Multidrug comparison (lorazepam, triazolam, zolpidem, and zopiclone) in situational insomnia: polysomnographic analysis by means of the cyclic alternating pattern

Association between psychotropic medication and sleep microstructure: evidence from large population studies

STUDY OBJECTIVES

To assess the association between psychotropic medications and sleep microstructure in large community-based cohorts of older people.

METHODS

We analyzed overnight polysomnograms of 381 women from the Study of Osteoporotic Fractures (SOF) and 2,657 men from the Osteoporotic Fractures in Men Sleep Study (MrOS), who either used no psychotropic medication (n = 2,819), only benzodiazepines (n = 112), or only selective serotonin reuptake inhibitors (SSRI) (n = 107). Sleep microstructure (cyclic alternating pattern, CAP) was compared between the no medication group and psychotropic medication groups using the Mann-Whitney U test. Significant differences were investigated using multivariable linear regression adjusted for confounders.

RESULTS

CAP rate, arousal index, apnea-hypopnea index, and the frequency of slow, low-amplitude electroencephalography activation phases were significantly lower in MrOS participants using benzodiazepines than participants not taking psychotropic medication. SSRI users in MrOS experienced no altered sleep microstructure compared to those with no psychotropic use. SOF participants using benzodiazepines did not show similar associations with sleep microstructure. However, SSRI users from SOF had a significantly higher frequency of rapid, high-amplitude electroencephalography activation phases (A2 + 3) and periodic limb-movement index than participants not taking psychotropic medication. Multivariable linear regression adjusted for demographic, lifestyle, mood disorders, and health variables indicated additional significant associations between benzodiazepine usage and CAP rate and A2 + 3 index, respectively, in older men, and between CAP rate and SSRI usage in older women.

CONCLUSIONS

We identified significant associations between sleep microstructure and psychotropic drugs in MrOS and SOF, highlighting the importance of comprehensive sleep analysis, including CAP. Our results may improve understanding of the differences in sleep-wake mechanisms based on psychotropic usage.

CLINICAL TRIAL REGISTRATION

Registry: ClinicalTrials.gov; Title: Outcomes of Sleep Disorders in Older Men; Identifier: NCT00070681; URL: https://clinicaltrials.gov/ct2/show/record/NCT00070681.

CITATION

Hartmann S, Parrino L, Ensrud K, et al. Association between psychotropic medication and sleep microstructure: evidence from large population studies. J Clin Sleep Med. 2023;19(3):581-589.

Automatic Cyclic Alternating Pattern (CAP) analysis: Local and multi-trace approaches

The Cyclic Alternating Pattern (CAP) is composed of cycles of two different electroencephalographic features: an activation A-phase followed by a B-phase representing the background activity. CAP is considered a physiological marker of sleep instability. Despite its informative nature, the clinical applications remain limited as CAP analysis is a time-consuming activity. In order to overcome this limit, several automatic detection methods were recently developed. In this paper, two new dimensions were investigated in the attempt to optimize novel, efficient and automatic detection algorithms: 1) many electroencephalographic leads were compared to identify the best local performance, and 2) the global contribution of the concurrent detection across several derivations to CAP identification. The developed algorithms were tested on 41 polysomnographic recordings from normal (n = 8) and pathological (n = 33) subjects. In comparison with the visual CAP analysis as the gold standard, the performance of each algorithm was evaluated. Locally, the detection on the F4-C4 derivation showed the best performance in comparison with all other leads, providing practical suggestions of electrode montage when a lean and minimally invasive approach is preferable. A further improvement in the detection was achieved by a multi-trace method, the Global Analysis—Common Events, to be applied when several recording derivations are available. Moreover, CAP time and CAP rate obtained with these algorithms positively correlated with the ones identified by the scorer. These preliminary findings support efficient automated ways for the evaluation of the sleep instability, generalizable to both normal and pathological subjects affected by different sleep disorders.

Zolpidem's use for insomnia

Zolpidem is a short-acting non-benzodiazepine hypnotic drug that belongs to the imidazopyridine class. In addition to immediate-release (IR) and extended-release (ER) formulations, the new delivery forms including two sublingual tablets [standard dose (SD) and low dose (LD)], and an oral spray form have been recently developed which bypass the gastrointestinal tract. So far, Zolpidem has been studied in several clinical populations: cases poor sleepers, transient insomnia, elderly and non-elderly patients with chronic primary insomnia, and in comorbid insomnia. Peak plasma concentration (Tmax) of zolpidem-IR occurs in 45 to 60min, with the terminal elimination half-life (t½) equating to 2.4h. The extended-release formulation results in a higher concentration over a period of more than 6h. Peak plasma concentration is somewhat shorter for the sublingual forms and the oral spray, while their t½ is comparable to that of zolpidem-IR. Zolpidem-IR reduces sleep latency (SL) at recommended doses of 5mg and 10mg in elderly and non-elderly patients, respectively. Zolpidem-ER at doses of 6.25mg and 12.5mg, improves sleep maintenance in elderly and non-elderly patients, respectively, 4h after its administration. Sublingual zolpidem-LD (5mg) and zolpidem oral spray are indicated for middle-of-the-night (MOTN) wakefulness and difficulty returning to sleep, while sublingual zolpidem-SD (10mg) is marketed for difficulty falling asleep. With their array of therapeutic uses and their popularity among physicians and patients; this review describes the clinical pharmacology, indications and uses, identifying withdrawal symptoms, abuse and dependence potentials, and adverse drug reactions are discussed.

