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Biomedical subjects

O Benoit

Publications and source records attributed to O Benoit.

At least 37 records · Page 2Linked to original sources
PubMed1992

Sleep apneas in high altitude residents (3,800 m).

The question is: to what extent periodic breathing usually observed in translocated subjects at high altitude affects normal and polycythemic residents of high altitude? Standard sleep parameters, chest wall movements, temperature of ventilated gas and arterial O2 saturation (SaO2) were continuously recorded in 7 normal highlanders (mean hematocrit: 51%) and 14 polycythemic highlanders (mean hematocrit: 68%) during one night in La Paz, 3,850 m, Bolivia. The patterns of breathing instability were analysed by two ways: measuring duration of apneas and counting all the oscillations of SaO2 greater than 1%. Normal and polycythemic highlanders displayed a wide intersubject variability with regard to breathing instability, hence no significant difference in the total number of apneas and oscillations of SaO2 could be evidenced between the 2 groups. However, the longest apneas and the highest number of oscillations of SaO2 were found in the polycythemic highlanders.

Adaptation, Physiological↗
PubMed1992

Effects of a two-hour early awakening and of bright light exposure on plasma patterns of cortisol, melatonin, prolactin and testosterone in man.

Bright light is a synchronizing agent that entrains human circadian rhythms and modifies various endocrine and neuroendocrine functions. The aim of the present study was to determine whether and how the exposure to a bright light stimulus during the 2 h following a 2 h earlier awakening could modify the disturbance induced by the the sleep deprivation on the plasma patterns of hormones whose secretion is sensitive to light and/or sleep, namely melatonin, prolactin, cortisol and testosterone. Six healthy and synchronized (lights on: 07.00-23.00) male students (22.5 +/- 1.1 years) with normal psychological profiles volunteered for the study in winter. The protocol consisted of a baseline control night (customary sleep schedule) followed by three shortened nights with a rising at 05.00 and a 2 h exposure to either dim light (50 lux; one week) or bright light (2000 lux; other week). Our study showed a phase advance of the circadian rhythm of plasma cortisol without significant modifications of the hormone mean or peak concentration. Plasma melatonin concentration decreased following bright light exposure, whereas no obvious modifications of plasma testosterone or prolactin patterns could be observed in this protocol.

Adult↗
PubMed1991

Hypnotics and sleep physiology: a consensus report. European Sleep Research Society, Committee on Hypnotics and Sleep Physiology.

The effects of hypnotics on descriptive and functional aspects of electrophysiological sleep parameters are assessed in this report. Because of the arbitrary definition of some of the criteria underlying the conventional sleep stage scoring procedure, computer-aided methods of EEG analysis have become increasingly important for recording and interpreting pharmacological effects on sleep. Of particular interest are the changes of EEG slow-wave activity, since this parameter varies as a function of prior sleep and waking. Several types of interaction between hypnotics and sleep regulation are discussed, some recent pharmacological developments are highlighted, and some common problems in clinical trials are specified.

Anti-Anxiety Agents↗
PubMed1991

[Benefits and risks of hypnotics].

Rationalisation of the war of hypnotics has recently been under discussion in France: a review of the benefits and risks of these substances may therefore be useful. Chronic insomnia is a result of multiple factors, among which individual characteristics of the personality play an important role. Hypnotic treatment is symptomatic; its beneficial influence on sleep progressively vanishes in few weeks, while some negative residual effects on daytime functioning (mood, alertness, performance, memory impairment) may persist. The main problems posed by hypnotic treatment with benzodiazepines are related to tolerance effects during the treatment period and to rebound insomnia and withdrawal phenomena after discontinuation. Practical issues for the treatment of insomnia, based on international consensus, are presented.

France↗
PubMed1990

Modifications of sleep structure by brief forced awakenings at different times of the night.

Four subjects were awakened once a night for 10 min at either 01.30, 03.30 or 05.30 h. During the waking intervals, they performed a mental task while remaining in bed. The awakenings did not significantly modify the amount of different stages during subsequent sleep with no effect of time of occurrence in the night. In contrast, the timing of the awakening within the cycle had a significant influence on REM cycle structure. If awakening occurred during a REM episode or shortly thereafter, the following inter-REM interval was shortened; if it occurred late in the cycle, that is shortly before a REM episode, it increased the inter-REM interval beyond the reference length of the corresponding uninterrupted cycle. An explanation based on a model of sleep which implies the simultaneous activity of REM-on and REM-off neurones is proposed.

Adult↗
PubMed1990

Psychophysiological effects of early morning bright light exposure in young adults.

