Prior International Classification of Sleep Disorders (ICSD) nosology 'split' diagnostic phenotypes to address insomnia's heterogeneity and the DSM nosology 'lumped' them into primary insomnia, while both systems assumed causality for insomnia secondary to health conditions. In this systematic review, we discuss the historical phenotypes in prior insomnia nosology, present findings for currently proposed insomnia phenotypes based on more robust approaches, and critically appraise the most relevant ones. Electronic databases PsychINFO, PubMED, Web of Science, and references of eligible articles, were accessed to find diagnostic manuals, literature on insomnia phenotypes, including systematic reviews or meta-analysis, and assessments of the reliability or validity of insomnia diagnoses, identifying 184 articles. The data show that previous insomnia diagnoses lacked reliability and validity, leading current DSM-5-TR and ICSD-3 nosology to 'lump' phenotypes into a single diagnosis comorbid with health conditions. However, at least two new, robust insomnia phenotyping approaches were identified. One approach is multidimensional-multimethod and provides evidence for self-reported insomnia with objective short versus normal sleep duration linked to clinically relevant outcomes, while the other is multidimensional and provides evidence for two to five clusters (phenotypes) based on self-reported trait, state, and/or life-history data. Some approaches still need replication to better support whether their findings identify true phenotypes or simply different patterns of symptomatology. Regardless, these phenotyping efforts aim at improving insomnia nosology both as a classification system and as a mechanism to guide treatment.

Insomnia with objective, but not subjective, short sleep duration is associated with increased risk of incident hypertension: the Sleep Heart Health Study

STUDY OBJECTIVES

Insomnia with objective short sleep duration has been associated with higher risk of cardiometabolic morbidity. In this study, we examined the association between insomnia with objective short sleep duration, also based on subjective sleep duration, with incident hypertension in the Sleep Heart Health Study.

METHODS

We analyzed data from 1,413 participants free of hypertension or sleep apnea at baseline from the Sleep Heart Health Study, with a median follow-up duration of 5.1 years. Insomnia symptoms were defined based on difficulty falling asleep, difficulty returning to sleep, early morning awakening, or sleeping pill use more than half the days in a month. Objective short sleep duration was defined as polysomnography-measured total sleep time < 6 hours. Incident hypertension was defined based on blood pressure measures and/or use of antihypertensive medications at follow-up.

RESULTS

Individuals with insomnia who slept objectively < 6 hours had significantly higher odds of incident hypertension compared to normal sleepers who slept ≥ 6 hours (odds ratio = 2.00, 95% confidence interval = 1.09-3.65) or < 6 hours (odds ratio = 2.00, 95% confidence interval = 1.06-3.79) or individuals with insomnia who slept ≥ 6 hours (odds ratio = 2.79, 95% confidence interval = 1.24-6.30). Individuals with insomnia who slept ≥ 6 hours or normal sleepers who slept < 6 hours were not associated with increased risk of incident hypertension compared to normal sleepers who slept ≥ 6 hours. Finally, individuals with insomnia who self-reported sleeping < 6 hours were not associated with significantly increased odds of incident hypertension.

CONCLUSIONS

These data further support that the insomnia with objective short sleep duration phenotype based on objective, but not subjective measures, is associated with increased risk of developing hypertension in adults.

CITATION

Dai Y, Chen B, Chen L, et al. Insomnia with objective, but not subjective, short sleep duration is associated with increased risk of incident hypertension: the Sleep Heart Health Study. J Clin Sleep Med. 2023;19(8):1421-1428.

Sub-types of insomnia in adolescents: Insights from a quantitative/molecular twin study

Background

Insomnia with short sleep duration has been postulated as more severe than that accompanied by normal/long sleep length. While the short duration subtype is considered to have greater genetic influence than the other subtype, no studies have addressed this question. This study aimed to compare these subtypes in terms of: (1) the heritability of insomnia symptoms; (2) polygenic scores (PGS) for insomnia symptoms and sleep duration; (3) the associations between insomnia symptoms and a wide variety of traits/disorders.

Methods

The sample comprised 4000 pairs of twins aged 16 from the Twins Early Development Study. Twin models were fitted to estimate the heritability of insomnia in both groups. PGS were calculated for self-reported insomnia and sleep duration and compared among participants with short and normal/long sleep duration.

Results

Heritability was not significantly different in the short sleep duration group (A = 0.13 [95%CI = 0.01, 0.32]) and the normal/long sleep duration group (A = 0.35 [95%CI = 0.29, 0.40]). Shared environmental factors accounted for a substantial proportion of the variance in the short sleep duration group (C = 0.19 [95%CI = 0.05, 0.32]) but not in the normal/long sleep duration group (C = 0.00 [95%CI = 0.00, 0.04]). PGS did not differ significantly between groups although results were in the direction expected by the theory. Our results also showed that insomnia with short (as compared to normal/long) sleep duration had a stronger association with anxiety and depression (p < .05)-although not once adjusting for multiple testing.

Conclusions

We found mixed results in relation to the expected differences between the insomnia subtypes in adolescents. Future research needs to further establish cut-offs for 'short' sleep at different developmental stages and employ objective measures of sleep.