Sleep state instabilities in major depressive disorder: Detection and quantification with electrocardiogram-based cardiopulmonary coupling analysis

Sleep disruption is an important aspect of major depressive disorder but lacks an objective and inexpensive means of assessment. We evaluated the utility of electrocardiogram (ECG)-based cardiopulmonary coupling analysis to quantify physiologic sleep stability in patients with major depression. Relative to controls, unmedicated depressed patients had a reduction in high-frequency coupling, an index of stable sleep, an increase in low-frequency coupling, an index of unstable sleep, and an increase in very-low-frequency coupling, an index of wakefulness/REM sleep. The medicated depressed group showed a restoration of stable sleep to a level comparable with that of the control group. ECG-based cardiopulmonary coupling analysis may provide a simple, cost-efficient point-of-care method to quantify sleep quality/stability and to objectively evaluate the severity of insomnia in patients with major depression.

Bridging the gap between education and appropriate use of benzodiazepines in psychiatric clinical practice

More than half a century after their discovery, benzodiazepines (BDZs) still represent one of the largest and most widely prescribed groups of psychotropic compounds, not only in clinical psychiatry but also in the entire medical field. Over the last two decades, however, there has been an increased focus on the development of antidepressants and antipsychotics on the part of the pharmaceutical industry, clinicians, and researchers, with a reduced interest in BDZs, in spite of their widespread clinical use. As a consequence, many psychiatric residents, medical students, nurses, and other mental health professionals might receive poor academic teaching and training regarding these agents, and have the false impression that BDZs represent an outdated chapter in clinical psychopharmacology. However, recent advances in the field, including findings concerning epidemiology, addiction risk, and drug interactions, as well as the introduction of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition with related diagnostic changes, strongly encourage an updated appraisal of the use of BDZs in clinical practice. During a recent thematic event convened with the aim of approaching this topic in a critical manner, a group of young Italian psychiatrists attempted to highlight possible flaws in current teaching pathways, identify the main clinical pros and cons regarding current use of BDZs in clinical practice, and provide an updated overview of their use across specific clinical areas and patient populations. The main results are presented and discussed in this review.

Bupropion response on sleep quality in patients with depression: implications for increased cardiovascular disease risk

Depression could be an independent risk factor for cardiovascular disease. We assessed bupropion response in depressed patients by polysomnography (PSG) and cardiopulmonary coupling (CPC) variables. Nineteen subjects participated in a two-session, two consecutive night PSG protocol. Participants received either placebo or bupropion-SR 150 mg, orally, in a randomized, double-blind cross-over fashion on night two. Outcome variables were: sleep stages, REM latency, stable, unstable sleep and very low frequency coupling (VLFC). CPC analysis uses heart rate variability and the electrocardiogram's R-wave amplitude fluctuations associated with respiration to generate frequency maps. Bupropion increased REM latency (p=0.043) but did not impact PSG sleep continuity, architecture and CPC variables. A trend (p=0.092) was observed towards increasing VLFC duration. Bupropion increased the number of stable-unstable sleep transitions (p=0.036). Moderate to strong correlations between PSG and CPC variables were found on placebo and bupropion nights. Limitations include a small sample size, limited power to detect CPC changes and lack of normal controls for comparison. Increased stable-unstable sleep transitions and VLFC duration may indicate vulnerability to cardiovascular disease due to their association with low heart rate variability that has been associated with increased mortality raising the question whether the beneficial effects of the antidepressant medication outweighs the impact on cardiopulmonary dynamics.

Polysomnographic findings in a cohort of chronic insomnia patients with benzodiazepine abuse

STUDY OBJECTIVES

To evaluate sleep modifications induced by chronic benzodiazepine (BDZ) abuse.

METHODS

Cohort study, comparison of sleep measures between BDZs abusers and controls. Drug Addiction Unit (Institute of Psychiatry) and Unit of Sleep Disorders (Institute of Neurology) of the Catholic University in Rome. Six outpatients affected by chronic BDZ abuse were enrolled, (4 men, 2 women, mean age 53.3 ± 14.8, range: 34-70 years); 55 healthy controls were also enrolled (23 men, 32 women, mean age 54.2 ± 13.0, range: 27-76 years). All patients underwent clinical evaluation, psychometric measures, ambulatory polysomnography, scoring of sleep macrostructure and microstructure (power spectral fast-frequency EEG arousal, cyclic alternating pattern [CAP]), and heart rate variability.

RESULTS

BDZ abusers had relevant modification of sleep macrostructure and a marked reduction of fast-frequency EEG arousal in NREM (patients: 6.6 ± 3.7 events/h, controls 13.7 ± 4.9 events/h, U-test: 294, p = 0.002) and REM (patients: 8.4 ± 2.4 events/h, controls 13.3 ± 5.1 events/h, U-test: 264, p = 0.016), and of CAP rate (patients: 15.0 ± 8.6%, controls: 51.2% ± 12.1%, U-test: 325, p < 0.001).

DISCUSSION

BDZ abusers have reduction of arousals associated with increased number of nocturnal awakenings and severe impairment of sleep architecture. The effect of chronic BDZ abuse on sleep may be described as a severe impairment of arousal dynamics; the result is the inability to modulate levels of vigilance.

Association between heart rate variability, blood pressure and autonomic activity in cyclic alternating pattern during sleep

STUDY OBJECTIVES

Cyclic alternating pattern (CAP) is frequently followed by changes in heart rate (HR) and blood pressure (BP), but the sequential associations between CAP and autonomic nerve activity have not been studied. The study aimed to reveal the precise changes in heart rate variability (HRV) during phase A of the CAP cycle.

DESIGN

Polysomnography was recorded according to the CAP Atlas (Terzano, 2002), and BP and electrocardiogram were simultaneously recorded. The complex demodulation method was used for analysis of HRV and evaluation of autonomic nerve activity.

