Biomedical subjects

Pierre Philip

Publications and source records attributed to Pierre Philip.

18 recordsLinked to original sources

PubMed2006

Insomniac complaints interfere with quality of life but not with absenteeism: respective role of depressive and organic comorbidity.

BACKGROUND AND PURPOSE: Insomnia is common and associated with poor health status and quality of life. We designed a study to evaluate the impact of insomniac complaints with and without comorbidity on health status and absenteeism. PATIENTS AND METHODS: This is a cross-sectional study performed within a 1-year follow up study on a prospective cohort of French employees. Insomniac subjects (n=986) were compared to control subjects (n=584). Insomniacs suffering from self-reported depressive feelings and behavioral and organic sleep complaints were excluded. RESULTS: Subjects with insomniac complaints (whether with mood or behavioral and organic sleep complaints or not) reported poorer quality of life and had a higher absenteeism rate than controls (9.6+/-31 versus 5.8+/-19 days, P<0.01). A logistic regression model adjusting for depressive and behavioral and organic sleep complaints showed that insomniac complaints were no longer predictive of absenteeism. CONCLUSIONS: Insomniac complaints are strongly associated with deterioration in quality of life but not necessarily with higher absenteeism.

Absenteeism↗

PubMed2006

Transport and industrial safety, how are they affected by sleepiness and sleep restriction?

This review shows that impaired/shortened sleep is a major cause of accidents in industry and transport. The reason is either sleep pathology, voluntary (non-pathological) sleep reduction, or activity during the circadian low. Night or morning work is a prominent factor with regard to the latter two. However, the link between sleep restriction (or shift work) and safety is much better established in the transport industry than in other industrial areas. The reason is that driving a vehicle is a task with continuous demand for attention and immediate punishment for lapses, whereas industrial work in most cases does not have the same demands. Still, there are effects and the consequences may be far-reaching.

Accidents, Traffic↗

PubMed2006

The effects of coffee and napping on nighttime highway driving: a randomized trial.

BACKGROUND: Sleep-related accidents often involve healthy young persons who are driving at night. Coffee and napping restore alertness, but no study has compared their effects on real nighttime driving performances. OBJECTIVE: To test the effects of 125 mL of coffee (half a cup) containing 200 mg of caffeine, placebo (decaffeinated coffee containing 15 mg of caffeine), or a 30-minute nap (at 1:00 a.m.) in a car on nighttime driving performance. DESIGN: Double-blind, randomized, crossover study. SETTING: Sleep laboratory and open highway. PARTICIPANTS: 12 young men (mean age, 21.3 years [SD, 1.8]). MEASUREMENTS: Self-rated fatigue and sleepiness, inappropriate line crossings from video recordings during highway driving, and polysomnographic recordings during the nap and subsequent sleep. INTERVENTION: Participants drove 200 km (125 miles) between 6:00 p.m. and 7:30 p.m. (daytime reference condition) or between 2:00 a.m. and 3:30 a.m. (coffee, decaffeinated coffee, or nap condition). After intervention, participants returned to the laboratory to sleep. RESULTS: Nighttime driving performance was similar to daytime performance (0 to 1 line crossing) for 75% of participants after coffee (0 or 1 line crossing), for 66% after the nap (P = 0.66 vs. coffee), and for only 13% after placebo (P = 0.041 vs. nap; P = 0.014 vs. coffee). The incidence rate ratios for having a line crossing after placebo were 3.7 (95% CI, 1.2 to 11.0; P = 0.001) compared with coffee and 2.9 (CI, 1.7 to 5.1; P = 0.021) compared with nap. A statistically significant interindividual variability was observed in response to sleep deprivation and countermeasures. Sleep latencies and efficiency during sleep after nighttime driving were similar in the 3 conditions. LIMITATIONS: Only 1 dose of coffee and 1 nap duration were tested. Effects may differ in other patient or age groups. CONCLUSIONS: Drinking coffee or napping at night statistically significantly reduces driving impairment without altering subsequent sleep.

Adult↗

PubMed2006

The effect of CNS activation versus EEG arousal during sleep on heart rate response and daytime tests.

