SLEEP

Deurveilher, Samuel; Hars, Bernard; Hennevin, Elizabeth

doi: 10.1093/sleep/20.8.593pmid: N/A

SummaryIt has been repeatedly shown in cats that acute administration of carbachol into the pontine reticular formation (PRF) readily evokes a state that closely mimics natural paradoxical sleep (PS). Surprisingly, there are few corresponding studies in rats. In order to further characterize the effects of pontine carbachol in rats, 151 injections of different doses (from 3 μg to 0.005 μg in 0.1 μl saline) of carbachol were made at different sites . within the PRF of 70 rats. Sleep-waking states obtained in the 4 hours following carbachol administration were compared to control values, obtained both under baseline condition (no injection) and following pontine injection of 0.1 μl saline. On the one hand, from the whole set of carbachol injections, it appeared that: 1) most injections (112/151) did not significantly alter the sleep—wake states; 2) when carbachol was effective, it induced either increased PS (20 injections) or increased waking (19 injections); and 3) effective injection sites were intermingled with noneffective sites. Dose- or site-dependency effects can account in part, but not totally, for these discordant results. On the other hand, in accordance with previous rat studies, we found that: 1) the PRF medial and ventral to the motor trigeminal nucleus was the most effective region for carbachol to increase PS; 2) carbachol-induced PS enhancement was of moderate magnitude ( + 60% above control saline level over the 4-hour recording time); 3) latency to onset of the first PS episode was not shortened; and 4) only the number of PS episodes was increased, their duration was not prolonged. These characteristics of carbachol-induced PS enhancement strongly differ, both in terms of magnitude and timing, from those described in cats. We suggest that the less reliable and weaker effects of pontine carbachol injection in rats compared to cats can be due to methodological problems inherent in the intracerebral microinjection technique and also to species-related differences in the mechanisms controlling the PS state.

Young, Terry; Blustein, Joseph; Finn, Laurel; Palta, Mari

doi: 10.1093/sleep/20.8.608pmid: 9351127

SummaryStudies have consistently shown that sleep apnea patients have high accident rates, but the generalizability of the association beyond clinic populations has been questioned. The goal of this investigation was to determine if unrecognized sleep-disordered breathing in the general population, ranging from mild to severe, is associated with motor vehicle accidents. The sample comprised 913 employed adults enrolled in an ongoing study of the natural history of sleep-disordered breathing. Sleep-disordered breathing status was determined by overnight in-laboratory polysomnography and motor vehicle accident (MVA) history was obtained from a statewide data base of all traffic violations and accidents from 1988 to 1993. Men with five or more apneas and hypopneas per hour of sleep [apnea-plus-hypopnea index (AHI) >5], compared to those without sleep-disordered breathing, were significantly more likely to have at least one accident in 5 years (adjusted odds ratio = 3.4 for habitual snorers, 4.2 for AHI 5–15, and 3.4 for AHI >15). Men and women combined with AHI >15 (vs. no sleep-disordered breathing) were significantly more likely to have multiple accidents in 5 years (odds ratio = 7.3). These results, free of clinic selection bias, indicate that unrecognized sleep-disordered breathing in the general population is linked to motor vehicle accident occurrence. If the association is causal, unrecognized sleep-disordered breathing may account for a significant proportion of motor vehicle accidents.

Kecklund, Göran; Åkerstedt, Torbjörn

doi: 10.1093/sleep/20.8.614pmid: 9351128

SummaryThe aim of the present pilot study was to study the effects of sleep in a truck berth. Experiment A included eight subjects who slept during two conditions (laboratory and in a truck berth during quiet conditions). Experiment B included two conditions (truck-berth sleep during quiet and noisy/disturbed conditions, respectively); six subjects participated. Polysomnography was recorded and ratings of sleep quality and postsleep sleepiness were made. During the truck-berth conditions, noise was continuously recorded. When two-tailed t tests were used, the results showed no significant effects (alpha level = 0.05) for any of the experiments. However, when one-tailed tests were used, experiment A showed a longer rapid eye movement (REM) latency for the truck-berth condition. Experiment B showed less-refreshing sleep for the disturbed condition (one-tailed test). The noise level was significantly higher during the disturbed condition. The results showed that electroencephalograph (EEG)-recorded sleep was not affected by sleeping in a truck, even when the truck was parked at a noisy location (truck terminal). However, considering some limitations of the experiments, for example small sample size, lack of adaptation night, etc., the present results should be interpreted with some caution and need to be replicated

Aldrich, Michael S.; Chervin, Ronald D.; Malow, Beth A.

