Sleep and sleepiness among working and non-working high school evening students

The aim of this study was to evaluate patterns of sleepiness, comparing working and non-working students. The study was conducted on high school students attending evening classes (19:00-22:30 h) at a public school in S?o Paulo, Brazil. The study group consisted of working (n=51) and non-working (n=41) students, aged 14-21 yrs. The students answered a questionnaire about working and living conditions and reported health symptoms and diseases. For seven consecutive days, actigraphy measurements were recorded, and the students also filled in a sleep diary. Sleepiness ratings were given six times per day, including upon waking and at bedtime, using the Karolinska Sleepiness Scale. Statistical analyses included three-way ANOVA and t-test. The mean sleep duration during weekdays was shorter among workers (7.2 h) than non-workers (8.8 h) (t=4.34; p<.01). The mean duration of night awakenings was longer among workers on Tuesdays and Wednesdays (28.2 min) and shorter on Mondays (24.2 min) (t=2.57; p=.03). Among workers, mean napping duration was longer on Mondays and Tuesdays (89.9 min) (t=2.27; p=.03) but shorter on Fridays and Sundays (31.4 min) (t=3.13; p=.03). Sleep efficiency was lower on Fridays among non-workers. Working students were moderately sleepier than non-workers during the week and also during class on specific days: Mondays (13:00-15:00 h), Wednesdays (19:00-22:00 h), and Fridays (22:00-00:59 h). The study found that daytime sleepiness of workers is moderately higher in the evening. This might be due to a work effect, reducing the available time for sleep and shortening the sleep duration. Sleepiness and shorter sleep duration can have a negative impact on the quality of life and school development of high school students.     

Diurnal variation in temperature, mental and physical performance, and tasks specifically related to football (soccer)

Football (soccer) training and matches are scheduled at different times throughout the day. Association football involves a variety of fitness components as well as psychomotor and game-related cognitive skills. The purpose of the present research, consisting of two separate studies, was to determine whether game-related skills varied with time of day in phase with global markers of both performance and the body clock. In the first study, eight diurnally active male association football players (19.1+/-1.9 yrs of age; mean+/-SD) with 10.8+/-2.1 yrs playing experience participated. Measurements were made on different days at 08:00, 12:00, 16:00, and 20:00 h in a counterbalanced manner. Time-of-day changes in intra-aural temperature (used as a marker of the body clock), grip strength, reaction times, flexibility (markers of aspects of performance), juggling and dribbling tasks, and wall-volley test (football-specific skills) were compared. Significant (repeated measures analysis of variance, ANOVA) diurnal variations were found for body temperature (p<0.0005), choice reaction time (p<0.05), self-rated alertness (p<0.0005), fatigue (p<0.05), forward (sit-and-reach) flexibility (p<0.02), and right-hand grip strength (p<0.02), but not left-hand grip strength (p=0.40) nor whole-body (stand-and-reach) flexibility (p=0.07). Alertness was highest and fatigue lowest at 20:00 h. Football-specific skills of juggling performance showed significant diurnal variation (p<0.05, peak at 16:00 h), whereas performance on the wall-volley test tended to peak at 20:00 h and dribbling showed no time-of-day effect (p=0.55). In a second study, eight diurnally active subjects (23.0+/-0.7 yrs of age) completed five test sessions, at the same times as in the first study but with a second session at 08:00 h. Test-re-test comparisons at 08:00 h for all components indicated good reliability. Intra-aural temperature showed a significant time-of-day effect (p<0.001) with mean temperature at 16:00 h (36.4 degrees C) higher than at 08:00 h (35.4 degrees C). There was no significant effect of chronotype on the temperature acrophase (peak time) (p>0.05). Diurnal variation was found for performance tests, including sit-and-reach flexibility (p<0.01) and spinal hyper-extension (p<0.05). Peaks occurred between 16:00 and 20:00 h and the daytime changes paralleled the temperature rhythm. Diurnal variation was also found for football-specific tests, including dribbling time (p<0.001, peak at 20:00 h) and chip test performance (p<0.01), being more accurate at 16:00 h (mean error=0.75 m) than at 08:00 h (mean error=1.01 m). Results indicate football players perform at an optimum between 16:00 and 20:00 h when not only football-specific skills but also measures of physical performance are at their peak. Body temperature peaked at a similar time, but positive mood states seemed to peak slightly earlier. While causal links cannot be established in these experiments, the results indicate that the diurnal variation of some aspects of football performance is affected by factor(s) other than body temperature alone.     

