REM and NREM power spectral analysis on two consecutive nights in psychophysiological and paradoxical insomnia sufferers

The objectives of the study were to examine EEG activities using power spectral analysis (PSA) of good sleepers (GS), psychophysiological (PsyI) and paradoxical (ParI) insomnia sufferers on two consecutive nights. Participants completed three nights of PSG recordings in a sleep laboratory following a clinical evaluation. Participants were 26 PsyI, 20 ParI and 21 GS (mean age = 40 years, SD = 9.4). All sleep cycles of Nights 2 and 3 were retained for PSA. The absolute and relative activity in frequency bands (0.00 to 125.00 Hz) were computed at multiple frontal, central and parietal sites in REM and NREM sleep. Mixed model ANOVAs were performed with absolute and relative PSA data to assess differences between groups and nights. Over the course of the two nights, more absolute delta activity at F3, C3, and P3 was observed in ParI compared with PsyI suggesting deactivation of the left hemisphere in ParI and/or hyperactivation in PsyI. Further analysis on absolute PSA data revealed that differences between groups relate mostly to NREM. In REM, lower relative activity in slower frequency bands was found in ParI in comparison with GS and less relative theta activity was found in PsyI compared with GS implying higher activation in insomnia. In addition, between nights variability has been found in absolute powers of faster frequency bands (beta to omega). Signs of decreased cortical activity in absolute PSA in NREM combined with increased relative cortical activation in REM were found in ParI which might contribute to the misperception of sleep in ParI.     

Event-related potentials in patients with insomnia and sleep-related breathing disorders: evening-to-morning changes

STUDY OBJECTIVES: The relationship between event-related potentials (ERPs) and sleep alterations in patients with sleep disorders is still controversial. Whether the ERP alterations are affected by sleep loss and sleep discontinuity can be addressed by studying presleep-to-postsleep changes in ERPs. We investigated if presleep-to-postsleep ERP latencies and amplitudes differ in patients with insomnia and sleep-related breathing disorders and whether these changes are affected by the degree of subjective and objective sleep alterations. METHODS: Fifteen patients with a diagnosis of insomnia, 45 patients with sleep-related breathing disorders, and 13 healthy controls were examined. Auditory ERPs were measured in the evening before sleep and in the morning after polysomnography. Subjective sleepiness and sleep quality were assessed by the Epworth Sleepiness Scale and the Saint Mary's Hospital Quality of Sleep Questionnaire. RESULTS: Analysis of evening-to-morning ERP variations did not reveal significant between-group differences in N100 latency and amplitude or in P200 and P300 amplitudes. Patients with sleep-related breathing disorders had a significant lengthening of P200 and P300 latencies in the morning, compared with controls and insomniacs. A trend to delayed morning P300 was present in patients with insomnia but did not reach statistical significance. The evening-to-morning ERP differences were not significantly related to subjective sleep quality, indexes of sleep fragmentation, or total sleep time. CONCLUSIONS: ERPs are sufficiently sensitive to assess attention dysfunction in patients with sleep disorders when presleep-to-postsleep changes are considered. The lack of relationship between indexes of sleep loss and sleep fragmentation and presleep-to-postsleep ERP changes might suggest that other factors outside sleep alterations affect ERP deterioration in patients with sleep disorders.     

Are individuals with paradoxical insomnia more hyperaroused than individuals with psychophysiological insomnia? Event-related potentials measures at the peri-onset of sleep

Preliminary QEEG studies suggest that individuals with paradoxical insomnia (Para-I) display higher cortical arousal than those with psychophysiological insomnia (Psy-I). Lately, finer measures, such as event-related potentials, and especially the N1 and P2 components have been used to document arousal processes in individuals with insomnia. The objective of the present study was to further circumscribe arousal in Psy-I and Para-I using N1, P2 and the waking processing negativity (wPN). N1 and P2 were recorded in the evening, at sleep-onset and in early stage 2 sleep in 26 good sleepers, 26 Psy-I and 26 Para-I. An oddball paradigm was used and participants received the instruction to ignore all stimuli at all times. Three difference waves (wPNs) were computed to evaluate the transition from wakefulness to sleep onset, from sleep onset to sleep and from wakefulness to sleep. Results revealed that N1 was smaller during wakefulness and sleep onset for Psy-I, while it was larger for Para-I during these same times. P2 was smaller at sleep onset for Psy-I than for Para-I and GS, while P2 during wakefulness and stage 2 sleep was larger for Para-I than GS. WPNs revealed that Psy-I showed fewer changes in information processing, while Para-I showed larger changes between recording times. Psy-I appear to present an inability to inhibit information processing during sleep onset, while Para-I seem to present overall enhanced attentional processing that results in a greater need for inhibition.     