SETTING

Academic sleep laboratory.

PARTICIPANTS

Ten healthy males.

MEASUREMENTS AND RESULTS

The increase in HR (median [first quartile - third quartile]) for each subtype was as follows: A1, 0.64 (-0.30 to 1.69), A2, 1.44 (0.02 to 3.79), and A3, 6.24 (2.53 to 10.76) bpm (A1 vs. A2 P < 0.001, A1 vs. A3 P < 0.001, A2 vs. A3 P < 0.001). The increase in BP for each subtype was as follows: A1, 1.23 (-2.04 to 5.75), A2, 1.76 (-1.46 to 9.32), and A3, 12.51 (4.75 to 19.94) mm Hg (A1 vs. A2 P = 0.249, A1 vs. A3 P < 0.001, A2 vs. A3 P < 0.001). In all of phase A, the peak values for HR and BP appeared at 4.2 (3.5 to 5.4) and 8.4 (7.0 to 10.3) seconds, respectively, after the onset of phase A. The area under the curve for low-frequency and high-frequency amplitude significantly increased after the onset of CAP phase A (P < 0.001) and was higher in the order of subtype A3, A2, and A1 (P < 0.001).

CONCLUSIONS

All phase A subtypes were accompanied with increased heart rate variability, and the largest heart rate variability was seen in subtype A3, while a tendency for less heart rate variability was seen in subtype A1.

Electrocardiogram-based sleep spectrogram measures of sleep stability and glucose disposal in sleep disordered breathing

STUDY OBJECTIVES

Sleep disordered breathing (SDB) is independently associated with insulin resistance, glucose intolerance, and type 2 diabetes mellitus. Experimental sleep fragmentation has been shown to impair insulin sensitivity. Conventional electroencephalogram (EEG)-based sleep-quality measures have been inconsistently associated with indices of glucose metabolism. This analysis explored associations between glucose metabolism and an EEG-independent measure of sleep quality, the sleep spectrogram, which maps coupled oscillations of heart-rate variability and electrocardiogram (ECG)-derived respiration. The method allows improved characterization of the quality of stage 2 non-rapid eye movement (NREM) sleep.

DESIGN

Cross-sectional study.

SETTING

N/A.

PARTICIPANTS

Nondiabetic subjects with and without SDB (n = 118) underwent the frequently sampled intravenous glucose tolerance test (FSIVGTT) and a full-montage polysomnogram. The sleep spectrogram was generated from ECG collected during polysomnography.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Standard polysomnographic stages (stages 1, 2, 3+4, and rapid eye movement [REM]) were not associated with the disposition index (D(I)) derived from the FSIVGTT. In contrast, spectrographic high-frequency coupling (a marker of stable or "effective" sleep) duration was associated with increased, and very-low-frequency coupling (a marker of wake/REM/transitions) associated with reduced D(I). This relationship was noted after adjusting for age, sex, body mass index, slow wave sleep, total sleep time, stage 1, the arousal index, and the apnea-hypopnea index.

CONCLUSIONS

ECG-derived sleep-spectrogram measures of sleep quality are associated with alterations in glucose-insulin homeostasis. This alternate mode of estimating sleep quality could improve our understanding of sleep and sleep-breathing effects on glucose metabolism.

Cyclic alternating pattern (CAP): the marker of sleep instability

Cyclic alternating pattern CAP is the EEG marker of unstable sleep, a concept which is poorly appreciated among the metrics of sleep physiology. Besides, duration, depth and continuity, sleep restorative properties depend on the capacity of the brain to create periods of sustained stable sleep. This issue is not confined only to the EEG activities but reverberates upon the ongoing autonomic activity and behavioral functions, which are mutually entrained in a synchronized oscillation. CAP can be identified both in adult and children sleep and therefore represents a sensitive tool for the investigation of sleep disorders across the lifespan. The present review illustrates the story of CAP in the last 25 years, the standardized scoring criteria, the basic physiological properties and how the dimension of sleep instability has provided new insight into pathophysiolology and management of sleep disorders.

Alterations in cyclic alternating pattern associated with phase advanced sleep are differentially modulated by gaboxadol and zolpidem

OBJECTIVE

to evaluate cyclic alternating pattern (CAP) in a phase advance model of transient insomnia and the effects of gaboxadol and zolpidem.

DESIGN

a randomized, double-blind, cross-over study in which habitual sleep time was advanced by 4 h.

SETTING

6 sleep research laboratories in US PARTICIPANTS: 55 healthy subjects (18-57 y)

INTERVENTIONS

Gaboxadol 15 mg (GBX), zolpidem 10 mg (ZOL), and placebo (PBO).

MEASUREMENTS

routine polysomnographic (PSG) measures, CAP, spectral power density, and self-reported sleep measures

RESULTS

The phase advance model of transient insomnia produced significant changes in CAP parameters. Both GBX and ZOL significantly and differentially modified CAP parameters in the direction of more stable sleep. GBX brought the CAP rate in stage 1 sleep and slow wave sleep (SWS) closer to baseline levels but did not significantly change the CAP rate in stage 2. ZOL reduced the CAP rate in stage 2 to near baseline levels, whereas the CAP rate in stage 1 and SWS was reduced substantially below baseline levels. The CAP parameter A1 index (associated with SWS and sleep continuity) showed the highest correlation with self-reported sleep quality, higher than any traditional PSG, spectral, or other self-reported measures.

CONCLUSION

disruptions in CAP produced by phase advanced sleep were significantly and differentially modulated by gaboxadol and zolpidem. The relative independence of CAP parameters from other electrophysiological measures of sleep, their high sensitivity to sleep disruption, and their strong association with subjective sleep quality suggest that CAP variables may serve as valuable endpoints in future insomnia research.