Sleepiness and performance in response to repeated sleep restriction and subsequent recovery during semi-laboratory conditions

There is an ongoing debate of how best to measure the effects of sleep loss in a reliable and feasible way, partly because well controlled laboratory studies and field studies have come to different conclusions. The aims of the present study were to investigate both sleepiness and performance in response to long-term sleep restriction and recovery in a semi-laboratory environment, investigate order effects (i.e., whether levels return to baseline) in a study with seven days of recovery, and characterize individual differences in tolerance to restricted sleep. Nine healthy men (age 23-28 yrs) participated in the protocol, which included one habituation day (sleep 23:00-07:00 h), two baseline days (23:00-07:00 h), five days with restricted sleep (03:00-07:00 h), and seven recovery days (23:00-07:00 h). Participants went outdoors at least twice each day. Reaction-time tests were performed at 08:00, 14:00, and 20:00 h each day in the laboratory. Sleepiness was self-rated by the Karolinska Sleepiness Scale (KSS)after each test. The mixed-effect regression models showed that each day of restricted sleep resulted in an increase of sleepiness by 0.64+/- .05 KSS units (a nine-step scale, p < .001), increase of median reaction times of 6.6+/- 1.6 ms ( p = .003), and increase of lapses/test of 0.69 +/- .16 ms ( p < .001). Seven days of recovery allowed participants to return to the baseline for sleepiness and median reaction time, but not for lapses. The individual differences were larger for performance measures than for sleepiness; the between-subject standard deviation for the random intercept was in the magnitude of the effects of 1.1 days of restricted sleep for sleepiness, 6.6 days of restricted sleep for median reaction time, and 3.2 days for lapses. In conclusion, the present study shows that sleepiness is closely related to sleep pressure, while performance measures, to a larger extent, appear determined by specific individual traits. Moreover, it is suggested to measure sleepiness in a standardized situation so as to minimize the influences of contextual factors.     

Diurnal Variation in Oral Temperature, Sleepiness, and Performance of High School Girls

Evaluation of rhythmic fluctuations of physical and mental variables should be of special significance for the understanding of students' performance and setting the schedules of school activities. The present study investigated the pattern of diurnal variation in oral temperature, sleepiness and performance of a group of adolescents undergoing a daytime school schedule. Eighteen girls (mean age 16 years-old), who attended the same class from 0715h to 1645h, were tested on seven days. They measured their oral temperature, quantified their sleepiness level by means of a visual analogue scale, and completed the following tests: letter cancellation test, addition test, and a simple motor task. One-way ANOVA statistics for repeated measures was used in order to verify the effect of test time on oral temperature, sleepiness and performance. Possible correlations between the level of sleepiness and performance were investigated by means of Spearman rank correlation. The results revealed significant time of day effect on all variables, except for the number of addition errors. Oral temperature values showed an increase from morning to afternoon. Letter cancellation, motor task and addition scores increased from early morning to late afternoon, showing rapid fluctuations throughout the day. Sleepiness level was negatively correlated with letter cancellation scores during the first three tests of the day. In agreement with other work, the diurnal variation of oral temperature, letter cancellation and addition test showed an improvement as the day progressed. Sleepiness, on the other hand, decreased throughout the day, with the highest level associated with the first test of the day, suggesting a circadian pattern of variation rather than a cumulative effect due to school activities.     