Attentional bias towards sleep‐related stimuli in insomnia disorder: a behavioural and ERP study

Many studies have used behavioural experiments to show an attentional bias towards sleep‐related stimuli in people with insomnia disorder. A measurement of event‐related potential is needed to investigate the cognitive processing mechanism of the attentional process. The present study used the emotional Stroop paradigm and event‐related potentials to measure attentional bias towards sleep‐negative, sleep‐positive and sleep‐unrelated neutral words. The study comprised 16 participants with insomnia disorder and 15 participants who were good sleepers. Behavioural data indicated that there was a significant interference effect of sleep‐positive words between the insomnia group and the good sleepers, and a marginally significant interference effect from sleep‐negative words between groups. In the insomnia group, event‐related potential data showed that sleep‐negative words elicited higher amplitudes of P1 and N1 components than did sleep‐positive and sleep‐unrelated words. Our results provide evidence for the early cognitive processing of sleep‐negative stimuli, which suggests that the psychological treatment of insomnia could benefit from addressing early hypervigilance towards these stimuli.     

Working memory performance of older adults with insomnia

Older individuals suffering insomnia typically report declines in their cognitive performance beyond what they consider to be normal changes due to the aging process. Recent neuro‐imaging studies have demonstrated frontal lobe hypo‐activation among insomniac populations when compared with healthy, good sleepers. However, research is yet to confirm whether frontal lobe hypo‐activation translates into objective declines when performing tasks hypothesized to draw upon this brain region. This study aimed to investigate whether older insomnia sufferers demonstrate significantly impaired performance on a challenging working memory task when compared with age‐matched good sleepers. Forty‐nine older individuals (mean age = 69.43 years, SD = 4.83) suffering from sleep maintenance insomnia were compared with 49 age‐matched good sleepers. Cognitive performance was assessed using the Double Span Memory Task, a computer‐based working memory task that requires participants to indicate the names and/or spatial locations of increasingly longer sequences of visually presented objects. After controlling for general intelligence, the individuals suffering from insomnia did not perform differently when compared with the good sleepers on either the simpler or more cognitively demanding components of the task. Older individuals with insomnia did not display an observable impairment of working memory in this study relative to good sleepers. Despite the mixed results from previous research, this study adds weight to the absence of objective impairment in insomniacs, at least while performing short‐term demanding cognitive tasks.     

Chronic Psychophysiological Insomnia: Hyperarousal and/or Inhibition Deficits? An ERPs Investigation

STUDY OBJECTIVES: Chronic primary insomnia has been hypothesized to result from conditioned arousal or the inability to initiate normal sleep processes. The event-related potentials (ERPs) N1, P2, and N350 are useful indexes of arousal. The objective is to compare these ERPs in primary chronic psychophysiological insomniacs (INS) and good sleepers (GS) during multiple recordings. PARTICIPANTS: Participants were 15 INS (mean age = 46 years, SD = 7.5) and 16 GS (mean age = 37 years, SD = 10.1). METHODS AND PROCEDURE: Following a multistep clinical evaluation, INS and GS participants underwent 4 consecutive nights of PSG recordings (N1 to N4). ERPs were recorded on the 3rd and 4th nights in the sleep laboratory (N3 and N4). ERPs recordings were made during wake on both nights (in the evening and upon awakening), with the addition of sleep-onset recordings on N4. Auditory stimuli consisted of "standard" and "deviant" tones. STATISTICAL ANALYSIS: Repeated measures ANOVAs were computed for each ERP for each recording for each type of stimulus. RESULTS: The amplitude of P2 and N350 was greater for the deviant than for the standard stimulus in both groups. The amplitude of N1 was larger in INS than GS in the morning and the evening. While the amplitude of N350 was larger in GS than in INS at sleep onset, the amplitude of P2 was greater in INS than in GS at that time. CONCLUSION: Signs of greater cortical arousal in psychophysiological insomnia individuals are observed, especially upon awakening in the morning. However, at sleep onset, difficulties from disengaging from wake processes and some inability at initiating normal sleep processes appear also present in individuals with insomnia compared to good sleepers.     

