EEG sleep patterns as a function of normal and pathological aging in man

The GABA uptake inhibitor tiagabine promotes slow wave sleep in normal elderly subjects

Aging is associated with a dramatic decrease in slow wave sleep (SWS) and sleep consolidation. Previous studies revealed that various GABA(A) agonists and the GABA uptake inhibitor tiagabine augment slow frequency components in the EEG within non-REM sleep, and thus promote deep sleep in young individuals and/or rats. In the present double-blind, placebo-controlled study, we assessed the effect of a single oral dose of 5 mg tiagabine on nocturnal sleep in ten healthy elderly volunteers (6 females). During the placebo night the subjects displayed a low sleep efficiency, due to high amounts of intermittent wakefulness, and little SWS. Tiagabine significantly increased sleep efficiency, tendentially decreased wakefulness and prominently increased both SWS and low-frequency activity in the EEG within non-REM sleep. The present findings demonstrate that tiagabine increases sleep quality in aged subjects. Moreover, the effects of tiagabine closely match those evoked by the GABA(A) agonist gaboxadol in young subjects and indicate that such compounds may have prospects in the treatment of sleep disturbances, particularly of those commonly occurring in the elderly.

Sleep spindle characteristics in healthy subjects of different age groups

OBJECTIVES

Few studies have quantified the various characteristics of sleep spindles (SS) in groups of normal human subjects. The aim of the present study was to look at the effects of age on the number, density, duration, intra-spindle frequency, and periodicity of SS during stage 2 sleep in normal subjects of different age groups.

METHODS

Thirty-six healthy subjects participated in the study. They were divided into 6 age groups: 10-19, 20-29, 30-39, 40-49, 50-59 and 60-69 years.

RESULTS

The results show that there is a progressive decrease in SS number, density, duration and a progressive increase in intra-spindle frequency with age. These changes occur mainly in the first 4 decades, except for SS number and density, for which the changes seem to continue until the sixth decade. The present study also reveals a clear periodicity of SS in human sleep. SS occur every 3-6 s, and the modal value of inter-spindle intervals increases with aging.

CONCLUSIONS

The progressive decrease in the number of SS and slow-wave sleep time with age suggests that SS are part of sleep promoting mechanisms. The negative correlation found between SS density and sleep efficiency in the present study is congruent with the sleep maintenance role of SS.

High internight reliability of computer-measured NREM delta, sigma, and beta: biological implications

BACKGROUND

Computer analysis of the sleep electroencephalogram (EEG) waveforms is widely employed, but there have been no systematic studies of its reliability.

METHODS

The most commonly used computer methods are power spectral analysis with the fast-Fourier transform (FFT) and period amplitude analysis (PAA) with zero cross or zero first derivative half-wave measurement. We applied all three computer methods to the digitized EEG of 16 normal subjects who underwent 5 consecutive nights of baseline (placebo) recording. We evaluated the internight reliability of three non-rapid eye movement (NREM) frequency bands of special importance to sleep research: delta (0.3-3 Hz), sigma (12-15 Hz), and beta (15-23 Hz).

RESULTS

Both FFT and the two methods of PAA gave excellent internight reliability for delta and sigma. Even a single night of recording correlated highly (r >.9) with the 5-night mean. Beta reliability was lower but still highly significant for both the PAA and the FFT measures.

CONCLUSIONS

Computer-analyzed sleep EEG data are highly reliable. Period amplitude methods demonstrate that wave incidence and period as well as amplitude are reliable, indicating that the reliability of composite measures (FFT power, PAA integrated amplitude) is not solely based on individual differences in EEG amplitude. The high internight stability of NREM delta indicates that it possesses traitlike characteristics and is relatively independent of day-to-day variations in state.

Effects of hypnotics on the sleep EEG of healthy young adults: new data and psychopharmacologic implications

Benzodiazepine hypnotics increase NREM sleep and alter its EEG by reducing delta (0.3-3 Hz) and increasing sigma (12-15 Hz) and beta (15-23 Hz) activity. We tested whether the nonbenzodiazepine hypnotic, zolpidem (10 mg), produced the same pattern of sleep and EEG changes as two "classical" benzodiazepines, triazolam (0.25 mg) and temazepam (30 mg). Sleep EEG of 16 subjects was analyzed with period amplitude analysis for 3 nights during drug administration or placebo. The effects of zolpidem were in the same direction but generally of smaller magnitude than those of the classical benzodiazepines. These differences are more likely the result of non-equivalent dosages than different pharmacologic actions. Period amplitude analysis showed that the decreased delta activity resulted mainly from a decrease in wave amplitude. In contrast, the increased sigma and beta activity were produced by increased wave incidence. Delta suppression increased with repeated drug administration but sigma and beta stimulation did not. While these findings have little relevance for the clinical choice of hypnotics they may hold important implications for the brain mechanisms involved in hypnotic tolerance and withdrawal delirium.

