Advances in understanding the relationship between sleep and attention deficit-hyperactivity disorder (ADHD)

Abstract: Starting from the consolidated relationship between sleep and cognition, we reviewed the available literature on the association between Attention Deficit-Hyperactivity Disorder (ADHD) and sleep. This review analyzes the macrostructural and microstructural sleep features, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria (PRISMA).We included the polysomnographic studies published in the last 15 years. The results of macrostructural parameters are mixed. Almost half of the 18 selected investigations did not find dierences between sleep architecture of children with ADHD and controls. Five studies observed that children with ADHD show a longer Rapid Eye Movement (REM) sleep duration than controls. Eight studies included microstructural measures. Remarkable alterations in sleep microstructure of ADHD are related to slow wave activity (SWA) and theta oscillations, respectively, during Non-REM (NREM) and REM sleep. Specifically, some studies found higher SWA in the ADHD group than controls. Similarly, higher theta activity appears to be detrimental for memory performance and inhibitory control in ADHD. These patterns could be interpreted as a maturational delay in ADHD. Also, the increased amount of these activities would be consistent with the hypothesis that the poor sleep could imply a chronic sleep deprivation in children with ADHD, which in turn could aect their cognitive functioning

Not only a problem of fatigue and sleepiness: Changes in psychomotor performance in Italian nurses across 8-h rapidly rotating shifts

Although many studies have detailed the consequences of shift work in nurses concerning health, fatigue, sleepiness, or medical errors, no study has been carried out trying to disentangle the contribution of sleepiness and fatigue associated to shift work from the attentional performance. The aim of this pilot study is (A) to investigate the effects of an 8-h rapidly rotating shift on fatigue and sleepiness among staff nurses and (B) how these factors affect their psychomotor performance. Fourteen nurses were selected for a within-subject cross-sectional study according to this sequence of shifts: morning–afternoon–night, which were compared as function of tiredness, sleepiness, and performance at the Psychomotor Vigilance Task (PVT). Subsequently, a within-subject Analysis of Covariance (ANCOVA) evaluated if the observed differences between shifts persist when the contribution of sleepiness is controlled. Our results clearly indicate that night shifts are associated with significant greater sleepiness and tiredness, and worsened performance at the PVT. As hypothesized, ANCOVA showed that these differences disappear when the contribution of sleepiness is controlled. Results point to a lower psychomotor performance in night compared to day shifts that depends on sleepiness. Hence, interventions to minimize the consequences of the night shift should consider a reduction of sleepiness

Sleep-related declarative memory consolidation in children and adolescents with developmental dyslexia

Sleep has a crucial role in memory processes, and maturational changes in sleep electrophysiology are involved in cognitive development. Albeit both sleep and memory alterations have been observed in Developmental Dyslexia (DD), their relation in this population has been scarcely investigated, particularly concerning topographical aspects. The study aimed to compare sleep topography and associated sleep-related declarative memory consolidation in participants with DD and normal readers (NR). Eleven participants with DD and 18 NR (9–14 years old) underwent a whole-night polysomnography. They were administered a word pair task before and after sleep to assess for declarative memory consolidation. Memory performance and sleep features (macro and microstructural) were compared between the groups, and the intercorrelations between consolidation rate and sleep measures were assessed. DD showed a deeper worsening in memory after sleep compared to NR and reduced slow spindles in occipito-parietal and left fronto-central areas. Our results suggest specific alterations in local sleep EEG (i.e., sleep spindles) and in sleep-dependent memory consolidation processes in DD.We highlight the importance of a topographical approach, which might shed light on potential alteration in regional cortical oscillation dynamics in DD. The latter might represent a target for therapeutic interventions aimed at enhancing cognitive functioning in DD

In search of sleep biomarkers of Alzheimer's disease: K-Complexes do not discriminate between patients with mild cognitive impairment and healthy controls

