0053 Effect of Changes in Intracellular Adhesion Molecule-1 on Measures of Sleepiness and 24-hour Ambulatory Blood Pressure After 4 Months of Continuous Positive Airway Pressure

Introduction

Previous studies have shown that continuous positive airway pressure (CPAP) therapy of adults with obstructive sleep apnea (OSA) reduces circulating levels of intercellular adhesion molecule 1 (ICAM-1). ICAM-1 levels may affect daytime sleepiness and elevated blood pressure associated with OSA. Our goals were to explore associations between changes in ICAM-1 and objective and subjective measures of sleepiness, as well as 24-hour ambulatory blood pressure monitor (ABPM) parameters in adults with OSA following 4 months of CPAP treatment.

Methods

We identified 140 adults with newly diagnosed OSA in the Penn Icelandic Sleep Apnea (PISA) Study, with a mean (±SD) body mass index (BMI) of 31.5±4.2 kg/m2 and apnea-hypopnea index (AHI) of 36.8±15.3 events/hour; 83.3% were males. Plasma ICAM-1 levels, 24-hour ABPM, Epworth Sleepiness Scale (ESS), and Psychomotor Vigilance Task (PVT) measures were obtained at baseline and after 4 months of CPAP treatment. Associations between changes in natural log ICAM-1 and both sleepiness and 24-hour mean arterial blood pressure (MAP) were assessed using multivariate regression models, controlling for a priori baseline covariates of age, sex, BMI, race, site, smoking status, physical activity, use of anti-hypertensive medications, AHI and hours/night of CPAP usage.

Results

Overall, there was no significant change in ICAM-1 from baseline to follow-up among all participants after 4 months (0.027 ng/ml, p=0.52). There were no statistically significant associations between the change in ICAM-1 and change in sleepiness measures (all p>0.05) or 24-hour MAP (1.124 mm Hg, p=0.07). A nominal association between increased ICAM-1 and increased daytime MAP after 4 months was observed (1.39 mm Hg, p=0.033), although this result was not significant after correction for multiple comparisons.

Conclusion

Our results do not support changes in ICAM-1 as the biological pathway linking changes in sleepiness or ABPM following CPAP treatment of adults with OSA.

Support

P01-HL094307 (NHLBI, PI: Pack AI)

0569 Soft Palate Fat Between Lean Adults with Obstructive Sleep Apnea and Healthy Control

Introduction

Previous studies have shown that obese patients with obstructive sleep apnea (OSA) have a significantly greater percentage of fat tissue in soft palate than normal subjects. However, the influence of soft palate fat is not clear in non-obese adults with OSA. This study compared the volume of fat in the soft palate between lean adults with OSA and lean controls.

Methods

We examined soft palate fat in 21 lean OSA cases and 16 lean controls with body mass index (BMI) <25 kg/m2. All subjects underwent a magnetic resonance imaging (MRI) with three-point Dixon scan. We used volumetric reconstruction algorithms to quantify the amount of soft palate fat, which was compared between apnecis and controls. Analysis reproducibility was quantified using intraclass correlation coefficients (ICC) from repeated analyses of 20 randomly-chosen MRIs.

Results

Analysis of soft palate fat was highly reproducible, with an ICC (95% confidence interval) of 0.968 (0.923, 0.987). Lean apneics were younger than lean controls (45.3±13.0 vs. 62.1±10.4 years; p<0.0001). No significant differences between apneics and controls were observed in the average BMI (23.4±2.2 vs. 23.5 ± 2.6 kg/m2; p=0.824), the fat pads volume (4198±1728 vs. 3880±1544 mm3; p=0.646), and the proportion of males (61.9% vs. 68.8%; p=0.666). In unadjusted analyses, the lean OSA group showed significantly higher soft palate fat volume than lean controls (7605±2109 vs. 5327±1783 mm3; p=0.003). When adjusting for age, gender and BMI, no differences was observed between groups in soft palate fat volume (p=0.122) and fat pads volume (p=0.702).

Conclusion

Analysis of soft palate fat volume from Dixon MRI is highly reproducible. Our results indicate no significant difference in deposition of fat at soft palate between lean patients with OSA and lean controls when accounting for age, gender and BMI.

Support

This study is supported by National Institutes of Health Grant: 2P01HL094307-06A1. LX is supported by Young Elite Scientists Sponsorship Program of China Association for Science and Technology.

0282 Correlation Between Sleep Depth in the Right and Left Cerebral Hemispheres Following Sleep Deprivation, Restriction or Noise Exposure

Introduction

The Odds-Ratio-Product (ORP) is a highly-validated continuous index of sleep depth (range 0=deep sleep; 2.5=full wakefulness). ORP values fluctuate within this range as sleep state changes between wake and different sleep stages. In healthy non-sleep deprived adults, intra-class correlation coefficient of concurrent right vs. left ORP values (R / L coefficient) is typically >0.80. In a recent study R / L coefficient was markedly reduced in many critically-ill patients and these patients failed to be weaned from mechanical ventilation. Given the high prevalence of sleep loss in such patients we hypothesized that reduction in R/L coefficient might result from sleep loss. This retrospective EEG analysis of data from 3 independent research studies investigated if R / L coefficient decreases in pure models of sleep deprivation, restriction or noise exposure during sleep in healthy subjects.