Sleep and Sleepiness among Working and Non‐Working High School Evening Students

The aim of this study was to evaluate patterns of sleepiness, comparing working and non‐working students. The study was conducted on high school students attending evening classes (19:00–22:30 h) at a public school in São Paulo, Brazil. The study group consisted of working (n=51) and non‐working (n=41) students, aged 14–21 yrs. The students answered a questionnaire about working and living conditions and reported health symptoms and diseases. For seven consecutive days, actigraphy measurements were recorded, and the students also filled in a sleep diary. Sleepiness ratings were given six times per day, including upon waking and at bedtime, using the Karolinska Sleepiness Scale. Statistical analyses included three‐way ANOVA and t‐test. The mean sleep duration during weekdays was shorter among workers (7.2 h) than non‐workers (8.8 h) (t=4.34; p<.01). The mean duration of night awakenings was longer among workers on Tuesdays and Wednesdays (28.2 min) and shorter on Mondays (24.2 min) (t=2.57; p=.03). Among workers, mean napping duration was longer on Mondays and Tuesdays (89.9 min) (t=2.27; p=.03) but shorter on Fridays and Sundays (31.4 min) (t=3.13; p=.03). Sleep efficiency was lower on Fridays among non‐workers. Working students were moderately sleepier than non‐workers during the week and also during class on specific days: Mondays (13:00–15:00 h), Wednesdays (19:00–22:00 h), and Fridays (22:00–00:59 h). The study found that daytime sleepiness of workers is moderately higher in the evening. This might be due to a work effect, reducing the available time for sleep and shortening the sleep duration. Sleepiness and shorter sleep duration can have a negative impact on the quality of life and school development of high school students.     

Diurnal Variation in Oral Temperature,Sleepiness, and Performance of High School Girls

Evaluation of rhythmic fluctuations of physical and mental variables should be of special significance for the understanding of students' performance and setting the schedules of school activities. The present study investigated the pattern of diurnal variation in oral temperature, sleepiness and performance of a group of adolescents undergoing a daytime school schedule. Eighteen girls (mean age 16 years-old), who attended the same class from 0715h to 1645h, were tested on seven days. They measured their oral temperature, quantified their sleepiness level by means of a visual analogue scale, and completed the following tests: letter cancellation test, addition test, and a simple motor task. One-way ANOVA statistics for repeated measures was used in order to verify the effect of test time on oral temperature, sleepiness and performance. Possible correlations between the level of sleepiness and performance were investigated by means of Spearman rank correlation. The results revealed significant time of day effect on all variables, except for the number of addition errors. Oral temperature values showed an increase from morning to afternoon. Letter cancellation, motor task and addition scores increased from early morning to late afternoon, showing rapid fluctuations throughout the day. Sleepiness level was negatively correlated with letter cancellation scores during the first three tests of the day. In agreement with other work, the diurnal variation of oral temperature, letter cancellation and addition test showed an improvement as the day progressed. Sleepiness, on the other hand, decreased throughout the day, with the highest level associated with the first test of the day, suggesting a circadian pattern of variation rather than a cumulative effect due to school activities.     

Explaining sleep duration in adolescents: the impact of socio-demographic and lifestyle factors and working status

Previous studies found students who both work and attend school undergo a partial sleep deprivation that accumulates across the week. The aim of the present study was to obtain information using a questionnaire on a number of variables (e.g., socio-demographics, lifestyle, work timing, and sleep-wake habits) considered to impact on sleep duration of working (n = 51) and non-working (n = 41) high-school students aged 14-21 yrs old attending evening classes (19:00-22:30 h) at a public school in the city of S?o Paulo, Brazil. Data were collected for working days and days off. Multiple linear regression analyses were performed to assess the factors associated with sleep duration on weekdays and weekends. Work, sex, age, smoking, consumption of alcohol and caffeine, and physical activity were considered control variables. Significant predictors of sleep duration were: work ( p < 0.01), daily work duration (8-10 h/day; p < 0.01), sex ( p = 0.04), age 18-21 yrs (0.01), smoking( p = 0.02) and drinking habits ( p = 0.03), irregular physical exercise (p < 0.01), ease of falling asleep ( p = 0.04), and the sleep-wake cycle variables of napping ( p < 0.01), nocturnal awakenings ( p < 0.01), and mid-sleep regularity ( p < 0.01). The results confirm the hypotheses that young students who work and attend school showed a reduction in night-time sleep duration. Sleep deprivation across the week, particularly in students working 8-10 h/day, is manifested through a sleep rebound (i.e., extended sleep duration) on Saturdays. However, the different roles played by socio-demographic and lifestyle variables have proven to be factors that intervene with nocturnal sleep duration. The variables related to the sleep-wake cycle-naps and night awakenings-proved to be associated with a slight reduction in night-time sleep, while regularity in sleep and wake-up schedules was shown to be associated with more extended sleep duration, with a distinct expression along the week and the weekend. Having to attend school and work, coupled with other sociodemographic and lifestyle factors, creates an unfavorable scenario for satisfactory sleep duration.     