doi: 10.1093/sleep/20.8.620pmid: N/A

SummarySince its introduction, the multiple sleep latency test (MSLT) has played a major role in the diagnosis of narcolepsy. We assessed its diagnostic value in a series of 2,083 subjects of whom 170 (8.2%) were diagnosed with narcolepsy. The sensitivity of the combination of two or more sleep onset rapid eye movement (REM) periods (SOREMPs) with a mean sleep latency of <5 minutes on an initial MSLT was 70% with a specificity of 97%, but 30% of all subjects with this combination of findings did not have narcolepsy. In some narcoleptics who had more than one MSLT, the proportion of naps with SOREMPs varied substantially from the initial MSLT to the follow-up test. The highest specificity (99.2%) and positive predictive value (PPV) (87%) for MSLT findings was obtained with the criteria of three or more SOREMPs combined with a mean sleep latency of <5 minutes, but the sensitivity of this combination was only 46%. The combination of a SOREMP with a sleep latency <10 minutes on polysomnography yielded a specificity (98.9%) and PPV (73%) almost equal to those obtained from combinations of MSLT findings, but the sensitivity was much lower. Our results suggest that the MSLT cannot be used in isolation to confirm or exclude narcolepsy, is indicated only in selected patients with excessive daytime sleepiness, and is most valuable when interpreted in conjunction with clinical findings.

Bassetti, Claudio; Aldrich, Michael S.; Quint, Douglas J.

doi: 10.1093/sleep/20.8.630pmid: 9351130

SummaryThe neuropathology of narcolepsy is unknown. Recently, Plazzi et al. (1) reported magnetic resonance imaging (MRI) abnormalities in the pontine tegmentum of three patients with long-standing idiopathic narcolepsy. Considering the localization of the neuroradiological findings in the pontine reticular formation, where rapid eye movement (REM) sleep is generated, the authors suggested a causal relationship between narcolepsy and MRI abnormalities. Frey and Heiserman, however, found pontine MRI abnormalities in only two of 12 patients with narcolepsy, both of whom had long-standing hypertension (2). Pullicino et al. noted similar pontine MRI abnormalities in patients with subcortical arteriosclerotic encephalopathy-like ischemic rarefaction of the pons (3). Thus, the changes noted by Plazzi et al. may have been caused by small-vessel disease rather than narcolepsy. To assess whether altered pontine MRI signals are a regular feature of idiopathic narcolepsy, we selected randomly from our database seven patients with narcolepsy with cataplexy. Of these seven, three agreed to have brain MRIs; their cases are described below. None had pontine MRI abnormalities.

Drewes, Asbjørn Mohr; Nielsen, Kim Dremstrup; Arendt-Nielsen, Lars; Birket-Smith, Lene; Hansen, Lene Marie

doi: 10.1093/sleep/20.8.632pmid: 9351131

SummaryThe interaction between sleep and pain has been insufficiently studied, and no experiments have investigated whether pathologic sleep patterns as seen in pain patients can be replicated experimentally by welldefined pain stimuli. An experimental model would therefore be valuable for further studies on the interaction between pain and sleep. In this study, three well-defined experimental stimuli (muscle, joint, and cutaneous pain) were applied during sleep, and the electroencephalogram (EEG) pattern was quantified.The pain stimuli were applied during slow-wave sleep in 10 healthy subjects. Using nine surface recordings, the EEG was sampled before and during pain stimuli. Frequency analysis was performed, resulting in 10 EEG features describing the responses to pain.During the muscle-pain stimulus an arousal effect was observed and a decrease in delta (0.5–3.5 Hz) and sigma (12–14 Hz) as well as increases in alpha 1 (8–10 Hz) and beta (14.5–25 Hz) activities were seen. During joint pain, however, more universal EEG changes were seen with a decrease in the lowest frequency bands [delta, theta (3.5–8 Hz) and alpha 1] and an increase in the higher frequencies [alpha 2 (10–12 Hz), sigma and beta bands]. No background EEG changes were observed during the cutaneous stimulus. There were several differences in the responses from the nine EEG channels, but no derivation seemed especially sensitive to detect the evoked changes.The study highlights the complexity of pain on the sleep EEG. The experimental model has shown that pain from different body structures, as well as signals from various EEG derivations, may give different responses in sleep microstructure.