The K-complex (KC) is one of the hallmarks of Non-Rapid Eye Movement (NREM) sleep. Recent observations point to a drastic decrease of spontaneous KCs in Alzheimer's disease (AD). However, no study has investigated when, in the development of AD, this phenomenon starts. The assessment of KC density in mild cognitive impairment (MCI), a clinical condition considered a possible transitional stage between normal cognitive function and probable AD, is still lacking. The aim of the present study was to compare KC density in AD/ MCI patients and healthy controls (HCs), also assessing the relationship between KC density and cognitive decline. Twenty amnesic MCI patients underwent a polysomnographic recording of a nocturnal sleep. Their data were compared to those of previously recorded 20 HCs and 20 AD patients. KCs during stage 2 NREM sleep were visually identified and KC densities of the three groups were compared. AD patients showed a significant KC density decrease compared with MCI patients and HCs, while no differences were observed between MCI patients and HCs. KC density was positively correlated with Mini-Mental State Examination (MMSE) scores. Our results point to the existence of an alteration of KC density only in a full-blown phase of AD, which was not observable in the early stage of the pathology (MCI), but linked with cognitive deterioratio

Sleep EEG oscillations in neurodevelopmental disorders without intellectual disabilities

Neurodevelopmental disorders (NDDs) are often characterised by sleep problems, and recent evidence indicates alterations of the sleep electroencephalographic (EEG) oscillations in these patients. Sleep microstructure plays a crucial role in cognitive functioning and brain maturation. In this view, modifications in sleep EEG oscillations in NDDs could further impair the cognitive maturation process in these patients. We provide an overview of sleep microstructure alterations observed in three NDDs without intellectual disabilities (attention-deficit/hyperactivity disorder, high-functioning autism/Asperger syndrome and developmental dyslexia) and their relationships with the disorders' phenomenology. For each NDD, we discuss empirical evidence of altered EEG oscillations, and we consider their interaction with patients' cognitive and behavioural functioning, with the aim to elucidate their functional meaning. We highlight the limits of the present literature and propose possible future directions while underlining the clinical relevance of the research in this field. Beyond confirming the importance of sleep management in atypically developing children, the review findings suggest that sleep EEG oscillations in NDDs could become a target for specific clinical intervention

Advances in Understanding the Relationship between Sleep and Attention Deficit-Hyperactivity Disorder (ADHD)

Starting from the consolidated relationship between sleep and cognition, we reviewed the available literature on the association between Attention Deficit-Hyperactivity Disorder (ADHD) and sleep. This review analyzes the macrostructural and microstructural sleep features, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses criteria (PRISMA). We included the polysomnographic studies published in the last 15 years. The results of macrostructural parameters are mixed. Almost half of the 18 selected investigations did not find differences between sleep architecture of children with ADHD and controls. Five studies observed that children with ADHD show a longer Rapid Eye Movement (REM) sleep duration than controls. Eight studies included microstructural measures. Remarkable alterations in sleep microstructure of ADHD are related to slow wave activity (SWA) and theta oscillations, respectively, during Non-REM (NREM) and REM sleep. Specifically, some studies found higher SWA in the ADHD group than controls. Similarly, higher theta activity appears to be detrimental for memory performance and inhibitory control in ADHD. These patterns could be interpreted as a maturational delay in ADHD. Also, the increased amount of these activities would be consistent with the hypothesis that the poor sleep could imply a chronic sleep deprivation in children with ADHD, which in turn could affect their cognitive functioning

The heritability of the human K-complex. A twin study

Sleep electroencephalogram (EEG) has a trait-like nature. Several findings highlighted the heritability of spectral power in specific frequency ranges and sleep spindles during NREM sleep. However, a genetic influence on the K-complex (KC), one of the electrophysiological hallmarks of NREM sleep, has never been assessed. Here, we investigated the heritability of the KC detected during NREM stage 2 comparing 10 monozygotic (MZ) and 10 dizygotic (DZ) twin pairs. Genetic variance analysis (GVA) and Intraclass Correlation Coefficients (ICCs) were performed to assess the genetic effect and within-pair similarity for KC density, amplitude, and for the area-under-the-curve (AUC) of the KC average waveform at Fz, Cz and Pz scalp locations. Moreover, cluster analysis was performed on the KC average waveform profile. We observed a significant genetic effect on KC AUC at Cz and Pz, and on amplitude at Pz. Within-pair similarity (ICCs) was always significant for MZ twins except for KC density at Fz, while DZ twins always exhibited ICCs below the significance threshold, with the exception of density at Pz. The largest differences in within-pair similarity between MZ and DZ groups were observed again for AUC at Cz and Pz. MZ pairs accurately clustered for the KC average waveform with a higher frequency (successful clustering rate for MZ pairs: Fz=60%; Cz=80%; Pz=90%) compared to DZ pairs (successful clustering rate for DZ pairs: Fz=10%; Cz=10%; Pz=none). Our results suggest the existence of a genetic influence on the human KC, particularly related to its morphology and maximally observable in central and parietal location

PREVALENCE OF SLEEP TALKING IN AN ITALIAN SAMPLE, ASSOCIATION WITH OTHER ALTERED NOCTURNAL BEHAVIOURS AND QUALITY OF SLEEP: PRELIMINARY FINDINGS.

