Shine light on sleep: Morning bright light improves nocturnal sleep and next morning alertness among college students

The relationship between daytime light, especially morning light and sleep, has not been well documented. People who work in an office spend most of their time indoors and thus have less access to high-level daylight. The current study employed a field intervention approach to investigate whether exposure to 1.5 h of bright electric light in the early morning for 1 workweek would benefit sleep among students who spent most of their time in an office at the university. Twelve students (24.92 ± 1.78 years) underwent a 2 workday baseline measurement and two inconsecutive 5 workday interventions (with 1 week washout) with morning bright light and regular office light (1000 lx, 6500 K vs. 300 lx, 4000 K, at eye level). The sleep outcomes were recorded with actigraphy and a sleep diary. In addition, self-ratings of daytime sleepiness, mood, mental fatigue, perceived effort, and next morning sleepiness were measured each workday. The results showed that exposure to morning bright light versus regular office light yielded a higher sleep efficiency (83.82% ± 1.60 vs. 80.35% ± 1.57, p = 0.02), a smaller fragmentation index (15.26% ± 1.31 vs. 17.18% ± 1.28, p = 0.05), and a shorter time in bed (7.12 ± 0.13 vs. 7.51 ± 0.12, p = 0.03). Meanwhile, an earlier sleep onset time, shorter sleep latency, and lower morning sleepiness were observed after a 5 workday morning bright light intervention compared with the baseline (ps <0.05), no such benefit was found for self-ratings (ps >0.05). These findings support existing evidence that morning bright light could function as an enhancer of sleep and alertness for office occupants.     

Lowering dialysate temperature improves sleep and alters nocturnal skin temperature in patients on chronic hemodialysis

Hemodialysis (HD) induces physiological changes that may affect the ability to dissipate heat and adversely affect sleep. We studied the effects of altering dialysate temperature on polysomnographic measures of nocturnal sleep and the time course of proximal skin temperature. The sample included seven stable HD patients. The three-phase randomized trial was conducted in a research facility. After one acclimatization night, subjects were readmitted in the evening on two additional occasions for 42 h and received HD the next morning in the warm condition (dialysate 37 degrees C) and cool condition (dialysate 35 degrees C) in random order. Continuous proximal skin temperature (axillary, T(ax)) and polysomnographic measures of sleep were recorded the nights before and after HD was administered. Highly significant findings included that the time course of T(ax) was markedly affected by dialysis temperature. There was a greater drop of T(ax) in the early morning following the warm condition than during the baseline nights or in the cool condition. Logistic regression indicated that the odds for the occurrence of sleep and its deeper stages were strongly and positively associated with T(ax). Time of sleep onset was earlier in the cool condition (P = 0.03) with trends toward longer total sleep times (P = 0.09) and shorter rapid-eye-movement latencies (P = 0.09). These observations suggest that the use of cool dialysate during HD may improve nocturnal sleep by decreasing sympathetic activation and sustaining the normally elevated nocturnal skin temperature until later into the morning hours.     

The effect of self-awakening from nocturnal sleep on sleep inertia

The present study examined the effects of self-awakening on sleep inertia after nocturnal sleep. Ten undergraduate and graduate students participated in the study. Their polysomnograms were recorded for five consecutive nights; the first, second, and third to fifth nights were adaptation, forced-awakening, and self-awakening nights, respectively. Participants rated sleepiness, fatigue, comfort, and work motivation, and these ratings were followed by switching (7 min) and auditory reaction time tasks (6 min), both before bedtime (15 min) and immediately after awakening (4 min × 15 min). Although reaction times on the auditory were task prolonged, and participants complained of feeling uncomfortable immediately after forced-awakening, reaction times were shortened after self-awakening, and the participants did not complain of feeling uncomfortable on these nights. The results of this study suggest that sleep inertia occurs after forced-awakening and that it can be prevented by self-awakening.     

Tests of memory in narcoleptics

This study attempted to evaluate the validity of self-reports of memory deficits in narcoleptics by comparing the scores of these patients with the scores of matched control subjects on standardized tests of memory function. After completing a short interview designed to elicit qualitative information about memory difficulties, 30 narcoleptic subjects and 30 control subjects completed the Wechsler Memory Scale (WMS), Rey-Auditory Verbal Learning Test, the Rey Complex Figure Test, Strub and Black's List of Letters, and the Symbol Digits Modalities Test (SDMT). In addition, the Profile of Mood States (POMS) was used to detect variation in performance due to anxiety or fatigue. Continuous polygraphic recordings were obtained during the testing to detect any changes in alertness. Subjects with narcolepsy experienced more difficulty in maintaining attention than control subjects, as evidenced by significantly more perseveration errors (p less than or equal to 0.01) on Strub and Black's List of Letters. Despite differences in their ability to sustain attention, there were no significant differences between narcoleptic and control subjects on measures of concentration (Digit Span from the WMS, and the SDMT). Furthermore, there was no objective evidence of memory impairment when the scores of narcoleptic and control subjects were compared on standardized tests of immediate and delayed recall, as well as on tests of verbal and visual memory.     