Paradoxical insomnia: the role of CAP and arousals in sleep misperception

OBJECTIVE

The relationship between CAP parameters and subjective time perception during sleep in primary insomnia was investigated.

PATIENTS AND METHODS

Data collected from all-night PSG recordings of 20 patients with a diagnosis of paradoxical insomnia (misperceptors) were compared with those of 20 normal gender- and age-matched subjects (controls). Besides sleep staging, scoring measures included CAP parameters and EEG arousals.

RESULTS

Patients and controls presented non-significant differences in the amounts of objective sleep time (464 min vs. 447 min) and objective sleep latency (9 min vs. 8 min). Compared to controls, misperceptors reported a significantly shorter time of perceived sleep (285 min vs. 461 min) and a significantly longer duration of perceived sleep latency (51 min vs. 22 min). In spite of the 11 objective awakenings, misperceptors reported only 4 subjective awakenings, while controls described 2 of the 5 objective awakenings. Arousal index (31.7/h vs. 18.6/h) and total CAP rate (58.1% vs. 35.5%) were significantly higher in misperceptors. In the sleep period between objective and subjective sleep onset, CAP rate was 64.4% in misperceptors and 45.1% in controls (p<0.002). Insomniacs showed significantly higher amounts of CAP rate in stage 1 (62.7% vs. 37.5%) and in stage 2 (53.3% vs. 33.1%), but not in slow wave sleep. CAP phase A2 subtypes were significantly increased in misperceptors (31% vs. 24%).

CONCLUSIONS

The study points out the topical role of enhanced activation and arousal instability not only in the first part of the night (mismatch between objective and subjective sleep onset) but also in the misperception of consecutive objective awakenings which are subjectively grouped together as a single prolonged event.

Cyclic alternating pattern sequences and non-cyclic alternating pattern periods in human sleep

OBJECTIVE

The CAP cycle is a module of activation (phase A) and inhibition (phase B) which repeats itself in sequences. The study aims at testing the hypothesis that the duration of CAP sequences is determined primarily by the number and not by the length of CAP cycles.

METHODS

The polysomnographic recordings of 24 normal subjects, 12 males and 12 females, ranging in age from 20 to 35 years (mean 27.8+/-7.2), were examined.

RESULTS

A total of 1053 CAP sequences were counted with an average of 43.9 sequences per night. The mean duration of CAP sequences was 2 min and 33 s. Each CAP sequence was composed of an average of 5.6 CAP cycles. All subjects presented CAP sequences lasting at least 5 min and 30s. The mean duration of CAP cycles was 26.9+/-4.1s. CAP cycles including subtypes A1 presented the highest correlation with the CAP sequence length (r=0.92; p<0.0001).

CONCLUSIONS

The progressive increase of CAP sequences length is linked to the progressive accumulation of CAP cycles.

SIGNIFICANCE

CAP sequences can be considered as strings of time-constant modules, i.e., CAP cycles, which are involved in the dynamic tailoring of sleep structure.

Small-world network organization of functional connectivity of EEG slow-wave activity during sleep

OBJECTIVE

To analyze the functional connectivity patterns of the EEG slow-wave activity during the different sleep stages and Cyclic Alternating Pattern (CAP) conditions, using concepts derived from Graph Theory.

METHODS

We evaluated spatial patterns of EEG slow-wave synchronization between all possible pairs of electrodes (19) placed over the scalp of 10 sleeping healthy young normal subjects using two graph theoretical measures: the clustering coefficient (Cp) and the characteristic path length (Lp). The measures were obtained during the different sleep stages and CAP conditions from the real EEG connectivity networks and randomized control (surrogate) networks (Cp-s and Lp-s).

RESULTS

Cp and Cp/Cp-s increased significantly from wakefulness to sleep while Lp and Lp/Lp-s did not show changes. Cp/Cp-s was higher for A1 phases, compared to B phases of CAP.

CONCLUSIONS

The network organization of the EEG slow-wave synchronization during sleep shows features characteristic of small-world networks (high Cp combined with low Lp); this type of organization is slightly but significantly more evident during the CAP A1 subtypes.

SIGNIFICANCE

Our results show feasibility of using graph theoretical measures to characterize the complexity of brain networks during sleep and might indicate sleep, and the A1 phases of CAP in particular, as a period during which slow-wave synchronization shows optimal network organization for information processing.

Regional scalp EEG slow-wave synchronization during sleep cyclic alternating pattern A1 subtypes

The levels of EEG synchronization, in the 0.25-2.5 Hz band, during the A1 subtypes of the sleep "cyclic alternating pattern" (CAP) were measured in five healthy subjects by means of the synchronization likelihood (SL) algorithm. SL was measured for seven electrode pairs (F4-F3, C4-C3, P4-P3 for the analysis of interhemispheric SL and F4-C4, C4-P4, F3-C3, and C3-P3, for the analysis of intrahemispheric SL). During the A1 CAP subtypes, SL tended to be highest between pairs of electrodes situated over different hemispheres; in particular, SL obtained from F4-F3 was the highest, followed by that of P4-P3. These results indicate that the transient high level of synchronization in the slow-wave EEG range, during the sleep A1 CAP subtypes, is a phenomenon involving mostly the anterior parts of the brain and is probably based on interhemispheric interactions, possibly mediated by transcallosal connections.

All-night EEG power spectral analysis of the cyclic alternating pattern components in young adult subjects

OBJECTIVE

To analyze in detail the frequency content of the different EEG components of the Cyclic Alternating Pattern (CAP), taking into account the ongoing EEG background and the nonCAP (NCAP) periods in the whole night polysomnographic recordings of normal young adults.

