Cognitive impairment in individuals with insomnia : clinical significance and correlates

Study Objectives: The aims of this study were to (1) investigate the nature of cognitive impairment in individuals with insomnia, (2) document their clinical significance, (3) examine their correlates, and (4) explore differences among individuals with insomnia with and without cognitive complaints. Design: Participants underwent 3 consecutive nights of polysomnography. On the morning following the third night, they completed a battery of questionnaires and neuropsychological tests. Participants: The sample included 25 adults with primary insomnia (mean age: 44.4 ± 11.5 y, 56% women) and 16 controls (mean age: 42.8 ± 12.9 y, 50% women) matched for sex, age, and education. Intervention: N/A. Measurement and Results: Participants completed neuropsychological tests covering attention, memory, working memory, and executive functions, as well as questionnaires assessing the subjective perception of performance, depression, anxiety, fatigue, sleepiness, and hyperarousal. There were significant group differences for the attention and episodic memory domains. Clinically significant deficits were more frequent in the insomnia group. Within the insomnia group, individuals with cognitive complaints exhibited significantly poorer performance on a larger number of neuropsychological variables. All impaired aspects of performance were significantly associated with either subjective or objective sleep continuity, and some were also independently related to sleep microstructure (i.e., relative power for alpha frequencies) or selected psychological variables (i.e., beliefs or arousal). Conclusions: These findings suggest clinically significant alterations in attention and episodic memory in individuals with insomnia. Objective deficits were more pronounced and involved more aspects of performance in a subgroup of individuals with cognitive complaints. These deficits appear associated with sleep continuity, and may also be related to sleep microstructure and dysfunctional beliefs

Caractérisation des atteintes cognitives associées à l'insomnie chronique

Cette thèse vise à améliorer la compréhension du fonctionnement cognitif des personnes souffrant d’insomnie. Plus spécifiquement, elle vise à : 1) préciser la nature, la magnitude et la signification clinique des atteintes cognitives associées à l’insomnie, 2) explorer les différences entre les personnes souffrant d’insomnie qui présentent des plaintes cognitives et celles qui n’en présentent pas et 3) documenter les relations entre les atteintes cognitives observées, les perturbations du sommeil et les manifestations d’hyperactivation diurne associées à l’insomnie. Dans un premier temps, une méta-analyse résumant les études préexistantes a permis de mettre en évidence des différences légères à modérées entre les personnes souffrant d’insomnie et les bons dormeurs pour quelques sphères cognitives, soit la mémoire de travail (rétention et manipulation d’informations), la mémoire épisodique et la résolution de problèmes. Dans un deuxième temps, un groupe de 25 participants souffrant d’insomnie a été comparé à 16 participants sans difficultés de sommeil, appariés pour l’âge, le sexe et la scolarité. Ces participants ont dormi trois nuits consécutives en laboratoire, puis ont complété une batterie de tests cognitifs ainsi que des questionnaires évaluant la perception de leur fonctionnement cognitif et différentes manifestations d’hyperactivation diurne. Les résultats suggèrent des différences significatives de grandes magnitudes entre les personnes souffrant d’insomnie et les bons dormeurs pour certains aspects des performances attentionnelles et mnésiques, alors que les performances aux épreuves évaluant la mémoire de travail et le fonctionnement exécutif semblent préservées. La fréquence des déficits considérés cliniquement significatifs est plus élevée chez les participants souffrant d’insomnie. En outre, les personnes souffrant d’insomnie et ayant des plaintes cognitives présentent des atteintes touchant un plus grand nombre de sphères cognitives, et dont la magnitude est plus importante. Les différentes atteintes cognitives sont toutes associées aux perturbations du sommeil, et certaines sont également associées à différentes dimensions de l’hyperactivation diurne. Dans l’ensemble, les résultats de la thèse suggèrent que l’insomnie est caractérisée par des atteintes cognitives compatibles avec un léger dysfonctionnement des régions préfrontales, mais soulignent également la coexistence possible de différents profils cognitifs parmi les personnes souffrant d’insomnie. Pour certains individus, ces atteintes seraient suffisantes pour être considérées cliniquement significatives. Différentes atteintes cognitives paraissent associées à différents aspects du sommeil et des manifestations d’hyperactivation diurne, ce qui pourrait signaler la présence des mécanismes distincts.This thesis seeks to improve the understanding of cognitive functioning in individuals with insomnia. More specifically, it aims to: 1) specify the nature, magnitude and clinical significance of cognitive impairments associated with insomnia, 2) explore differences between individuals with insomnia who complain about their cognitive functioning and those who do not, and 3) document the relations between cognitive impairments, sleep disturbances and manifestations of daytime hyperarousal associated with insomnia. Two studies were completed to meet these objectives. First, a meta-analysis summarizing existing studies showed mild to moderate differences between individuals with insomnia and normal sleepers for several cognitive domains, namely working memory, episodic memory and problem solving. In the second study, a group of 25 individuals with insomnia was compared to 16 normal sleepers matched for age, gender and education. These participants spent three consecutive nights in the sleep laboratory, then completed a battery of cognitive tests as well as questionnaires assessing perception of their cognitive functioning and different manifestations of daytime hyperarousal. Results suggest significant differences of large magnitude between individuals with insomnia and normal sleepers for specific aspects of attentional and memory performance, while performance on tasks assessing working memory and executive functions is preserved. The frequency of clinically significant deficits is higher in individuals with insomnia. In addition, individuals with insomnia and cognitive complaints had cognitive impairment of larger magnitude, and in a larger number of cognitive domains. The different cognitive impairments are all associated with sleep disturbances, and some aspects of cognitive impairment are also associated with different dimensions of daytime hyperarousal. Taken together, results suggest that insomnia is characterized by cognitive impairment compatible with a mild dysfunction of prefrontal areas, but also point to a possible coexistence of different cognitive profiles among individuals with insomnia. For a number of individuals, these deficits would be sufficient to be considered clinically significant. Different cognitive impairments appear associated with different aspects of sleep and daytime hyperarousal, which could suggest distinct mechanisms