Slow-wave sleep and waking cognitive performance II: Findings among middle-aged adults with and without insomnia complaints

Previous studies showing a relationship between nocturnal slow-wave sleep (SWS) and subsequent diurnal performance among young normal sleepers and older insomnia sufferers have provided limited support for the notion that this sleep stage serves a restorative role for neurocognitive functioning. The current study, which examined the relationship between SWS and reaction time performance among middle-aged adults with and without insomnia complaints, was conducted to further explore this possibility. A sample of 31 noncomplaining middle-aged (ages 40 to 59 years) normal sleepers and a like-aged sample of 27 insomnia sufferers, provided data for the current investigation. All participants underwent nocturnal sleep monitoring immediately prior to undergoing a battery of daytime tests that measured simple reaction time, vigilance/signal detection, and complex reaction time. Results showed relationships between reaction time performances on some tasks and some SWS measures among both the normal sleepers and insomnia sufferers. Findings supported our prediction that the presence of sleep pathology (e.g., insomnia) alters the SWS-performance relationship observed, but the results failed to show a consistent relationship between SWS and subsequent performance within either sample. The findings suggest that the specific performance demands of the task in question as well as physiological parameters other than SWS may determine performance as well. Findings for this and previous studies do provide some support for the contention that the neurocognitive restorative value of SWS may change across the lifespan. Possible implications of the study's findings are discussed and directions for future research are considered.

Age-related changes in initiation and maintenance of sleep: a meta-analysis

The purpose of this meta-analysis was to determine the magnitude of change over the adult life span in four key sleep characteristics and to explore research design features that may account for variability in reported age-related sleep change. Forty-one published studies (combined N = 3293) provided 99 correlational effect sizes. Waking frequency and duration increased with age as previously concluded by narrative reviewers. Although narrative reviewers were less certain whether nighttime sleep amount or the ability to initiate sleep decreased with age, the meta-analysis suggested that both decreased. When sleep variables were measured by polysomnography rather than self-report, larger age-related changes were found. Few researchers who studied normal sleep controlled for important health moderators or studied women.

Limitations of Rechtschaffen and Kales

The guidelines of Rechtschaffen and Kales (R&K) were meant as a reference method. However, it became, unintentionally, a gold standard. The rules have never been appropriately validated. It is used for the scoring of recordings of, for instance, pathological sleep, for which it was not designed. Today R&K is an insufficient description of sleep processes. In practice, the rules are often difficult or impossible to follow and deviations are common, although not reported. The major drawbacks are: low temporal resolution, ignorance of spatial information, insufficient number of stages, low correspondence between electrophysiological activity and stages, and ignorance of other physiological parameters such as autonomous nervous system activity and body motility. The original idea of the committee should be followed; the guidelines should be revised with the accumulation of new knowledge and development of technology. This is especially true for the analysis of delta waves, which should replace visual scoring of the NREM sleep stages. Many of the problems related to the use of the manual are not due to the system itself but the way it has been applied. This has evidently had a serious impact on the way of thinking and the development of the field in general.

Slow-wave sleep and waking cognitive performance among older adults with and without insomnia complaints

Previous research has shown that healthy young adults with relatively fast reaction times on daytime testing have significantly more nocturnal slow-wave sleep than do age-matched subjects with relatively slow reaction times on such testing. The current study was conducted to examine the relationship between slow-wave sleep and cognitive performance among older adults with and without insomnia complaints. A sample of 32 noncomplaining older (age > or = 60 years) normal sleepers and a like-aged sample of 32 insomniacs, recruited to participate in a larger study, served as subjects. All subjects underwent nocturnal sleep monitoring immediately prior to undergoing a battery of daytime tests that measured simple reaction time, vigilance/signal detection, and complex reaction time. Results from the normal sleepers showed no relationship between daytime cognitive performance measures and a variety of computer-derived nocturnal slow-wave sleep measures. In contrast, insomniac subjects with relatively slow reaction times showed relative deficits in a spectral analytically derived measure of slow-wave power in the 2 to 4 Hz bandwidth. These results suggest that relative performance deficits among some older insomniacs may be related to specific slow-wave sleep deficiencies. However, among older normal sleepers, intersubject differences in performance appear unrelated to slow-wave sleep measures. Additional research is needed to further explore the possible restorative role slow-wave sleep may serve for cognitive functions other than those examined herein.

Polygraphic sleep criteria as predictors of successful aging: an exploratory longitudinal study

BACKGROUND

A cohort of 57 elderly healthy volunteers (34 male, 23 female) was studied in a sleep laboratory on four consecutive nights when their average age was 63.5 +/- 3.7 years. Thirty subjects (20 male, 10 female) were assessed 14 years later; 21 had either died in the meantime or were very ill, and 6 did not participate for other reasons.

METHODS

Two operationalizations of successful aging were applied: survival in relatively good health (30 survivors vs. 21 nonsurvivors), and cognitive competence as assessed in the survivors by means of tests of cognitive function.

RESULTS

Whereas none of the sleep characteristics determined at baseline distinguished the survivors from the nonsurvivors, several parameters [REM (rapid eye movement) sleep latency, REM density, and NREM (non-REM) shifts] were significantly correlated with one or more measures of cognitive functioning at follow-up. These polygraphic sleep parameters also distinguished a subgroup of cognitively fully competent subjects from those who, according to their performance in tests of cognitive function, could be considered as mildly demented.

CONCLUSIONS

While the REM latency and density findings support the theory of a functional link between brain cholinergic activity, timing, and density of REM sleep and cognitive functioning, the positive association between the number of NREM shifts at baseline and cognitive performance 14 years later is difficult to explain. It is suggested that the findings of the present study, in particular the potential predictive value of REM latency and REM density for cognitive functioning in the old, need replication in other subject samples followed for similar time periods.

