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PubMed2001

Insufficient sleep--a population-based study in adults.

STUDY OBJECTIVES: Insufficient sleep (sleep deprivation) is a common problem of considerable health, social, and economical impact. We assessed its prevalence and associations, and the role of genetic influences. DESIGN: Panel study based on questionnaires administered in 1981 and 1990. SETTING/PATIENTS: 12.423 subjects aged 33-60 years included in the Finnish Twin Cohort, representative of the Finnish population. INTERVENTIONS: N/A. MEASUREMENTS: A difference of 1 hour between the self-reports of the sleep need and the sleep length was considered insufficient sleep. Associations with education, life style, work, psychological characteristics and sleep-wake variables were assessed. Structural equation modelling techniques were used to compare genetic models among monozygotic and dizygotic twin pairs. RESULTS: In 1990, the prevalence of insufficient sleep was 20.4% (16.2% in men and 23.9% in women). 44% of those with insufficient sleep in 1981 also had it 9 years later (Spearman correlation for persistence 0.334). In multivariate analyses, the strongest positively associated factors were daytime sleepiness (women: odds ratio 3.87, 95% confidence limits 3.24-4.63/men: 3.77, 2.98-4.75), insomnia (2.48, 1.92-3.19/2.91, 2.17-3.90), not able to sleep without disturbance (1.95, 1.47-2.60/2.54, 1.66-3.89), and evening type (2.10, 1.65-2.69/1.73, 1.25-2.41). Among men, also weekly working hours > or =75 was strongly associated (3.23, 1.54-6.78). "Not working" was negatively associated in both genders (0.68, 0.51-0.89/0.59, 0.42-0.83). Two thirds of the interindividual variability in the liability to insufficient sleep was attributed to non-genetic factors. CONCLUSIONS: Insufficient sleep is a common and long-standing condition, most strongly associated with sleep/wake variables. One third of the liability to it is attributed to genetic influences. Sleep sufficiency should be assesssed in health examinations of working adults.

Adult↗
PubMedDate not supplied

[Kinetic characteristics of enzymes of ethanol metabolism in rats].

Experimental animals were separated as for narcotic sleep length into short-sleeping and long-sleeping rat groups and as for alcohol motivation to rats preferring ethanol or water or an intermediate group as well. Alcohol- and aldehyde dehydrogenase reaction maximum speed as well as Michaelis-Menten constants for these enzymes were measured for each of these groups. Alcohol dehydrogenase affinity to cofactor in the reverse reaction was an order of magnitude higher as compared with the affinity to substrate in all the animal groups. Apparent Michaelis-Menten constant values were 1.5-2 times higher in short-sleeping and ethanol preferring rats in the direct reaction. There were no such differences for the reverse reaction. Alcohol dehydrogenase reaction maximum speed for short-sleeping group is close to that for animals preferring ethanol or water. For different forms of aldehyde dehydrogenase an increase of the apparent maximum speeds was distributed as follows: water preferring group < intermediate group < ethanol preferring group. Aldehyde dehydrogenase-1 Michaelis-Menten apparent constants for acetaldehyde were changed in the same way. Thus, data obtained suggest that ethanol metabolism speed along the path alcohol/aldehyde dehydrogenases are close in ethanol-preferring and short-sleeping rats.

Alcohol Dehydrogenase↗
PubMed2001

[Sleep disorders of patients in intensive care].

The objective of this article is to present a literature review of German and English literature concerning sleep disturbances of critically ill adults in intensive care units. It represents mainly nursing research-based studies which focused on characteristics and possible causes of sleep disturbances. The literature revealed that patients suffer from moderate to severe sleep deprivation characterized by a decrease of total sleep length and quality, and by sleep fragmentation. The causes are multifactorial. Nurses have an important role to play in recognizing and assessing factors that contribute to sleep deprivation and in intervening to reduce the effects of sleep deprivation. The research studies in this review represent the positivistic scientific perspective where sleep deprivation research has been objectified and controlled. A broader, more indepth understanding is needed, however, so that the subjective view of critically ill persons can be represented.

Clinical Nursing Research↗
PubMed1994

The effect of four-day round trip flights over 10 time zones on the sleep-wakefulness patterns of airline flight attendants.