Lammers, G. J.; Middelkoop, H. A. M.; Smilde-van den Doel, D. A.; Mourtazaev, M.; van Dijk, J. G.

doi: 10.1093/sleep/20.8.641pmid: 9351132

SummarySleep scoring of whole-night polysomnograms is labor intensive. Scoring fewer epochs saves labor at the cost of accuracy; this study investigates the trade-off between the two. Whole-night sleep measures of 12 patients with sleep apnea syndrome, 10 patients with narcolepsy, and 35 controls were first computed using conventional successive 30-second epochs. Using the resulting list of sleep stages, a variable number of epochs was skipped among remaining epochs; the measures were recomputed for the reduced lists. The Bland-Altman analysis was used to define the agreements among the sleep measures at the conventional resolution and those at the lower resolutions. Scoring one-half to one-third of the number of epochs changes the duration of sleep stages only up to 2.5% and 5%, respectively, for all groups and sleep stages. In apnea patients, rapid eye movement (REM) latency deviates <15 minutes when half of the epochs are scored. In controls and narcoleptics, much lower resolutions can be used before reaching the same level. Potential restrictions for the application of the method are discussed.

Peker, Yiiksel; Hedner, Jan; Johansson, Åke; Bende, Mats

doi: 10.1093/sleep/20.8.645pmid: 9351133

SummaryCardiovascular and pulmonary disease (CVPD) is common in patients with obstructive sleep apnea syndrome (OSAS). This retrospective study addressed the accumulated in-hospital time during 2 years prior to treatment with nasal continuous positive airway pressure (nCPAP) as compared to 2 years after initiating of nCPAP in patients with OSAS and CVPD. A cohort representing all patients (n = 88) receiving nCPAP during the period 1988–1994 at the Skövde Central Hospital, Skövde, Sweden, was studied. Data collection was based on interviews with patients as well as reviews of clinic charts. All hospitalizations and diagnostic codes by any type were thereby successfully gathered for the whole group. Six patients with confounding serious diseases were excluded from the analysis. A CVPD diagnosis (ICD-9, codes 401–435 and 490–496) was found in 54 out of 82 patients (66%), of whom 36 of 58 were nCPAP users (62%) and 18 of 24 were nonusers (75%). In 54 sleep apneics with CVPD, 31 were hospitalized acutely under one or more of these diagnostic codes during the study period of 4 years. The total number of in-hospital days due to CVPD in the nCPAP users (n = 19) before nCPAP prescription was 413 days (median 10, range 3–66) compared to 54 days (median 0, range 0–25) after nCPAP (p < 0.0001). The corresponding values for the nonuser group (n = 12) was 137 days (median 8.5, range 0–42) before and 188 days (median 9.5, range 0–47) after the nCPAP prescription (ns). We conclude that nCPAP treatment reduces the need for acute hospital admission due to CVPD in patients with OSAS. This reduction of concomitant health care consumption should be taken into consideration when assessing the cost-benefit evaluation of nCPAP therapy.

Berry, Richard B.; Gleeson, Kevin

doi: 10.1093/sleep/20.8.654pmid: 9351134

SummaryThe mechanisms by which respiratory stimuli induce arousal from sleep and the clinical significance of these arousals have been explored by numerous studies in the last two decades. Evidence to date suggests that the arousal stimulus in nonrapid eye movement sleep (NREM) is related to the level of inspiratory effort rather than the individual stimuli that contribute to ventilatory drive. A component of the arousal stimulus proportional to the level of inspiratory effort may originate in mechanoreceptors either in the upper airway or respiratory pump. Medullary centers responsible for ventilatory drive may also send a signal proportionate to the level of drive to higher centers in the brain which are responsible for arousal. Thus, the arousal stimulus may consist of multiple components, each increasing as inspiratory effort increases. The level of effort triggering arousal is an index of the arousability of the brain (arousal threshold). A deeper stage of sleep, central nervous system depressants, prior sleep fragmentation, and the presence of obstructive sleep apnea (OSA) have been observed to increase the arousal threshold to airway occlusion. Less information is available concerning the mechanisms of arousal from rapid eye movement (REM) sleep. While REM sleep is associated with the longest obstructive apneas in patients with OSA, normal human subjects appear to have a similar or lower arousal threshold to respiratory stimuli in REM compared to NREM sleep. Recent studies have challenged the assumption that the termination of all obstructive apnea is dependent on arousal from sleep. Improvements in methods to detect and quantitate changes in the cortical electroencephalogram (EEG) may better define the relationship between arousal and apnea termination. This may result in improved criteria for identifying EEG changes of clinical significance. While little is known concerning the mechanisms of arousal in central sleep apnea, arousal may play an important role in inducing this type of apnea in some patients.

Izquierdo-Vicario, Ysabel; Ramos-Platón, Maria-José; Conesa-Peraleja, Dolores; Lozano-Parra, Ana Belén; Espinar-Sierra, Javier

doi: 10.1093/sleep/20.8.676pmid: N/A