Slow wave sleep (SWS) distribution across night sleep episode in the elderly

Slow wave sleep (SWS) distribution across night sleep was shown to be different between infants and young adults. The present research aimed at studying the SWS distribution across night sleep in elderly subjects. Nine healthy elderly subjects, 61-71 years old, were submitted to nocturnal polygraphic sleep recording. Eleven young subjects, 21-23 years old, were the control group. Recordings were visually analyzed according to Rechtschaffen and Kales rules; the method proposed by Webb and Dreblow was used for scoring SWS. An NREM-REM cycle was defined as a sequence of NREM and REM sleep not interrupted by a waking period longer than 15 minutes. SWS percentage was calculated for each successive NREM episode. No significant association between SWS percentage and cycle rank was shown in elderly subjects, whereas a significant association was observed in the young ones. This kind of SWS distribution could be interpreted as reflecting the restructuring of internal organization of sleep in the elderly.

The Pittsburgh study of normal sleep in young adults: focus on the relationship between waking and sleeping EEG spectral patterns

The effects of age and gender on spectral characteristics of the waking EEG were investigated in a large sample of young adult men and women. In addition, relationships between spectral characteristics of the waking and sleeping EEG within an individual were explored. The sample included 28 females and 33 males in two age groups: 20-29 years (n = 32), and 30-40 years (n = 29). Spectral analysis was used to quantify EEG frequency characteristics for waking EEG just prior to sleep onset, as well as for the entire sleep recording. Significant effects of age were seen in the waking EEG but only in the delta frequency range (0.5-4.5 Hz) with lower delta activity in the older group (F = 11.6, P = 0.001). No significant gender effects were found in the waking EEG. Independent of age and gender, spectral profiles in the delta, theta, alpha and beta frequency bands of a subject's waking EEG were found to be highly correlated with their sleep EEG. In addition, subjects with high voltage alpha profiles during waking were found to sleep significantly longer and deeper than those with low voltage records. Significant correlations between waking and sleep EEG suggest that the spectral signature of an individual's EEG may be found across sleep/wake states.

Changes in sleep spindle activity of subject with chronic somatosensitive and sensorial deficits. Preliminary results

We investigated the effects of the somatosensitive and sensory afferent inputs on the thalamic generators of sleep spindles (SS) in adult subjects affected by posterior funiculi lesions (five subjects), deafness (four subjects) or blindness (four subjects). The density, duration and frequency of SS, as well as the index of spindling, were analyzed during stage 2 NREM. The results show that the subjects with somatosensitive and sensorial lesions spent much more time on SS activity than the control group (eight subjects), and had a significantly increased density (< .0001), duration (< .0005) and index of spindling (< .0001). On the other hand, the frequency of spindling was little modified (< .05). Moreover, among the three groups of patients, those with somatosensitive deficits showed the greatest SS activity. In conclusion, our results suggest that the thalamic generators of SS are markedly modulated by peripheral inputs in man.

Effect of age on the sleep EEG: slow-wave activity and spindle frequency activity in young and middle-aged men

The effect of age on sleep and the sleep EEG was investigated in middle-aged men (mean age: 62.0 years) and in young men (mean age: 22.4 years). Even though the older men reported a higher number of nocturnal awakenings, subjective sleep quality did not differ. Total sleep time, sleep efficiency, and slow wave sleep were lower in the middle-aged, while stage 1 and wakefulness after sleep onset were higher. The differences in wakefulness within nonREM-REM sleep cycles was most pronounced in the third and fourth cycle. In the older men, EEG power density in nonREM sleep was reduced in frequencies below 14.0 Hz, whereas in REM sleep age-related reductions were limited to he delta-theta (0.25-7.0 Hz) and low alpha (8.25-10.0 Hz) band. Slow-wave activity (SWA, power density in the 0.75-4.5 Hz range) decreased in the course of sleep in both age groups. The between-group difference in SWA diminished in the course of sleep, whereas the difference in activity in the frequency range of sleep spindles (12.25-14.0 Hz) increased. It is concluded that frequency and state specific changes occur as a function of age, and that sleep dependent decline in SWA and increase in sleep spindle activity are attenuated with age.

Mild electrical stimulation of pontine tegmentum around locus coeruleus reduces rapid eye movement sleep in rats

The norepinephrinergic neurons in the locus coeruleus (LC) cease firing during REM sleep (REMS) and increase firing during REMS deprivation. Most of the earlier studies used lesion and transection techniques which could not confirm the role of LC in REMS generation and/or its maintenance, if at all. Hence, in this study it was hypothesized that if the LC REM-off neurons must cease firing before the onset of REMS, its continuous activation should eliminate or at least reduce REMS. Electrophysiological parameters characterizing sleep-wakefulness-REMS were recorded in freely moving male albino rats. In an attempt not to allow the REM-off LC neurons to cease firing, low intensity (200 microA), low frequency (2 Hz) rectangular (300 microseconds) pulses were continuously delivered to the LC bilaterally through chronically implanted electrodes, and the effects on sleep-wakefulness-REMS were investigated. Although the stimulation did not affect sleep state of the animals, it reduced REMS significantly. The effect on REMS was similar to that of REMS deprivation. Total duration of REMS was significantly reduced during stimulation and showed a rebound increase during the post stimulation period. This reduction in REMS duration was primarily due to a significant reduction in the REMS frequency/h while the mean REMS duration/episode was not affected. Thus, the results of this study suggest that the stimulated area (LC) affects REMS, most likely by suppression of REMS generation process.