METHODS

Sixteen normal healthy subjects were included in this study. Each subject underwent one polysomnographic night recording; sleep stages were scored following standard criteria. Subsequently, each CAP A phase was detected in all recordings, during NREM sleep, and classified into 3 subtypes (A1, A2, and A3). The same channel used for the detection of CAP A phases (C3/A2 or C4/A1) was subdivided into 2-s mini-epochs. For each mini-epoch, the corresponding CAP condition was determined and power spectra calculated in the frequency range 0.5-25 Hz. Average spectra were obtained for each CAP condition, separately in sleep stage 2 and SWS, for each subject. Finally, the first 6h of sleep were subdivided into 4 periods of 90 min each and the same spectral analysis was performed for each period.

RESULTS

During sleep stage 2, CAP A subtypes differed from NCAP periods for all frequency bins between 0.5 and 25 Hz; this difference was most evident for the lowest frequencies. The B phase following A1 subtypes had a power spectrum significantly higher than that of NCAP, for frequencies between 1 and 11 Hz. The B phase after A2 only differed from NCAP for a small but significant reduction in the sigma band power; this was evident also after A3 subtypes. During SWS, we found similar results. The comparison between the different CAP subtypes also disclosed significant differences related to the stage in which they occurred. Finally, a significant effect of the different sleep periods was found on the different CAP subtypes during sleep stage 2 and on NCAP in both sleep stage 2 and SWS.

CONCLUSIONS

CAP subtypes are characterized by clearly different spectra and also the same subtype shows a different power spectrum, during sleep stage 2 or SWS. This finding underlines a probable different functional meaning of the same CAP subtype during different sleep stages. We also found 3 clear peaks of difference between CAP subtypes and NCAP in the delta, alpha, and beta frequency ranges which might indicate the presence of 3 frequency components characterizing CAP subtypes, in different proportion in each of them. The B component of CAP differs from NCAP because of a decrease in power in the sigma frequency range.

SIGNIFICANCE

This study shows that A components of CAP might correspond to periods in which the very-slow delta activity of sleep groups a range of different EEG activities, including the sigma and beta bands, while the B phase of CAP might correspond to a period in which this activity is quiescent or inhibited.

Is insomnia a neurophysiological disorder? The role of sleep EEG microstructure

Unlike other sleep disorders, such as sleep-related breathing disorders and periodic limb movement (PLM), the nature and severity of which are quantified by specific respiratory and motor indexes, no apparent organ dysfunction underlies several cases of insomnia (in particular primary insomnia), which can be objectively diagnosed only through the structural alterations of sleep. Polysomnography (PSG) investigation indicates that insomnia is the outcome of a neurophysiological disturbance that impairs the regulatory mechanisms of sleep control, including sleep duration, intensity, continuity and stability. In particular, analysis of sleep microstructure has permitted to establish that etiologic factors of different nature (including depressive disorders) exert a common destabilizing action on sleep, which is reflected in an increase of cyclic alternating pattern (CAP) rate. These premises allow us to attribute a more objective identity to insomnia, which risks otherwise to be considered as an unexplainable mental complaint. In conclusion, PSG remains the "gold standard" for measuring sleep, and especially insomnia.

The nature of arousal in sleep

The role of arousals in sleep is gaining interest among both basic researchers and clinicians. In the last 20 years increasing evidence shows that arousals are deeply involved in the pathophysiology of sleep disorders. The nature of arousals in sleep is still a matter of debate. According to the conceptual framework of the American Sleep Disorders Association criteria, arousals are a marker of sleep disruption representing a detrimental and harmful feature for sleep. In contrast, our view indicates arousals as elements weaved into the texture of sleep taking part in the regulation of the sleep process. In addition, the concept of micro-arousal (MA) has been extended, incorporating, besides the classical low-voltage fast-rhythm electroencephalographic (EEG) arousals, high-amplitude EEG bursts, be they like delta-like or K-complexes, which reflects a special kind of arousal process, mobilizing parallely antiarousal swings. In physiologic conditions, the slow and fast MA are not randomly scattered but appear structurally distributed within sleep representing state-specific arousal responses. MA preceded by slow waves occurs more frequently across the descending part of sleep cycles and in the first cycles, while the traditional fast type of arousals across the ascending slope of cycles prevails during the last third of sleep. The uniform arousal characteristics of these two types of MAs is supported by the finding that different MAs are associated with an increasing magnitude of vegetative activation ranging hierarchically from the weaker slow EEG types (coupled with mild autonomic activation) to the stronger rapid EEG types (coupled with a vigorous autonomic activation). Finally, it has been ascertained that MA are not isolated events but are basically endowed with a periodic nature expressed in non-rapid eye movement (NREM) sleep by the cyclic alternating pattern (CAP). Understanding the role of arousals and CAP and the relationship between physiologic and pathologic MA can shed light on the adaptive properties of the sleeping brain and provide insight into the pathomechanisms of sleep disturbances. Functional significance of arousal in sleep, and particularly in NREM sleep, is to ensure the reversibility of sleep, without which it would be identical to coma. Arousals may connect the sleeper with the surrounding world maintaining the selection of relevant incoming information and adapting the organism to the dangers and demands of the outer world. In this dynamic perspective, ongoing phasic events carry on the one hand arousal influences and on the other elements of information processing. The other function of arousals is tailoring the more or less stereotyped endogenously determined sleep process driven by chemical influences according to internal and external demands. In this perspective, arousals shape the individual course of night sleep as a variation of the sleep program.