Methods

Polysomnograms were obtained from three studies: A) 200 subjects who underwent 36 hours of total sleep deprivation; B) 21 subjects who underwent 4 consecutive nights of sleep restriction (5 hrs. / night); C) 72 subjects who were exposed to intermittent traffic noise events with maximum sound pressure levels ranging from 45–65 dB(A) for 10 consecutive nights. For study A, R / L coefficient was calculated from pre- and post-deprivation sleep studies and the two values were compared. For study B, coefficient was calculated at baseline and in each restriction night. For study C, the coefficient was calculated in each of the 10 exposure nights and the slope of the change was calculated.

Results

In study A, the coefficient decreased from 0.82±0.12 at baseline to 0.74±0.16 after sleep deprivation (p &lt 0.0001). In study B, the coefficient decreased from 0.83±0.11 at baseline to 0.75±0.15 on the 4th restriction night (p &lt 0.01). In study C, coefficient decreased at a rate of 0.003±0.001 per exposure night (p &lt 0.001).

Conclusion

The correlation between sleep depth in the right and left hemispheres deteriorates following sleep deprivation, restriction or noise-induced sleep fragmentation.

Support

NIH P50 HL060287

1020 Sleep and Glycemic Control in Adults With Long-Standing Type 1 Diabetes and Hypoglycemia Unawareness

Introduction

Nocturnal hypoglycemia is life threatening for individuals with type 1 diabetes (T1D) due to loss of hypoglycemia symptom recognition (hypoglycemia unawareness) and impaired glucose counterregulation. These individuals also show disturbed sleep, which may result from glycemic dysregulation. Whether use of a hybrid closed loop (HCL) insulin delivery system with integrated continuous glucose monitoring (CGM) designed for improving glycemic control, relates to better sleep across time in this population remains unknown.

Methods

Six adults (median age=58y,T1D duration=41y) participated in an 18-month ongoing clinical trial assessing the effectiveness of an HCL system. Sleep and glycemic control were measured concurrently using wrist actigraphs and CGM at baseline (1 week) and months 3 and 6 (3 weeks) following HCL initiation. BMI and hemoglobin A1c (HbA1c) were collected at all timepoints. Spearman’s correlations modeled associations between sleep, BMI, and glycemic control at each time point. Repeated ANOVAs modeled sleep and glycemic control changes from baseline to 3 months and to 6 months.

Results

Sleep and glycemic control indices showed significant associations at baseline and 3 months. More time-in-bed and later sleep offset related to higher HbA1c levels at baseline. Later sleep onset, midpoint and offset, and greater sleep efficiency associated with greater %time with hyperglycemia (glucose >180 mg/dL) or hypoglycemia (glucose <70 mg/dL) at baseline and 3 months. Longer sleep duration and greater sleep efficiency related to greater %time with hyperglycemia at 3 months. At 3 months, more wake after sleep onset associated with lower HbA1c levels and longer nocturnal awakenings and more sleep fragmentation associated with less glycemic variability. While both sleep and glycemic control improved from baseline to 3 and 6 months, these were not statistically significant.

Conclusion

Various dimensions of actigraphic sleep related to concurrently estimated glycemic indices indicative of poorer glycemic control and HbA1c across time in adults with long-standing T1D and hypoglycemia unawareness.

Support

This work was supported by NIH R01DK117488 (NG), R01DK091331 (MRR), and K99NR017416 (SKM).

Estimating sleep parameters using an accelerometer without sleep diary

Wrist worn raw-data accelerometers are used increasingly in large-scale population research. We examined whether sleep parameters can be estimated from these data in the absence of sleep diaries. Our heuristic algorithm uses the variance in estimated z-axis angle and makes basic assumptions about sleep interruptions. Detected sleep period time window (SPT-window) was compared against sleep diary in 3752 participants (range = 60-82 years) and polysomnography in sleep clinic patients (N = 28) and in healthy good sleepers (N = 22). The SPT-window derived from the algorithm was 10.9 and 2.9 minutes longer compared with sleep diary in men and women, respectively. Mean C-statistic to detect the SPT-window compared to polysomnography was 0.86 and 0.83 in clinic-based and healthy sleepers, respectively. We demonstrated the accuracy of our algorithm to detect the SPT-window. The value of this algorithm lies in studies such as UK Biobank where a sleep diary was not used.

Transcriptional Signatures of Sleep Duration Discordance in Monozygotic Twins

Introduction

Habitual short sleep duration is associated with adverse metabolic, cardiovascular, and inflammatory effects. Co-twin study methodologies account for familial (eg, genetics and shared environmental) confounding, allowing assessment of subtle environmental effects, such as the effect of habitual short sleep duration on gene expression. Therefore, we investigated gene expression in monozygotic twins discordant for actigraphically phenotyped habitual sleep duration.

Methods

Eleven healthy monozygotic twin pairs (82% female; mean age 42.7 years; SD = 18.1), selected based on subjective sleep duration discordance, were objectively phenotyped for habitual sleep duration with 2 weeks of wrist actigraphy. Peripheral blood leukocyte (PBL) RNA from fasting blood samples was obtained on the final day of actigraphic measurement and hybridized to Illumina humanHT-12 microarrays. Differential gene expression was determined between paired samples and mapped to functional categories using Gene Ontology. Finally, a more comprehensive gene set enrichment analysis was performed based on the entire PBL transcriptome.

Results

The mean 24-hour sleep duration of the total sample was 439.2 minutes (SD = 46.8 minutes; range 325.4-521.6 minutes). Mean within-pair sleep duration difference per 24 hours was 64.4 minutes (SD = 21.2; range 45.9-114.6 minutes). The twin cohort displayed distinctive pathway enrichment based on sleep duration differences. Habitual short sleep was associated with up-regulation of genes involved in transcription, ribosome, translation, and oxidative phosphorylation. Unexpectedly, genes down-regulated in short sleep twins were highly enriched in immuno-inflammatory pathways such as interleukin signaling and leukocyte activation, as well as developmental programs, coagulation cascade, and cell adhesion.

