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Frequent sleep disturbances and desaturation during sleep are common at high altitude, but few data are available from the highest altitudes at which humans are known to sleep. Because sleep fragmentation at low altitude may impair mental function and oxygen deprivation produces lasting central nervous system abnormalities, a better understanding of the severity of sleep disturbances and oxygen desaturation at extreme altitudes is important. The purpose of this study was to determine the severity of sleep disturbance and the extent of arterial oxygen desaturation at extreme simulated altitude. Out of eight healthy male subject volunteers who started, five aged 27.2 +/- 1.5 yr completed the study during 6 weeks of progressive hypobaric hypoxia in a decompression chamber. The men were studied at barometric pressures of 760, 429, 347, 282 mm Hg and following return to 760 mm Hg. All demonstrated frequent nighttime awakenings (37.2 awakenings per subject per night at 282 mm Hg, decreasing significantly to 14.8 on return to sea level, p less than 0.05). Total sleep time decreased from 337 +/- 30 min at 760 mm Hg to 167 +/- 44 min at 282 mm Hg (p less than 0.01). Rapid eye movement (REM) sleep decreased from 17.9% +/- 6.0% of sleep time at sea level to 4.0% +/- 3.3% at 282 mm Hg (p less than 0.01). Sleep continuity as reflected by brief arousals increased from 22 +/- 6 arousals per hour of sleep at sea level to 161 +/- 66 arousals per hour at 282 mm Hg (p less than 0.01). All subjects showed arterial oxygen desaturation proportional to the altitude. The average oxygen saturation (SaO2) was 79% +/- 3% at 429 mm Hg, 66% +/- 6% at 347 mm Hg, and 52% +/- 2% at 282 mm Hg. Sleep stage had only a minimal effect on SaO2 at any altitude. SaO2 was negatively correlated with brief sleep arousals, r = -0.72, p less than 0.01. All subjects demonstrated periodic breathing with apneas throughout much of the night at 347 and 282 mm Hg. These data indicate that sleep quality progressively worsens as SaO2 decreases despite lack of progressive changes in sleep stages at altitude. This study extends previous information on the severity of desaturation during sleep, and suggests that improvements in oxygenation might prove beneficial in restoring consolidated sleep, possibly even improving daytime performance.

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Performance on a simple addition task was measured during three schedules of frequent sleep disruption for 2 nights. Five young adults had their sleep briefly disturbed for 2 nights in 3 separate weeks either every 1 min, every 10 min, or at sleep onset after an undisrupted 2.5-h sleep period. Subjects were required to perform a two-number, two-digit addition problem as rapidly as possible on awakening. Main effects were found for sleep disruption condition and time of night, and a significant interaction between the two was also observed. Latency to response was longest for the 10-min condition on night 1, on night 2, however, response latencies were longest in the 1-min condition. Response latencies were fastest in the 2.5-h condition for both nights of disruption. Arousal thresholds were also gathered across both nights. Arousal thresholds were consistently the highest in the 1- and 10-min conditions for both nights of disruption, reaching maximum threshold levels at the end of night 1. Arousal threshold was significantly positively correlated with response latency. Sleep stages (slow-wave sleep (SWS), SWS + REM (SWSR), and total sleep time minus stage 1 sleep) were poor predictors of performance changes across the 2 disruption nights. The data were best explained by sleep continuity theory, which posits that a period of at least 10 min of uninterrupted sleep is required for restoration to take place.

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Background: There are validated measures assessing insomnia and disturbed sleep, but few psychometrically sound instruments to assess perceptions of the restorative or inadequate properties of sleep are available. Study Objectives: To develop and evaluate a new instrument, the Restorative Sleep Questionnaire (RSQ). Design and Setting: Focus groups were conducted using participants with and without nonrestorative sleep complaints. Questions were designed to elicit the feelings and experiences people have about their sleep and their view of daytime consequences of sleep. Expert panels confi rmed the importance of nonrestorative sleep (NRS) as a frequently encountered problem either with or without other sleep complaints. The resulting RSQ was administered in three studies: (1) a telephone interview with healthy controls and individuals with sleep problems; (2) a randomized clinical trial of patients with primary insomnia assessed by polysomnography (PSG); (3) a PSG study of subjects with NRS complaints. Measurement and Results: Across all studies, the new measures were shown to be signifi cantly correlated with health-related quality of life (HRQL) domains hypothesized to be related to NRS. The RSQ had good psychometric properties (α > 0.90; r test-retest > 0.80), and factor analysis confi rmed the unidimensionality of the measure. The RSQ was able to distinguish between healthy controls, patients with primary insomnia, and insomnia patients with isolated NRS complaints but without PSG defi ned sleep onset, duration, or maintenance problems. Normal sleepers reported sleep that was about a standard deviation more restorative than that of those with NRS on the RSQ. Conclusions:The results of the study provide support for the reliability and validity of the RSQ as a measure of NRS in subjects with and without self-reported or PSG confi rmed sleep initiation and maintenance diffi culties. ClinicalTrials.gov Identifi ers: NCT00655369; NCT00705601

Simplex and nonsimplex models containing personality and perceived environment variables as predictors of current use of alcohol, marijuana, and other drug use were compared in this reanalysis of data reported in a study by Potvin and Lee (1980). Contrary to the results given in the original study, we found that a nonsimplex pattern of relations among different forms of drug use allowed for a more adequate representation of the data than a simplex model for two of the three different age groups of adolescents sampled. Conformity-commitment and religiousness had consistent negative effects on drug use in each sample; parental support-affection and parental approval of friends tended to have small negative effects on drug use; self-esteem and alienation were unrelated to drug use. In general it appears that a nonsimplex model of current drug use provides a more adequate representation of the data than does a simplex model and that religiousness and conformity-commitment are constraining influences on adolescent involvement in drug use.