Comparison of Lorazepam and Zopiclone for Insomnia in Patients with Stroke and Brain Injury

OBJECTIVES

To determine if lorazepam or zopiclone is more effective in providing a restful night of sleep and to assess the effects of these medications on cognition.

DESIGN

A randomized, double-blinded, crossover trial was performed at a tertiary care rehabilitation inpatient unit in a teaching hospital. A total of 18 brain-injured and stroke patients, aged 20-78 yrs, were administered lorazepam, 0.5-1.0 mg, orally at bedtime as needed for 7 days and zopiclone, 3.75-7.5 mg, orally at bedtime as needed for 7 days. Total sleep time and characteristics of sleep were measured. Effects on cognition were also measured using the Folstein Mini Mental Status Exam.

RESULTS

There was no difference in average sleep duration or in subjective measures of sleep. Cognition as assessed by the Mini Mental Status Exam revealed no difference in the zopiclone arm compared with the lorazepam arm.

CONCLUSION

Zopiclone is equally effective as lorazepam in the treatment of insomnia in stroke and brain-injured patients.

Ceiling and floor effects in sleep research

Ceiling and floor effects dictate that the efficacy of sleep-promoting stimuli should be proportional to the degree of pre-stimulus sleep impairment. This review addressed CF effects in polysomnographic research involving hypnotic drugs and exercise. Correlations of placebo/baseline levels of sleep with changes in sleep following hypnotic or exercise treatment were assessed across both literatures. CF effects were further addressed by comparing sleep-promoting effects of hypnotics vs exercise, after ANCOVA control for substantial baseline differences reported in studies of these stimuli. Significant correlations between placebo-baseline levels and sleep changes were observed following both hypnotic and exercise stimuli. Indeed, approximately 60% of the variance in improvement in sleep latency (SOL), wakefulness after sleep onset (WASO) and total sleep time (TST) following hypnotic treatment was associated with differences in baseline levels. ANCOVAs revealed significantly greater decreases in SOL and WASO following hypnotics compared with exercise. However, no significant difference between stimuli was found for TST, and exercise elicited a significantly greater increase in slow wave sleep. Similar results were found when a comparison between hypnotics and exercise was limited to good sleepers. The results show powerful CF influences on sleep responses to hypnotics and exercise and suggest a need for comparing these treatments in poor sleepers.

Cyclic alternating pattern and positive airway pressure titration

OBJECTIVE

To demonstrate that stability of the upper airway during continuous positive airway pressure (CPAP) titration is influenced by the microstructure of sleep as defined by the cyclic alternating pattern (CAP).

METHODS

Retrospective review of 12 CPAP titration records. The patterns of flow-limitation during CPAP at subtherapeutic pressures were characterized as 'stable' (persistent and non-progressive inspiratory flow limitation) or 'unstable' (progressive increase in inspiratory flow-limitation terminating in an arousal), and continuous periods of at least 10 min were identified. Sleep stage scoring by both conventional Rechtshaffen and Kales criteria and the CAP were done. The relationship between flow type and CAP was determined. Responses to an increase in applied pressure on flow-limitation were noted.

RESULTS

There were a total of 50 periods fulfilling the above criteria, totaling 1113 min of titration time. Thirty periods (757 min, 68% of total) showed a stable flow-limitation pattern. A total of 29/30 periods showing a stable flow pattern during sleep was scored as non-CAP, and only a single 18-min period of stable flow was scored as CAP. A total of 19/20 periods showing an unstable flow pattern was in sleep with CAP characteristics, the exception being a single 14-min period where unstable flow was noted in non-CAP. Flow-limitation was stable and non-progressive or absent during non-CAP, even at less than optimal pressures. This was noted irrespective of the presence or absence of delta sleep as scored by conventional criteria. Pressure increases during non-CAP, when the profile of the inspiratory flow was flattened, never resulted in a discernable change in the flow profile, while at least two-thirds of pressure increments during CAP periods improved flow.

CONCLUSIONS

The microstructure of sleep as determined by CAP and non-CAP have practical implications for manual pressure titration algorithms and research on upper airway physiology during sleep. The appearance of a period of non-CAP, irrespective of conventionally scored delta sleep, may falsely suggest that the CPAP is optimal or close to it. Large increases in non-CAP that may be seen during a titration night can reduce the window of opportunity for titration. Increases in CPAP should be avoided in non-CAP.

CAP variables and arousals as sleep electroencephalogram markers for primary insomnia

OBJECTIVE

Polysomnographic (PSG) measures consistently reflect poor sleep quality and effective treatment in insomniac patients.

METHODS

The PSG findings of 47 patients (18 M and 29 F, 42.5+/-10 years) meeting the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for a diagnosis of primary insomnia were compared with those of 25 age- and gender-balanced healthy subjects (controls) without sleep complaints. After one adaptation night to the sleep lab, each patient underwent two randomized double-blind PSG recordings. Twenty-four patients followed a placebo-drug sequence and 23 a drug-placebo succession. Active treatment consisted of widely used hypnotic drugs, i.e. zolpidem, triazolam, zopiclone, brotizolam. Conventional PSG measures, electroencephalogram (EEG) arousals and CAP variables (including phase A subtypes) were quantified and statistically analyzed.

RESULTS

Compared to controls, insomniac patients under placebo showed a significant increase of CAP rate, subtypes A1 and A2, EEG arousals, nocturnal wakefulness and stage 1, associated with reduced values of total sleep time and slow wave sleep (stages 3 and 4). In insomniac patients, sleep quality was significantly improved by hypnotic treatment. Compared to placebo, active medication significantly reduced CAP rate, subtypes A1 and A2, but had only marginal effects on subtypes A3 and on EEG arousals. Under hypnotic treatment total sleep time, nocturnal awakenings, stage 1 and slow wave sleep recuperated normal values. The most significant correlation between sleep quality and PSG variables was found for CAP rate (P<0.0001).