Acute administration of triazolam for the daytime sleep of rotating shift workers

Ten rotating shift workers, who changed shifts every 1 to 4 weeks, slept in the laboratory during the first four daytime sleep periods of two consecutive tours of night shift. Prior to the first two sleep periods of one tour, the subjects were given 0.5 mg triazolam. Placebo was administered prior to sleep periods one and two of the other night shift tour. Neither drug nor placebo was given before the third and fourth sleep period of either tour of night shift. Conditions were counterbalanced among subjects. Polysomnography demonstrated that triazolam significantly increased total sleep time and sleep efficiency relative to placebo, primarily by promoting sleep maintenance. No adaptation to daytime sleep was seen during the four consecutive sleep periods without triazolam (placebo, then no drug). Triazolam did not appear to promote adaptation to daytime sleep on the 2 days following triazolam administration.     

Polysomnographic study of nocturnal sleep in idiopathic hypersomnia without long sleep time

We investigated nocturnal sleep abnormalities in 19 patients with idiopathic hypersomnia without long sleep time (IH) in comparison with two age‐ and sex‐ matched control groups of 13 normal subjects (C) and of 17 patients with narcolepsy with cataplexy (NC), the latter considered as the extreme of excessive daytime sleepiness (EDS). Sleep macro‐ and micro‐ (i.e. cyclic alternating pattern, CAP) structure as well as quantitative analysis of EEG, of periodic leg movements during sleep (PLMS), and of muscle tone during REM sleep were compared across groups. IH and NC patients slept more than C subjects, but IH showed the highest levels of sleep fragmentation (e.g. awakenings), associated with a CAP rate higher than NC during lighter sleep stages and lower than C during slow wave sleep respectively, and with the highest relative amount of A3 and the lowest of A1 subtypes. IH showed a delta power in between C and NC groups, whereas muscle tone and PLMS had normal characteristics. A peculiar profile of microstructural sleep abnormalities may contribute to sleep fragmentation and, possibly, EDS in IH.     

Effects of early and late nocturnal sleep on priming and spatial memory.

A wordstem priming task (nondeclarative memory), and a mental spatial rotation task (declarative memory) were presented to subjects of an experimental "sleep" group (n = 11) and of a "wake" control group (n = 10). Repetition priming effects and recall of spatial memory were tested after 3-hr retention intervals, which followed learning and were placed either in the early or in the late half of the night. Sleep group subjects slept during the retention intervals while subjects of the wake group stayed awake. As expected, early retention sleep was dominated by slow wave sleep (SWS), whereas rapid eye movement (REM) sleep prevailed during late retention sleep. After early retention sleep, recall of spatial memory was superior to that after late retention sleep (p < 0.01), and also to that after retention intervals of wakefulness (p < 0.05). In contrast, priming was more effective after late than early retention sleep (p < 0.05). It appears that early sleep dominated by SWS facilitates consolidation of declarative memory whereas late sleep dominated by REM sleep facilitates consolidation of nondeclarative memory.     

Effect of gradual withdrawal on the rebound sleep disorder after discontinuation of triazolam

Sixty volunteers with insomnia participated in a randomized, double-blind, controlled clinical trial. After an initial six nights of placebo, 30 subjects (the abrupt-withdrawal group) received 0.5 mg of triazolam nightly for 7 to 10 nights, after which they received placebo. The other 30 subjects (the tapered-dosage group) received the same initial placebo treatment, then triazolam at 0.5 mg for seven nights, at 0.25 mg for two nights, and at 0.125 mg for two nights, and then placebo. As compared with the initial placebo period, the triazolam period significantly reduced the interval before the onset of sleep (sleep latency), and it prolonged sleep duration, reduced the number of awakenings, and improved the self-rated soundness of sleep in all cohorts. In the abrupt-withdrawal group, plasma levels of triazolam were undetectable the morning after the first night of placebo substitution, and subjects reported prolongation of sleep latency (57 minutes longer than base line), reduction in sleep duration (1.4 hours less than base line), and increased awakenings (1.2 per night above base line). The symptoms of rebound sleep disorder lasted one or possibly two nights, and there was a reversion toward base line on subsequent placebo nights. In the tapered-dosage group, however, plasma triazolam levels fell gradually to zero, and rebound symptoms were decreased or eliminated. Thus, rebound sleep disorder following abrupt discontinuation of triazolam can be attenuated by a regimen of tapering.     