Sleep‐related attentional bias in poor versus good sleepers is independent of affective valence

Contradictory evidence exists relating to the presence of an attention bias to sleep‐related stimuli in poor sleepers/insomnia using the emotional Stroop task (EST). These inconsistencies may be due to methodological issues related to the affective valence of the sleep‐related stimuli. Thus, individuals may attend differentially to sleep‐related stimuli not because of their ‘sleep’ properties, but their negativity. The current study addresses this by controlling the affective valence of sleep‐related words. A total of 107 participants [mean age = 33.22 years, standard deviation (SD) = 12.31 years; 61.7% female] were recruited during an evening event at the Newcastle Science Festival. Participants completed the Pittsburgh Sleep Quality Index (PSQI) and a computerized EST containing 20 non‐affective sleep‐related, 20 neutral and 20 negatively valenced threat words. Good and poor sleepers were categorized using the PSQI. There were no significant differences between groups on response latency to sleep‐related words (t₍₁₀₅₎ = –0.30, P = 0.76). However, the interaction between good versus poor sleepers and word‐type on response latency was significant (F_(2,210) = 3.06, P < 0.05). Poor sleepers took longer to respond to sleep‐related words (mean = 723.35, SD = 172.55) compared to threat words (mean = 694.63, SD = 162.17) than good sleepers (mean = 713.20, SD = 166.32; and mean = 716.65, SD = 181.14). The results demonstrate the presence of an attention bias towards sleep‐related stimuli compared to threat stimuli in poor sleepers. Accordingly, poor sleepers may be consumed by stimuli relevant to their specific difficulties, as well as being more highly attuned to negative cues that signal anxious states. Thus, the present research suggests that there are two opposing forces at play: one which facilitates performance (non‐specific threats) and one which hinders performance (personally relevant threats).     

The relationship between a night's sleep and subsequent daytime functioning in older poor and good sleepers

Those suffering insomnia symptoms generally report daytime impairments. However, research has not assessed whether this relationship holds on a nightly basis, despite the strongly held belief that a night of poor sleep impairs mood and functioning the following day. The objective of this study was to test this relationship in a group of older poor sleepers with insomnia symptoms compared with good sleepers. This study utilized a within‐subjects design to investigate day‐to‐day subjective daytime functioning and its relation to the previous night's sleep. Seventeen older individuals (mean age: 67.5 years) were identified with a retrospective questionnaire and 2 weeks of sleep–wake diary to have poor sleep consistent with insomnia. Seventeen good sleepers (mean age: 67.8 years) were selected using the same measures. Participants reported their beliefs about sleep and daytime functioning on the Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS‐16). One week later they commenced a 14‐day period of sleep–wake diaries and concurrent responses to a modified Daytime Insomnia Symptom Scale (DISS). Results showed significant night‐to‐day covariation between sleep efficiency and daytime functioning for individuals with poor sleep (r = 0.34), but not for good sleepers (r = 0.08). Those poor sleepers who held this covariation belief most strongly were those who subsequently showed this night‐to‐day relationship the most strongly (r = 0.56). This was not true for good sleepers. For those suffering insomnia, these findings demonstrate their belief that a poor sleep is followed by an impaired daytime, consistent with their experience.     

P3 event-related potential impairments in antisocial and psychopathic individuals: A meta-analysis

Prior findings on P3 event-related potential deficits in antisocial populations are mixed and it has been suggested that these abnormalities may not apply to psychopaths. A meta-analysis of 38 studies (total N = 2616) was conducted to investigate the relationship of P3 measures to antisocial behavior. Reduced P3 amplitudes (d = 0.252, p < .001) and longer P3 latencies (d = 0.130, p = .019) were significantly associated with antisocial behavior across all electrode sites, and when using both normal and non-normal control groups. A significant moderating effect of electrode site indicated longer latencies at Fz but not Pz. Compared to non-psychopathic offenders, psychopathic offenders showed P3 amplitudes impairments in standard oddball tasks, but not other tasks. Findings suggest that reduced P3 amplitudes and prolonged P3 latencies may reflect inefficient deployment of neural resources in processing cognitive task-relevant information in individuals characterized with generic antisocial behavior (i.e., aggression, antisocial personality disorder, conduct disorder/oppositional-defiant disorder, and psychopathy), whereas this association in psychopaths may be moderated by the type of tasks.     