Delay in manifestations of aging by grafting NGF cultured chromaffin cells in adulthood

Dopamine agonists or grafts compensate impaired motor functions in aged rats. However, there is no evidence showing whether grafting in adulthood retard aging manifestations. Motor performance of 13-month-old rats was tested on 2 meter-long wooden beams which had a 15 degree inclination and whose thickness varied from 3, 6, 12, 18, to 24 mm. Rats at 14 months were randomly assigned to 3 groups: sham graft (Group 1); intrastriatal graft of chromaffin cells cultured with NGF (Group 2); intrastriatal graft of chromaffin cells (Group 3). Motor performance was tested at monthly intervals up until rats were 26 months old. Two more groups were included: 26-month-old naive rats (Group 4); and 3- to 5-month-old naive rats (Group 5) both evaluated only once. At 26 months, the basal activity of ventral mesencephalic dopaminergic neurons was recorded. Results showed in Group 2 delay of motor detriments seen in aged rats, maintenance of basal firing rates of nigral cells compared to those of younger rats, and greater survival of substantia nigra cells. It is suggested that NGF cultured chromaffin cells produce a delay of motor detriments in aged rats, as a result of inducing survival and firing rates of nigral cells comparable to those seen in young rats.

Biological correlates of slow wave sleep deficits in functional psychoses: 31P-magnetic resonance spectroscopy

Deficits in slow wave sleep (SWS) are consistently seen in schizophrenia and related psychotic disorders. However, the pathophysiological significance of this finding is uncertain. In 19 patients with psychotic illness, sleep and 31P-magnetic resonance spectroscopy (MRS) studies were carried out before the patients began medication treatment. Polysomnographic studies were carried out in 2-3 consecutive nights. MRS studies were performed with a surface coil and a depth-resolved pulse sequence focusing on the dorsal prefrontal cortex. Phosphomonoesters were correlated with visually scored delta and Stage 4 sleep, as well as with automated delta wave counts. An inverse relation was also seen between negative symptoms scores and SWS. The association between decreases brain anabolic processes (reflected by decreased PME) and decreased SWS may be related either to processes of accelerated aging or to developmentally mediated alterations in cortical synaptic pruning, postulated to underlie the pathophysiology of functional psychoses.

Symposium: Cognitive processes and sleep disturbances: Sleep/wake patterns in Alzheimer's disease: relationships with cognition and function

Alzheimer's disease (AD), the most common dementing disorder of aging, is a progressive neurodegenerative disease of unknown etiology. Two of the common clinical features of AD are progressive cognitive and functional impairment, and disturbed sleep/wake patterns. We examined sleep/wake patterns and cognitive and functional status measures in a large sample of AD subjects ranging from mild to moderate-severe in impairment. All subjects survived at least 2 years after initial diagnosis. Regression analyses revealed that sleep/wake variables were highly correlated with and explained significant variance in cognitive and functional measures. More wakefulness during the night and longer REM latencies were associated with impaired cognition and function while more REM and slow-wave sleep were associated with preserved cognition and function. These results indicate that with advancing severity of the disease, sleep/wake patterns are disrupted in parallel with the disturbances in cognition and function that are the hallmarks of AD. Further, they suggest that the neural substrates underlying each process degenerate at somewhat comparable rates.

Dreams and Dementia: A Laboratory Exploration of Dream Recall and Dream Content in Chronic Brain Syndrome Patients

Seventeen (seven mild and ten severe) chronic brain syndrome patients were tested in the sleep laboratory for dream recall and content. The mildly organic patients had 57 per cent recall while the severely organic patients had 35 per cent recall. We also studied four aged severely organic patients. These patients showed a recall rate of 8 per cent.

The difference between the recall rates in mildly and severely organic middle-aged patients was not statistically significant. The difference between the recall rates of the aged severely organic patients and either or both of the middle-aged groups was statistically significant (p < .001).

In addition, we found dream content differences between the mildy and severely organic middle-aged groups and between the combined group and normal young men.

Sleep in non-institutionalized Alzheimer's disease patients

The sleep of Alzheimer's disease (AD) patients is often disturbed by medications, depression, circadian rhythm changes and sleep disorders. Institutionalization is often precipitated by the effect of the patient's sleep and wakefulness on the caregiver. We examined reports of sleep disturbance in mild AD patients. The study cohort consisted of 246 AD patients and 94 controls. Self-reports of sleep disturbance in mild AD patients were examined as was the relationship of sleep and medication use. Results were compared to those of normal controls, and the patients' responses to the reports of their caregivers. Dementia was assessed with the Mini Mental Status Exam, the Blessed Dementia Scale, the Mattis Dementia Rating Scale, and the Pfeiffer Outpatient Disability Test. The more demented the patients, the more time they spent in bed, the more fragmented their sleep, and the more naps they took. Caregivers reports of increased wandering at night and more aggressive behavior during the day were associated with increased use of sedative-hypnotics and with going to bed early. Lengthy sleep was associated with disruptive behavior. We conclude that increased sleep may be associated with dementia and with more disruptive behavior.