To study the effect of a four-day-round trip flight on the sleep-wakefulness of airline flight attendants, subjective sleep-wakefulness and autonomic sleep phases were measured. Forty flight attendants (mean age 33 years, range 21-50) kept daily logs on sleepiness, the time when going to bed, and sleep quality. In addition, the autonomic sleep phases of 21 subjects were studied by the static charge sensitive bed (SCSB) method. After the westward flight, the subjects went to bed approximately 1-3 h local time earlier during the first few days and were very sleepy compared to the week before the flight. There was a significant increase in the number of awakenings and in the feeling of 'not being at all rested' in the mornings. After the return flight eastwards, the subjects were very sleepy on the first evening but slept rather well for about 11 h. During the three following days, sleep restlessness, difficulties in falling asleep, and the feelings of sleepiness in the mornings increased compared to the week before the flights. Four days after the return flight, sleep length and the quality of sleep were, on average, the same as before the flights. According to the SCSB method, there were only small changes in the autonomic sleep phases due to the flights. After the westward flight, quiet sleep increased and intermediate sleep decreased compared to the sleep before the flight. The results indicate that most flight attendants have significant disturbances in sleep quality after transmedian flights. Sleep disturbances increase after both westward and eastward transmedian flights, but differ from each other in specific features.

Adult↗
PubMed1982

Energy expenditure and total sleep time: effect of physical exercise.

The energy conservation model proposes that the main function of sleep is to lower metabolic requirements periodically and thus to conserve energy. However, certain variations in energy expenditure, such as that produced by physical exercise, have not been found to be consistently related to sleep length. We hypothesized that, because sleep variables may adapt relatively slowly to metabolic changes, the effect of exercise on sleep time would be observed as a function of habitual exercise patterns, not of daily variations. The study consisted of a retrospective analysis of five experiments. Although the design of each experiment was idiosyncratic, all involved physically fit and/or unfit subjects whose sleep was assessed following daytime exercise and/or no exercise conditions. As predicted, fit subjects slept significantly longer than unfit subjects, and daytime exercise had no consistent effect on sleep duration. However, for several reasons, the relevance of the data to the energy conservation model is uncertain.

Adult↗
PubMed2005

Oculomotor changes are associated to daytime sleepiness in the multiple sleep latency test.

Sleep onsets in the diurnal multiple sleep latency test (MSLT), following different sleep lengths of the preceding night sleep (8, 5, 4, 3, 2, 1 h) and following the corresponding recovery nights, were considered for a study on changes of oculomotor activity during sleep onset. The study aimed to assess the individual time course in spontaneous blinks (SBs) and slow eye movements (SEMs) during the sleep onset period and also the relationship with sleep latencies in the MSLT. Group analyses compared oculomotor changes between conditions characterized by a different level of daytime sleepiness. The results show a clear inverse relation between the two oculomotor measures, with a linear SB decrease and quadratic SEM increase across the wake-sleep transition. A 150 s sample of SB and SEM activity at the start of MSLT trials correlates with individual subsequent sleep latency. Finally, mean changes in daytime sleepiness as measured by the MSLT are paralleled by coherent oculomotor changes, with a significant linear decrease of SB as sleepiness increases as a consequence of previous sleep reduction. Both individual and group results show that endogenous blinking is associated with moderate changes in daytime sleepiness.

Adult↗
PubMed1983

Relationships in sleep characteristics of identical and fraternal twins.

We recorded EEGs for 14 identical and 14 fraternal young adult twin pairs during one night of sleep in our laboratory. They were instructed to sleep as long as possible. The extended sleep of the identical and fraternal twins was correlated. The structural measures of sleep of the fraternal twins were not correlated. The onset latencies, awakening measures, stage changes, and rapid eye movement amounts were significantly correlated in the identical twins. The nature of the measures used supports an interpretation of hereditary aspects of sleep length and certain structural components of sleep.

Adolescent↗
PubMed1995

Work hours, sleepiness and the underlying mechanisms.

Severe subjective and physiological sleepiness occur in night work, afflict almost all individuals and are associated with a performance impairment severe enough to explain night-work accident data. The alertness deficit is caused by the displacement of work to the circadian phase which is least conducive to alert behaviour, by extension of the time spent awake and by the reduction of sleep length (due to circadian interference with sleep). Sleepiness will be extreme when the three causes are operative simultaneously. The three factors may be used quantitatively to predict sleepiness.

Journal Article↗
PubMed1996

Prolonged interval from body temperature nadir to sleep offset in patients with delayed sleep phase syndrome.