Conclusions

Objectively assessed habitual sleep duration in monozygotic twin pairs appears to be associated with distinct patterns of differential gene expression and pathway enrichment. By accounting for familial confounding and measuring real life sleep duration, our study shows the transcriptomic effects of habitual short sleep on dysregulated immune response and provides a potential link between sleep deprivation and adverse metabolic, cardiovascular, and inflammatory outcomes.

Running-induced anxiety is dependent on increases in hippocampal neurogenesis

Exercise, specifically voluntary wheel running, is a potent stimulator of hippocampal neurogenesis in adult mice. In addition, exercise induces behavioral changes in numerous measures of anxiety in rodents. However, the physiological underpinnings of these changes are poorly understood. To investigate the role of neurogenesis in exercise-mediated anxiety, we examined the cellular and behavioral effects of voluntary wheel running in mice with a reduction in hippocampal neurogenesis, achieved through conditional deletion of ataxia telangiectasia-mutated and rad-3-related protein (ATR), a cell cycle checkpoint kinase necessary for normal levels of neurogenesis. Following hippocampal microinjection of an adeno-associated virus expressing Cre recombinase to delete ATR, mice were exposed to 4 weeks of voluntary wheel running and subsequently evaluated for anxiety-like behavior. Wheel running resulted in increased cell proliferation and neurogenesis, as measured by bromodeoxyuridine and doublecortin, respectively. Wheel running also resulted in heightened anxiety in the novelty-induced hypophagia, open field and light-dark box tests. However, both the neurogenic and anxiogenic effects of wheel running were attenuated following hippocampal ATR deletion, suggesting that increased neurogenesis is an important mediator of exercise-induced anxiety.

Identification of craniofacial risk factors for obstructive sleep apnoea using three-dimensional MRI

The alteration of craniofacial structures has been associated with obstructive sleep apnoea (OSA). We hypothesised that: 1) a smaller mandible is a risk factor for OSA; and 2) the previously observed inferiorly positioned hyoid bone in apnoeics is associated with enlarged tongue volume. This is a case-control study using three-dimensional magnetic resonance imaging cephalometry. 55 apneics and 55 controls were matched for age, sex and race. The analysis was stratified by sex and controlled for age, race, height, neck visceral fat, skeletal type and tongue volume. We found that a 1-sd increase in mandibular length and depth were associated with decreased risk of sleep apnoea (OR 0.52, 95% CI 0.28-0.99 and OR 0.46, 95% CI 0.23-0.91, respectively) in males but not in females. Greater hyoid-to-nasion (OR 2.64, 95% CI 1.19-5.89 in males and OR 5.01, 95% CI 2.00-12.52 in females) and supramentale-to-hyoid (OR 2.39, 95% CI 1.12-5.14) in males and OR 3.38, 95% CI 1.49-7.68 in females) distances were associated with increased risk of OSA. The difference for hyoid position between apnoeics and controls was lost after controlling for tongue volume. Enlargement of tongue is likely to be the pathogenic factor for inferior-posterior positioning of hyoid. A small and shallow mandible is an independent risk factor for OSA in males but not in females.

Analysis of the QTL for sleep homeostasis in mice:Homer1ais a likely candidate

Electroencephalographic oscillations in the frequency range of 0.5–4 Hz, characteristic of slow-wave sleep (SWS), are often referred to as the delta oscillation or delta power. Delta power reflects sleep intensity and correlates with the homeostatic response to sleep loss. A published survey of inbred strains of mice demonstrated that the time course of accumulation of delta power varied among inbred strains, and the segregation of the rebound of delta power in BxD recombinant inbred strains identified a genomic region on chromosome 13 referred to as the delta power in SWS (or Dps1). The quantitative trait locus (QTL) contains genes that modify the accumulation of delta power after sleep deprivation. Here, we narrow the QTL using interval-specific haplotype analysis and present a comprehensive annotation of the remaining genes in the Dps1 region with sequence comparisons to identify polymorphisms within the coding and regulatory regions. We established the expression pattern of selected genes located in the Dps1 interval in sleep and wakefulness in B6 and D2 parental strains. Taken together, these steps reduced the number of potential candidate genes that may underlie the accumulation of delta power after sleep deprivation and explain the Dps1 QTL. The strongest candidate gene is Homer1a, which is supported by expression differences between sleep and wakefulness and the SNP polymorphism in the upstream regulatory regions.

An algorithm to stratify sleep apnea risk in a sleep disorders clinic population

Obstructive sleep apnea may lead to complications if not identified and treated. Polysomnography is the diagnostic standard, but is often inaccessible due to bed shortages. A system that facilitates prioritization of patients requiring sleep studies would thus be useful. We retrospectively compared the accuracy of a two-stage risk-stratification algorithm for sleep apnea using questionnaire plus nocturnal pulse oximetry against using polysomnography to identify patients without apnea (Objective 1) and those with severe apnea (Objective 2). Patients were those referred to a university-based sleep disorders clinic due to suspicion of sleep apnea. Subjects completed a sleep apnea symptom questionnaire, and underwent oximetry and two-night polysomnography. We used bootstrap methodology to maximize sensitivity of our model for Objective 1 and specificity for Objective 2. We calculated sensitivity, specificity, positive and negative predictive values, and rate of misclassification error of the two-stage risk-stratification algorithm for each of our two objectives. The model identified cases of sleep apnea with 95% sensitivity and severe apnea with 97% specificity. It excluded only 8% of patients from sleep studies, but prioritized up to 23% of subjects to receive in-laboratory studies. Among sleep disorders clinic referrals, a two-stage risk-stratification algorithm using questionnaire and nocturnal pulse oximetry excluded few patients from sleep studies, but identified a larger proportion of patients who should receive early testing because of their likelihood of having severe disease.

