Sleep related breathing disorders in older men: A search for underlying mechanisms

—The incidence of sleep-related breathing disorders (SRBDs) associated with hemoglobin desaturation was determined by nocturnal polygraphic evaluations in 26 healthy men, aged 55–70 years. Sixteen subjects (62%) had abnormal rates of at least 12 episodes per hour of sleep: 8 had occlusive, and 8 had central apnea or hypopnea. During waking ten of 16 SRBD subjects and only one subject without SRBDs exhibited either an elevated nasopharyngeal airway resistance (n=4) or a reduced ventilatory response to hypercapnia (n=4) and/or hypoxia (n=3). However, these abnormalities were not related to the type or severity of SRBDs, and 6 subjects with SRBDs demonstrated no respiratory defect. We conclude that SRBDs have a very high incidence in older males and are not usually secondary to pulmonary cardiac, neurological, or behavioral disorders. Additionally, we hypothesize that abnormalities in ventilatory control or upper airway resistance contribute to SRBDs, but depression of brain stem reticular formation activity during sleep plays a primary role in these disorders. Factors related to both aging and SRBDs are reviewed. These include reduced chemoreceptor responses, altered steroid hormone metabolism, and use and metabolism of hypnotic drugs and alcohol.     

Scalp topography of the spontaneous K-complex and of delta-waves in human sleep

Objective: Together with spindles, K-complexes are well known hallmarks of stage 2 sleep (S2). However, little is known about their topographical distribution in comparison to delta-waves and to K-complexes superimposed by spindles. Patients and methods: In this study, the topographical distribution of spontaneous K-complexes and delta-waves in S2 and delta-waves in stage 4 sleep (S4) in 10 healthy young adults (aged 20 to 35 years, 7 female) was investigated. K-complexes with and without spindles in S2, delta-waves with and without spindles in S2, and delta-waves in S4 distributed all over the night were visually selected. EEG power maps and statistical parametric maps were calculated. Results: Absolute delta power of S2 K-complexes appeared to be significantly higher than of S2 delta-waves and delta power of S4 delta-waves was higher than of S2 delta-waves. In K-complexes and delta-waves, power was found to be highest over medio-frontal regions in the delta frequency band (0.5 - 4.0 Hz) with a second maximum occipitally in delta-waves, no matter whether superimposed by a spindle or not. Conclusion: K-complexes and delta-waves in S2 differ in topographical distribution. Even though in S2 delta-waves have less power, they have a similar topographical distribution in S2 and S4, supporting the hypothesis that delta-waves in S2 further develop towards delta-waves in slow wave sleep. The delta frequency components of K-complexes and delta-waves are unaffected by spindles.     

Proportional Jerk: A New Measure of Motion as Applied to Eye Movements in Sleep and Waking

The third derivative of motion or the change in the rate of acceleration (also known as jerk) is examined in terms of its applicability to the study of psychophysiological function. An algorithm of this third derivative is presented to show that jerk can be derived from the arithmetic difference of two slopes which constitute the portion of motion being differentiated. By modifying the algorithm, a new parameter termed “proportional jerk’ or PJ is formulated whereby one slope is measured relative to the other slope; this PJ provides information about the smoothness of movement without being influenced by the velocity as is the traditional jerk measure. A practical application of the PJ to waking saccades and REMs in 11 human subjects revealed that REMs are significantly “jerkier’ or less smooth than waking calibration eye movements. Whereas the waking eye movements had a well-defined negative phase of the PJ, the REMs did not show such stereotypical behavior. This is in accord with previous work which showed that waking saccade velocity increases to a maximum and then decreases whereas REMs maintain their peak or near peak velocities for varying periods. It was suggested that PJ can be useful in detecting subtle temporal changes in the course of movements and may be used as a parameter of motion even when the absolute amplitude is unknown.     

Facial Muscle Tonus During REM and NREM Sleep

Equipment and procedures were devised for quantifying relatively noise-free recordings of low amplitude chin and lip electromyograms (EMGs) during sleep. A total of 28 REM periods were recorded from 5 young adult female Ss. Tonic EMG levels tended to decline toward their lowest level of the night beginning 5 min in advance of REM periods. With very rare exceptions, the lowest EMG levels of the night were maintained throughout REM sleep. During the 20 min of NREM sleep which followed REM periods, mean EMG levels increased over the REM levels but were lower than those recorded during the 20 min of NREM sleep which preceded the REM periods. This pattern of tonic EMG variation obtained for each of the first 3 REM periods of the night.     

QUANTIFICATION OF THE REM SLEEP CYCLE AS A RHYTHM

The goal of this study was to develop an objective quantitative method for representing the temporal organization of sleep in terms of the period and rhythmicity of REM sleep occurrences. Data on normative human sleep, already scored for stage REM and not stage REM, were subjected to a “binary autocorrelation.” The mean period over 92 nights of sleep for 10 Ss was 101.5 min and quite stable. Data is also presented on variability of the rhythm in terms of an “index of rhythmicity.” Measures of temporal organization may prove to be as significant for sleep research as amount of the various sleep stages.     