OBJECTIVE: To induce a heart rate change in normal subjects using auditory stimulation without inducing EEG arousals and to assess the effects on daytime functioning and compare results to auditory stimulation leading to short EEG arousals. METHODS: Six normal young men initially randomized into two groups (A and B) underwent 4 nights of nocturnal polysomnography (normal sleep on night 1, auditory stimulation without EEG arousal or normal sleep on nights 2 and 3 using Latin square design, and auditory stimulation with EEG arousal on night 4). MSLT and PVT were performed during days following nights 2-4. RESULTS: MSLT and PVT results showed significant differences after EEG arousal compared to stimulation without EEG arousal and to normal sleep; there were no significant differences after normal sleep compared to stimulation without EEG arousal. RR interval showed significant differences during undisturbed sleep compared to stimulation without EEG arousal and to stimulation with EEG arousal; RR interval without EEG arousal also differed significantly from RR interval with EEG arousal. CONCLUSION: Activation of the brain-stem can lead to autonomic nervous system (ANS) response without objective consequences the next day. SIGNIFICANCE: ANS responses induced by auditory stimulation during sleep without EEG arousal do not have the same effects on daytime sleepiness and performance as sleep fragmentation associated with EEG arousals.

Acoustic Stimulation↗

PubMed2006

Functional imaging of working memory following normal sleep and after 24 and 35 h of sleep deprivation: Correlations of fronto-parietal activation with performance.

Working memory was evaluated after normal sleep, and at 24 and 35 h of sleep deprivation (SD) in 26 healthy young adults to examine the neural correlates of inter-individual differences in performance. The extent of performance decline was not significantly different between the two SD test periods although there was greater variability in performance at SD35. In both SD sessions, there was reduced task-related activation (relative to normal sleep) in both superior parietal regions and the left thalamus. Activation of the left parietal and left frontal regions after normal sleep was negatively correlated with performance accuracy decline from normal sleep to SD24 thus differentiating persons who maintained working memory performance following SD from those who were vulnerable to its effects.

Adult↗

PubMed2006

Nocturnal sustained attention during sleep deprivation can be predicted by specific periods of subjective daytime alertness in normal young humans.

In our 24-h society, nocturnal sleep-related accidents are common. Because all individuals are not equal in their responses to sleep loss, it is very important to identify predictors of vulnerability to sleep deprivation in normal subjects. We investigated the performance of a cognitive test of sustained attention, electroencephalogram theta/alpha power, subjective sleepiness, and two circadian markers (core temperature and melatonin) in 18 healthy men (nine morning types and nine evening types, 21.4 +/- 1.9 years) during a 36-h sleep deprivation in a constant routine protocol. Sleep need (self-reported) and baseline sleep structure were also investigated. Nighttime performance impairment was defined as the difference between the mean nocturnal number of lapses (00:00-07:30 [corrected] hours) and the mean diurnal number of lapses (07:30-20:30 hours) expressed as a percentage. Feeling fully alert in the morning just after awakening and/or sleepy in early afternoon were the only two factors (Multiple R > 0.80, > 60% of explained variance) which better predicted the decrease in performances of nocturnal operational tasks requiring sustained attention.

Adult↗

PubMed2005

Effects of sleep deprivation on Color-Word, Emotional, and Specific Stroop interference and on self-reported anxiety.

The aim of this study was principally to assess the impact of sleep deprivation on interference performance in short Stroop tasks (Color-Word, Emotional, and Specific) and on subjective anxiety. Subjective sleepiness and performance on a psychomotor sustained attention task were also investigated to validate our protocol of sleep deprivation. Twelve healthy young subjects were tested at four-hourly intervals through a 36-h period of wakefulness under a constant routine protocol. Analyses of variance for repeated measurements revealed that self-assessment of sleepiness on a visual analogue scale as well as mean reaction time performance on the sustained attention task, both for the first minute and for 10 min of testing, were worsened by sleep deprivation. Analyses revealed an increase in self-reported anxiety scores on the STAI questionnaire but did not reveal any significant effect after sleep deprivation either on indexes of interference or on accuracy in Stroop tasks. However, analyses showed sensitivity to circadian effect on verbal reaction times in the threat-related (Emotional) and sleep-related (Specific) Stroop tasks. We concluded that 36 h of prolonged wakefulness affect self-reported anxiety and Emotional Stroop task resulting in a cognitive slowing. Moreover, total sleep deprivation does not affect interference control in any of the three short Stroop tasks.