Modafinil as adjunct therapy for daytime sleepiness in obstructive sleep apnea

Patients with obstructive sleep apnea/hypopnea syndrome can experience residual daytime sleepiness despite regular use of nasal continuous positive airway pressure therapy. This randomized, double-blind, placebo-controlled, parallel group study assessed the efficacy and safety of modafinil for the treatment of residual daytime sleepiness in such patients. Patients received modafinil (n = 77) (200 mg/d, Week 1; 400 mg/d, Weeks 2 to 4) or matching placebo (n = 80) once daily for 4 wk. Modafinil significantly improved daytime sleepiness, with significantly greater mean changes from baseline in Epworth Sleepiness Scale scores at Weeks 1 and 4 (p < 0.001) and in multiple sleep latency times (MSLT) at Week 4 (p < 0.05). The percentage of patients with normalized daytime sleepiness (Epworth score < 10) was significantly higher with modafinil (51%) than with placebo (27%) (p < 0.01), but not for MSLT (> 10 min; 29% versus 25%). Headache (modafinil, 23%; placebo, 11%; p = 0.044) and nervousness (modafinil, 12%; placebo, 3%; p = 0.024) were the most common adverse events. During modafinil or placebo treatment, the mean duration of nCPAP use was 6.2 h/night, with no significant change from baseline observed between groups. Modafinil may be a useful adjunct treatment for the management of residual daytime sleepiness in patients with obstructive sleep apnea/hypopnea syndrome who are regular users of nasal continuous positive airway pressure therapy.

Central administration of a 5-HT2 receptor agonist and antagonist: lack of effect on rapid eye movement sleep and pgo waves

Serotonin (5-HT) has a role in regulating behavioral state and controlling the production of ponto-geniculo-occipital (PGO) waves, though the exact mechanism of action is not known. The most prevailing explanation is that 5-HT exerts its influence on behavioral state and PGO waves by inhibiting and disinhibiting cholinergic cells in the pedunculopontine tegmentum (PPT) and laterodorsal tegmentum (LDT), which have been implicated in their generation. Recent work in rats has demonstrated 5-HT2 receptors on most cholinergic cells in PPT/LDT. We microinfused the relatively specific 5-HT2 agonist, DOI (1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane), the relatively specific 5-HT2 antagonist, ketanserin, and the nonspecific 5-HT antagonist, methysergide, locally into the peribrachial region of PPT in cats and monitored behavioral state and PGO waves. Neither drug significantly affected behavioral state or PGO wave activity. These results suggest that 5-HT2 receptors associated with cholinergic cells are minimally involved in the control of behavioral state and, together with the recent findings of others, suggest that 5-HT may not modulate PGO wave generation via direct action on cholinergic neurons in PPT/LDT, a departure from the long-held but minimally-tested view.

Magnetic resonance imaging of the upper airway structure of children with obstructive sleep apnea syndrome

The anatomical relationships between lymphoid, bony, and other tissues affecting the shape of the upper airway in children with obstructive sleep apnea syndrome (OSAS) have not been established. We therefore compared the upper airway structure in 18 young children with OSAS (age 4.8 +/- 2.1 yr; 12 males and 6 females) and an apnea index of 4.3 +/- 3.9, with 18 matched control subjects (age, 4.9 +/- 2.0 yr; 12 males and 6 females). All subjects underwent magnetic resonance imaging under sedation. Axial and sagittal T1- and T2-weighted sequences were obtained. Images were analyzed with image-processing software to obtain linear, area, and volumetric measurements of the upper airway and the tissues comprising the airway. The volume of the upper airway was smaller in subjects with OSAS in comparison with control subjects (1.5 +/- 0.8 versus 2.5 +/- 1.2 cm(3); p < 0.005) and the adenoid and tonsils were larger (9.9 +/- 3.9 and 9.1 +/- 2.9 cm(3) versus 6.4 +/- 2.3 and 5.8 +/- 2.2 cm(3); p < 0.005 and p < 0.0005, respectively). Volumes of the mandible and tongue were similar in both groups; however, the soft palate was larger in subjects with OSAS (3.5 +/- 1.1 versus 2.7 +/- 1.2 cm(3); p < 0.05). We conclude that in children with moderate OSAS, the upper airway is restricted both by the adenoid and tonsils; however, the soft palate is also larger in this group, adding further restriction.