Prevalence of insomnia in elderly general practice attenders and the current treatment modalities

This study aimed to assess the prevalence and treatment modalities of elderly practice attenders. A total of 330 patients aged over 65 years were investigated with a questionnaire in general practice. To assess insomnia, operationalized diagnostic criteria according to DSM-III-R were applied. Twenty-three percent of the elderly patients suffered from severe, 17% from moderate and 17% from mild insomnia. More than 80% of the patients reported suffering from insomnia for 1-5 years or longer, which indicates a chronic course. Elderly patients showed unrealistic expectations concerning duration of sleep and spend more time in bed than they realistically can expect to sleep. More than half of the elderly patients reported habitual daytime napping. Sleep-disturbed elderly patients did not differ significantly from good sleepers in their habit of taking daytime naps, but even when taking daytime naps, good sleepers slept significantly longer than the sleep-disturbed patients. A significant association was found between insomnia and mental disorders, i.e., depression and organic brain syndrome according to the diagnosis of the general physician. In about half of the cases the primary care physician was not aware that the elderly patient suffered from severe insomnia. More than half of the elderly severe insomniacs took prescribed hypnotics habitually, mainly benzodiazepines.

Morning bright light therapy for sleep and behavior disorders in elderly patients with dementia

Fourteen inpatients with dementia showing sleep and behavior disorders (average age = 75 years), and 10 control elderly people (average age = 75 years) were carefully observed for 2 months. Four weeks of morning light therapy markedly improved sleep and behavior disorders in the dementia group. The measurement of sleep time and the serum melatonin values suggests that sleep and behavior disorders in the dementia group are related to decreases in the amplitude of the sleep-wake rhythm and decreases in the levels of melatonin secretions. Morning light therapy significantly increased total and nocturnal sleep time and significantly decreased daytime sleep time. These results indicate that morning bright light is a powerful synchronizer that can normalize disturbed sleep and substantially reduce the frequency of behavior disorders in elderly people with dementia.

Sleep in depression: the influence of age, gender and diagnostic subtype on baseline sleep and the cholinergic REM induction test with RS 86

One hundred and eight healthy controls and 178 patients with a major depressive disorder according to DSM-III were investigated in the sleep laboratory after a 7-day drug wash-out period. Subsamples of 36 healthy controls and 56 patients additionally took part in the cholinergic rapid eye movement (REM) sleep induction test with RS 86. Data analysis revealed that age exerted powerful influences on sleep in control subjects and depressed patients. Sleep efficiency and amount of slow wave sleep (SWS) decreased with age, whereas the number of awakenings, early morning awakening, and amounts of wake time and stage 1 increased with age. REM latency was negatively correlated with age only in the group of patients with a major depression. Statistical analysis revealed group differences for almost all parameters of sleep continuity with disturbed indices in the depressed group. Differences in SWS were not detected. REM latency and REM density were altered in depression compared to healthy subjects. Sex differences existed for the amounts of stage 1 and SWS. The cholinergic REM induction test resulted in a significantly more pronounced induction of REM sleep in depressed patients compared with healthy controls, provoking sleep onset REM periods as well in those depressed patients showing baseline REM latencies in the normal range. Depressed patients with or without melancholia (according to DSM-III) did not differ from each other, either concerning baseline sleep or with respect to the results of the cholinergic REM induction test. The results stress the importance of age when comparing sleep patterns of healthy controls with those of depressed patients. Furthermore they underline the usefulness of the cholinergic REM induction test for differentiating depressed patients from healthy controls and support the reciprocal interaction model of nonREM-REM regulation and the cholinergic-aminergic imbalance hypothesis of affective disorders.

Aging and changes in phasic events during sleep

Changes in phasic events in the elderly are reviewed. Such phasic events may in part be determined by the macrostructure of sleep (sleep stages). Therefore, a brief description of sleep architecture and EEG morphology in the aged person is given. Second, there is a marked variability among individuals in the number of spindles and K-complexes and more so in older individuals than in younger. However, there is an overall decrease in these events with age. The characteristics of these events (amplitude, frequency content, and distribution) change simultaneously. Third, the number of rapid eye movement occurring during REM sleep decreases with aging, but important gender differences exist, in that women generally maintain a higher REM density. The degree of changes in phasic events might correlate with mental deterioration (sleep cognition theory), but physical factors might also be the underlying reason for the observed changes. Whether these changes are indicative of the individual's ability to maintain sleep remains to be determined.

Clinical applications of cyclic alternating pattern

Sleep-related disorders are revisited in the light of the physiological modality of NREM sleep expressed by the cyclic alternating pattern (CAP). Owing to its fluctuating properties on vigilance, muscle tone, and vegetative activities, CAP represents a highly favorable condition for the occurrence of interictal generalized and focal lesional EEG discharges, for motor seizures, and for periodic jerks in nocturnal myoclonus. All these manifestations are significantly associated with the components of activation during CAP, i.e., the A phases. On the contrary, the B phases of CAP appear chronologically linked to inhibitory phenomena in epileptic patients and in nocturnal myoclonus. The two phases of CAP seem especially involved in sleep apnea syndrome, where respiration is interrupted during a phase B and restored during a phase A. CAP rate, that measures the effort of the brain to maintain sleep, is increased by all conditions that induce vigilance instability such as noise, clinical insomnia, interictal EEG paroxysms, nocturnal seizures, periodic leg movements, and in certain extreme pathologic conditions such as Creutzfeldt-Jakob disease and stage 2 coma.