Adolescent↗

PubMed2005

Sleep duration and caffeine consumption in a French middle-aged working population.

OBJECTIVE/BACKGROUND: To explore the association between sleep duration and daily caffeine intake in a working population. Caffeine acutely disrupts sleep in the laboratory, but the inter-relations between sleep and caffeine intake in daily life are ill-known. METHODS: Questionnaire and diary based survey of 1498 persons from the GAZEL cohort of employees of the National Electricity and Gas Company (EDF-GDF) working in various locations in the Paris and South-West France areas. We analyzed total sleep time, our primary measure, and time in bed, both by sleep logs. We assessed daily intake of caffeine, consumption of alcohol and tobacco, use of hypnotics, and daytime somnolence, all by questionnaire. RESULTS: Multiple linear regression analysis did not find a significant relationship between total sleep time and daily caffeine intake less than 8 cups of coffee per day, after controlling for age, gender, alcohol intake, smoking status, and use of hypnotics. By contrast, time in bed was reduced as caffeine intake increased (beta=-0.125; P<0.001). Higher caffeine intake was not related to a higher daytime somnolence. CONCLUSION: Despite the well-known acute effects of caffeine on sleep, habitual use of up to 7 cups of coffee (or 600 mg of caffeine equivalent) per day was not associated with decreased duration of sleep.

Beverages↗

PubMed2005

Fatigue, sleep restriction and driving performance.

We ran a randomized cross-over design study under sleep-deprived and non-sleep-deprived driving conditions to test the effects of sleep restriction on real driving performance. The study was performed in a sleep laboratory and on an open French highway. Twenty-two healthy male subjects (age = 21.5 +/- 2 years; distance driven per year = 12,225 +/- 4739 km (7641 +/- 2962 miles) [mean +/- S.D.]) drove 1000 km (625 miles) over 10 h during five 105 min sessions on an open highway. Self-rated fatigue and sleepiness before each session, number of inappropriate line crossings from video recordings and simple reaction time (RT) were measured. Total crossings increased after sleep restriction (535 crossings in the sleep-restricted condition versus 66 after non-restricted sleep (incidence rate ratio (IRR): 8.1; 95% confidence interval (95% CI): 3.2-20.5; p < 0.001)), from the first driving session. The interaction between the two factors (conditionxtime of day) was also significant (F(5, 105) = 3.229; p < 0.05). Increasing sleepiness score was associated with increasing crossings during the next driving session in the sleep-restricted (IRR: 1.9; 95% CI: 1.4-2.4) but not in the non-restricted condition (IRR: 1.0; 95% CI: 0.8-1.3). Increasing self-perceived fatigue was not associated with increasing crossings in either condition (IRR: 0.95; 95% CI: 0.93-0.98 and IRR: 1.0; 95% CI: 0.98-1.02). Rested subjects drove 1000 km with four shorts breaks with only a minor performance decrease. Sleep restriction induced important performance degradation even though time awake (8h) and session driving times (105 min) were relatively short. Major inter-individual differences were observed under sleep restriction. Performance degradation was associated with sleepiness and not fatigue. Sleepiness combined with fatigue significantly affected RT. Road safety campaigns should encourage drivers to avoid driving after sleep restriction, even on relatively short trips especially if they feel sleepy.

Adolescent↗

PubMed2005

Fatigue, sleepiness, and performance in simulated versus real driving conditions.