CONCLUSIONS

PSG investigation extended to CAP variables and EEG arousals can be an important procedure for the diagnosis of primary insomnia and evaluation of treatment efficacy.

Consensus on Drug Treatment, Definition and Diagnosis for Insomnia

Thirty-four experts and a literature supervisor got together in order to reach a 'consensus' regarding the definition, diagnosis and pharmacological treatment of insomnia. Insomnia is a subjective perception of dissatisfaction with the amount and/or quality of sleep. It includes difficulty in initiating or maintaining sleep or early awakening with inability to fall asleep again. It is associated with complaints of non-restorative sleep and dysfunction of diurnal alertness, energy, cognitive function, behaviour or emotional state, with a decrease in quality of life. The diagnosis is based on clinical and sleep history, physical examination and additional tests, although polysomnography is not routinely indicated. Therapy should include treatment of the underlying causes, cognitive and behavioural measures and drug treatment. Hypnotic therapy can be prescribed from the onset of insomnia and non-benzodiazepine selective agonists of the GABA-A receptor complex are the drugs of first choice. It is recommended that hypnotic treatment be maintained in cases where withdrawal impairs the patient's quality of life and when all other therapeutic measures have failed. Experience suggests that intermittent treatment is better than continuous therapy. The available data do not confirm safety of hypnotics in pregnancy, lactation and childhood insomnia. Benzodiazepines are not indicated in decompensated chronic pulmonary disease but no significant adverse effects on respiratory function have been reported with zolpidem and zopiclone in stable mild to moderate chronic obstructive pulmonary disease and in treated obstructive sleep apnoea syndrome. Data for zaleplon are inconclusive. If the patient recovers subjective control over the sleep process, gradual discontinuation of hypnotic treatment can be considered.

Noise-induced sleep maintenance insomnia: hypnotic and residual effects of zaleplon

AIMS

The primary objective of the study was to assess the residual effects of zaleplon in the morning, 4 h after a middle-of-the-night administration. The secondary objective was to investigate the effectiveness of zaleplon in promoting sleep in healthy volunteers with noise-induced sleep maintenance insomnia.

METHODS

Thirteen healthy male and female volunteers (aged 20-30 years) with normal hearing, who were sensitive to the sleep-disrupting effects of noise, participated in a double-blind, placebo- and active-drug controlled, four-period cross-over study. The subjects were permitted to sleep for 5 h (22.45-03.45 h) in a quiet environment before they were awoken. At 04.00 h they ingested 10 mg zaleplon, 20 mg zaleplon, 7.5 mg zopiclone (active control), or placebo before a second period of sleep (04.00-08.00 h), during which they were exposed to an 80 dB(A) 1 kHz pure tone pulse with an inter-tone interval of 1 s and a duration of 50 ms. The sound stimulus was stopped after 10 min of persistent sleep or after 2 h if the subject had not fallen asleep. Residual effects were assessed at 08.00 h (4 h after drug administration) using the digit symbol substitution test (DSST), choice reaction time (CRT), critical flicker fusion (CFF), and immediate and delayed free recall of a 20 word list. The data were analysed by analysis of variance. A Bonferroni adjustment was made for the three active treatments compared with placebo.

RESULTS

There were no residual effects of zaleplon (10 and 20 mg) compared with placebo. Zopiclone impaired memory by delaying the free recall of words (P = 0.001) and attenuated performance on DSST (P = 0.004) and CRT (P = 0.001), compared with placebo. Zaleplon reduced the latency to persistent sleep (10 mg, P = 0.001; 20 mg, P = 0.014) and the 20 mg dose reduced stage 1 sleep (P = 0.012) compared with placebo. Zopiclone reduced stage 1 sleep (P = 0.001), increased stage 3 sleep (P = 0.0001) and increased total sleep time (P = 0.003), compared with placebo.

CONCLUSIONS

Zaleplon (10 mg and 20 mg), administered in the middle of the night 4 h before arising, shortens sleep onset without impairing next-day performance.

Sleep in Lennox-Gastaut syndrome: the role of the cyclic alternating pattern (CAP) in the gate control of clinical seizures and generalized polyspikes

Non-rapid eye movement (NREM) sleep contains periods of arousal instability (cyclic alternating pattern or CAP) and periods of arousal stability (non-CAP). During CAP, arousal oscillates between higher (phase A) and lower (phase B) levels of activation. We evaluated the relationship between CAP and the occurrence of epileptic events, i.e. clinical seizures and generalized interictal discharges, during sleep in 10 patients with Lennox-Gastaut syndrome (LGS). The macro- and microstructure of sleep of 10 attended overnight polysomnograms were analyzed. Compared with 10 age- and gender-matched controls, patients with LGS had significantly less stage 2 and REM sleep and higher amounts of CAP rate (68% vs. 33%; P<0.0001). The number of generalized polyspike bursts per hour of sleep was highest in slow wave sleep (226.5+/-57.6) and lowest in REM sleep (3.9+/-1.5). The polyspike burst frequency was significantly greater (P<0.017) during CAP (213.2+/-60.1) than during non-CAP (100.3+/-40), and within CAP, generalized polyspikes occurred more often (P=0.005) during phase A (461.1+/-127.2) than during phase B (6.1+/-1.9). The total amount of generalized polyspike bursts identified in NREM sleep correlated positively both with the number of A phases containing at least one generalized polyspike (P=0.005) and with the mean number of polyspikes within each of these A phases (P<0.0001). Nocturnal clinical seizures occurred in 8 of the 10 patients and showed a similar trend. We conclude from our results that CAP modulates the occurrence of both clinical seizures and generalized epileptic discharges in LGS by means of a gate-control mechanism: an independent spike generator is inhibited in phase B and non-CAP and bursts with its intrinsic activity in phase A.