Magnetic resonance imaging of the upper airway in children with Down syndrome

As compared with control subjects, children with Down syndrome have different size and shape relationships among tissues composing the upper airway, which may predispose them to obstructive sleep apnea (OSA). We hypothesized that Down syndrome children without OSA have similar subclinical differences. We used magnetic resonance imaging to study the upper airway in 11 Down syndrome children without OSA (age, 3.2 +/- 1.4 yr) and in 14 control subjects (age, 3.3 +/- 1.1 yr). Sequential T1- and T2-weighted spin-echo axial and sagittal images were obtained. We found a smaller airway volume in subjects with Down syndrome (1.4 +/- 0.4 versus 2.3 +/- 0.8 cm(3) in controls, p < 0.005). Subjects with Down syndrome had a smaller mid- and lower face skeleton. They had a shorter mental spine-clivus distance (5.7 +/- 0.6 versus 6.2 +/- 0.4 cm, p < 0.05), hard palate length (3.2 +/- 0.4 versus 3.7 +/- 0.2 cm, p < 0.005), and mandible volume (11.5 +/- 3.7 versus 16.9 +/- 2.9 cm3, p < 0.0005). Adenoid and tonsil volume was significantly smaller in the subjects with Down syndrome. However, the tongue, soft-palate, pterygoid, and parapharyngeal fat pads were similar to those of control subjects. This study shows that Down syndrome children without OSA do not have increased adenoid or tonsillar volume; reduced upper airway size is caused by soft tissue crowding within a smaller mid- and lower face skeleton.

Abnormal sleep/wake cycles and the effect of environmental noise on sleep disruption in the intensive care unit

Little is known about sleep/wake abnormalities in intensive care and less is known about the mechanisms responsible for these abnormalities. We studied 22 (20 mechanically ventilated) medical intensive care unit (ICU) patients with continuous polysomnography (PSG) and environmental noise measurements for 24-48 h to characterize sleep-wake patterns and objectively determine the effect of environmental noise on sleep disruption. All 22 patients demonstrated sleep-wake cycle abnormalities. There were large variations in total sleep time (TST) with the mean total sleep time per 24-h study period of 8.8 +/- 5.0 h. Sleep-wake cycles were fragmented and nonconsolidated with a mean of 57 +/- 18% and 43 +/- 18% of the TST occurring during the day and night, respectively. Environmental noise was responsible for 11.5 and 17% of the overall arousals and awakenings from sleep, respectively. The mean noise arousal index was 1.9 +/- 2.1 arousals/h sleep.

CONCLUSIONS

(1) ICU patients are qualitatively, but not necessarily quantitatively, sleep deprived; and (2) although environmental noise is in part responsible for sleep-wake abnormalities, it is not responsible for the majority of the sleep fragmentation and may therefore not be as disruptive to sleep as the previous literature suggests.

Simultaneous assessment of ecto- and cytosolic-5'-nucleotidase activities in brain micropunches

We propose a new methodology for simultaneous assessment of ecto- and cytosolic-5'-nucleotidase that can be utilized in brain to measure the activity of these enzymes in micropunches of tissues. It is based on the differential sensitivity of both enzymes to alpha,beta-methyleneadenosine 5'-diphosphate (AMP-CP) and the requirements for magnesium as a co-factor. The design of assay protocol contains an internal validation by allowing comparisons between total level of 5'-nucleotidase activity with that calculated from the sum of individual activities of the ecto- and cytosolic-5'-nucleotidases. We have applied this new approach to assess the activity of ecto- and cytosolic-5'-nucleotidase in the brain regions relevant to sleep regulation. The level of both enzymes was significantly lower in the cerebral cortex than other brain regions tested.

Activity of adenosine deaminase in the sleep regulatory areas of the rat CNS

There are data to support the notion that adenosine (ADO), a neuromodulator in the CNS, is an important regulator of sleep homeostasis. It has been demonstrated that ADO agonists and antagonists strongly impact upon sleep. In addition, the level of adenosine varies across the sleep/wake cycle and increases following sleep deprivation. Adenosine deaminase (ADA) is a key enzyme involved in the metabolism of ADO. We questioned, therefore, whether there are differences in adenosine deaminase activity in brain regions relevant to sleep regulation. We found that ADA exhibits a characteristic spatial pattern of activity in the rat CNS with the lowest activity in the parietal cortex and highest in the region of the tuberomammillary nucleus (15.0+/-4.8 and 63.4+/-28.0 nmoles/mg protein/15 min, mean+/-S.D., respectively). There were significant differences among the brain regions by one-way ANOVA (F=31.33, df=6, 123, P=0.0001). The regional differences in ADA activity correlate with variations in the level of its mRNA. This suggests that spatial differences in ADA activity are the result of changes in the expression of the ADA gene. We postulate that adenosine deaminase plays an important role in the mechanism that controls regional concentration of adenosine in the brain and thus, it is a part of the sleep-wake regulatory mechanism.

The need for a simple animal model to understand sleep

Simple animal models have allowed biologists to apply the tools of modern molecular genetics to such complex behaviors as circadian rhythms and long-term memory consolidation. The mechanisms and molecules discovered in these simple animals are evolutionarily conserved in other species, including mammals. Sleep research lacks a simple animal model because criteria based on the electroencephalogram have been met only in birds and mammals. We argue that straightforward behavioral criteria could allow the identification of a sleep-like rest state that might be useful for molecular investigations to understand the regulation and function of sleep. Candidate model systems are discussed, leading to the conclusion that several species have complementary strengths. Specifically, techniques developed for larval zebrafish can be used to visualize neural firing patterns in the living animal, and the fruit fly Drosophila melanogaster has been used successfully for molecular and genetic dissection of complex behaviors. We conclude with a hypothesis that one putative function of sleep, the optimization of neural plasticity, would also have adaptive value in simple organisms and might therefore be evolutionarily conserved.

Rest in Drosophila is a sleep-like state

To facilitate the genetic study of sleep, we documented that rest behavior in Drosophila melanogaster is a sleep-like state. The animals choose a preferred location, become immobile for periods of up to 157 min at a particular time in the circadian day, and are relatively unresponsive to sensory stimuli. Rest is affected by both homeostatic and circadian influences: when rest is prevented, the flies increasingly tend to rest despite stimulation and then exhibit a rest rebound. Drugs acting on a mammalian adenosine receptor alter rest as they do sleep, suggesting conserved neural mechanisms. Finally, normal homeostatic regulation depends on the timeless but not the period central clock gene. Understanding the molecular features of Drosophila rest should shed new light on the mechanisms and function of sleep.