Time estimation during nocturnal sleep in human subjects

It has been postulated that time estimation during nocturnal sleep in humans can be explained by an interval timing clock inside the brain. However, no systematic investigations have been carried out with respect to how the human brain perceives the passage of time during sleep. The brain mechanisms of over- or underestimation of time spent in sleep have not yet been clarified. Here, we carried out an experimental study in which 11 healthy volunteers participated in time estimation trials scheduled six times during 9 h nocturnal sleep periods, under carefully controlled conditions. The time estimation ratio (TER: a ratio of subjective passage of time to actual time interval) decreased significantly from the first to the sixth trial. Individual TER was positively correlated with slow wave sleep prior to the trial, while it was negatively correlated with REM sleep. Our results indicate that the human brain has an ability to estimate the passage of time during nocturnal sleep without referring to time cues, and that the accuracy of this function fluctuates from overestimation in the early hours of sleep to underestimation in the last hours of sleep.     

Rhythmic slow wave observed on nocturnal sleep encephalogram in children with idiopathic nocturnal enuresis

All-night sleep polygraphs, except the first night, were recorded for 15 patients with idiopathic nocturnal enuresis and 10 normal controls. Relations between sleep and the mechanism by which nocturnal enuresis is caused, with special emphasis on the occurrence of rhythmic slow waves (RSW), was studied. The following results were obtained. (a) There was no significant difference between the two groups in the proportions of the electroencephalographic (EEG) sleep stages, under the same conditions. (b) Nocturnal enuresis occurred with almost the same frequency in all sleep stages except stage 1 sleep and was higher in the second and third cycles. (c) Immediately before a nocturnal enuretic event, 6-7 Hz RSW continued for as long as 15-40 s in NREM sleep, or 3-5 Hz RSW was observed in REM sleep. (d) RSW was observed in enuretics and controls, and decreased with increase in age. However, RSW occurred more often, and age-related decrease was delayed in enuretic children. (e) RSW was induced by stimuli such as changes in sleep stages or body movement. During RSW, the variance of heart rate and respiration tended to be low. These results and the similarity between RSW and diffuse rhythmic theta suggest that RSW may be an expression of the process of maintaining a given sleep stage in children. These results may also be caused by the immaturity of the sleep mechanism in enuretic children. The long-lasting RSW on the sleep EEG was considered to be a sign of the onset of nocturnal enuresis.     

The effect of triazolam on arousal and respiration in central sleep apnea patients

It was hypothesized that triazolam might decrease central apneas associated with arousal periods in patients with central sleep apnea by hastening the onset of consolidated sleep. Five male patients, diagnosed as having central sleep apnea on a screening night, participated in a double-blind randomized crossover study of the effect of placebo, 0.125 mg triazolam, and 0.25 mg triazolam on sleep, respiration, and daytime function. Results indicated that the medication increased total sleep and decreased central apnea index and number of brief arousals. Improved sleep quality was reflected in improved daytime psychomotor performance and alertness. These data, if replicated, imply that benzodiazepine use may be beneficial in patients with central sleep apnea.     

Structure of nocturnal sleep in patients with cerebral insult

The aim of the present work was to study the structure of nocturnal sleep in patients who had sustained brain insults, and to relates sleep structure to the stage of disease and the location of the focal lesion. Studies were performed on 18 patients with ischemic insult, 8 affected in the right hemisphere, 6 affected in the left hemisphere, and 4 with brainstem lesions; controls consisted of 5 healthy subjects. Diagnoses were in all cases confirmed by computer tomography. Clinical and neurological studies were performed, along with recording of polygraph traces of nocturnal sleep (electroencephalograms, electrooculograms, electromyograms). Sleep parameters were analyzed using a program developed at the Sleep Studies Center, I. M. Sechenov Moscow Medical Academy; along with standard parameters, this program included analysis of the segmental structure of sleep. Sleep quality—the level of normality or disturbance to its structure—was assessed using a sleep index (SI). Patients showed profound disorganization of nocturnal sleep structure, with disruption of the mechanisms organizing sleep as a whole and generating and maintaining the individual stages. The greatest sleep disturbances were seen in ischemic insult in the right hemisphere and in patients with lesions in medial deep structures. Center for Sleep Studies and Department of Nervous Diseases, Faculty of Postgraduate Professional Education, I. M. Sechenov Moscow Medical Academy, Moscow City Sleep Center, Committee of Health of the Moscow City Council, A. A. Ostroumov City Clinical Hospital No. 33. Translated from Zhurnal Nevrologii i Psikhiatrii imeni S. S. Korsakova, Vol. 97, No. 4, pp. 11–14, April, 1997.     