Understanding neuron-glia crosstalk and biological clocks in insomnia

According to the World Health Organization, about one-third of the population experiences insomnia symptoms, and about 10-15% suffer from chronic insomnia, the most common sleep disorder. Sleeping difficulties associated with insomnia are often linked to chronic sleep deprivation, which has a negative health impact partly due to disruption in the internal synchronisation of biological clocks. These are regulated by clock genes and modulate most biological processes. Most studies addressing circadian rhythm regulation have focused on the role of neurons, yet glial cells also impact circadian rhythms and sleep regulation. Chronic insomnia and sleep loss have been associated with glial cell activation, exacerbated neuroinflammation, oxidative stress, altered neuronal metabolism and synaptic plasticity, accelerated age-related processes and decreased lifespan. It is, therefore, essential to highlight the importance of glia-neuron interplay on sleep/circadian regulation and overall healthy brain function. Hence, in this review, we aim to address the main neurobiological mechanisms involved in neuron-glia crosstalk, with an emphasis on microglia and astrocytes, in both healthy sleep, chronic sleep deprivation and chronic insomnia.

Insomnia with objective short sleep duration is associated with hypertension

Insomnia with objective short sleep duration has been proposed as the most biologically severe phenotype of the disorder associated with cardiometabolic morbidity in population-based samples. In this study, we investigated the association between insomnia with objective short sleep duration and hypertension in a large clinical sample. We studied 348 patients diagnosed with chronic insomnia disorder based on International Classification of Sleep Disorders Third Edition criteria and 150 normal sleepers. Objective short sleep duration was defined by the median total sleep time of the sample (< 7 hr) measured with 1-night polysomnography. Hypertension was defined based on blood pressure levels, antihypertensive medication use and/or a physician diagnosis. After adjusting for potential confounders, patients with chronic insomnia disorder who slept < 7 hr were associated with 2.8-fold increased odds of hypertension compared with normal sleepers who slept ≥ 7 hr (odds ratio = 2.81, 95% confidence interval = 1.068-7.411) or < 7 hr (odds ratio = 2.75, 95% confidence interval = 1.005-7.542), whereas patients with chronic insomnia disorder who slept ≥ 7 hr (odds ratio = 1.52, 95% confidence interval = 0.537-4.285) or normal sleepers who slept < 7 hr (odds ratio = 1.07, 95% confidence interval = 0.294-3.904) were not significantly associated with increased odds of hypertension compared with normal sleepers who slept ≥ 7 hr. Linear regression analyses showed that, for every hour decrease in total sleep time, systolic and diastolic blood pressure increased by 1.014 mmHg (p = 0.045) and 0.923 mmHg (p = 0.015), respectively, in patients with chronic insomnia disorder but not in normal sleepers. Our findings further support that insomnia with objective short sleep duration is a risk factor for hypertension, and objective short sleep duration may be a useful marker of the biological severity of chronic insomnia disorder in clinical practice.

The impact of insomnia on frailty and the hallmarks of aging

Throughout the course of life, there are age-related changes in sleep. Despite these normal changes, there is a high percentage of older adults that report sleep dissatisfaction with a high pervasiveness of chronic insomnia, the most common sleep disorder worldwide, with its prevalence being expected to continuously increase due to the growing rates of aging and obesity. This can have different adverse health outcomes, especially by promoting both physical and cognitive decline, which ultimately may aggravate frailty in older adults. Moreover, age-related frailty and sleep dysfunction may have a common mechanism related to the hallmarks of cellular aging. Cellular aging was categorized into nine hallmarks, such as DNA damage, telomere attrition and epigenetic changes. In the context of geriatric and chronic insomnia research, this review aims at discussing the current evidence from both animal models and human cohorts addressing the link between chronic insomnia, the hallmarks of aging and their impact on frailty. Moreover, the most recent research about the putative effect of insomnia therapeutic approaches on hallmarks of aging will be also highlighted.

Consequences of Sleep Deprivation in Adult Diabetes Mellitus Type 2 Patients: An Integrative Review

BACKGROUND: Sleep deprivation in individuals with diabetes mellitus type 2 is more prevalent than in ordinary people. At present, the adverse effects of diabetes type 2 people with sleep disorders and sleep deprivation on blood sugar control are irrefutable. Thorough assessments covering the whole structure should be of concern in health-care treatment. It is precipitated and delivered to the physical, mental health, and social environment, but no systematic review or minimal data were published. Furthermore, it may significantly affect the system more than existing research. AIM: An integrative review aims to clarify the results or consequences of sleep disturbance/deprivation or insomnia symptoms among diabetes mellitus type 2 patients. METHODS: The writers implemented a literature search in PubMed, CINAHL, and Medline using the terms DM type 2, insomnia, adult, effect, DM, sleep disturbance, sleep disorder, and a consequence between 2012 and 2022. Inclusion criteria selected through considering the entire article, and providing an abstract, were 20 articles. RESULTS: Integrative data extraction and information were analyzed thematically. Identified were nine ideas: Association with blood sugar control, blood pressure control, risk of CVD, diabetes self-care behavior, weight gained and Obstructive Sleep Apnea (OSA), lifestyle and physical activity, mood/depression and anxiety symptoms, daily calories distribution, cholesterol/triglyceride, and liver enzyme levels. CONCLUSION: The adverse effects of sleep deprivation in type 2 diabetes significantly affect all pathophysiologically, mentally, and lifestyle modifications, including diabetes self-care. Therefore, to highlight the importance of promoting optimum sleep in diabetes type2 patients, a health-care system is inevitably as necessary as diet and exercise management.

B serum proteome profiles revealed dysregulated proteins and mechanisms associated with insomnia patients: A preliminary study

Background

Insomnia is a clinical problem of significant public health importance; however, the underlying pathogenesis of this disorder is not comprehensively understood.

Methods

To identify potential treatment targets and unfold one of the gaps that were involved in insomnia pathological mechanisms, we employed a tandem mass tag-based (TMT) quantitative proteomics technology to detect differentially expressed proteins (DEPs) in serum from patients with insomnia and controls. DEPs were further analyzed by bioinformatics platforms. In addition, parallel reaction monitoring (PRM) was used to verify the TMT results.