Insomnie et microstructure du sommeil : impact du traitement comportemental-cognitif

L’objet du présent mémoire consiste à évaluer l ’effet du traitement comportemental-cognitif (ICC) de l’insomnie sur la microstructure du sommeil. Un groupe de participants souffrant d ’insomnie chronique et un groupe témoin de bons dormeurs sont d'abord soumis à une évaluation polysomnographique (PSG) effectuée en laboratoire. Les personnes souffrant des 4 premiers cycles de sommeil. Les résultats confirment la présence de perturbations de la microstructure du sommeil chez les participants souffrant d ’insomnie. Ces perturbations se manifestent par une activité plus dense pour les bandes de fréquences delta, thêta, alpha, sigma, bêta et gamma durant le stade 2 et pour les bandes de fréquence delta, thêta, alpha, sigma et bêta durant les stades 3-4. Les résultats suggèrent un effet global du TCC sur la microstructure du sommeil des stades 3-4 mais cet effet ne semble pas se traduire par des changements spécifiques des rythmes évalués. Des écarts entre les bons dormeurs et les personnes souffrant d ’insomnie sont toujours présents après le traitement, mais les différences ne sont pas statistiquement significatives. Les améliorations de la continuité du sommeil sont fortement corrélées avec une augmentation de la densité des rythmes lents et modérément corrélées avec une augmentation de la densité des rythmes thêta, alpha, sigma et bêta. Les résultats suggèrent donc que le TCC peut induire des changements subtils de la microstructure du sommeil et que ces changements sont associés aux améliorations de la continuité du sommeil.The aim of this paper is to examine the effect o f the cognitive behavioral treatment (CBT) of insomnia on sleep microstracture. A group o f participants with chronic insomnia and a control group of normal sleepers are submitted to polysomnographic (PSG) assessment completed at the sleep laboratory. Participants with insomnia receive a 6-week TBC and return to the sleep laboratory for additional PSG recordings. The sleep microstructure is examined through powerspectral analysis o f the electroencephalogram (EEG) which is computed for stages 2, 3 and 4 ofthe first 4 sleep cycles. Results confirm the presence o f altered sleep microstructure inparticipants suffering from insomnia. These disruptions are evident from increased density fordelta, theta, alpha, sigma, beta and gamma bands during stage 2 and for delta, theta, alpha, sigma and beta bands during slow' wave sleep (SWS). Results suggest a global effect of CBT on themicrostructure o f SWS but this effect does not translate in specific changes within given rhythms. There are still discrepancies between participants with insomnia and normal sleepers atpost treatment but the differences no longer reach statistical significance. Improvements in sleep continuity parameters are strongly correlated with increased density in slow rhythms and moderately correlated with increased density in theta, alpha, sigma and beta rhythms. Results thus suggest that CBT could induce subtle changes in the SWS microstructure of insomnia sufferers and that such changes are associated with improved sleep continuity