In order to clarify the relationship between sleep-wake and core body temperature rhythms in the delayed sleep phase syndrome (DSPS), we conducted simultaneous monitoring of these rhythms in seven patients with DSPS and nine healthy control subjects for 6-10 days during their conventional sleep-wake schedules. The sleep onset and offset times were determined visually from sleep logs, and the temperature data were fitted to 24-hour cosinor curves by the least squares method. The sleep onset and offset times and temperature nadir were delayed significantly in patients with DSPS compared with the control subjects (p = 0.01, 0.003 and 0.02, respectively). We also found that sleep length and the temperature nadir to sleep offset interval were significantly longer in the DSPS than the control group (p = 0.03 and 0.02, respectively). The latter finding suggests that the inability of the patients with DSPS to normally phase-advance their circadian rhythm may be a consequence of masking of the advance portion of their phase-response curve by the last hours of their prolonged sleep episodes.

Adult↗
PubMed2005

Self-report naps in irregular work schedules.

Few studies have examined napping in irregular work schedules such as those experienced by freight locomotive engineers. The current study examined the effect of napping in irregular work schedules on sleep length and three subjective measures: ability to go to sleep, ability to stay asleep, and a feeling of being well-rested upon awakening. One hundred and seventy-nine freight engineers completed a 14-d activity log, providing information on sleep times and subjective evaluations of sleep. The results indicated that days with naps resulted in significantly more total sleep but less sleep in the main sleep period of the day. The days with naps also resulted in somewhat more difficulty with going to sleep, staying asleep and with feeling well-rested upon awakening. It is important to note, however, that when examining the days with naps, nap length was not significantly correlated with main sleep time, ability to go to sleep, ability to stay asleep, or feeling well-rested upon awakening. These results suggest that napping may be useful when working irregular work schedules if the engineer is willing to accept a slight decrease in ability to go to sleep, stay asleep, and feeling rested.

Adult↗
PubMed1977

Individual differences in human circadian rhythms.

Research into individual differences in circadian rhythms is reviewed, particularly morningness-eveningness. It was hypothesised that extraverts would be inclined towards eveningness and introverts towards morningness. Forty-eight subjects took regularly their oral temperature. Peak times were identified from smoothed temperature curves. Results showed that extraverts had a peak time insignificantly later than introverts. Re-grouping of the data into the morningness-eveningness dimension, based upon the results of a self assessment questionnaire, showed that evening types had significantly later peak times than morning types. Morningness-eveningness was not significantly ocrrelated with extraversion-introversion, although there was a trend. No significant differences were found for sleep lengths with either groupings, or for sleep-wake habits within extraversion-introversion. Morning types retired and arose significantly earlier than evening types. Although sleep-wake habits and extraversion-introversion help to determine peak times there are other contributory factors to peak time which appear to be partly covered by the questionnaire.

Adolescent↗
PubMed2006

Short sleep is associated with obesity among truck drivers.

Recent studies suggest that short-sleep duration is independently associated with obesity in the general population. The population of truck drivers is of particular interest, because they frequently work irregular shifts that in turn are associated with short-sleep duration. In addition, truck drivers have a high prevalence of sedentary habits, poor diet, and obesity. The present study aimed at verifying the association between sleep patterns and factors associated with obesity in this population. The study sample consisted in 4,878 truck drivers who participated in a campaign promoted by a highway company in the State of São Paulo, Brazil. This campaign offered highway truck drivers a medical and laboratorial evaluation. The truck drivers completed a questionnaire concerning demographic data, sleep duration, consumption of medications, and medical problems, such as diabetes, cardiopathy, and hypertension; as well as the Berlin questionnaire, which is able to discriminate low and high risk for obstructive sleep apnea. Blood samples were collected to measure glucose and cholesterol levels. Also, body weight and height were registered to calculate the body mass index (BMI). The mean age (+/-SD) of the truck drivers studied was 40+/-10 years. Out of the truck drivers analyzed, 28.3% (n = 1,379) had a BMI > or =30.0 Kg/m2 (obesity). Among the 4,878 drivers included in the study, 1,199 (24.6%) were on medications and 334 (6.8%) were diabetic. Drivers (26.9%) with the greater BMI had a short sleep length. The independent factors associated with obesity were sleep duration <8 h/day (OR = 1.24), age >40 years (OR = 1.20), glucose levels >200 (OR = 2.02), cholesterol levels >240 (OR = 1.57), snoring (OR = 1.74), and hypertension (OR = 2.14). Smoking was not associated with obesity (OR = 0.69), and diabetes was considered a control variable. In conclusion, this study supports the hypothesis that short sleep duration as well as age >40 years are independently associated with obesity. This particular combination (short-sleep duration and obesity) is independently associated with several healthcare problems, including high levels of cholesterol, glucose, snoring, and hypertension. However, due to the cross-sectional nature of this study, no cause-effect relationship can be drawn from these results.