Results

Patients with insomnia had poorer sleep quality compared with healthy controls. A total of 106 DEPs were identified among patients with insomnia and controls. They were mainly enriched in immune and inflammation-related biological functions and signaling pathways. Using the protein–protein interaction network, we screened the 10 most connected proteins as key DEPs. We predicted that four key DEPs were subject to targeted regulation by natural compounds of herbs. Eight key DEPs were validated using PRM in an additional 15 patients with insomnia and 15 controls, and the results also supported the experimental findings.

Conclusion

We identified aberrantly expressed proteins in insomnia that may be involved in the immune-inflammatory response. The 10 key DEPs screened may be potential targets for insomnia, especially FN1, EGF, HP, and IGF1. The results of this study will broaden our understanding of the pathological mechanisms of insomnia and provide more possibilities for pharmacotherapy.

Insomnia disorder: State of the science and challenges for the future

Insomnia disorder comprises symptoms during night and day that strongly affect quality of life and wellbeing. Prolonged sleep latency, difficulties to maintain sleep and early morning wakening characterize sleep complaints, whereas fatigue, reduced attention, impaired cognitive functioning, irritability, anxiety and low mood are key daytime impairments. Insomnia disorder is well acknowledged in all relevant diagnostic systems: Diagnostic and Statistical Manual of the American Psychiatric Association, 5th revision, International Classification of Sleep Disorders, 3rd version, and International Classification of Diseases, 11th revision. Insomnia disorder as a chronic condition is frequent (up to 10% of the adult population, with a preponderance of females), and signifies an important and independent risk factor for physical and, especially, mental health. Insomnia disorder diagnosis primarily rests on self-report. Objective measures like actigraphy or polysomnography are not (yet) part of the routine diagnostic canon, but play an important role in research. Disease concepts of insomnia range from cognitive-behavioural models to (epi-) genetics and psychoneurobiological approaches. The latter is derived from knowledge about basic sleep-wake regulation and encompass theories like rapid eye movement sleep instability/restless rapid eye movement sleep. Cognitive-behavioural models of insomnia led to the conceptualization of cognitive-behavioural therapy for insomnia, which is now considered as first-line treatment for insomnia worldwide. Future research strategies will include the combination of experimental paradigms with neuroimaging and may benefit from more attention to dysfunctional overnight alleviation of distress in insomnia. With respect to therapy, cognitive-behavioural therapy for insomnia merits widespread implementation, and digital cognitive-behavioural therapy may assist delivery along treatment guidelines. However, given the still considerable proportion of patients responding insufficiently to cognitive-behavioural therapy for insomnia, fundamental studies are highly necessary to better understand the brain and behavioural mechanisms underlying insomnia. Mediators and moderators of treatment response/non-response and the associated development of tailored and novel interventions also require investigation. Recent studies suggest that treatment of insomnia may prove to add significantly as a preventive strategy to combat the global burden of mental disorders.

Effect of Long-Term Benzodiazepines for Chronic Insomnia on Cognitive Function and Waking Electroencephalography: A Case-Control Study

OBJECTIVE

The relationship between benzodiazepine use and cognitive decline in insomnia patients has been reported, but still conflicting. Thus, we tried to determine whether long-term exposure of benzodiazepine might be associated with changes of cognition and electroencephalography (EEG) findings in patients with chronic insomnia.

METHODS

Insomniacs using benzodiazepines (n=29), drug-free insomniacs (n=27), and age- and sex-matched controls (n=28) were recruited. Neurocognitive function tested with Korean version of the Consortium to Establish a Registry for Alzheimer's Disease Assessment Packet Neuropsychological Assessment Battery, quantitative EEG in awake state, and information of benzodiazepine usage were obtained.

RESULTS

Drug-free insomniacs reported more severe symptoms than insomniacs using benzodiazepine (p<0.001). Insomniacs using benzodiazepine showed a decrease of executive function in Trail Making Test A than drug-free insomniacs and controls (0.73±0.66 vs. 1.27±0.38 vs. 1.09±0.47, p<0.001) and in categorical fluency than drug-free insomniacs (-0.01±0.99 vs. 1.26±0.97, p=0.002). However, such decrease of executive function was not proportional to daily dose or cumulative dose of benzodiazepine. The EEG was not significantly different between insomniacs using benzodiazepine and drug-free insomniacs, while EEG of insomniacs showed low relative theta power in frontal and parietal regions but high relative beta power in frontal region than that of controls.

CONCLUSION

Benzodiazepine users with chronic insomnia showed an impairment of executive function compared to drug-free insomniacs and controls although they showed relatively decreased severity of insomnia symptoms. Chronic insomniacs showed a hyper-arousal manifestation in front-parietal region of brain regardless of benzodiazepine exposure.

Trajectories of Insomnia Symptoms From Childhood Through Young Adulthood

OBJECTIVES

Insomnia symptoms are transdiagnostic to physical and mental health disorders. Given the lack of population-based cohorts with objective sleep measures and long-term follow-ups, little is known about the chronicity of childhood insomnia symptoms. We determined the developmental trajectories of insomnia symptoms, their evolution into adult insomnia, and the role of objective sleep duration in the transition to adulthood.

METHODS

A total of 502 children (median 9 years old, 71.7% response rate) were studied 7.4 years later as adolescents (median 16 years old) and 15 years later as adults (median 24 years old). Insomnia symptoms were ascertained as moderate-to-severe difficulties initiating and/or maintaining sleep via parent- or self reports at all 3 time points, adult insomnia via self-report in young adulthood, and objective short-sleep duration via polysomnography in childhood and adolescence.