Event-related potentials during the transition to sleep for individuals with sleep-onset insomnia

Event-related potentials may be applied to directly measure information-processing deficits associated with the problem of insomnia. This study is a systematic investigation of cortical hyperarousal during the sleep-onset period in participants with sleep-onset insomnia complaints. Thirteen poor sleepers and twelve good sleepers (GS) were administered an oddball task while awake in the morning and evening and during repeated sleep-onset attempts. Participants signaled detection of a higher pitch target tone as they fell asleep. P2 amplitude was significantly smaller for poor sleepers compared to GS, following standard stimuli at all fronto-central sites, in the pre-sleep waking period at sleep onset. Groups did not differ for N1, N350, or P300 in wake, Stage 1, or Stage 2. The smaller P2 indicates that poor sleepers failed to inhibit the irrelevant standard stimuli. This hyper-attentiveness may explain chronic problems with sleep initiation and could be the target of behavioral and pharmaceutical treatment strategies.     

Evaluation of auditory, visual and olfactory event-related potentials for comparing interspersed- and single-stimulus paradigms

Background

An interspersed-stimulus paradigm (ISP) for event-related potential (ERP) recordings in which different sensory modality stimuli are presented within the same test session was developed to minimize recording time and facilitate modality comparison. The present study compared the ISP with a single-stimulus paradigm (SSP), using auditory, visual, and olfactory stimuli.

Method

Normal participants (n = 16) were assessed on two independent test occasions to obtain data on inter-paradigm and test-retest reliability. Peak amplitude/latency and area measures were obtained for the N1, P2 and P3 peaks for each paradigm.

Results

Except for larger auditory and visual P3 peaks and smaller visual P2 peaks in the ISP, no significant differences in amplitudes or latencies were found between the two paradigms. Correlation coefficients between paradigms were generally fairly high (amplitude mean r = 0.76; latency r = 0.42). Test-retest reliability within paradigms for amplitudes (ISP r = 0.70; SSP r = 0.68) and latencies (ISP r = 0.44; SSP r = 0.42) was similar across paradigms.

Conclusion

The findings suggest that the ISP, compared to the SSP, produces, in general, highly comparable auditory, visual, and olfactory peak amplitudes and latencies, and comparable reliability estimates, even though the ISP takes much less time to record (25 vs. 50 min). The larger auditory and visual P3 peaks and smaller visual P2 peaks in the ISP may be attributable to a less predictable stimulus environment. Thus, this method enables systematic comparisons of ERP peaks across sensory modalities while reducing testing time. Practical implications are discussed.     

The role of vulnerability in stress‐related insomnia,social support and coping styles on incidence and persistence of insomnia

Individuals who are more prone to experience situational insomnia under stressful conditions may also be at greater risk to develop subsequent insomnia. While cross‐sectional data exist on the link between sleep reactivity (heightened vulnerability to stress‐related insomnia) and insomnia, limited data exist on its predictive value. The aim of the study was to evaluate prospectively whether sleep reactivity was associated with increased risk of incident and persistent insomnia in a population‐based sample of good sleepers. Social support and coping styles were also investigated as potential moderators. Participants were 1449 adults (M_age = 47.4 years, standard deviation = 15.1; 41.2% male) without insomnia at baseline and evaluated four times over 3 years. Sleep reactivity was measured using the Ford Insomnia Response to Stress Test (FIRST). Additional measures included depressive symptoms, the frequency and perceived impact of stressful life events, social support and coping styles. After controlling for prior sleep history, depressive symptoms, arousal predisposition, stressful life events and perceived impact, individuals with higher sleep reactivity had an odds ratio (OR) of 1.56 [95% confidence interval (CI): 1.13–2.16], 1.41 (95% CI: 0.87–2.30) and 2.02 (95% CI: 1.30–3.15) of developing insomnia symptoms, syndrome and persistent insomnia, respectively. Social support and coping styles did not moderate these associations. Results suggest that heightened vulnerability to insomnia is associated with an increased risk of developing new‐onset subsyndromal and persistent insomnia in good sleepers. Knowledge of premorbid differences is important to identify at‐risk individuals, as this may help to develop more targeted prevention and intervention strategies for insomnia.     

