Investigations concerning the temporal organization of the sleep/wake cycle (SWC) in healthy active elderly, specially focusing possible relationships between regular daily routines, sleep fragmentation and sleep quality in aging are still scarce. We studied the SWC of 23 healthy active elderly (65-76 years old) of both sexes (15 female, 8 male), engaged in an exercise program for old people, considering that physical exercise sessions could represent a strategy for keeping structured daily routines. We report the relationships between SWC characteristics and performance of physical exercises viewed as time cues. We collected SWC data by means of sleep logs and data about light exposition by means of actigraphy during 23 consecutive days. Individuals who chose earlier times for exercising showed longer exposition to natural bright light and reported better sleep quality. Indications that physical exercises could be beneficial upon sleep were scarce (better subjective sleep quality). Strength of semicircadian component of the SWC was greater for subjects who exercised longer, suggesting they have advantageously used naps as part of their active and healthy lifestyle, and indicating the need for studying more closely the temporal organization of naps.

Sleep Research Online

The P1/P50 midlatency auditory evoked potential is a sleep state-dependent waveform present during waking and rapid eye movement (REM) sleep and absent during slow-wave sleep. The P50 potential was studied in normal male and female subjects of various ages including post-pubertal adolescents (12-19 yrs), young adults (24-39 yrs), middle-aged adults (40-55 yrs) and older adults (55-78 yrs). There were no statistically significant differences in the mean peak amplitude or mean peak latency of the P50 potential between males and females or between age groups. Using a paired stimulus paradigm, the degree of sensory gating of the P50 potential was tested at three different interstimulus intervals (ISIs), 250, 500 and 1000 msec. There were no statistically significant differences in the sensory gating of the P50 potential between males and females. However, there was a significant decrease in sensory gating of the P50 potential in the adolescent group compared to each of the other age groups at the 250 msec ISI, but not at the 500 or 1000 msec ISI. These results suggest the presence of decreased sensory gating in normal adolescents compared to normal, older age groups.

Sleep Research Online

Cluster headaches (CH) frequently recur at the same point in the circadian cycle, often during sleep. They may, in some cases, represent a susceptible individual's response to hypoxemia or other physiological changes induced by obstructive sleep apnea (OSA). If and when this mechanism exists, timing of CH close to the onset of sleep-and therefore OSA-might be expected. We questioned 36 subjects with CH about the times at which their CH usually occurred and about several symptoms known to be predictive of OSA, including habitual snoring, loud snoring, observed apneas and excessive daytime sleepiness. We then used logistic regression to determine whether occurrence of CH in each of six time periods was associated with OSA symptoms. The 23 subjects (64%) who reported CH in the first half of a typical night's sleep also tended to report headaches during the midday/afternoon period. Symptoms of OSA, and in particular habitual snoring, were predictive of both first-half-of-the-night and midday/afternoon CH (p<.05). Thirty-one subjects (86%) reported that their CH were sleep-related, usually occurring during any part of the night or on awakening, but symptoms of OSA were not predictive of this timing pattern. In short, several OSA symptoms showed an association with CH occurrence in the first half of the night but not with sleep-related CH in general. These findings suggest that in some patients, physiological consequences of OSA may trigger CH during the first few hours of sleep and thereby influence the timing of subsequent daytime headaches.

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The squirrel monkey (Saimiri sciureus) exhibits a robust daily rhythm of sleep-wakefulness that is under circadian control, but the nature of homeostatic sleep regulation in this diurnal primate is poorly understood. Since delta frequency (0.5-2.0 Hz) activity in the electroencephalogram (EEG) during non-Rapid Eye Movement (NREM) sleep is thought to reflect homeostatic factors contributing to sleep tendency, we measured EEG delta power density and slow wave incidence and amplitude during NREM sleep during spontaneous sleep, occurring when monkeys were housed undisturbed in a 24-hour light-dark (LD) cycle and in constant light (LL). In LD and LL conditions, monkeys exhibited circadian rhythms in delta power density, wave incidence and wave amplitude that peaked in the middle of the subjective night, several hours after consolidated sleep onset. These results differ from predictions of a purely homeostatic model of sleep that would include maximal levels of delta activity at sleep onset.

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The role, if any, of exercise training in the management of individuals with obstructive sleep apnea syndrome (OSAS) is unclear. Anecdotally, patients have reported improvement in symptoms with regular participation in an exercise regime. In this study, we evaluated the effects of an exercise training program and weight loss on physical and subjective measures associated with OSAS. Nine subjects with mild to moderate OSAS completed a six month supervised exercise program. Pre and post-training measures on polysomnographic testing, physical training, anthropometric measures, quality of life (QOL), daytime somnolence and mood states were assessed. A significant decrease in the AHI (p=0.002) was noted along with improvements (p<0.05) in total sleep time, sleep efficiency, number of awakenings/hour, arousals/hour, apnea index and mean exercise training workloads. Significant decreases (p<.001) in weight (-6.2 kg) and body mass index (-1.6) were observed. Evaluation of QOL measures by the Health Status Questionnaire, Profile of Mood States and Epworth Sleepiness Scale showed significant changes in health status, affective state, and a decrease in daytime somnolence. Regular exercise training had a positive impact on the AHI, aerobic capacity, body mass index and QOL. However, exercise training alone was not an adequate intervention strategy for most individuals with OSAS but may serve well as an adjunct treatment strategy in the conservative management of individuals with mild to moderate OSAS.

Sleep Research Online

This study investigated the effects of a short afternoon nap (<30 min) in the elderly on subjective mood, performance and electroencephalograms (EEG). Ten healthy elderly persons who habitually napped in the afternoon three or more times a week participated in the present study. They participated in two experimental conditions with an interval of more than five days. In the nap condition, the participants went to bed at 13:00 hours and slept for 30 min, whereas they just had a rest while watching television in the no-nap condition. In both conditions, subjective sleepiness, fatigue, performance and EEG activities with eyes opened and closed were repeatedly measured before and after the nap or rest. The nap significantly reduced subjective sleepiness and fatigue in the afternoon. It also improved performance levels and EEG theta, alpha 1 or alpha 2 band activities with eyes opened and closed. These findings suggest that a short afternoon nap is useful for the elderly in maintaining their daytime psychological, behavioral and physiological arousal at an adequate level.

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The changes in sleep-wakefulness were studied in rats during their exposure to different ambient temperatures of 18°C, 24°C and 30°C, before and after the destruction of the medial preoptic area neurons by N-Methyl D-aspartic acid. In normal rats, there was an increase in paradoxical sleep and slow wave sleep and a decrease in wakefulness at higher ambient temperatures. The increase in sleep was primarily due to an increase in the duration of sleep episodes. Destruction of the medial preoptic area neurons produced a decrease in sleep at all three different ambient temperatures. But, there was a linear increase in sleep with higher temperatures in the lesioned rats that was qualitatively different from that in the normal animals, as the increase in sleep was associated with an increase in the number of short duration slow wave sleep episodes. The findings indicate that the medial preoptic area is essential for sleep maintenance and improving the quality of sleep with higher ambient temperatures. It is possible that the medial preoptic area serves as a fine-tuning mechanism to regulate sleep for energy homeostasis, including thermoregulation.

Sleep Research Online