The effects of bright light on circadian rhythms in man are well documented. Nevertheless the theoretical basis and the rules for the practical utilization of light exposure as therapy need still to be better defined. The present study determined to what extent a 2-hr bright light exposure (0500-0700 h) improved the adjustment to an early rising in normal adults. Phase changes were assessed in subjective alertness, performance in several search tasks, time estimation, and a visual discrimination task, as well as in body motility, plasma cortisol concentrations, and body temperature. In comparison with a dim light exposure, the bright light resulted in increased motor activity during waking, in earlier peak of subjective alertness, and an improvement in performance speed in three out of five tasks in the morning. Cortisol and body temperature also were phase-advanced. In summary, light applied to a portion of the circadian cycle sensitive to phase advance shifts influenced rhythms with strong endogenous components (temperature and cortisol), while other rhythms with strong exogenous components were more sensitive to sleep deprivation caused by the early rising time.

Adult↗
PubMed1990

The Multiple Sleep Latency Test: individual variability and time of day effect in normal young adults.

The influence of individual characteristics on diurnal physiological sleep tendency was investigated in young good sleepers. Fifty-five subjects underwent a Multiple Sleep Latency Test (MSLT) procedure. Among them 11 also participated in Repeated Test Sustained Wakefulness (RTSW) procedure. The MSLT results were analyzed as a function of both the number of sleep onsets per day and the time of day. Diurnal sleepiness seemed to be better appreciated by sleep onset (SO) frequency than by the traditional criteria of sleep latency. SO frequency, unlike latency, was influenced by factors such as usual sleep duration, morning/evening score, and RTSW procedure. Time of day effect was characterized by a decrease in sleep tendency at the beginning and at the end of the day (decrease in SO frequency and increase in SO latencies); between these two points a peak of sleepiness around 1400 was observed. The morning and evening periods of high alertness could represent important anchor points for the coupling of the sleep/wake and temperature rhythms.

Adult↗
PubMed1990

Periodic breathing and O2 saturation in relation to sleep stages at high altitude.

This study was designed to compare sleep organization at high altitude (HA) and sea level (SL) and to estimate the extent periodic breathing (PB) negatively influences arterial O2 saturation (SaO2). Six lowlanders were studied at SL and after 3 weeks spent at 3,800 m (La Paz, Bolivia). Three EEG leads, EOG, submental EMG, chest and abdominal motion, temperature of ventilated gas, and SaO2 were polygraphically recorded. Comparison of HA and SL data disclosed that: 1) Sleep organization was identical, with the same percentage of REM and stage 4. 2) PB (cycle length: 20 s; central apnea: 9 s) occurred in three subjects during all stages of sleep except REM (43-60% of total sleep). A periodic lowering in heart rate occurred during ventilatory oscillation. 3) During PB, SaO2 oscillated very regularly from 78-90%, which resulted in a mean SaO2 value calculated during oscillations similar to that of the non-periodic breathers. We conclude that lung O2 uptake during PB is preserved.

Altitude↗
PubMed1988

Psychological profile and sleep organization in young subjects with poor quality of sleep.

The personality traits defined by the Minnesota Multiphasic Personality Inventory (MMPI) and sleep data were analyzed in 45 young subjects with poor quality of sleep. The subjects were divided into three groups: Group 1 had no T score greater than or equal to 70, Group 2 had one or more single T scores greater than or equal to 70, and Group 3 had T scores greater than or equal to 70 in one or more specific groups of scales. The first 2 nights of sleep were polygraphically recorded. Subjects in Group 1 were considered to be normal, those in Group 2 were characterized by depression and anxiety, and those in Group 3 had psychopathic personality traits and somatic disorders. Differences in sleep data were noted among groups. The severity of the sleep disorders was related to the degree of the psychological problems.

Adult↗
PubMed1988

[Circadian regulation of the sleep-wake cycle].

A review of the studies considering the sleep/wake alternation as a biological circadian cycle is presented. The methods designed to evaluate respectively the role of both the endogenous component and the external synchronizers of isolation (free-running protocols). There are mutual relations between wake/sleep cycle and some other circadian rhythms, particularly body temperature rhythm. When sleep is subjected to any time manipulation, the homeostatic regulation of some sleep characteristics (REM-sleep amount, sleep onset probability, sleep length) remains very strong. Alertness appears to be linked both to sleep characteristics and to internal temperature evolution. In addition, it proved to present some degree of independence of the two afore mentioned factors, specially when motivation and/or other psychological factors are involved. The afternoon nap, far from being simply after lunch reaction, is a normal manifestation of circadian rhythmicity.