ERP evidence of enhanced excitatory and reduced inhibitory processes of auditory stimuli during sleep in patients with primary insomnia

STUDY OBJECTIVES: Increased information processing around the onset of sleep and during sleep has been suggested as an important factor for the pathogenesis of insomnia. The purpose of the present study was to examine the processing of auditory information during sleep in patients with insomnia through the recording of event-related potentials (ERPs). DESIGN: A mixed design was used in which subject group was a between-subject factor and sleep stage and type of tone presented were within-subject factors. PARTICIPANTS: Fifteen patients with primary insomnia and 15 normal sleepers (controls) were studied. MEASUREMENTS AND RESULTS: An odd-ball paradigm was conducted to evoke ERPs throughout the night. Patients with insomnia showed larger N1 and smaller P2 to rare tones, smaller N350 to standard tones, and slower P900 to both tones during the first 5 minutes of continuous stage 2 sleep. No consistent ERP differences were detected between the 2 groups when the waveforms were averaged across the whole night. CONCLUSIONS: Patients with insomnia showed an enhancement in attention and a reduction in the inhibitory process that normally facilitates sleep onset in the beginning part of sleep. The results partially support the hyperarousal theory, ie, enhanced information processing during the initiation of sleep is a contributing factor for insomnia.     

Nocturnal cardiac autonomic profile in young primary insomniacs and good sleepers

We investigated cardiac vagal and sympathetic activity in 13 young primary insomniacs (PI; 24.4 ± 1.6 years) and 14 good sleepers (GS; 23.3 ± 2.5 years) during nocturnal sleep. Pre-ejection period (PEP; inversely related to beta-adrenergic sympathetic activity), interval between consecutive R-waves (RR), and vagal-related indices of time- and frequency-domain heart rate variability were computed during pre-sleep wakefulness and undisturbed arousal-free sleep stages (N2, SWS, REM) as well as across the whole night irrespective of the presence of disruptive sleep events (e.g. sleep arousals/awakenings) and/or sleep stage transitions. Groups exhibited a similar vagal activity throughout each undisturbed sleep stage as well as considering the whole night, with a higher modulation during sleep compared to prior wakefulness. However, PEP was constantly shorter (higher sympathetic activity) during pre-sleep wakefulness and each sleep stage in PI compared to GS. Moreover, pre-sleep RR intervals were positively associated with sleep efficiency and negatively associated with wake after sleep onset in PI. Altogether our findings indicated a dysfunctional sympathetic activity but a normal parasympathetic modulation before and during sleep in young adults with insomnia.     

Executive brain functions after exposure to nocturnal traffic noise: effects of task difficulty and sleep quality

The after-effects of nocturnal traffic noise on cognitive performance and inhibitory brain activity were investigated. Twenty participants (18–30 years) performed an easy and a difficult visual Go/Nogo task with simultaneous EEG recording after a quiet night and then during three nights when aircraft noise was presented with equivalent noise levels of 39, 44, and 50 dBA, respectively, between 11 p.m. to 7 a.m. Based on subjective sleep quality rating, participants were separated into “good” versus “bad” sleepers. The performance and inhibition-related components (N2, P3) of event-related potentials were analysed. The N2 and P3 amplitudes were smaller and latencies were prolonged in the difficult than in the easy task. This effect was more pronounced for Nogo than for Go trials. The Nogo-P3 amplitude was smaller in Noise than in “Quiet” conditions in the difficult task only. In the difficult task, the Nogo-P3 latency was prolonged in bad sleepers than in good sleepers. The Nogo-P3 amplitude was reduced in Noise as compared to “Quiet” conditions in bad sleepers only. Sleep quality in bad sleepers worsened steadily with increasing noise levels. No effects of noise or subjective sleep quality on performance were found. Inhibitory processes appear to be selectively impaired after nocturnal noise exposure. The task difficulty and perceived sleep quality are important factors modulating noise effects. The results suggest that nocturnal traffic noise increase physiological costs for inhibitory functioning on the day even if no overt performance decrement is observed.     