The effects of trazodone with L-tryptophan on sleep-disordered breathing in the English bulldog

Obstructive sleep apnea hypopnea syndrome (OSAHS) is a prevalent disorder, for which there are no universally effective pharmacotherapeutics. We hypothesized that in OSAHS, excitatory serotoninergic influences are important for maintaining patency of the upper airway in waking, and that in sleep, reduced serotoninergic drive plays a significant role in upper airway collapse and OSAHS. The previously reported small responses in humans with OSAHS to serotoninergics may relate, in part, to study design and the drugs/doses selected. We therefore performed multitrials/dose, multidose, randomized sleep studies testing the effectiveness of a combination of serotoninergics, trazodone, and L-tryptophan, in our animal model of OSAHS, the English bulldog. Trazodone/L-tryptophan caused dose-dependent reductions in respiratory events in non-rapid-eye-movement sleep (NREMS) and rapid-eye-movement sleep (REMS). During NREMS, the respiratory disturbance index (RDI) +/- standard error was 6.3 +/- 1.4 events/h (placebo) and 0.9 +/- 0.3 (highest dose), p < 0.01. During REMS, the RDI was 31.4 +/- 6.1 events/h (placebo) and 11.5 +/- 4.3 (highest dose), p = 0.002. Trazodone/ L-tryptophan dose-dependently reduced sleep fragmentation, p = 0.03, increased sleep efficiency, p = 0.005, enhanced slow-wave sleep, p = 0.0004, and minimized sleep-related suppression of upper airway dilator activity, p < 0.02. Trazodone with L-tryptophan can treat sleep-disordered breathing (SDB) in an animal model of OSAHS; the effectiveness of this therapy may be related to increased upper airway dilator activity in sleep and/or enhanced slow-wave sleep.

Indications for positive airway pressure treatment of adult obstructive sleep apnea patients: a consensus statement

We developed a short-length document that clearly delineates a prudent approach to and criteria for reimbursement of positive airway pressure (PAP) costs for the treatment of obstructive sleep apnea (OSA). Treatment modalities for OSA with PAP include continuous positive airway pressure, bilevel or variable PAP, and autotitrating PAP. This guidance on the appropriate criteria for PAP use in OSA is based on widely acknowledged peer-reviewed studies and widely accepted clinical practice. These criteria reflect current opinion on the appropriate clinical management of OSA in lieu of data pending from the Sleep Heart Health Study and upcoming outcome studies. This document is not intended to provide a complete review and analysis of the OSA clinical literature. The key to the success of this document is to foster consensus within and outside the clinical sleep community by providing a common sense and easily understood approach to the treatment of OSA with PAP.

MRI study of regional variations of pharyngeal wall compliance in cats

Upper airway compliance indicates the potential of the airway to collapse and is relevant to the pathogenesis of obstructive sleep apnea. We hypothesized that compliance would vary over the rostral-to-caudal extent of the pharyngeal airway. In a paralyzed isolated upper airway preparation in cats, we controlled static upper airway pressure during magnetic resonance imaging (MRI, 0.391-mm resolution). We measured cross-sectional area and anteroposterior and lateral dimensions from three-dimensional reconstructed MRIs in axial slices orthogonal to the airway centerline. High-retropalatal (HRP), midretropalatal (MRP), and hypopharyngeal (HYP) regions were defined. Regional compliance was significantly increased from rostral to caudal regions as follows: HRP < MRP < HYP (P < 0.0001), and compliance differences among regions were directly related to collapsibility. Thus our findings in the isolated upper airway of the cat support the hypothesis that regional differences in pharyngeal compliance exist and suggest that baseline regional variations in compliance and collapsibility may be an important factor in the pathogenesis and treatment of obstructive sleep apnea.

Differential suppression of upper airway motor activity during carbachol-induced, REM sleep-like atonia

Microinjections of carbachol into the pontine tegmentum of decerebrate cats have been used to study the mechanisms underlying the suppression of postural and respiratory motoneuronal activity during the resulting rapid eye movement (REM) sleep-like atonia. During REM sleep, distinct respiratory muscles are differentially affected; e.g., the activity of the diaphragm shows little suppression, whereas the activity of some upper airway muscles is quite strong. To determine the pattern of the carbachol-induced changes in the activity of different groups of upper airway motoneurons, we simultaneously recorded the efferent activity of the recurrent laryngeal nerve (RL), pharyngeal branch of the vagus nerve (Phar), and genioglossal branch of the hypoglossal (XII) and phrenic (Phr) nerves in 12 decerebrate, paralyzed, vagotomized, and artificially ventilated cats. Pontine carbachol caused a stereotyped suppression of the spontaneous activity that was significantly larger in Phar expiratory (to 8.3% of control) and XII inspiratory motoneurons (to 15%) than in Phr inspiratory (to 87%), RL inspiratory (to 79%), or RL expiratory motoneurons (to 72%). The suppression in upper airway motor output was significantly greater than the depression caused by a level of hypocapnia that reduced Phr activity as much as carbachol. We conclude that pontine carbachol evokes a stereotyped pattern of suppression of upper airway motor activity. Because carbachol evokes a state having many neurophysiological characteristics similar to those of REM sleep, it is likely that pontine cholinoceptive neurons have similar effects on the activity of upper airway motoneurons during both states.

