Jacques Taillard

Morningness/eveningness and the need for sleep.

The purpose of this study was to determine, in a large sample of adults of all ages (17–80 years), the effect of morningness/eveningness on sleep/wake schedules, sleep needs, sleep hygiene and subjective daytime somnolence. A total of 617 subjects (219 subjects per chronotype group) matched for age, sex and employment status, completed an abridged morningness/eveningness questionnaire, a questionnaire on sleep habits and the quality of sleep, and the Epworth Sleepiness Scale. Eveningness was associated with a greater need for sleep, less time in bed during the week compared to ideal sleep needs, more time in bed at the weekend, a later bedtime and waking‐up time especially at the weekend, more irregular sleep/wake habits and greater caffeine consumption. These subjects built up a sleep debt during the week and extended their duration of sleep at the weekend. They did not, however, rate themselves more sleepy than other types, despite the fact that our results showed a clear link between subjectively evaluated daytime somnolence and sleep debt. Why they were less affected by sleep deprivation is not clear. This raises the question of individual susceptibility to the modification of sleep parameters.

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 Horne 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.

Fatigue, alcohol, and serious road crashes in France: factorial study of national data

Editorial by Feyer France has a high rate of road traffic crashes.1 Although driver fatigue may be an important factor,2–4 it has not been investigated in France, and no comparisons have been made with alcohol related crashes.5 We investigated the role of fatigue in serious road crashes using the French national database.1 We obtained data from the French Ministry of Transport on all road crashes during 1994–8 (640 670) in which at least one person was severely injured (confirmed by paramedics) or died. Crashes were attended by police officers, who completed a standard ministry questionnaire that covered time of incident, location, road and weather conditions, vehicles involved, mechanical defects, health of driver, and alcohol consumption as well as giving summaries of interviews and probable causes. As crashes related to fatigue can be difficult …

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.

Melatonin is able to influence its secretion in humans : description of a phase-response curve

A single physiological dose of melatonin (20 micrograms for 3 h given intravenously at different times of the day (04.00-12.00, 16.00 and 20.00 h) was able to shift the endogenous plasma melatonin profile of healthy volunteers under entrained conditions according to a phase-response curve (PRC). ANOVA showed an effect of the time of administration on the onset, the acrophase or the offset of the melatonin profiles. These profiles were significantly delayed when the infusion was administered at 12.00 h and advanced when the infusion was given at 20.00 h. Further, the AUCs evaluated on the nocturnal melatonin profiles were increased after the 04.00 h infusion (+20.5%, p < 0.05), whereas they were decreased after the 12.00 h infusion (-20%, p < 0.05). Lastly, no alteration was observed for cortisol rhythm, whatever the time of melatonin administration. These results, which show that according to a PRC the system regulating melatonin secretion is sensitive to a single short-term administration of the hormone given at a low dose, support the paradigm of the endogenous synchronizer melatonin.

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.

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 ≥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.

Sleep disorders and accidental risk in a large group of regular registered highway drivers

OBJECTIVE Despite convincing evidence regarding the risk of highway accidents due to sleepiness at the wheel, highway drivers still drive while sleepy. Sleep disorders can affect driving skills, but the relative impact of sleep complaints among a large population of highway drivers is still unknown. METHODS Out of 37,648 questionnaires completed by frequent highway users (registered in an electronic payment system), we ran our analyses on 35,004 drivers who responded to all items. The questionnaire previously used in a telephone survey included socio-demographics, driving and sleep disorders items (Basic Nordic Sleep Questionnaire) and the Epworth Sleepiness Scale. RESULTS Of all drivers, 16.9% complained of at least one sleep disorder, 5.2% reported obstructive sleep apnea syndrome, 9.3% insomnia, and 0.1% narcolepsy and hypersomnia; 8.9% of drivers reported experiencing at least once each month an episode of sleepiness at the wheel so severe they had to stop driving. One-third of the drivers (31.1%) reported near-miss accidents (50% being sleep-related), 2520 drivers (7.2%) reported a driving accident in the past year, and 146 (5.8%) of these driving accidents were sleep-related. The highest risk of accidents concerned patients suffering from narcolepsy and hypersomnia (odds ratio 3.16, p<.01) or multiple sleep disorders (odds ratio 1.46, p<.001). Other major risk factors were age [18-30 years (OR 1.42, p<.001)] and being unmarried (OR 1.21-fold, p<.01). CONCLUSIONS In regular highway drivers, sleepiness at the wheel or sleep disorders such as hypersomnia and narcolepsy are responsible for traffic accidents independent of age, sex, marital status or socio-professional categories.

CPAP treatment does not affect glucose–insulin metabolism in sleep apneic patients

Objective: We investigated glucose metabolism and insulin resistance in non-obese and moderately overweight sleep apnea patients, as well as their response to nasal CPAP treatment.Methods: A group of subjects with glucose intolerance was screened for sleep disordered breathing by clinical interview and ambulatory recordings. Ten subjects were found to have untreated sleep apnea and were asked to participate in further investigation. This included nocturnal polysomnography, oral glucose tolerance test and indirect calorimetry. Subjects then had calibration of nasal CPAP with polysomnography. Two months after start of treatment, all subjects were restudied as at baseline. In parallel, six obstructive sleep apnea syndrome (OSAS) subjects, diagnosed through the sleep clinic, were matched for gender, age and oxygen desaturation index with the other group, and had a euglycemic hyperinsulinemic clamp at baseline and after 2 months of nasal CPAP.Results: The first ten patients showed no change in total glucose oxidation, glucose oxidation by weight or by fat free mass, or insulin energetic expenditure, despite nocturnal usage of nasal CPAP. Similarly, when comparing baseline to the treatment at 2 months, the six OSAS patients had no change in mean glycemia, insulin, C peptide and hemoglobin (Hgb) A1C measurements. No difference in the amount of glucose infused during the duration of the clamp was noted either.Conclusion: Our data do not support the existence of a significant relationship between glucose and insulin metabolism and obstructive sleep apnea. Obesity, when present, is the important variable.

Simple reaction time, duration of driving and sleep deprivation in young versus old automobile drivers

Car accidents are one of the major causes of death in modern society and sleepiness is identified as one major risk factor. The purposes of the present study were: (1) to relate the sleep loss and driving time to a performance indicator and (2) to identify risk factors of performance decrement. We investigated 294 drivers (age < 30 years, n=100; age ≥ 30 years, n=194) who drove into a rest stop area. All were asked to fill out a questionnaire about the drive and previous sleep/wake pattern, and to carry out a 10 min, simple reaction time (RT) test. The level of performance is identified by the 10% slowest RTs. Multiple regression analysis, with the mean of the 10% Slowest RTs as the dependent variable, showed that age, duration of drive, and duration (shortness) of previous breaks were the main predictors. Our study suggests that public awareness may need to be raised with respect excessive length of driving, especially in young drivers.