STUDY OBJECTIVES: To determine whether real-life driving would produce different effects from those obtained in a driving simulator on fatigue, performances and sleepiness. DESIGN: Cross-over study involving real driving (1200 km) or simulated driving after controlled habitual sleep (8 hours) or restricted sleep (2 hours). SETTING: Sleep laboratory and open French Highway. PARTICIPANTS: Twelve healthy men (mean age +/- SD = 21.1 +/- 1.6 years, range 19-24 years, mean yearly driving distance +/- SD = 6563 +/- 1950 miles) free of sleep disorders. MEASUREMENTS: Self-rated fatigue and sleepiness, simple reaction time before and after each session, number of inappropriate line crossings from the driving simulator and from video-recordings of real driving. RESULTS: Line crossings were more frequent in the driving simulator than in real driving (P < .001) and were increased by sleep deprivation in both conditions. Reaction times (10% slowest) were slower during simulated driving (P = .004) and sleep deprivation (P = .004). Subjects had higher sleepiness scores in the driving simulator (P = .016) and in the sleep restricted condition (P = .001). Fatigue increased over time (P = .011) and with sleep deprivation (P = .000) but was similar in both driving conditions. CONCLUSIONS: Fatigue can be equally studied in real and simulated environments but reaction time and self-evaluation of sleepiness are more affected in a simulated environment. Real driving and driving simulators are comparable for measuring line crossings but the effects are of higher amplitude in the simulated condition. Driving simulator may need to be calibrated against real driving in various condition.

Adult↗

PubMed2005

Sleepiness of occupational drivers.

Drowsiness and sleeping at the wheel are now identified as the reasons behind fatal crashes and highway accidents caused by occupational drivers. For many years, fatigue has been associated to risk of accidents but the causes of this symptom were unclear. Extensive or nocturnal driving was associated to accidents but few reports differentiated fatigue from sleepiness. In the early nineties, epidemiological data started investigating sleepiness and sleep deprivation as cause of accidents. Sleepiness at the wheel, sleep restriction and nocturnal driving have been incriminated in 20% of traffic accidents. Drugs affecting the central nervous system (i.e., narcotic analgesics, antihistamine drugs), nocturnal breathing disorders and narcolepsy have been also associated with an increasing risk of accidents. Treatments improving daytime vigilance (i.e., nasal Continuous Positive Airway Pressure) reduce significantly the risk of traffic accidents for a reasonable economical cost. Sleep disorders among occupational drivers need to be systematically investigated. Chronic daytime sleepiness is still under diagnosed and sleep disorders (i.e. obstructive sleep apnea syndrome) are not enough explored and treated in this exposed population of sedentary males. Drivers education and work schedules integrating notions of sleep hygiene as well as promotion of sleep medicine could significantly improve road safety.

Accidents, Traffic↗

PubMed2004

Age, performance and sleep deprivation.

Young subjects are frequently involved in sleep-related accidents. They could be more affected than older drivers by sleep loss and therefore worsen their driving skills quicker, or have a different perception of their level of impairment. To test these hypotheses we studied variations of reaction time (RT), a fundamental prerequisite for safe performing, as measured by lapses, i.e. responses > or = 500 ms and self-assessment of performance and sleepiness after a night awake and after a night asleep in a balanced crossover design in young versus older healthy subjects. Ten young (20-25 years old) and 10 older volunteers (52-63 years old) were tested with and without 24 h of sleep deprivation. Without sleep deprivation, RTs were slower in older subjects than in the younger ones. However, after sleep deprivation, the RTs of young subjects increased while that of the older subjects remained almost unaffected. Sleepiness and self-perception of performance were equally affected in both age groups showing different perception of performance in the age groups. Our findings are discussed in terms of vulnerability to sleep-related accidents.

Accidents, Traffic↗

PubMed2004

Validation of Horne and Ostberg morningness-eveningness questionnaire in a middle-aged population of French workers.

As suggested by the authors, the Horne and Ostberg morning/evening questionnaire (MEQ) has never been adapted to evaluate a nonstudent population. The purpose of this study was to validate this MEQ in a sample of middle-aged workers by modifying only the cutoffs. It was administered in 566 non-shift-workers aged 51.2 to 3.2 years who presented no sleep disorders. According to the Home and Ostberg classification, the sample consisted of 62.1% morning type, 36.6% neither type, and 2.2% evening type. Multiple correspondence analysis, which determines the principal components, was performed on all MEQ items. Then an ascending hierarchical classification was applied to determine 3 clusters from these principal components. On the basis of these 3 clusters, new cutoffs were determined: evening types were considered as scoring under 53 and morning types above 64, thus giving 28.1% morning type, 51.7% neither type, and 20.2% evening type. As an external validation, eveningness was associated with later bedtime and waking-up time (more pronounced at the weekend), greater need for sleep, larger daily sleep debt, greater morning sleepiness, and ease of returning to sleep in the early morning. A positive correlation between age and morningness was again found. This study confirms that "owls" are not rare in a middle-aged sample. We conclude that this adapted MEQ could be useful when investigating age-related changes in sleep.