Physiological sleep tendency on a simulated night shift: adaptation and effects of triazolam

Daytime sleep and nocturnal sleepiness were examined in 18 normal sleepers (9 young adults, 9 middle-age adults) for 5.5 days following acute sleep/wake schedule inversion. Triazolam and placebo were compared in a counterbalanced, crossover design. Triazolam improved daytime sleep, but did not produce significant changes in sleep tendency at night. Physiological sleep tendency in the early morning hours (0200 to 0600) was profound, but decreased significantly within 3 to 4 days following sleep/wake inversion, irrespective of treatment condition. Nocturnal performance data generally were consistent with changes in physiological sleep tendency. We conclude that extending daytime sleep by an average of approximately 50 min per day via administration of a hypnotic does not appear to significantly reduce circadian sleep tendency in the early morning hours. Further, considerable adaptation, in terms of sleep tendency, occurred within a weak of simulated night shift despite a relatively constant daytime sleep pattern.     

Short-term total sleep deprivations does not selectively impair higher cortical functioning.

Previous research has shown that total sleep deprivation produces impairment in sustained attention and vigilance especially if the deprivation period is greater than 48 hours. However little is known about the effects of sleep deprivation on performance of tasks considered to be measures of higher cortical functioning such as tests of cognitive flexibility and the capacity to shift from one response set to another. One current hypothesis is that sleep deprivation of a shorter duration (34-36 hours) adversely affects higher cortical function while effects on attention and vigilance tasks are relatively mild. Performance on an intelligence test, a test of sustained attention and tests designed to measure higher cortical function were compared in a group of 29 subjects who underwent 34-36 hours of continuous sleep deprivation and 32 normal sleeping control subjects. No significant group performance differences in the hypothesized direction were noted on any measure. One night of total sleep deprivation does not appear to impair performance on tasks that are designed to assess higher cortical functioning.     

Quotidian nocturnal hemodialysis improves cytokine profile and enhances erythropoietin responsiveness

Inflammation is implicated in the pathogenesis of erythropoietin (EPO) resistance in patients with end-stage renal disease. Interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha are suggested to suppress erythropoiesis in uremia. Insulin like growth factor (IGF)-1 has been proposed to stimulate erythropoiesis. Nocturnal hemodialysis (NHD) has been demonstrated to improve anemia management with enhanced EPO responsiveness without altering survival of red blood cells. We tested the hypothesis that augmentation of uremia clearance by NHD results in a reduction of proinflammatory cytokine levels, thereby enhancing EPO responsiveness. Using a cross-sectional study design, 14 prevalent patients on NHD and 14 patients on conventional hemodialysis (CHD) matched for age and comorbidities and controlled for hemoglobin concentrations and iron status were studied. Outcome variables included EPO requirement and plasma levels of EPO, parathyroid hormone, C reactive protein, IL-6, TNF-alpha, and IGF-1. The primary outcome was to determine the between group differences in (1) cytokine profile and (2) EPO requirement. The secondary outcome was to examine the potential correlation between cytokine levels and EPO requirement. There were no significant differences in patient characteristics, comorbidities, hemoglobin, iron indices, and parathyroid hormone levels between the two cohorts. EPO requirement was significantly lower in the NHD cohort [90.5 +/- 22.1 U/kg/ week (NHD) vs. 167.2 +/- 25.4 U/kg/week (CHD), p = 0.04]. Plasma IL-6 levels were lower in the NHD cohort [3.9 +/- 0.7 pg/ml (NHD) vs. 6.5 +/- 0.8 pg/ml (CHD), p = 0.04]. C reactive protein tended to decrease [4.59 +/- 1.34 (NHD) vs. 8.43 +/- 1.83 mg/L (CHD), p = 0.14]. TNF-alpha, and IGF-1 levels did not differ between the two groups. Direct associations were found between EPO requirement and C reactive protein levels (R = 0.62, p = 0.001), and IL-6 levels (R = 0.57, p = 0.002). Augmentation of uremic clearance by NHD improves EPO responsiveness in end-stage renal disease. A possible mechanism for this improvement is through better control of inflammation, as manifested by lowering of plasma IL-6 levels. Further studies are required to clarify the mechanisms by which NHD decreases inflammation.     

Do nocturnal penile tumescence recordings alter electroencephalographic sleep?

While concurrent monitoring of sleep is considered to be a necessary component of evaluating nocturnal penile tumescence (NPT), in order to ensure that NPT data are not invalidated by fragmented sleep or diminished REM sleep, it is not known whether NPT recording itself disrupts sleep beyond the expected first night effect. In this study of 42 outpatient men with major depression and 36 normal control subjects, we found no effect of NPT recording on measures of sleep continuity, proportion of NREM to REM sleep, or REM sleep in either depressed or healthy control subjects.