Microinjections into the pedunculopontine tegmentum: effects of the GABAA antagonist, bicuculline, on sleep, PGO waves and behavior

Neurons in the peribrachial region (PB) at the pontine border are implicated in the generation of ponto-geniculo-occipital (PGO) waves, which appear spontaneously during rapid eye movement sleep (REM) and in association with alerting behaviors during waking, as well as in the regulation of REM itself. It has been hypothesized that PGO-related bursting in a subpopulation of these neurons results from low threshold spikes triggered by phasic hyperpolarizations or by excitatory inputs reaching a steadily hyperpolarized neuron. The hyperpolarization necessary for triggering the low threshold spikes may come from local GABA neurons or from GABAergic input into PB. To test the hypothesis that antagonizing GABA would alter PGO wave generation and/or behavioral state, we microinfused, in cats, the GABAA antagonist, bicuculline, locally into PB and monitored behavior, behavioral state and PGO waves recorded in the lateral geniculate bodies. Bicuculline produced no significant alteration in PGO wave activity. In 3 cats, bicuculline produced behaviors ranging from spontaneous orienting and startle (4 cats) to flight behaviors (2 cats) and aggressiveness (2 cats), an effect probably due to diffusion into the central gray region. Thus, the results do not support a GABAA-ergic role in PB in the generation of PGO waves.

Elicited pontogeniculooccipital waves and phasic suppression of diaphragm activity in sleep and wakefulness

Fractionations are 20- to 100-ms pauses in diaphragm activity that occur spontaneously during rapid-eye-movement (REM) sleep, sometimes in association with pontogeniculooccipital (PGO) waves. Auditory stimuli can elicit fractionations or PGO waves during REM sleep, non-REM (NREM) sleep, and waking; however, their interrelationship has not been investigated. To determine whether the two phenomena are produced by a common phasic-event generator in REM sleep, we examined PGO waves and fractionations that were elicited by auditory stimuli (tones) presented to freely behaving cats across states. Tones elicited PGO waves and two types of fractionations: short-latency fractionation responses (SFRs; 10- to 60-ms latencies) and long-latency fractionation responses (LFRs; 60- to 120-ms latencies). Both a PGO wave and a SFR were elicited in 60-70% of trials across states, but each could be elicited alone. The latencies and durations of elicited SFRs were similar across states, but the latencies of elicited PGO waves in REM sleep (mean 62.5 ms) were significantly longer than in waking or NREM sleep. Elicited SFRs consistently occur with shorter latencies than do PGO waves, in contrast to spontaneous fractionations, which have a variable relationship to PGO waves and usually occur 10-40 ms after the onset of the PGO wave. The LFR then, elicited most frequently during REM sleep, resembles a spontaneous fractionation in its temporal relationship to the PGO wave and may reflect the bias toward motoneuronal inhibition characterizing REM sleep but not NREM sleep or waking. We conclude that, although PGO waves and SFRs share some features, like LFRs they probably are generated by different neuronal populations. In three cats there was no correlation between PGO waves and fractionations, whereas in one cat they were associated in REM sleep (LFRs and SFRs) and waking (SFRs only). Thus the majority of evidence argues against the existence of a common phasic-event generator in REM sleep.

Activation of a distinct arousal state immediately after spontaneous awakening from sleep

In contrast to the many neural studies into the mechanisms of sleep onset and maintenance, few studies have focused specifically on awakening from sleep. However, the abrupt electrographic changes and large brief cardio-respiratory activation at awakening suggest that a distinct, transiently aroused, awake state may exist compared to later wakefulness. To test this hypothesis we utilized the acoustic startle reflex, a standard un-conditioned reflex elicited by a sudden loud noise. This reflex is modulated under specific conditions, one being a diminution of startle when a quieter pre-stimulus is presented immediately before the loud stimulus. This pre-pulse inhibition (PPI) is used as a measure of sensorimotor gating, with smaller PPI indicating less filtering of sensory inputs and increased responsiveness to external stimuli. Eight rats with electrodes for recording sleep-wake state were studied. An accelerometer measured startle responses. The startle reflex was elicited by 115 dB, 40 ms tones. PPI was produced by 74 dB, 20 ms tones preceding the 115 dB tone by 100 ms. Responses within 100 ms were measured. Stimuli were applied either 3-10 s after spontaneous awakenings, or in established wakefulness (> 30 s). Responses to the startle stimuli alone were similar in the different awake states (P = 0.821). However, PPI was smaller at awakening from non-REM sleep compared to established wakefulness (45.4 +/- 7.5% vs. 74.3 +/- 6.1%, P = 0.0002). PPI after awakening from REM sleep (52.8 +/- 17.9%) was not significantly different than established wakefulness (P = 0.297). Reduced PPI of the startle reflex at awakening from non-REM sleep supports the hypothesis that wakefulness immediately after spontaneous sleep episodes is neurophysiologically distinct from later wakefulness and associated with reduced gating of motor responses to sensory inputs. Spontaneous activation of this distinct, transiently aroused, state upon awakening may serve a protective function, preparing an animal to respond immediately to potentially threatening stimuli.