Sleep and "sundowning" in nursing home patients with dementia

"Sundowning," a term that is sometimes equated with sleep disturbance or nocturnal delirium in dementia, is a poorly understood psychiatric phenomenon. In this study, we performed systematic, temporally specific, behavioral observations of nine profoundly demented nursing home patients 4 times an hour over a 12-hour period (1300 to 0100h) to determine whether their agitation was more likely to occur at a particular time of day. Results indicated only equivocal evidence that agitation was any worse nocturnally or during the time near sunset, thus raising the possibility that at least some components of sundowning may reflect disruptive behaviors occurring with identical frequency throughout the day but with differential impact upon nursing staff. Additional data indicated that awakening from sleep during darkness was also associated with agitation. A final result was a trend indicating the apparent worsening of agitation seasonally (greater agitation during winter), which may suggest involvement of the circadian timing system.

Nocturnal activity and immobility across aging (50-98 years) in healthy persons

OBJECTIVE

To measure the influence of age on measures of nocturnal activity and immobility in 100 healthy subjects aged 50 to 98 years.

DESIGN

Cross-sectional study.

SETTING

Urban population in Leiden. Recordings were performed at home while the subjects maintained their habitual 24-hour pattern of activities.

PARTICIPANTS

100 subjects without a history of major medical disorders and a normal neurological examination and performance-oriented assessment of gait (Tinetti).

MEASUREMENTS

Motor activity was recorded during six successive nights with a wrist-worn activity monitor. The occurrence of supra-threshold motor activity was recorded over 15-second epochs. A questionnaire was used to evaluate sleep habits and the occurrence of sleep disturbances. Four mean measures reflecting activity or immobility during the nocturnal period were calculated for each subject.

RESULTS

Only one out of four measures, (ie, the nocturnal proportion of time with movement, increased with age for females. For males, no age effects emerged. The mean duration of nocturnal immobility periods was higher in females than in males. Also, for females, the use of hypnotics increased with successive decades. Sex and the use of hypnotics were significantly related to the mean duration of immobility periods.

CONCLUSION

If care is taken not to confound aging with illness, measures of nocturnal activity and immobility reveal only marginal effects of aging.

Assessment of autonomic nervous activity by heart rate spectral analysis in patients with variant angina

The purpose of this study was to assess the role of the autonomic nervous system in the pathogenesis of coronary artery spasm in patients with variant angina. We evaluated cardiac sympathetic and parasympathetic activity from the power (logarithmic scale) of the low-frequency (approximately 0.04 to 0.12 Hz) and the high-frequency (approximately 0.22 to 0.32 Hz) spectral components of heart rate variability with Holter monitoring in seven patients with nocturnal variant angina and in 11 healthy men who served as control subjects. None of the patients had organic coronary artery stenosis as determined by angiography. Low-frequency and high-frequency logarithmic values were calculated for each 5-minute period from 30 minutes before to immediately before each angina attack. The logarithmic low-frequency value during the 5-to-0-minute period was greater than the low-frequency values during most of the other periods (p < 0.05 - p < 0.01). The logarithmic high-frequency values during the 10-to-5-minute and 5-to-0-minute periods were greater than those during the 30-to-25-minute period (p < 0.05 and p < 0.01, respectively). These data indicate that parasympathetic activity increased during the 10 minutes before attacks of nocturnal variant angina, whereas sympathetic activity with vagal modulation increased during the 5 minutes before such attacks. The same pattern of changes in heart rate variability was found in the absence of ST-segment elevation in patients and in control subjects. So this phenomenon was not just associated with coronary spasm and variant angina. It is suggested that circadian variation in disease activity is also associated with spontaneous attacks.

Neuropsychological function and REM sleep in schizophrenic patients

To test the hypothesis that rapid eye movement (REM) sleep in schizophrenic patients is associated with cognitive function, we studied 18 schizophrenic inpatients by means of electroencephalograms taken during sleep in their own hospital beds after a minimum 2-wk medication withdrawal period. Patients underwent neuropsychological tests to measure memory function and other aspects of cognitive performance. REM sleep measures demonstrated positive and negative correlations with cognition and memory measures, depending on when REM occurred after sleep onset. Minutes of REM sleep and REM density in the first period correlated negatively with performance, while REM minutes occurring after the first REM period correlated positively with neuropsychological performance. Further work should test whether phasic REM sleep regulation at the beginning of the night plays a compensatory role for neuropsychological dysfunction in schizophrenics.

Napping and 24-hour sleep/wake patterns in healthy elderly and young adults

OBJECTIVE

To examine differences between healthy elderly and young adults in daytime napping, nocturnal sleep, and 24-hour sleep/wake patterns. A second objective was to determine whether elderly subjects with more and less frequent naps differed in their clinical features or nocturnal sleep.

DESIGN

Survey by sleep/wake logs and polysomnography. Comparison by age.

SETTING

Sleep/wake logs were completed in the subjects' homes. Polysomnographic studies were conducted on an outpatient basis in a sleep and chronobiology research laboratory.

SUBJECTS

Convenience samples of forty-five healthy subjects over 78 years of age (21M, 24F) and 33 healthy adults between 20 and 30 years of age (20M, 13F).