RESULTS

Among children with insomnia symptoms, the most frequent trajectory was persistence (43.3%), followed by remission (26.9% since childhood, 11.2% since adolescence) and a waxing-and-waning pattern (18.6%). Among children with normal sleep, the most frequent trajectory was persistence (48.1%), followed by developing insomnia symptoms (15.2% since adolescence, 20.7% in adulthood) and a waxing-and-waning pattern (16.0%). The odds of insomnia symptoms worsening into adult insomnia (22.0% of children, 20.8% of adolescents) were 2.6-fold and 5.5-fold among short-sleeping children and adolescents, respectively.

CONCLUSIONS

Early sleep interventions are a health priority because pediatricians should not expect insomnia symptoms to developmentally remit in a high proportion of children. Objective sleep measures may be clinically useful in adolescence, a critical period for the adverse prognosis of the insomnia with short-sleep duration phenotype.

Considering Psychosocial Factors When Investigating Blood Pressure in Patients with Short Sleep Duration: A Propensity Score Matched Analysis

Few studies have considered psychosocial characteristics when investigating the associations between sleep duration and blood pressure (BP). In this study, we took propensity score matching (PSM) to adjust for psychosocial characteristics when comparing BP between individuals with short sleep duration and those with normal sleep duration. A total of 429 participants were included. 72 participants with sleep duration ≤6 h and 65 participants with sleep duration >6 h were matched after PSM. We compared office BP, 24-hour BP, and prevalence of hypertension in the populations before and after PSM, respectively. In the unmatched population, participants with sleep duration ≤6 h were observed with higher office diastolic BP (DBP) and 24-h systolic BP (SBP)/DBP (all P < 0.05). In the matched populations, the differences between the two groups (sleep duration ≤6 h vs. sleep duration >6 h) in office DBP (88.4 ± 10.9 vs. 82.5 ± 11.1 mm Hg; P=0.002), 24-h SBP (134.7 ± 12.0 vs. 129.3 ± 11.6 mm Hg; P=0.009), and 24-h DBP (83.4 ± 9.9 vs. 78.1 ± 10.1 mm Hg; P=0.002) become more significant. Participants with sleep duration ≤6 h only show higher prevalence of hypertension based on 24-h BP data, while analysis after PSM further revealed that these with sleep duration ≤6 h presented about 20% higher prevalence of elevated BP up to office diagnosed hypertension threshold. Therefore, psychosocial characteristics accompanied with short sleep duration should be fully valued in individuals at risks for elevated BP. This trial is registered with NCT03866226.

Blood biomarker levels by total sleep duration: cross-sectional analyses in UK Biobank

BACKGROUND

Short or long sleep duration has been associated with some major chronic diseases, but whether disease-related blood biomarkers vary according to habitual sleep duration is unclear. This cross-sectional study aimed to assess blood biomarker levels in relation to total sleep duration.

METHODS

The analysis includes 459,796 white British adults aged 40-69 during 2006-2010 in UK Biobank. At recruitment, blood samples and self-reported information on total sleep duration were collected from participants. A panel of blood biomarkers were measured. Using linear regression, we estimated geometric mean concentrations of blood biomarkers and mean ratio of ApoB/ApoA1 by sleep duration adjusted for sex, age at data collection, time of blood collection, and lifestyle covariates.

RESULTS

Percentage differences in the concentrations of most biomarkers by sleep duration were modest. The largest differences were for C-reactive protein (CRP, an inflammatory biomarker) and gamma glutamyltransferase (GGT, a liver function biomarker), and the differences were markedly attenuated after multivariable-adjustment. The multivariable-adjusted geometric means of CRP and of GGT were 14% and 14% higher in <6 h vs 7-8 h of sleep; and 22% and 12% higher in >9 h vs 7-8 h of sleep, respectively.

CONCLUSION

In white British adults, most blood biomarker levels varied only modestly with sleep duration and the remaining associations may be due to residual confounding.

Gender differences in the association of insomnia symptoms and coronary artery calcification in the multi-ethnic study of atherosclerosis

STUDY OBJECTIVES

To quantify the gender-specific associations between insomnia symptoms and subclinical atherosclerosis, measured by coronary artery calcium (CAC) scores, which has strong predictive value for incident cardiovascular disease.

METHODS

We analyzed data from 1,429 participants in the Multi-Ethnic Study of Atherosclerosis (MESA). Participants completed standardized questionnaires and underwent polysomnography (PSG) and 7-day actigraphy. Insomnia symptoms were defined as: self-reported trouble falling, staying or returning to sleep, early-morning awakenings, or hypnotic use, for ≥5 nights/week. MESA assessed CAC using computed tomography. We employed multivariable linear regression to model the probability of CAC >0 overall and to model the linear continuous effect among those with nonzero CAC.

RESULTS

Our sample was a mean age of 68.1 ± 9.1 years, 53.9% female, and 36.2% white, 28.0% black, 24.2% Hispanic, and 11.5% Chinese-American. Insomnia symptoms were present in 49.7% of men and 47.2% of women. In multivariable-adjusted analyses, insomnia symptoms was associated with an 18% higher prevalence of CAC (PR 1.18, 95% CI 1.04, 1.33) among females, but no association was observed among males (PR 1.00, 95% CI 0.91, 1.08). There was no evidence that the association between insomnia symptoms and prevalence of CAC >0 differed by objective sleep duration status (by single-night PSG or multi-night actigraphy) in females or males.