Adult↗
PubMed1988

Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels. IV. Rhythms in performance and alertness.

Performance scores on both a simple detection task and a complex visual judgment task, together with subjective alertness ratings, were collected 4-hourly from 19 watchkeepers working a "4-on/8-off" routine, and from 20 dayworkers, over consecutive days of voyages on merchant ships. Adaptation of the circadian rhythms in the measures to the shifted hours of work of the three sections of the watchkeeping crews was at best only partial. These rhythms resulted in a depression of the levels of most measures during the night hours, which was exacerbated by the effects of recent awakening from sleep. It is suggested that these unwanted variations in operational effectiveness could be largely removed by replacing the 4-on/8-off watchkeeping system, with its associated "split" sleep pattern, by one which allows a single full length sleep each day. Such a system would encourage better adaptation of the rhythms; effects of recent awakening could be avoided by the provision of an adequate "waking up" period before duty begins.

Arousal↗
PubMed2006

Sleep on the job partially compensates for sleep loss in night-shift nurses.

Nursing personnel in Brazil are usually submitted to fixed 12 h shifts with no consecutive working days or nights. Moonlighting is common in this group, with a consequent increase in the number of working hours. The possibility of sleeping on the job during the night shift in the studied hospitals had already been described. The present study aims to analyze whether the time devoted to daily activities (sleep, rest, leisure, housework, commuting, personal needs, care of children or other people, non-paid work, and study) is related to the number of worked hours and to nap-taking during the night shift. The field study took place at two public hospitals in Rio de Janeiro, Brazil. Workers filled out a structured form on time devoted to the above-mentioned activities for at least four consecutive days. The time devoted to sleep was analyzed according to its occurrence at home or on the job. Workers were classified according to the number of jobs (one job/two jobs) and the time dedicated to work according to the median of the whole series (below the median/above the median). All workers who had at least one working night were analyzed as to nap-taking on the job. They were classified according to the sleep occurrence during the night shift-the sleep group and the non-sleep group, both of which were compared to daytime workers. Statistical treatment of data included non-parametrical procedures. The study group comprised 144 workers (mean age: 35.7+/-10.5 years old; 91% women; 78% nurse assistants, the remainder registered nurses). They recorded their daily activities for 4-11 days; 829 cumulative days were analyzed for the whole group. A total of 165 working nights were analyzed; sleep or rest occurred during 112 (68%) of them, with mean sleep/rest duration of 141+/-86 min. Time devoted to sleep and leisure varied according to the number of working hours, being significantly reduced in those submitted to longer work hours (p < 0.001 and p = 0.002, respectively). Results close to significance point to a reduction in the time dedicated to housework among workers with long work hours (p = 0.053). The time spent on sleep/rest per working night did not differ according to the number of worked hours (p = 0.490). A tendency was observed for those who have two jobs to devote more time to sleep/rest on the job (p = 0.058). The time of personal needs was significantly lower among those who did not sleep on the job as compared to day workers (p = 0.036). The total sleep time was significantly lower among those who did not sleep on the job, as compared to day workers and to those who slept on the job (p = 0.004 and p = 0.05, respectively). As to home sleep length, workers who slept and those who did not sleep on the job were similar and slept significantly less than exclusively daytime workers (p < 0.001 and p = 0.002, respectively). Sleeping on the job during the night shift seems to partially compensate for the shorter sleep at home among night workers and may play a beneficial effect in coping with two jobs.

Adult↗
PubMed1983

Exercise and sleep: body-heating effects.

Eight physically trained subjects underwent three experimental conditions on separate occasions between 1400 and 1800 h. Two conditions acted as controls for a high-intensity exercise (HI) condition of treadmill running at 80% VO2 max for a total of 80 min. The rate of body heating was modelled in a no-exercise passive heating condition (PH), and the total exercise load was replicated in a low-intensity condition (LI) at 40% VO2 max for 160 min. LI produced no slow-wave sleep (SWS--stages 3 + 4 sleep) changes, but was the only condition to produce significant increases in sleep length and in non-rapid eye movement (REM) sleep (stages 1 + 2 + 3 + 4), and a significant decrease in sleep onset time. Although HI and PH produced similar SWS increases, these consisted of significant increases in stage 3 sleep for HI and in stage 4 sleep for PH. No REM sleep parameter was affected under any condition. Self-estimates of presleep tiredness produced no significant findings. It was concluded that a high and sustained rate of body heating for 1-2 h, particularly the inherent rapid rates of core temperature increase and of body dehydration, may trigger a SWS response, and that exercise may simply be a vehicle for these effects.

Adult↗