Differential sensitivity of laryngeal and pharyngeal motoneurons to iontophoretic application of serotonin

Serotonergic neurons decrease their activity during sleep, especially rapid eye movement sleep, thereby reducing their facilitatory effect on upper airway motoneurons. The magnitude of teh sleep-related loss of tone varies among upper airway muscles (e.g., pharyngeal dilator motoneurons are more suppressed than laryngeal motoneurons). We hypothesized that these differences may be related to the sensitivity of different groups of upper airway motoneurons to serotonin. Experiments were done on decerebrate, vagotomized, paralysed and artificially-ventilated cats. Hypoglossal and laryngeal motoneurons were recorded extracellularly using five-barrel pipettes filled with: serotonin, glutamate and methysergide (serotonergic antagonist) for iontophoresis, and NaCl for recording and current balancing. All but two of the 65 hypoglossal motoneurons (45 inspiratory, 10 expiratory, 10 tonic) and 27 out of 32 laryngeal motoneurons (14 inspiratory, 18 expiratory) were excited by serotonin, and the excitation was abolished by methysergide. To compare the magnitude of the excitatory effect among distinct motoneuronal groups, we applied small ejection currents in a standardized manner (+15 nA for 3 min; 10 mM serotonin in 150 NaCl) onto spontaneously active motoneurons (13 inspiratory hypoglossal, 11 inspiratory laryngeal and 11 expiratory laryngeal). Serotonin increased the number of spikes per respiratory burst of inspiratory hypoglossal motoneurons from 19 +/- 4.0 (S.E.M.) to 35 +/- 4.8, of inspiratory laryngeal motoneurons from 44 +/- 8.3 to 55 +/- 8.8, and of expiratory laryngeal motoneurons from 23 +/- 4.8 to 33 +/- 6.2. The relative increases in activity (to 220% +/- 24, 147% +/- 23 and 148% +/- 9 of control, respectively) were significantly higher in hypoglossal than in laryngeal motoneurons. In addition, the excitatory effect developed significantly faster in hypoglossal than in laryngeal motoneurons. Methysergide reduced the spontaneous activity of about half the hypoglossal and laryngeal motoneurons to 66% +/- 5 of control. Thus, the sensitivity to the excitatory effects of serotonin varies among different pools of upper airway motoneurons. These differences correlate with the pattern of airway muscle hypotonia seen during sleep.

Serotonin at the laterodorsal tegmental nucleus suppresses rapid-eye-movement sleep in freely behaving rats

Serotonin [5-hydroxytryptamine (5-HT)] is believed to play an important inhibitory role in the regulation of rapid-eye-movement (REM) sleep. 5-HT may exert this effect on neurons of the laterodorsal tegmental (LDT) nuclei that are implicated as important in the generation of REM sleep and phasic REM events such as ponto-geniculo-occipital (PGO) waves and respiratory variability. In rat brainstem in vitro, 5-HT hyperpolarizes and inhibits the bursting properties of LDT neurons assumed to be involved in generating REM sleep and PGO waves. This study tests the hypothesis that in vivo 5-HT at the LDT nuclei suppresses REM sleep and phasic REM events. Ten rats were implanted with bilateral cannulae aimed at the LDT and with electrodes for recording the electroencephalogram, neck electromyogram, PGO waves, and diaphragm electromyogram. During REM sleep, 5-HT (100 nl; 1-1.5 mM), saline, or sham microinjections were performed; repeated microinjections were separated by approximately 1 hr. After the first microinjection, REM sleep as a percent of the total sleep time was reduced with 5-HT (mean percent REM, 19.9 +/- 2.5% for 5-HT vs 26.8 +/- 2.4% for saline; p = 0.02). REM duration was reduced by 37% with 5-HT (p = 0.01), but REM episode frequency was changed less consistently (p = 0.21), suggesting that 5-HT mainly disrupted REM sleep maintenance. Per unit time of REM sleep, 5-HT had no effect on the amount or variability of REM PGO activity (p > 0.740) or on the mean or coefficient of variation of REM respiratory rate (p > 0.11). With subsequent microinjections, the effects of 5-HT on REM sleep were similar. A dose-dependent REM sleep suppression with 5-HT was observed in five rats tested. These data suggest that in vivo 5-HT at the LDT nuclei suppresses REM sleep expression. Although 5-HT did not disproportionately reduce the occurrence of phasic events within REM, total REM phasic activity was reduced because of less REM sleep after 5-HT.

An instrument to measure functional status outcomes for disorders of excessive sleepiness

This article reports the development of the functional outcomes of sleep questionnaire (FOSQ). This is the first self-report measure designed to assess the impact of disorders of excessive sleepiness (DOES) on multiple activities of everyday living. Three samples were used in the development and psychometric analyses of the FOSQ: Sample 1 (n = 153) consisted of individuals seeking medical attention for a sleep problem and persons of similar age and gender having no sleep disorder; samples 2 (n = 24) and 3 (n = 51) were composed of patients from two medical centers diagnosed with obstructive sleep apnea (OSA). Factor analysis of the FOSQ yielded five factors: activity level, vigilance, intimacy and sexual relationships, general productivity, and social outcome. Internal reliability was excellent for both the subscales (alpha = 0.86 to alpha = 0.91) and the total scale (alpha = 0.95). Test-retest reliability of the FOSQ yielded coefficients ranging from r = 0.81 to r = 0.90 for the five subscales and r = 0.90 for the total measure. The FOSQ successfully discriminated between normal subjects and those seeking medical attention for a sleep problem (T157 = -5.88, p = 0.0001). This psychometric evaluation of the FOSQ demonstrated parameters acceptable for its application in research and in clinical practice to measure functional status outcomes for persons with DOES. Thus, the FOSQ can be used to determine how disorders of excessive sleepiness affect patients' abilities to conduct normal activities and the extent to which these abilities are improved by effective treatment of DOES.