CONCLUSIONS

We found that among women, insomnia symptoms were associated with an 18% higher prevalence of CAC compared to no insomnia. Insomnia symptoms were not associated with CAC prevalence in men. Additionally, there was no evidence that the association between insomnia symptoms and CAC score >0 differed by objective short sleep duration status.

Insomnia disorder: clinical and research challenges for the 21st century

BACKGROUND AND PURPOSE

Insomnia is a common and debilitating disorder that is frequently associated with important consequences for physical health and well-being.

METHODS

An international expert group considered the current state of knowledge based on the most relevant publications in the previous 5 years, discussed the current challenges in the field of insomnia and identified future priorities.

RESULTS

The association of trajectories of insomnia with subsequent quality of life, health and mortality should be investigated in large populations. Prospective health economics studies by separating the costs driven specifically by insomnia and costs attributable to its long-term effects are needed. Ignoring the heterogeneity of insomnia patients leads to inadequate diagnosis and inefficient treatment. Individualized interventions should be promoted. More data are needed on both the impact of sleep on overnight effects, such as emotion regulation, and the potential compensatory effort to counteract diurnal impairments. Another gap is the definition of neurocognitive deficits in insomnia patients compared to normal subjects after chronic sleep loss. There are also a number of key gaps related to insomnia treatment. Expert guidelines indicate cognitive-behavioural therapy for insomnia as first-line treatment. They neglect, however, the reality of major healthcare providers. The role of combined therapy, cognitive-behavioural therapy for insomnia plus pharmacological treatment, should be evaluated more extensively.

CONCLUSION

Whilst insomnia disorder might affect large proportions of the population, there are a number of significant gaps in the epidemiological/clinical/research studies carried out to date. In particular, the identification of different insomnia phenotypes could allow more cost-effective and efficient therapies.

The association of insomnia disorder characterised by objective short sleep duration with hypertension, diabetes and body mass index: A systematic review and meta-analysis

Insomnia disorder with objective short sleep duration (less than 6 h of objective sleep or sleep efficiency less than 85%) has been considered as a biologically severe subtype of insomnia associated with a higher risk of cardiometabolic disease morbidity. This systematic review and meta-analysis firstly compared insomnia disorder with objective short and normal sleep duration, and subsequently, objective short sleep duration with and without insomnia disorder, and their associations with hypertension, type 2 diabetes and body mass index. A systematic search of five databases yielded 2345 non-duplicated articles, of which 11 individual studies were used for the qualitative review and 10 individual studies for the meta-analysis. The sample size varied from 30 to 4994 participants. A higher risk of hypertension (RR 1.54, 95% CI: [1.30; 1.82] p < 0.0001) and type 2 diabetes (RR 1.63 [1.37; 1.94], p < 0.0001) was associated with insomnia disorder with objective short sleep compared to normal sleep duration, but not for body mass index. Comparisons between insomnia disorder with objective short sleep and objective short sleep without insomnia disorder showed no significant differences. However, the majority of these studies were cross-sectional, and there is a need for more cohort study data.

Treating sleep disorders to improve blood pressure control and cardiovascular prevention: a dream come true?-a narrative review

Hypertension is one of the primary risk factors for heart disease and stroke, the leading causes of death worldwide. Current evidence supports the treatment of high blood pressure (BP) values in order to obtain a substantial reduction of cardiovascular burden. Sleep plays an important role in maintaining nocturnal BP control and nocturnal hypertension which, in turn, can be affected by the presence of sleep disorders. Whilst respiratory disturbances have been extensively studied and their causal role in the development of nocturnal hypertension has been demonstrated in both cross sectional and prospective studies, less is known about the impact of other sleep disorders such as insomnia. In this review, we aim to describe the role of sleep disorders in the development of nocturnal and diurnal hypertension. Furthermore, we aim to discuss the potential impact of the treatment of such sleep disorders on BP values as an adjunct treatment for patients with hypertension.

Objective sleep disturbance is associated with poor response to cognitive and behavioral treatments for insomnia in postmenopausal women

STUDY OBJECTIVES

To determine whether insomnia patients with objective sleep disturbance are less responsive to cognitive and behavioral treatments than those without objective sleep disturbance, characterize effects of insomnia therapy on objective sleep, and determine whether reductions in nocturnal cognitive arousal correspond to changes in objective sleep.

METHODS

Secondary analysis of a single-site, randomized controlled trial. 113 postmenopausal women (56.40 ± 5.34 years) with menopause-related insomnia disorder were randomized to three treatment conditions: cognitive-behavioral therapy for insomnia (CBTI), sleep restriction therapy (SRT), or sleep education control. Primary outcomes were the Insomnia Severity Index (ISI) and polysomnography (PSG) sleep parameters and were collected at pretreatment, posttreatment, and six-month follow-up.

RESULTS

Patients with lower pretreatment PSG sleep efficiency had lower rates of insomnia remission after active treatment relative to those with higher sleep efficiency (37.8% vs 61.8%). Neither CBTI and SRT produced clinically meaningful effects on PSG sleep. Exploratory analyses revealed that reductions in nocturnal cognitive arousal were associated with decreases in PSG sleep latency, but not wake after sleep onset.

CONCLUSIONS

Our findings support an emerging literature suggesting that insomnia patients with objective sleep disturbance may have blunted response to insomnia therapy. Research is needed to enhance treatments to better improve insomnia in patients with objective sleep disturbance. A lack of observed CBTI and SRT effects on PSG sleep suggests that these therapies may be presently ill-designed to improve objective sleep. Nocturnal cognitive arousal may represent an entry point to improve objective sleep latency in insomnia. NAME: Behavioral Treatment of Menopausal Insomnia: Sleep and Daytime Outcomes. URL: clinicaltrials.gov. Registration: NCT01933295.