Diurnal Variation in Temperature,Mental and Physical Performance,and Tasks Specifically Related to Football (Soccer)

Football (soccer) training and matches are scheduled at different times throughout the day. Association football involves a variety of fitness components as well as psychomotor and game‐related cognitive skills. The purpose of the present research, consisting of two separate studies, was to determine whether game‐related skills varied with time of day in phase with global markers of both performance and the body clock. In the first study, eight diurnally active male association football players (19.1±1.9 yrs of age; mean±SD) with 10.8±2.1 yrs playing experience participated. Measurements were made on different days at 08:00, 12:00, 16:00, and 20:00 h in a counterbalanced manner. Time‐of‐day changes in intra‐aural temperature (used as a marker of the body clock), grip strength, reaction times, flexibility (markers of aspects of performance), juggling and dribbling tasks, and wall‐volley test (football‐specific skills) were compared. Significant (repeated measures analysis of variance, ANOVA) diurnal variations were found for body temperature (p<0.0005), choice reaction time (p<0.05), self‐rated alertness (p<0.0005), fatigue (p<0.05), forward (sit‐and‐reach) flexibility (p<0.02), and right-hand grip strength (p<0.02), but not left-hand grip strength (p=0.40) nor whole‐body (stand‐and‐reach) flexibility (p=0.07). Alertness was highest and fatigue lowest at 20:00 h. Football‐specific skills of juggling performance showed significant diurnal variation (p<0.05, peak at 16:00 h), whereas performance on the wall‐volley test tended to peak at 20:00 h and dribbling showed no time‐of‐day effect (p=0.55). In a second study, eight diurnally active subjects (23.0±0.7 yrs of age) completed five test sessions, at the same times as in the first study but with a second session at 08:00 h. Test‐re‐test comparisons at 08:00 h for all components indicated good reliability. Intra‐aural temperature showed a significant time‐of‐day effect (p<0.001) with mean temperature at 16:00 h (36.4°C) higher than at 08:00 h (35.4°C). There was no significant effect of chronotype on the temperature acrophase (peak time) (p>0.05). Diurnal variation was found for performance tests, including sit‐and‐reach flexibility (p<0.01) and spinal hyper‐extension (p<0.05). Peaks occurred between 16:00 and 20:00 h and the daytime changes paralleled the temperature rhythm. Diurnal variation was also found for football‐specific tests, including dribbling time (p<0.001, peak at 20:00 h) and chip test performance (p<0.01), being more accurate at 16:00 h (mean error=0.75 m) than at 08:00 h (mean error=1.01 m). Results indicate football players perform at an optimum between 16:00 and 20:00 h when not only football‐specific skills but also measures of physical performance are at their peak. Body temperature peaked at a similar time, but positive mood states seemed to peak slightly earlier. While causal links cannot be established in these experiments, the results indicate that the diurnal variation of some aspects of football performance is affected by factor(s) other than body temperature alone.     