Attention↗
PubMed1987

Early rising or delayed bedtime: which is better for a short night's sleep?

The present study compares the effects on sleep and the subsequent period of wakefulness of delaying bedtime of 2 h or advancing rising time by 2 h in subjects clearly differentiated by morningness or eveningness in their circadian rhythms. Twelve young healthy good sleepers, six morning types (MT) and six evening types (ET), were selected. The data obtained from the second 24 h (night and day) with delayed bedtime (DB) and advanced rising time (AR) were compared with those obtained in the reference condition (R) with normal sleep schedules. Sleep was recorded polygraphically and rectal temperature was continuously monitored during the nights and during the day following the second night of each condition. Subjective estimations of alertness, performance tasks and urinary steroids were analysed. Early rising appeared to be more disturbing than a late bedtime. The second shortened night showed fewer characteristics of recovery sleep in AR than in DB. The decrease in self rated alertness was a function both of the type of condition (DB or AR) and of the morning-evening typology of the subject. The largest decrease was observed in AR and in the ET subjects. AR also resulted in the most pronounced decrease in performance tasks and in an increase in urinary 17 ketosteroids without changes in the 17 hydroxy-corticosteroids. The effects on rectal temperature were limited to short periods after bedtime in DB and rising time in AR.

17-Hydroxycorticosteroids↗
PubMed1986

[Comparison between good and poor sleep in the 20 to 30-year-old age range: polygraphic findings and psychopathologic aspects].

Fifty-six poor sleepers, aged from 20 to 30, were compared with 46 good sleepers of the same age regarding objective sleep parameters and personality. A gradation of sleep disorders was observed. The degree of sleep disorders was found to be directly proportional to the degree of psychological disturbance. Psychophysiological group of poor sleepers exhibited objective differences from good sleepers during the first cycle only (lack of SWS and REM sleep). Sleep organization in the first cycle seemed important for the estimation of poor or good sleep by the sleeper.

Adult↗
PubMed1986

[Sleep recovery after deprivation: comparison between good and poor sleepers of the same age].

Sleep organization was studied with and without a previous sleep deprivation. Sleep recovery was allowed during day or only at night. Two groups of good and poor sleepers were compared (15 subjects aged 22-26 years in each). The main differences between groups were observed for 1) the sleep onset latency 2) the ratio total sleep time/time in bed and on the total sleep time. The influence upon sleep of the various situations was less marked in poor sleepers than in good sleepers. This result suggests some deficiency in the mechanisms allowing sleep recovery after deprivation.

Adult↗
PubMed1986

Monitoring of long-term motor activity in depressed patients.

Wrist motor activity was continuously recorded by a solid-state monitor in 12 patients with major depression throughout their stay in hospital; their clinical state was evaluated using three scales. During the day, activity troughs and immobility peaks occurred before noon and around 1500 hrs. Activity level progressively increased, while the duration of immobility decreased, with clinical improvement. The immobility measurement appeared to be a valuable index of depression and is more sensitive than the activity level, mainly for agitated depressed patients. Immobility episodes during the day could suggest the release of an ultradian sleep-wake rhythm in depression.

Activity Cycles↗
PubMed1986

Diurnal variation in subjective and objective measures of sleepiness: the effects of sleep reduction and circadian type.

In young, good sleepers the diurnal evolution of alertness was studied as a function of degree of morningness: (1) during habitual sleep routine and (2) in a 2-hr sleep reduction protocol. During habitual sleep routine, alertness was assessed using both the subjective evaluation based on Thayer's Activation Deactivation Adjective Checklist (43 subjects) and the objective measurement of sleep latency (Multiple Sleep Latency Test, MSLT). Self-alertness scored highest around midday. Later it showed a dip, then stayed on a plateau until about 2200 hr. On average, 77% of the subjects fell asleep at the 1400 hr MSLT session while only 35.5% did at 1000 hr and 25.8% at 2000 hr. Morning-types (MT) and evening-types (ET) differed only during the morning: ET fell asleep more frequently at 1000 hr and 1200 hr and rated lower self-alertness on arising than did MT. Twelve subjects were given the protocol of a 2-hr sleep reduction (both in delayed bedtime and advanced rising time conditions). At 0700 hr, MT rated their alertness lower when they had only just gotten up (delayed bedtime condition) than when they had been awake for 2 hr (advanced rising time condition). In contrast, ET had the same low level of alertness at 0800 hr, independent of the time elapsed since arising. On average the advanced rising time condition affected the general pattern of alertness more than did delayed bedtime.

Adult↗