MAIN OUTCOME MEASURES

Using self-reports, we estimated the frequency and timing of daytime naps; timing, duration, and quality of nocturnal sleep; and 24-hour patterns of sleep and wakefulness. Also polysomnographic sleep measures.

RESULTS

Compared to young adults, elderly subjects reported a greater mean number of daytime naps (P = .004), shorter nocturnal sleep with more wakefulness and earlier sleep hours (P less than .003 for each), and a trend for a shorter 24-hour sleep fraction. Among the elderly, more-frequent and less-frequent nappers did not differ in clinical ratings, self-report sleep measures, or polysomnographic measures. There was a trend for more sleep-disordered breathing and periodic limb movements in more frequent nappers.

CONCLUSIONS

These findings are consistent with an age-related decrease in amplitude of the circadian sleep propensity rhythm, or with the expression of a semi-circadian (12-hour) sleepiness rhythm. However, we cannot exclude the additional possibility that napping results from lifestyle factors and nocturnal sleep pathologies in a subset of the elderly.

Ambulatory monitoring of sleep-wakefulness patterns in healthy elderly males and females (greater than 88 years): the "Senieur" protocol

OBJECTIVE

The study was designed to investigate sleep-wake patterns in healthy elderly men and women (greater than 88 years) using ambulatory recording techniques.

DESIGN

Cross-sectional observations on 2 consecutive days.

METHODS

Two consecutive 24-hour recordings were made. Each 30-second period of the recording was scored as characteristic of wakefulness, REM, and non-REM sleep (stages 1-4).

SETTING

Interviews and recordings were done in the home of the elderly, not interfering with the habitual routine.

PARTICIPANTS

Among eligible members of the "Senieur" protocol, screened for wellness, seven females (88-102 years) and seven males (88-98 years) volunteered to participate.

MAIN OUTCOME MEASURES

Organization of sleep, sleep structure, and daytime mapping.

RESULTS

There was no difference between the first and second night recording. Important gender differences were observed: males had significantly less total sleep, shorter REM latency, more transitions to wake from REM, less NREM 3 sleep, and virtually no NREM 4. Daytime napping, REM amount, and distribution did not show sex differences. Although the variability in the amount of napping was considerable, it occupied less than 10 percent of the total sleep time in both women and men. Daytime napping was unrelated to sleep characteristics.

CONCLUSIONS

Ambulatory sleep-wake recordings allow an objective and critical evaluation of sleep function in normal aging. Interesting findings include a shift of REM sleep to the first part of the sleep period an increased cycle variability, and non-correlation of night-time sleep with daytime napping. In contrast to earlier findings in elderly persons, a polygraphic and subjective first-night effect was lacking.

Sigma (12-15 Hz) and delta (0.3-3 Hz) EEG oscillate reciprocally within NREM sleep

Sleep EEG in the sigma and delta frequency bands was subjected to spectral analysis in 8 normal young adults. In each subject, power density of sigma and delta oscillated reciprocally during NREM sleep, confirming an observation made initially with period/amplitude analysis. In REM sleep, power density for both frequency bands was at its lowest levels. Correlation coefficients between power density of delta vs. 1/sigma for all artifact-free 20-s epochs of NREM sleep/night were highly significant for each subject. These results show that cyclic oscillation of EEG within sleep is not limited to delta frequencies. The reciprocal relation of sigma to delta holds implications for the EEG mechanisms of NREM sleep. This dynamic pattern may also prove useful for sleep stage scoring and for a finer empirical analysis of sleep in psychiatric and neurological disorders.

From early to late adulthood. Changes in EEG sleep of depressed patients and healthy volunteers

In order to evaluate the impact of aging on EEG sleep patterns we investigated the polysomnograms of 74 patients with major depression and 51 healthy volunteers aged 18-65 years. In most of the EEG sleep parameters, age-related changes were obvious in both the depressives and the normals. In the patients, some of these alterations occurred earlier and were more pronounced. The amount of slow-wave sleep decreased with age, but no differences were found between the depressives and the healthy volunteers at any particular age. Rapid-eye-movement (REM) latency was clearly affected by age, but there were no significant differences between patients and controls until the middle of the fourth decade of life. On the other hand, REM density measures did not vary with age and were increased in the depressives. Therefore, REM density appears to be a more likely candidate for a biologic marker for major depression than is REM latency.

Effect of REM sleep deprivation on rat brain acetylcholinesterase

Acetylcholinesterase activity was compared in control, rapid eye movement sleep-deprived and recovered rat brain. The activity was estimated in the whole brain, cerebrum, brain stem and cerebellum. Flower pot technique was used for continuing deprivation for two, four and eight days. The results showed that the enzyme activity increased significantly in the deprived rat brain and it returned to control/normal level on recovery. The enzyme activity increased first in the brain stem, while the activity in the cerebellum showed no significant change. Control experiments suggest that the increase was primarily caused by the deprivation. The finding fits well with existing knowledge and would possibly help in explaining earlier observations.