Sensitivity and specificity of measures of the insomnia experience: a comparative study of psychophysiologic insomnia, insomnia associated with mental disorder and good sleepers

STUDY OBJECTIVES: To explore proposed explanatory mechanisms in psychophysiologic insomnia by investigating the sensitivity and specificity of commonly used insomnia research tools in discriminating psychophysiologic insomnia, insomnia associated with mental disorder, and good sleepers. DESIGN: Cross-sectional, between-group comparison of responses from subjects with psychophysiologic insomnia, those with insomnia associated with mental disorder, and good sleepers to psychometrically robust self-report instruments. SETTING: Attendees at adult community outpatient clinics. PARTICIPANTS: Fifty-four adults (36 women, 18 men; average age 40 years) across 3 groups (n = 18 per group). Participants with psychophysiologic insomnia met combined Inteernational Classification of Sleep Disorders, Revised and Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria and had no history of mental disorder. Participants with insomnia associated with mental disorder satisfied the same criteria for sleep disturbance and met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (Structured Clinical Interview for DSM-IV axis-I Disorders) criteria for depressive disorder. The majority had comorbid anxiety disorder. Insomnia duration in the groups with psychophysiologic insomnia and insomnia associated with mental disorder was around 10 years. Good sleepers served as a control group and included self-reported good sleepers with no history of sleep problems or psychiatric disorder. INTERVENTION: N/A. MEASUREMENTS AND RESULTS: Analyses of variance, adjusted for multiple comparisons, indicated no between-group differences on a measure of sleep-related stimulus control, and self-reported somatic arousal was higher in subjects with insomnia associated with mental disorder than in good sleepers or those with psychophysiologic insomnia. Subjects with insomnia associated with mental disorder and psychophysiologic insomnia had poorer sleep hygiene and were characterized by heightened mental arousal. Logistic regression indicated that "effortful preoccupation with sleep" discriminated subjects with both psychophysiologic insomnia (100% sensitivity, 94% specificity) and insomnia associated with mental disorder (100%, 100%) from good sleepers and that only depressive symptomatology discriminated insomnia associated with mental disorder from psychophysiologic insomnia. CONCLUSION: Psychophysiologic insomnia and insomnia associated with mental disorder may be on a continuum of insomnia severity, rather than categorically distinct. Insomnia associated with mental disorder may respond to psychological intervention. Factors specifically discriminating insomniacs from good sleepers require further investigation.     

EEG spectral analysis of NREM sleep in a large sample of patients with insomnia and good sleepers: effects of age,sex and part of the night

Previous studies of the differences between patients with insomnia and good sleepers with regard to quantitative electroencephalographic measures have mostly utilized small samples and consequently had limited ability to account for potentially important confounding factors of age, sex and part of the night. We conducted a power spectral analysis using a large database of sleep electroencephalographic recordings to evaluate differences between patients with insomnia (N = 803) and good sleepers (N = 811), while simultaneously accounting for these factors and their interaction. Comparisons of power as a function of age and part of the night were made between cohorts (patients with insomnia versus good sleepers) by sex. Absolute power in the delta, theta and sigma bands declined with age for both females and males. Females had significantly greater power than males at all ages, and for each band, cohort and part of the night. These sex differences were much greater than differences between patients with insomnia and good sleepers. Compared with good sleepers, patients with insomnia under age 40–45 years had reduced delta band power during Part 1 of the night. Females with insomnia over age 45 years had increased delta and theta band power in Parts 2 and 3 of the night, and males with insomnia under age 40 years had reduced theta power in Part 1. Females with insomnia had increased beta2 power in all parts of the night, and males with insomnia had reduced alpha power during all parts of the night. Relative power (the proportion that an individual frequency band contributes to the total power) decreased in the delta band and increased in all other bands with age for both cohorts, sexes and all parts of the night. This analysis provides a unique resource for quantitative information on the differences in power spectra between patients with insomnia and good sleepers accounting for age, sex and part of the night.     