Insomnia and daytime cognitive performance : a meta-analysis

Objectives : Individuals with insomnia consistently report difficulties pertaining to their cognitive functioning (e.g., memory, concentration). However, objective measurements of their performance on neuropsychological tests have produced inconsistent findings. This meta-analysis was conducted to provide a quantitative summary of evidence regarding the magnitude of differences between individuals with primary insomnia and normal sleepers on a broad range of neuropsychological measures. Methods : Reference databases (PubMed, PsycInfo, Dissertation Abstracts International) were searched for studies comparing adults with primary insomnia to normal sleepers on neuropsychological measures. Dependent variables related to cognitive and psychomotor performance were extracted from each study. Variables were classified independently by two licensed neuropsychologists according to the main cognitive function being measured. Individual effect sizes (Cohen's d) were weighted by variability and combined for each cognitive function using a fixed effects model. Average effect sizes and their 95% confidence intervals were computed for each cognitive function. Results : Twenty-four studies met inclusion criteria, for a total of 639 individuals with insomnia and 558 normal sleepers. Significant impairments (p < 0.05) of small to moderate magnitude were found in individuals with insomnia for tasks assessing episodic memory (ES = −0.51), problem solving (ES = −0.42), manipulation in working memory (ES = −0.42), and retention in working memory (ES = −0.22). No significant group differences were observed for tasks assessing general cognitive function, perceptual and psychomotor processes, procedural learning, verbal functions, different dimensions of attention (alertness, complex reaction time, speed of information processing, selective attention, sustained attention/vigilance) and some aspects of executive functioning (verbal fluency, cognitive flexibility). Conclusion : Individuals with insomnia exhibit performance impairments for several cognitive functions, including working memory, episodic memory and some aspects of executive functioning. While the data suggests that these impairments are of small to moderate magnitude, further research using more ecologically valid measures and normative data are warranted to establish their clinical significance

Associations between self-reported sleep quality and white matter in community-dwelling older adults: A prospective cohort study.

Both sleep disturbances and decline in white matter microstructure are commonly observed in ageing populations, as well as in age-related psychiatric and neurological illnesses. A relationship between sleep and white matter microstructure may underlie such relationships, but few imaging studies have directly examined this hypothesis. In a study of 448 community-dwelling members of the Whitehall II Imaging Sub-Study aged between 60 and 82 years (90 female, mean age 69.2 ± 5.1 years), we used the magnetic resonance imaging technique diffusion tensor imaging to examine the relationship between self-reported sleep quality and white matter microstructure. Poor sleep quality at the time of the diffusion tensor imaging scan was associated with reduced global fractional anisotropy and increased global axial diffusivity and radial diffusivity values, with small effect sizes. Voxel-wise analysis showed that widespread frontal-subcortical tracts, encompassing regions previously reported as altered in insomnia, were affected. Radial diffusivity findings remained significant after additional correction for demographics, general cognition, health, and lifestyle measures. No significant differences in general cognitive function, executive function, memory, or processing speed were detected between good and poor sleep quality groups. The number of times participants reported poor sleep quality over five time-points spanning a 16-year period was not associated with white matter measures. In conclusion, these data demonstrate that current sleep quality is linked to white matter microstructure. Small effect sizes may limit the extent to which poor sleep is a promising modifiable factor that may maintain, or even improve, white matter microstructure in ageing. Hum Brain Mapp 38:5465-5473, 2017. © 2017 Wiley Periodicals, Inc