Factors associated with fatigue in patients with insomnia

Although fatigue is common in insomnia, the clinical associates of fatigue in patients with insomnia are largely unknown. We aimed to investigate the clinical associates of fatigue in patients with insomnia. Patients visiting the Stanford Sleep Medicine Center completed the Insomnia Severity Index (ISI), Insomnia Symptom Questionnaire (ISQ), the Fatigue Severity Scale (FSS), the Epworth Sleepiness Scale (ESS), and the Patient Health Questionnaire (PHQ-9). Among 6367 patients, 2024 were diagnosed with insomnia (age 43.06 ± 15.19 years; 1110 women and 914 men) according to the ISI and the ISQ. Insomnia patients with severe fatigue (n = 1306) showed higher insomnia symptoms, daytime sleepiness, depression and longer habitual sleep duration than those without severe fatigue (n = 718). Higher insomnia symptoms, daytime sleepiness and depressive symptoms, and longer habitual sleep duration, independently predicted higher fatigue scores. Among insomnia patients with daytime sleepiness (ESS≥10), only habitual sleep duration and depression predicted fatigue scores. The interaction between insomnia severity and daytime sleepiness significantly predicted the severity of fatigue. Depression was a significant mediator between insomnia and fatigue. For 598 insomnia patients undergoing overnight polysomnography (PSG), no significant correlations were found between fatigue and any PSG parameters. The current study suggests that managing insomnia or depression may reduce the fatigue of insomnia patients, whereas arbitrary efforts to prolong sleep duration may worsen their fatigue.

The acute effects of aerobic exercise on sleep in patients with depression: study protocol for a randomized controlled trial

BACKGROUND

Unipolar depression is one of the most important mental disorders. Insomnia is a symptom of cardinal importance in depression. It increases the risk to develop depression, negatively affects disease trajectory, is the most common symptom after remission, increases the risk of relapse, and is associated with higher suicide rates. Existing therapies for insomnia in depression have limitations. Further adjuvant therapies are therefore needed. Acute aerobic exercise has been shown to have beneficial effects on sleep in healthy individuals and patients with insomnia. We therefore hypothesize that a single session of aerobic exercise has a positive impact on sleep in patients with unipolar depression. This trial aims to investigate the effects of a single bout of aerobic exercise on the subsequent night's sleep in patients with depression.

METHODS/DESIGN

This is a two-arm parallel group, randomized, outcome assessor blinded, controlled, superiority trial. Patients between 18 and 65 years of age with a primary diagnosis of unipolar depression (without a psychotic episode) are included. Exclusion criteria are regular use of hypnotic agents, opioids, and certain beta-blockers, as well as the presence of factors precluding exercise, history of epilepsy, restless legs syndrome, moderate obstructive sleep apnea, and a BMI > 40. The intervention is a single bout of aerobic exercise, performed for 30 min on a bicycle ergometer at 80% individual anaerobic threshold. The control group sits and reads for 30 min. The primary outcome is sleep efficiency measured by polysomnography. Secondary outcomes include further polysomnographic variables, subjective pre-sleep arousal, nocturnal cardiovascular autonomic modulation, subjective sleep quality, daytime sleepiness, and adverse events. According to the sample size calculation, a total of 92 patients will be randomized using minimization.

DISCUSSION

This trial will add new information to the body of knowledge concerning the treatment of insomnia in patients with depression. Thereby, the results will inform decision makers on the utility of acute aerobic exercise.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03673397 . Protocol version 1 registered on 17 September 2018.

Evidence for Genetic Correlations and Bidirectional, Causal Effects Between Smoking and Sleep Behaviors

INTRODUCTION

Cigarette smokers are at increased risk of poor sleep behaviors. However, it is largely unknown whether these associations are due to shared (genetic) risk factors and/or causal effects (which may be bidirectional).

METHODS

We obtained summary-level data of genome-wide association studies of smoking (smoking initiation [n = 74 035], cigarettes per day [n = 38 181], and smoking cessation [n = 41 278]) and sleep behaviors (sleep duration and chronotype, or "morningness" [n = 128 266] and insomnia [n = 113 006]). Using linkage disequilibrium (LD) score regression, we calculated genetic correlations between smoking and sleep behaviors. To investigate causal effects, we employed Mendelian randomization (MR), both with summary-level data and individual-level data (n = 333 581 UK Biobank participants). For MR with summary-level data, individual genetic variants were combined with inverse variance-weighted meta-analysis, weighted median regression, MR-Robust Adjusted Profile Score, and MR Egger methods.

RESULTS

We found negative genetic correlations between smoking initiation and sleep duration (rg = -.14, 95% CI = -0.26 to -0.01) and smoking cessation and chronotype (rg = -.18, 95% CI = -0.31 to -0.06), and positive genetic correlations between smoking initiation and insomnia (rg = .27, 95% CI = 0.06 to 0.49) and cigarettes per day and insomnia (rg = .15, 95% CI = 0.01 to 0.28). MR provided strong evidence that smoking more cigarettes causally decreases the odds of being a morning person, (RAPS) and weak evidence that insomnia causally increases smoking heaviness and decreases smoking cessation odds.

CONCLUSIONS

Smoking and sleep behaviors show moderate genetic correlation. Heavier smoking seems to causally affect circadian rhythm and there is some indication that insomnia increases smoking heaviness and hampers cessation. Our findings point to sleep as a potentially interesting smoking treatment target.