Introduction: Sleep talking (ST) was described by the ICSD-II as "the utterance of speech or sounds during sleep without simultaneous subjective detailed awareness of the event" (ICSD-II, 2001), while the recent revision of the ICSD reports the phenomenon as "Isolated symptoms and normal variants" of parasomnias (ICSD-3, 2014). A cross-sectional epidemiological study reported a high presence of ST both in the lifetime (66%) and current prevalence (17%) (Bjorvatn et al., 2010). ST has been recently addressed as a diagnostic marker to differentiate Lewy body dementia from other kind of dementia (Honda et al., 2013; ICSD-3, 2014). Nonetheless, specific investigations about its quantitative features and the influence on sleep quality still lack. Materials and methods: 783 subjects (18-69 years) completed an on-line questionnaire about sleep quality and presence/frequency of parasomnia-related behaviours. The protocol included the Pittsburgh Sleep Quality Index Questionnaire (PSQI, Italian version - Curcio et al., 2013) and the Munich Parasomnia Screening (MUPS, 2008 - Fulda et al., 2008). The MUPS is a self-rating questionnaire, assessing the frequency of 21 nocturnal behaviors (from "never" to " every or nearly every night"). In order to evaluate the relation between ST frequency and frequency of other altered nocturnal behaviours in the whole sample, correlational analyses have been performed. Results: ST prevalence was of 72% in the lifetime of our sample, and 11.49% of declared a current prevalence (MUPS frequency 6 " one or more times per week", or 7 "every night or nearly every night"). 90 subjects (M= 33, F=57; 18-68 years, M= 25.15, SD= 6,24) declared a frequency of at least once a week and have been selected for further analyses. In a comparison between frequent ST and a control group (no self-report of altered nocturnal behaviours), values at PSQI showed a sleep quality significantly lower for ST compared to controls. The results of the correlational analysis showed a significant positive trend for: hypnic jerks, rhythmic movement disorder, hypnagogic hallucinations, sleep-related bruxism, sleep-related groaning, nightmares, sleep terrors, confusional arousal, sleepwalking, violent behaviour, REM sleep behaviour disorder (p< 0.02). Conclusions: The results confirm a high presence of declared ST in an Italian sample and a significant co- presence with other altered nocturnal behaviours, coherently with previous findings (ICSD-II, 2001; Bjorvatn et al., 2010; Nielsen et al., 2009). Nonetheless, the ICSD-3 (2014) defines this phenomenon as non-pathological parasomnia, the self-reported poor sleep quality suggests ST could be interesting to study as an independent factor influencing sleep quality. Due to these results, sleep studies on the quantitative EEG changes in ST and on the assessment of the association with cognitive performance are needed, both in healthy individuals and in pathological cohorts (i.e., dementia patients). Acknowledgements: This work was supported by the grant AR11715C545C9CF7 from "Sapienza", University of Rome

Spontaneous K-complex density decrease in Alzheimer’s disease

Although a slowing of electroencephalographic (EEG) activity during wakefulness and –to some extent- sleep of Alzheimer disease (AD) patients (i.e., increased slow-frequency activity) was documented, recent findings in healthy elderly show a decreased 0.6–1 Hz slow wave activity (SWA) during NREM, which was associated to β-amyloid deposition and impaired hippocampal memory consolidation. We hypothesize that the apparent contradiction may be explained by the partial overlap between 0.6–1 Hz EEG activity and K-Complex (KC). According to this view, we studied both frontal KCs and SWA in 20 AD patients and 20 healthy age-matched controls (HC) during nightly sleep, under the hypothesis that KCs better discriminate patients from healthy elderly than ≤1 Hz SWA. A drastic decrease of KC density during stage 2 NREM was found in AD compared to HC. Patients show more than 40% reduction of the KC density, allowing a correct classification of 80%. On the other hand, ≤1 Hz SWA of AD patients is slightly (not significantly) higher in most cortical areas compared to HC. Although no significant changes of ≤1 Hz SWA are detectable over frontal areas in AD, KC density decreases over the same location, and its decrease is related to the cognitive decline