Preferential attention towards the eye-region amongst individuals with insomnia

People with insomnia often perceive their own facial appearance as more tired compared with the appearance of others. Evidence also highlights the eye-region in projecting tiredness cues to perceivers, and tiredness judgements often rely on preferential attention towards this region. Using a novel eye-tracking paradigm, this study examined: (i) whether individuals with insomnia display preferential attention towards the eye-region, relative to nose and mouth regions, whilst observing faces compared with normal-sleepers; and (ii) whether an attentional bias towards the eye-region amongst individuals with insomnia is self-specific or general in nature. Twenty individuals with DSM-5 Insomnia Disorder and 20 normal-sleepers viewed 48 neutral facial photographs (24 of themselves, 24 of other people) for periods of 4000 ms. Eye movements were recorded using eye-tracking, and first fixation onset, first fixation duration and total gaze duration were examined for three interest-regions (eyes, nose, mouth). Significant group × interest-region interactions indicated that, regardless of the face presented, participants with insomnia were quicker to attend to, and spent more time observing, the eye-region relative to the nose and mouth regions compared with normal-sleepers. However, no group × face × interest-region interactions were established. Thus, whilst individuals with insomnia displayed preferential attention towards the eye-region in general, this effect was not accentuated during self-perception. Insomnia appears to be characterized by a general, rather than self-specific, attentional bias towards the eye-region. These findings contribute to our understanding of face perception in insomnia, and provide tentative support for cognitive models of insomnia demonstrating that individuals with insomnia monitor faces in general, with a specific focus around the eye-region, for cues associated with tiredness

Sleep-related attentional bias in insomnia: time to examine moderating factors?

Prominent cognitive models of insomnia have emphasized the notion that the disorder is in part maintained by an attentional bias for sleep related “threat” cues which may be internal (i.e., bodily sensations) or external (i.e., environmental) in nature (Harvey, 2002; Espie et al., 2006). To support this proposition, a growing number of studies have examined the presence of a sleep-related attentional bias for words and images using experimental tasks including the dot-probe, flicker, Posner, emotional Stroop, and eye-tracking paradigms (see Harris et al., 2015 for a review). Many of these studies have provided encouraging evidence for the presence of such a bias in insomnia. However, the evidence base advocating the presence of such a bias remains mixed with a number of studies yielding no statistically significant effects. While a recent review (Harris et al., 2015) cautiously suggests biased attention for sleep-related threat information to be a likely feature of insomnia, the authors highlight the need to understand the specificity of this bias and its relationship with mechanisms believed to underpin the disorder (e.g., sleep preoccupation). Furthermore, whilst it is possible that the mixed evidence may stem from methodological differences relating to the task or population used, the possible moderating influence of these factors on the relationship between attentional bias for sleep-related threat information and insomnia have only recently been examined (e.g., Zheng et al., 2018). With this in mind, we propose candidate factors that may play a crucial role in addressing moderating questions such as “when,” “for whom” and “under which” conditions are sleep-related attentional biases evident in individuals characterized by insomnia

Is insomnia associated with deficits in neuropsychological functioning? Evidence from a population-based study

Study Objectives: People with insomnia complain of cognitive deficits in daily life. Results from empirical studies examining associations between insomnia and cognitive impairment, however, are mixed. Research is needed that compares treatment-seeking and community-based insomnia study samples, measures subjective as well as objective cognitive functioning, and considers participants' pre-insomnia cognitive function. Design and Participants: We used data from the Dunedin Study, a representative birth cohort of 1,037 individuals, to examine whether insomnia in early midlife was associated with subjective and objective cognitive functioning. We also tested whether individuals with insomnia who reported seeking treatment for their sleep problems (treatment-seekers) showed greater impairment than other individuals with insomnia (non-treatment-seekers). The role of key confounders, including childhood cognitive ability and comorbid health conditions, was evaluated. Measurements: Insomnia was diagnosed at age 38 according to DSM-IV criteria. Objective neuropsychological assessments at age 38 included the WAIS-IV IQ test, the Wechsler Memory Scale, and the Trail-Making Test. Childhood cognitive functioning was assessed using the Wechsler Intelligence Scale for Children-Revised (WISC-R). Results: A total of 949 cohort members were assessed for insomnia symptoms and other study measures at age 38. Although cohort members with insomnia (n = 186, 19.6%) had greater subjective cognitive impairment than their peers at age 38, they did not exhibit greater objective impairment on formal testing. Treatment-seekers, however, exhibited significant objective impairment compared to non-treatment-seekers. Controlling for comorbidity, daytime impairment, and medications slightly decreased this association. Childhood cognitive deficits antedated the adult cognitive deficits of treatment-seekers. Conclusions: Links between insomnia and cognitive impairment may be strongest among individuals who seek clinical treatment. Clinicians should take into account the presence of complex health problems and lower premorbid cognitive function when planning treatment for insomnia patients