IMPLICATIONS

Using LD score regression, we found evidence that smoking and different sleep behaviors (sleep duration, chronotype (morningness), and insomnia) are moderately genetically correlated-genetic variants associated with less or poorer sleep also increased the odds of smoking (more heavily). MR analyses suggested that heavier smoking causally affects circadian rhythm (decreasing the odds of being a morning person) and there was some indication that insomnia increases smoking heaviness and hampers smoking cessation. Our findings indicate a complex, bidirectional relationship between smoking and sleep behaviors and point to sleep as a potentially interesting smoking treatment target.

Genome-wide analysis of insomnia in 1,331,010 individuals identifies new risk loci and functional pathways

Insomnia is the second most prevalent mental disorder, with no sufficient treatment available. Despite substantial heritability, insight into the associated genes and neurobiological pathways remains limited. Here, we use a large genetic association sample (n = 1,331,010) to detect novel loci and gain insight into the pathways, tissue and cell types involved in insomnia complaints. We identify 202 loci implicating 956 genes through positional, expression quantitative trait loci, and chromatin mapping. The meta-analysis explained 2.6% of the variance. We show gene set enrichments for the axonal part of neurons, cortical and subcortical tissues, and specific cell types, including striatal, hypothalamic, and claustrum neurons. We found considerable genetic correlations with psychiatric traits and sleep duration, and modest correlations with other sleep-related traits. Mendelian randomization identified the causal effects of insomnia on depression, diabetes, and cardiovascular disease, and the protective effects of educational attainment and intracranial volume. Our findings highlight key brain areas and cell types implicated in insomnia, and provide new treatment targets.

The paradox of paradoxical insomnia: A theoretical review towards a unifying evidence-based definition

Paradoxical insomnia is one of the most intriguing yet challenging subtypes of insomnia. Despite being recognized for a long time by the international community, it is still unclear whether this entity really exists, which are its features and boundaries. Much of the debate is fuelled by the lack of a consensus on its precise definition. To help filling some of the existing gaps, a systematic review of the literature was conducted, through which 19 different quantitative definitions were obtained. These definitions were then applied to two distinct datasets. The first consisted of 200 chronic primary insomnia patients, diagnosed according to the DSM-IV-TR criteria. The second consisted of 200 age- and sex-matched healthy persons without insomnia. For each dataset, available data from the objective sleep parameters and their subjective estimation were imported and analysed in MATLAB. Depending on the definition used, the prevalence of paradoxical insomnia ranged from 8 to 66%, while agreement between different definitions ranged from -0.19 to 0.9 (using Cohen's kappa coefficient). Based on the results garnered, necessary features for a quantitative definition of paradoxical insomnia were identified. Several open questions remain, such as whether there is a minimum number of hours a patient should sleep to fulfill the criteria for a diagnosis of paradoxical insomnia, and whether sleep latency can be used in the definition along with total sleep time. We conclude by advocating continued study of paradoxical insomnia and sleep state misperception and by providing specific directions for future research. STATEMENT OF SIGNIFICANCE: The current understanding of paradoxical insomnia and, more broadly, of sleep state misperception, is greatly hampered by the lack of agreement on a quantitative and evidence-base measure of the discrepancy between subjective and objective sleep evaluation. The current study provides a critical analysis about the strength and the limitations of the available definitions, using both a data-driven and a theory-driven approach. The overarching goal is to motivate a rigorous discussion involving the main experts of the field, to build a consensus, and develop an evidence-based measure of sleep state misperception and/or of paradoxical insomnia.

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.

Insomnia and hypertension: A systematic review

Insomnia is a prevalent sleep disorder that is associated with a multitude of health consequences. Particularly, insomnia has been associated with cardiovascular disease and its precursors, such as hypertension and blood pressure (BP) non-dipping. The present systematic review aimed to summarize the evidence on the concurrent and prospective associations between insomnia and hypertension and/or BP. Using electronic search engines (PubMed, SCOPUS, PsycINFO), 5,618 articles published from January 1970 to December 2017 were identified, and 64 met the inclusion criteria (26 to 162,121 participants; age range: 18-100; 46.4% male). Insomnia was based on diagnostic or non-diagnostic criteria. Hypertension was based on self-or physician-reports, antihypertensive medication use, and/or measured BP. Findings indicate that when insomnia is frequent, chronic, and/or accompanied with short sleep duration or objective markers of arousal, there is a strong association with hypertension/BP. Based on limited studies, hypertension did not significantly predict future insomnia in middle-aged adults, but did in older adults. Based on a majority of case-control studies, no differences in BP were found between participants with and without insomnia. Further research is needed to identify putative pathophysiological mechanisms underlying the link between insomnia and hypertension. The impact of insomnia therapy on BP should also be further examined in the future.

Cardiovascular autonomic dysfunction in insomnia patients with objective short sleep duration