Biological Clocks↗

PubMed2003

Anterior cervical spine fusion and sleep disordered breathing.

The authors reviewed 12 patients who developed obstructive sleep apnea (OSA) syndrome in association with anterior cervical spine fusion. Four subsequent patients were studied prospectively before C2 to C4 anterior fusion and documented to have OSA by questionnaire, visual analogue scales, polysomnography, and multiple sleep latency tests. The authors found that placement of the anterior cervical plates reduced the size of the upper airway. Symptoms and objective findings were controlled with nasal continuous positive airway pressure.

Airway Obstruction↗

PubMed2003

Fatigue, sleep restriction, and performance in automobile drivers: a controlled study in a natural environment.

OBJECTIVES: To test the neurobehavioral consequences of sleep restriction combined with fatigue from long-distance driving (1000 Km/600 miles). DESIGN: Counterbalanced study involving 3 experimental conditions: laboratory after controlled habitual sleep (8.5 hours), driving after controlled habitual sleep (8.5 hours) (Road 1), and driving after reduced sleep (2 hours) (Road 2). SETTING: Sleep laboratory and open French highway. PARTICIPANTS: 10 male participants (mean age 22 years, range 18-24 years, mean driving distance per year 15000 Km/9000 miles) free of sleep disorders. MEASUREMENTS: Simple reaction time, prospective self-assessment of performance, and instantaneous fatigue and sleepiness ratings measured at 2-hour intervals. RESULTS: A two-way repeated ANOVA with time of day and condition indicated a significant main effect for time of day (p < 0.05). The interaction between the two factors (condition * time of day) was also significant (p < 0.05). The effects of time of day were significant only in the condition of driving after sleep restriction, (p < 0.05). Under sleep restriction, some drivers presented an increase of 650 milliseconds compared to the laboratory condition, representing an increase of 23 meters in breaking distance at a speed of 75 miles per hour. Correlation analyses showed a significant linear correlation between self-assessment and reaction time in the laboratory condition (r = -0.58, p < 0.01) but not in the road conditions. Self-ratings during the breaks showed a significant increase in instantaneous self-rated fatigue and sleepiness between Road 1 and Road 2 conditions (Wilcoxon's test, Z = - 6.47, p < 0.0001 and Z = - 6.26, p < 0.0001). CONCLUSIONS: Sleep restriction combined with fatigue significantly affects reaction time. The lack of correspondence between reaction time and prospective self-evaluation of performance suggests that self-monitoring in real conditions is poorly reliable.

Adolescent↗

PubMed2003

Preliminary observations on the effects of sleep time in a sleep restriction paradigm.

OBJECTIVE: To evaluate of the effect of 7 days of sleep restriction--with sleep placed at the beginning of night or early morning hours - on sleep variables, maintenance of wakefulness test, and serum leptin. METHODS: After screening young adults with questionnaires and actigraphy for 1 week, eight young adult males were recruited to participate in a sleep restriction study. The subjects were studied for baseline data for 2.5 days, with 8.5 h per night in bed, and then over 7 days of sleep restriction to 4 h per night with a 22:30 h bedtime for half the group and a 02:15 h bedtime for the other half. At the end of study, after one night of ad libitum sleep, subjects again had 2 days of 8.5 h in bed. Wakefulness was continuously verified and tests, including Maintenance of Wakefulness (MWT), were performed during the scheduled wake time. Blood was drawn six times throughout the 24 h of the 7th day of sleep restriction and after 2 days of the post-restriction schedule. RESULTS: There was individual variability in response to sleep restriction, but independent of group distribution, MWT was significantly affected by sleep restriction, with the early morning sleep group having less decrease in MWT score. Sleep efficiency was also better in this group, which also had shorter sleep latency. Independent of group distribution there was a greater increase in the percentage of slow wave sleep than rapid eye movement sleep, despite a clear internal variability and variability between subjects. Peak serum leptin was significantly decreased with 7 days of sleep restriction for all subjects. CONCLUSION: Sleep restriction to 4 h affected all subjects, but there were individual and group differences in MWT and sleep data. In this group of young adult males (mean age 19 years), there was a better overall adaptation to the early morning sleep, perhaps related to the general tendency in most adolescents to present some phase-delay during late teen-aged years.