The incidence and temporal patterning of insomnia: a second study

Whether subjects with insomnia exhibit good sleep on some interval basis is unclear. Prior research suggests that patients with insomnia are highly variable with respect to night‐to‐night sleep continuity, that more than 40% of patients exhibit temporal patterning of good sleep, and that nearly 90% of patients exhibit better than average sleep following 1 to 3 nights of relatively poor sleep. The aim of the present study was to replicate and extend the above‐noted findings utilizing: (i) a large sample studied over an extended time interval (ii) absolute standards for ‘good’ and ‘poor’ sleep; and (iii) a formal statistical methodology to assess temporal patterning and the association of time in bed with bout duration of poor or average sleep. Thirty‐three subjects with insomnia and 33 good sleepers completed sleep diaries over the course of 110 days. It was found that subjects with insomnia (compared to good sleepers) had more poor nights (e.g. about 39 versus 7% of the assessed nights), a higher probability of a having a poor night on any given occasion (60% greater probability than good sleepers) and more consecutive nights of poor sleep between good sleep nights (median bout duration of approximately three versus one night). Lastly, it was found that (as would be predicted by both the Spielman model and the two‐process model) time in bed moderated bout duration in the insomnia group. That is, longer times in bed were associated with longer bouts of poor sleep.     

Sleep-onset insomniacs have delayed temperature rhythms

It was predicted from free running and ultradian cycle studies that sleep-onset insomniacs would have endogenous circadian rhythms that were phase delayed compared to good sleepers. Thirteen sleep-onset insomniacs and nine good sleepers were selected to differ only in their sleep-onset latencies as confirmed by polysomnography. their rectal temperatures were measured over a 26-h constant routine and analyzed with best-fit Fourier curves including 24-h fundamental and 12-h harmonic components. The temperature rhythm markers of the insomniacs' rhythms were approximately 2.5 h later than the respective phases of the good sleepers. The usual bedtimes of the insomniacs fell within the "wake maintenance zone" of their delayed temperature rhythm. The good sleepers had typical bedtimes several hours after their "wake maintenance zone" and closer to their body temperature minimum. It was suggested that manipulations to phase advance the insomniacs' rhythms would reduce their sleep-onset latencies. It was also predicted that early morning insomnia results from phase advanced circadian rhythms and that sleep maintenance insomnia results from an abnormal phase relationship between the 24-h temperature rhythm and 12-h sleep-alert rhythm.     

Family history of insomnia in a population-based sample

STUDY OBJECTIVES: To examine the rates of family history of insomnia in a population-based sample composed of self-defined good sleepers and individuals with insomnia and compare individuals with and without family history of insomnia on several characteristics presumably associated with insomnia. DESIGN: Cross-sectional comparisons of self-defined good sleepers and individuals with insomnia selected from a larger epidemiologic study using a randomly selected sample of 2001 adults of the province of Quebec in Canada. PARTICIPANTS: Nine hundred fifty-three adults (60.3% women; mean age = 43.9 years) completed several postal questionnaires, including a survey of past and current history of insomnia/sleep disorders for self and first-degree relatives. Participants were classified as good sleepers, individuals with insomnia symptoms, or individuals with an insomnia syndrome. INTERVENTIONS: N/A. RESULTS: Of the total sample, 34.9% reported at least 1 first-degree relative with past or current insomnia. The mother was the most frequently afflicted first-degree relative with insomnia (19.7%). Family history rates of insomnia were not significantly different when individuals with current insomnia symptoms or syndrome were compared with self-defined good sleepers. However, significant group differences emerged when good sleepers were subdivided according to the presence or absence of past personal history of insomnia. Individuals with past or current insomnia were significantly more likely to report a family history of insomnia than were good sleepers who had never experienced insomnia in the past (39.1% vs 29.0%). Participants with a family history of insomnia endorsed higher scores on measures of insomnia severity, anxiety symptomatology, and arousal predisposition. CONCLUSIONS: These findings provide additional evidence about the potential role of both family and personal history of insomnia as predisposing factors to insomnia. Longitudinal family studies are needed to further examine the relative contribution of genetic and environmental factors in the genesis and heritability of insomnia.