Histamine neurons in human hypothalamus: anatomy in normal and Alzheimer diseased brains

The anatomy of histamine-immunoreactive cell bodies in normal adult human brain was examined in detail. In addition, the distribution of these cells in three cases of Alzheimer's disease was compared to the distribution of neurofibrillary tangles. Histamine-immunoreactive cell bodies were confined to the tuberal and posterior hypothalamus, forming the tuberomammillary nuclear complex. Most of the about 64,000 histamine neurons were large and multipolar. They comprised four distinct parts: (i) a major ventral part corresponding to the classical tuberomammillary nucleus, (ii) a medial part including the supramammillary nucleus and part of the posterior hypothalamic area, (iii) a caudal paramammillary part, and (iv) a minor lateral part. The parts showed some similarity with the subgroups in rat. In human, as compared to rat, the histamine neurons occupy a larger proportion of the hypothalamus. Numerous neurofibrillary tangles were found in the Alzheimer hypothalami, concentrated in the tuberomammillary area. Most of them were of globular type and extracellular, and only a minority were histamine immunoreactive. They may represent remnants of degenerated tuberomammillary neurons.

Sleep patterns in rural elders: demographic, health, and psychobehavioral correlates

Altered sleep patterns, including changes in bedtime, sleep latency, total sleep time, and arising time, have been reported to occur with increasing age. We examine self-reported sleep patterns in a geographically-defined population (n = 3097) of persons aged 65 years and older. Sleep patterns were characterized according to demographic variables, clinical conditions, and physical, psychological, and social functioning. Sleep latency and total hours of sleep increased with age, and older respondents went to bed earlier. The percentage of respondents who reported feeling rested in the morning decreased with age. Women went to bed later, had longer sleep latency, and fewer hours of sleep than men, and were less likely to report feeling rested than men. Sleep patterns were also related to educational attainment, self-perceived health status, physical functional status, psychotropic drug use, alcohol use, depressive symptoms, life satisfaction, and social and recreational activity level. This population study suggests that sleep problems among the elderly are sometimes associated with treatable health conditions and modifiable behavioral and environmental characteristics.

Disturbance in daily sleep/wake patterns in patients with cognitive impairment and decreased daily activity

The sleep/wake patterns of 121 chronically ill, mentally and physically handicapped patients were visually monitored hourly for 14 consecutive days. Four types of sleep/wake patterns were found. In order to investigate how cognitive and physical functions correlated with sleep disorders, patients were classified based on a scale of mental function and the grading of daily activity. The percent of total sleep hours and the sleep rating, showing disturbances in sleep/wake pattern, were evaluated. We found a high degree of individuality in sleep/wake patterns. Sleep disturbance was associated with daily activity as well as with cognitive impairment. This monitoring system provides medical personnel with valuable information for clinical management.

Age-adjusted threshold values for reduced REM latency in unipolar depression using ROC analysis

To determine an age-adjusted, clinically meaningful depressive diathesis, we have implemented Receiver Operator Characteristic (ROC) analysis for mean rapid eye movement (REM) latency in patients with unipolar depression. Depressed patients were compared with age-matched normal control subjects. Sensitivity and specificity estimates were calculated for selected threshold values on the ROC curves as well as for the Research Diagnostic Criteria endogenous/nonendogenous subtype. The mean REM latency value of 65.0-66.0 min was most sensitive and specific for depressed patients aged 35-72. The threshold value of 70.0 min appeared optimally sensitive and specific for depressed patients aged 20-34. There was no effect of age on REM latency in the normal control sample. Among depressed patients there was an effect of age but this was clearly observable only in nonendogenous depressed patients.

A polysomnographic study in young psychiatric inpatients: major depression, anorexia nervosa, bulimia nervosa

The baseline EEG sleep patterns of 10 young depressed patients, 20 patients with anorexia nervosa, 10 patients with bulimia nervosa, and 10 healthy subjects were found to be indistinguishable, except for an increased REM density in the depressed patients. In eating disorder patients, a concomitant major depressive episode had no influence on EEG sleep. The results of the cholinergic REM sleep induction test revealed a significantly faster induction of REM sleep in the depressed patients when compared with the eating disorder patients and the control subjects. This indicates a subthreshold hypersensitivity of the REM sleep triggering cholinergic transmitter system in depressives, but not in eating disorder patients.

The intrasleep relationship between wake and stage 4 examined by transition probability analysis

The relationship between wake and stage 4 of slow-wave sleep (SWS), in particular the previously observed deficiency in SWS accompanying sleep containing long-wake periods, is examined in this study of 147 health subjects. Stage shift comportment is compared between those NREM/REM cycles with wake periods greater than 3 minutes and those with less, using the method of transition probabilities. It is shown that these long wake interruptions occur preferentially in light sleep, and systematically disrupt the regular normal descent towards SWS, but do not significantly reduce the number of SWS episodes. There is at the same time, however, a reduction in the average duration of stage 4 periods of SWS which accounts for the observed reduction in the total amount of SWS.

REM latency in Alzheimer's disease

Latency to the first episode of rapid eye movement sleep (REML) has been proposed as a potential biomarker for Alzheimer's disease (AD). In this study, we compared REML values from 28 AD patients and 28 age- and sex-matched controls. We employed multiple definitions of REML and multiple cutoffs to classify patients and controls. Results indicated that the best REML definition and optimal cutoff criterion resulted in only 65% correct classifications. We discuss the longer REML in AD patients relative to controls in terms of both overall sleep disturbance and selective deterioration of the REM-cholinergic system. As REML may be relatively short in other forms of psychopathology (e.g., affective disorders), REML may still hold promise in the differential diagnosis of dementia and pseudodementia.