Adolescent↗

PubMed2003

The circadian and homeostatic modulation of sleep pressure during wakefulness differs between morning and evening chronotypes.

The purpose of this study was to evaluate homeostatic and circadian sleep process in 'larks' and 'owls' under daily life conditions. Core body temperature, subjective sleepiness and waking electroencephalogram (EEG) theta-alpha activity (6.25-9 Hz) were assessed in 18 healthy men (nine morning and nine evening chronotypes, 21.4 +/- 1.9 years) during a 36-h constant routine that followed a week of a normal 'working' sleep-wake schedule (bedtime: 23.30 h, wake time: 07.30 h). The phase of the circadian rhythm of temperature and sleepiness occurred respectively, 1.5 h (P = 0.01) and 2 h (P = 0.009) later in evening- than in morning-type subjects. Only morning-type subjects showed a bimodal rhythm of sleep-wake propensity. The buildup of subjective sleepiness, as quantified by linear regression, was slower in evening than in morning types (P = 0.04). The time course of EEG theta-alpha activity of both chronotypes could be closely fitted by an exponential curve. The time constant of evening types was longer than that of morning types (P = 0.03), indicating a slower increase in sleep pressure during extended wakefulness. These results suggest that both the circadian signal and the kinetics of sleep pressure buildup differ between the two chronotypes even under prior naturalistic conditions mimicking the usual working day.

Adult↗

PubMed2003

[Inhibition and working memory: effect of acute sleep deprivation on a random letter generation task].

The literature contains inconsistent data on the effects of acute sleep deprivation on the superior cognitive functions. The primary purpose of this study is to determine the effectiveness of inhibition, one of the functions of the working memory executive centre (EC), over an extended, 36-hour waking period. Inhibition is a cognitive mechanism whereby individuals ignore non-relevant information recorded in their working memory. We also tested the effects of a 36-hour period of acute sleep deprivation on simple reaction time. Twelve young, healthy volunteers (M = 21.5 years, sigma = 2.3) performed a random generation task involving letters and a simple reaction time psychomotor test over four sessions held at 10-hour intervals. Each participant was assigned a "constant routine." Participants were kept awake in a prone position within a room whose environment was held strictly constant (light, noise, temperature, meals, etc.). This control procedure provided assurance that any variation in participant performance was solely caused by sleep deprivation. The random generation task, nearly two minutes in length, consisted in verbally producing a sequence of 100 letters in a random fashion (i.e. by inhibiting, for example, alphabetical order) and by keeping to a set rhythm. Our assumption was that capacity for inhibition diminished as the number of hours of sleep deprivation increased. The simple reaction test, 10 minutes in length, involved pressing a button as swiftly as possible to cause a black square to disappear from a screen. In this case our assumption was that acute sleep deprivation alters simple reaction time. Analysis of variance (ANOVA) through repeated measures using the "sessions" factor as an intra-subject variable showed no significant changes in randomization indices of the random generation task, contrary to analysis of average simple reaction times. Participants' reaction times deteriorated over the first two minutes of the test during the night they were deprived of sleep. It would seem that the contradictory results of previous studies of the effects of acute sleep deprivation on the inhibition function would be due to errors in factor identification. In conclusion, the inhibition function, as measured during the performance of a brief task, seems to remain intact during an extended, 36-hour waking period. Simple reaction time assessed by means of a brief psychomotor test is affected during a night of sleep deprivation. The working-memory inhibition executive function shows greater resistance to acute sleep deprivation than does psychomotor reaction time for the performance of short tasks.

Adolescent↗