基诺族睡眠状况调查及分析

目的:了解基诺族睡眠的一些基本情况、失眠症的发生率和治疗情况.方法:使用自拟的"基诺族睡眠情况调查表",通过入户调查和现场访谈对126名基诺族人进行调查.结果:随年龄增长基诺族人的睡眠时间渐减少.<30岁年龄组有午睡习惯的比例高于30岁以上年龄组,差异有统计学显著性.34.12%(43人)符合失眠症诊断,失眠原因以各种精神疾病(41.86%)和酒依赖(30.23%)最为常见.失眠患者中, 就诊率为25.58% (11例).结论:基诺族睡眠的基本情况与国内其他人群相比有一些共同之处;失眠发生率较高,但由于本研究样本量和样本选择的不足,此结果还需进一步证实.     

All night spectral analysis of EEG sleep in young adult and middle-aged male subjects

The sleep EEGs of 9 young adult males (age 20–28 years) and 8 middle-aged males (42–56 years) were analyzed by visual scoring and spectral analysis. In the middle-aged subjects power density in the delta, theta and sigma frequencies were attenuated as compared to the young subjects. In both age groups power density in the delta and theta frequencies declined from NREM period 1 to 3. In the sigma frequencies, however, no systematic changes in power density were observed over the sleep episode. In both age groups the decay of EEG power (0.75–7.0 Hz) over successive NREM-REM cycles and the time course of EEG power during NREM sleep was analyzed. The decay rate of both EEG power density over successive NREM-REM cycles and EEG power density during NREM sleep was smaller in the middle-aged subjects than in the young subjects. It is concluded that the age-related differences in human sleep EEG power spectra are not identical to the changes in EEG power spectra observed in the course of the sleep episode. Therefore age-related differences in EEG power spectra cannot be completely explained by assuming a reduced need for sleep in older subjects. The smaller decay rate of EEG power during NREM sleep in the middle-aged subjects is interpreted as a reduced sleep efficiency. The results are discussed in the frame work of the two-process model of sleep regulation.     

The effects of age and gender on sleep EEG power spectral density in the middle years of life (ages 20-60 years old)

The effects of age and gender on sleep EEG power spectral density were assessed in a group of 100 subjects aged 20 to 60 years. We propose a new statistical strategy (mixed-model using fixed-knot regression splines) to analyze quantitative EEG measures. The effect of gender varied according to frequency, but no interactions emerged between age and gender, suggesting that the aging process does not differentially influence men and women. Women had higher power density than men in delta, theta, low alpha, and high spindle frequency range. The effect of age varied according to frequency and across the night. The decrease in power with age was not restricted to slow-wave activity, but also included theta and sigma activity. With increasing age, the attenuation over the night in power density between 1.25 and 8.00 Hz diminished, and the rise in power between 12.25 and 14.00 Hz across the night decreased. Increasing age was associated with higher power in the beta range. These results suggest that increasing age may be related to an attenuation of homeostatic sleep pressure and to an increase in cortical activation during sleep.     

SLEEP CYCLES AND SKIN POTENTIAL IN NEWBORNS STUDIED WITH A SIMPLIFIED OBSERVATION AND RECORDING SYSTEM

A simple visual observation system, supplemented by measurement of skin potential, was devised for developmental studies of sleep cycles in settings where multiple electrode placement is not practicable. The findings replicated essential features of quiet and active sleep cycles which had been reported previously to exist against the background of decreasing level of physiological arousal, as sleep proceeds. Twelve newborns showed approximately one-half of their inter-feeding sleeping time in the rapid eye movement stage of sleep. Skin potential rapidly declined from the waking level, continued to decrease in level throughout sleep, increased in variability during REM sleep, and increased in level at the second waking period.     

Differential effects of two types of environmental novelty on activity and sleep in BALB/cJ and C57BL/6J mice

Change in the sleeping environment can produce significant alterations in sleep. To determine how these alterations may vary with the amount of change and the relative reactivity of the sleeper, we examined the influences of environmental novelty on sleep in two mouse strains that differ in behavioral anxiety. Mice [BALB/cJ (n=7) and C57BL/6J (n=8)] were implanted for recording EEG and activity via telemetry. Following baseline data collection, activity and sleep were examined over 46 h after routine cage change, after placing a simple novel object (PVC Tee) in the home cage, and after handling controls. Mice of both strains showed immediate increases in activity and decreases in rapid eye movement sleep (REM) and non-REM (NREM) after cage change and novel object. Within strain, changes in activity and sleep were greater after cage change than after novel object. Changes in activity and sleep time were significantly correlated in each strain. Compared to C57BL/6J mice, BALB/cJ mice exhibited greater and longer duration initial reductions in sleep time, and greater increases in EEG slow wave activity power after cage change and novel object, but these changes were not followed with subsequent increases in sleep time. In contrast, C57BL/6J mice showed significantly greater subsequent increases in sleep time following the initial reductions induced by both manipulations. The results suggest that initial decreases and subsequent increases in sleep time are related to putative differences in the intensity of environmental novelty (cage change>novel object) and to previously described strain differences in anxiety (BALB/cJ>C57BL/6J).