A double-blind comparative study of zolpidem versus zopiclone in the treatment of chronic primary insomnia

Zolpidem (10 mg/day) and zopiclone (7.5 mg/day), administered at night, were compared in a 14-day, double-blind, equivalence trial on 479 chronic primary insomniacs (zolpidem, 231; zopiclone, 248) throughout Japan, with a 1-week follow-up to assess rebound. The primary endpoint was the investigators' rating of global improvement of sleep disorders. A total of 32 patients in the zolpidem group (13.9%) and 45 patients in the zopiclone group (18.1%) withdrew from the study before the end of the treatment. In the zolpidem group, 67.9% (142/209) of patients were rated at least 'moderately improved' versus 61.6% (135/219) with zopiclone, zolpidem being at least as effective as zopiclone (90% confidence interval: -1.7, 14.3). With zolpidem, sleep onset latency improved in significantly more patients (85.8% versus 77.5%) and significantly fewer patients showed aggravated sleep onset latency relative to baseline at follow-up (4.5% versus 15.4%). Significantly fewer patients receiving zolpidem experienced drug-related adverse events (31.3% versus 45.3%), with bitter taste representing 5.8% (six of 104) of such complaints with zolpidem compared with 39.9% (69/173) with zopiclone. In conclusion, zolpidem was at least as effective as zopiclone, showed significantly less rebound on discontinuation and was better tolerated.

Comparison of the effects of zolpidem and triazolam on nocturnal sleep and sleep latency in the morning: a cross-over study in healthy young volunteers

1. Zolpidem (ZPD, 10 mg) was directly compared with triazolam (TRZ, 0.25 mg), a benzodiazepine hypnotic of a short action comparable to ZPD. The compounds were given to healthy young subjects for three nights, in a crossover design. 2. Polysomnographic data of three 150-min sections of the nights as well as the whole nights were analyzed, to clearly detect the proper effects of the very short acting hypnotics, which might be missed in the analysis of whole night. 3. Time courses were significantly different between the two compounds in the ratios (%) of stage wake (SW), stage 2 (S2), slow wave sleep (SWS) and stage REM (SR). 4. Compared to the baseline, SWS was increased by ZPD on the first night, not by TRZ. The separate analysis of the three 150-min sections revealed an increase of SWS during the first 150-min of the ZPD night, suggesting a proper action of ZPD to augment SWS. An increase of S2 and a decrease of SR were caused by TRZ, not by ZPD. However, the separate analysis indicated that ZPD might reduce SR during the first 150-min, which was cancelled by a subsequent rebound increase in the whole night analysis. 5. During the withdrawal period, TRZ, not ZPD, increased SW and SR with worsening of mood in the morning. ZPD did not affect sleep latency in the morning, while TRZ caused a trend of the reduction.

Origin and Significance of the Cyclic Alternating Pattern (CAP). REVIEW ARTICLE

This article reviews the 15 years of studies conducted on the cyclic alternating pattern (CAP), the electro- encephalogram (EEG) marker of arousal instability during sleep. Starting from the limits and drawbacks of conventional sleep parameters (macrostructure), investigation of the underground world (microstructure) is extensively carried out with particular attention to K-complexes and other arousal-related phasic events of non-rapid eye movement (NREM) sleep. The continuity between conventional and non-conventional arousals is stressed in the light of autonomic function and motor activity evidence. The similarities and differences between CAP and arousals are thoroughly illustrated as well as the putative biological bases of these phenomena. The oscillatory nature of CAP, the involvement of CAP in the modulation of EEG synchrony, the sleep-maintenance properties of CAP in response to arousing stimuli, the clinical applications of CAP parameters and the promising availability of automatic scoring systems are highlighted.

Cyclic alternating pattern (CAP) in normal sleep: polysomnographic parameters in different age groups

OBJECTIVES

The present study aimed at offering a standardized database for cyclic alternating pattern (CAP) parameters across representative ages of life.

METHODS

CAP parameters were quantified in 40 healthy sleepers and polygraphically investigated in a partially sound-proof recording chamber under a standard laboratory setting. Four age groups were investigated (teenagers: 10-19 years; young adults: 20-39 years; middle-aged: 40-59 years; elderly: 60 years). Each group included 10 subjects (5 males and 5 females). Nocturnal recordings were accomplished after adaptation to the sleep laboratory that also served to rule out the presence of sleep-related disorders. The study indicated that CAP is a natural phenomenon of NREM sleep, with specific age-related characteristics across the life cycle.

RESULTS

CAP rate in NREM sleep, defined as the percentage ratio of total CAP time to total NREM sleep time, showed a U-shape profile with minimum in young adults (31.9%), maximum in the elderly group (55.3%), and intermediate values in teenagers (43.4%) and in middle-aged subjects (37.5%). The longest duration of CAP cycles was found among the older subjects (31 s). The highest amounts of subtypes A1 were identified in teenagers (n = 261), while the highest amounts of A2 and A3 subtypes occurred in the elderly group (n = 183). Across the ages, the level of arousal mostly fluctuated in stages 1 and 3, whereas stage 4 emerged as the most stable NREM stage. Overall, stage 2 better reflected the CAP values referred to as total NREM sleep.

CONCLUSIONS

The periodic arousal fluctuations reflected by CAP are a natural phenomenon of NREM sleep with specific age-related variations across the life cycle.