Two phenotypes have been proposed: insomnia with objective near-normal sleep duration, related to increased psychological symptoms, and insomnia with objective short sleep duration, associated with cardiometabolic morbidity. Reduced heart rate variability has also been implicated in the pathophysiology of cardiometabolic disease; however, there are little data on whether cardiovascular function differs between patients with objective short sleep duration and near-normal sleep duration. Participants (Mage  = 49.9 ± 11.3 years; 62.8% female) were 180 adults with chronic insomnia (Mduration  = 15.7 ± 13.6). Objective sleep duration was based on total sleep time averaged across two consecutive nights of polysomnography and subjective sleep duration was based on 2-week sleep diaries. The sample was divided into two groups, with sleep duration shorter (polysomnography-total sleep time: n = 46; sleep diary: n = 95) or equal/longer (polysomnography-total sleep time: n = 134; sleep diary: n = 85) than 6 hr. Electrocardiogram data derived from polysomnography were used to obtain heart rate and heart rate variability during stage 2 (N2) and rapid eye movement sleep. Heart rate variability measures included absolute and normalized high-frequency component, an index of parasympathetic activation, and the ratio of low- to high-frequency (LF/HF ratio), an index of sympathovagal balance. After controlling for covariates (e.g., co-morbidity), patients with objective short sleep duration had reduced high-frequency (p < .05) and elevated low-frequency/high-frequency ratio (p = .036) and heart rate (p = .051) compared with patients with near-normal sleep duration. No differences were observed between phenotypes when subjective sleep duration was used. Insomnia patients with objective short sleep duration showed significantly dampened parasympathetic activation and increased sympathovagal imbalance relative to their counterparts with near-normal sleep duration. These findings highlight the importance of treating insomnia, as treatment may reduce the risk of cardiovascular disease.

Insomnia with objective short sleep duration and risk of incident cardiovascular disease and all-cause mortality: Sleep Heart Health Study

Study Objectives

To quantify the association between insomnia or poor sleep with objective short sleep duration and incident cardiovascular disease (CVD) and mortality in the general population.

Methods

We conducted a time-to-event analysis of Sleep Heart Health Study data. Questionnaires and at-home polysomnography (PSG) were performed between 1994 and 1998. Participants were followed for a median of 11.4 years (Q1-Q3, 8.8-12.4 years) until death or last contact. The primary exposure was insomnia or poor sleep with short sleep defined as follows: difficulty falling asleep, difficulty returning to sleep, early morning awakenings, or sleeping pill use, 16-30 nights per month; and total sleep of <6 hr on PSG. We used proportional hazard models to estimate the association between insomnia or poor sleep with short sleep and CVD, as well as all-cause mortality.

Results

Among 4994 participants (mean age: 64.0 ± 11.1 years), 14.1 per cent reported insomnia or poor sleep, of which 50.3 per cent slept <6 hr. Among 4437 CVD-free participants at baseline, we observed 818 incident CVD events. After propensity adjustment, there was a 29 per cent higher risk of incident CVD in the insomnia or poor sleep with short sleep group compared with the reference group (HR: 1.29, 95% CI: 1.00, 1.66), but neither the insomnia or poor sleep only nor short sleep only groups were associated with higher incident CVD. Insomnia or poor sleep with objective short sleep was not associated with all-cause mortality (HR: 1.07, 95% CI: 0.86, 1.33).

Conclusions

Insomnia or poor sleep with PSG-short sleep was associated with higher risk of incident CVD. Future studies should evaluate the impact of interventions to improve insomnia with PSG-short sleep on CVD.

Sleep and Obesity

Rising global prevalence and incidence of obesity lead to increased cardiovascular-renal complications and cancers. Epidemiological studies reported a worldwide trend towards suboptimal sleep duration and poor sleep quality in parallel with this obesity epidemic. From rodents and human models, it is highly plausible that abnormalities in sleep, both quantity and quality, impact negatively on energy metabolism. While excess dietary intake and physical inactivity are the known drivers of the obesity epidemic, promotion of healthy sleep habits has emerged as a new target to combat obesity. In this light, present review focuses on the existing literature examining the relationship between sleep physiology and energy homeostasis. Notably, sleep dysregulation perturbs the metabolic milieu via alterations in hormones such as leptin and ghrelin, eating behavior, neuroendocrine and autonomic nervous systems. In addition, shift work and trans-meridian air travel may exert a negative influence on the hypothalamic-pituitary-adrenal axis and trigger circadian misalignment, leading to impaired glucose tolerance and increased fat accumulation. Amassing evidence has also suggested that uncoupling of the circadian clock can increase the risk of adverse metabolic health. Given the importance of sleep in maintaining energy homeostasis and that it is potentially modifiable, promoting good sleep hygiene may create new avenues for obesity prevention and treatment.

Increased hippocampal-prefrontal functional connectivity in insomnia

Insomnia Disorder (ID) is the second-most common mental disorder and has a far-reaching impact on daytime functioning. A meta-analysis indicates that, of all cognitive domains, declarative memory involving the hippocampus is most affected in insomnia. Hippocampal functioning has consistently been shown to be sensitive to experimental sleep deprivation. Insomnia however differs from sleep deprivation in many aspects, and findings on hippocampal structure and function have been equivocal. The present study used both structural and resting-state functional Magnetic Resonance Imaging in a larger sample than previously reported to evaluate hippocampal volume and functional connectivity in ID. Included were 65 ID patients (mean age = 48.3 y ± 14.0, 17 males) and 65 good sleepers (mean age = 44.1 y ± 15.2, 23 males). Insomnia severity was assessed with the Insomnia Severity Index (ISI), subjective sleep with the Consensus Sleep Diary (CSD) and objective sleep by two nights of polysomnography (PSG). Seed-based analysis showed a significantly stronger connectivity of the bilateral hippocampus with the left middle frontal gyrus in ID than in controls (p = .035, cluster based correction for multiple comparisons). Further analyses across all participants moreover showed that individual differences in the strength of this connectivity were associated with insomnia severity (ISI, r = 0.371, p = 9.3e-5) and with subjective sleep quality (CSD sleep efficiency, r = -0.307, p = .009) (all p FDR-corrected). Hippocampal volume did not differ between ID and controls. The findings indicate more severe insomnia and worse sleep quality in people with a stronger functional connectivity between the bilateral hippocampus and the left middle frontal gyrus, part of a circuit that characteristically activates with maladaptive rumination and deactivates with sleep.