24-hour pattern of work-related injury risk of French firemen: nocturnal peak time

The first aim of the study was to assess clock-time patterning of work-related injuries (WRIs) of firemen (FM) of Sa?ne et Loire-71 (France) during the 4-yr span of 1 January 2004 to 31 December 2007. FM of this service are legally required to log every WRI and seek its evaluation by the medical service, whether the WRI was the result of worksite duties or exercise/sport activities at the station. WRI was defined specifically as a (nonexercise, nonsport, and nonemotional/stress) work-associated trauma, verified both by log book and medical records. For the corresponding years, the 24-h pattern of emergency calls (Calls) plus road traffic (Traffic) on the main roads of the service area was also assessed. Relative risk (R) of WRI was calculated as the quantity of WRIs/h divided by the quantity of Call responses/h?×?1000, which takes into account the number of at-risk FM/unit time, since each dispatched emergency vehicle is staffed with 4 FM. Comparably trained regular (RFM) and volunteer (VFM) FM experienced a total of 187 WRIs. The 24-h WRI curve patterns of RFM and VFM were correlated (r?=?0.4, p??.05). Analysis of variance (ANOVA) validated comparable clock-time patterns in WRIs of RFM and VFM each year and each season (all p??.0006; Cosinor analysis, p?相似文献   

24-hour pattern in lag time of response by firemen to calls for urgent medical aid

The aim of the study was to assess the group 24-h pattern of lag time (LT) in response by regular and volunteer firemen (RFM and VFM) to calls for medical help (CFMH), specifically calls for out-of-hospital cardiac arrest (OHCA). LT, duration in min between a CFMH and departure of service vehicle equipped with a semiautomated defibrillator and generally staffed with four well-trained and ready-to-go FM, represents the integrated duration of several processes, each with separate reaction and decision-making times. The exact time of each CFHM (in min, h, day, month, yr) was recorded electronically, and the exact departure time from the station of the responding FM vehicle was recorded by an on-duty FM. Overall, CFMH made up 53 ± 9% (SEM) of all emergencies calls for aid. To standardize the study methods, the reported findings are based on 568 CFMH specifically regarding OHCA that occurred during the 4-yr study span (January 2005 to December 2008). CFMH exhibited a 24-h pattern with a major peak at 10:00 h (mean ± SEM: n = 9.5 ± 1.6) and major trough at 01:00 h (n = 1.3 ± 0.3; t test, p??.05). In CFMH/h pooled time series, ANOVA-detected differences between the hourly means (p?相似文献   

Circadian adaptation of airline pilots during extended duration operations between the USA and Asia

This study tracked circadian adaptation among airline pilots before, during, and after trips where they flew from Seattle (SEA) or Los Angeles (LAX) to Asia (7--9 time zones westward), spent 7--12?d in Asia, and then flew back to the USA. In Asia, pilots' exposures to local time cues and sleep opportunities were constrained by duty (short-haul flights crossing ≤1 time zone/24?h). Fourteen captains and 16 first officers participated (median age?=?56 versus 48 yrs, p.U)?<?0.001). Their sleep was monitored (actigraphy, duty/sleep diaries) from 3?d pre-trip to 5?d post-trip. For every flight, Karolinska Sleepiness and Samn-Perelli Fatigue scales and 5-min psychomotor vigilance task (PVT) tests were completed pre-flight and at top of descent (TOD). Participants had ≥3 d free of duty prior to outbound flight(s). From 72--24?h prior to departure (baseline sleep), mean total sleep/24?h (TST)?=?7.00?h (SD?=?1.18?h) and mean sleep efficiency?=?87% (SD?=?4.9%). Most pilots (23/30) flew direct to and from Asia, but 7 LAX-based pilots flew via a 1-d layover in Honolulu (HNL). On flights with ≥2 pilots, mean total in-flight sleep varied from 0.40 to 2.09?h outbound and from 0.74 to 1.88?h inbound. Duty patterns in Asia were variable, with ≤2 flights/d (mean flight duration?=?3.53?h, SD?=?0.53?h). TST on days 17 in Asia did not differ from baseline (p.F)?=?0.2031). However, mean sleep efficiency was significantly lower than baseline on days 5--7 (p.F)?=?0.0041). More pilots were on duty between 20:00 and 24:00?h on days 57 (mean?=?21%) than on days 24 (mean?=?14%). Sleep propensity distribution phase markers and chi-square periodogram analyses suggest that adaptation to local time was complete by day 4 in Asia. On pre-flight PVT tests in Asia, the slowest 10% of responses improved for flights departing 14:00--19:59?h (p.F)?=?0.0484). At TOD, the slowest 10% of responses improved across days for flights arriving 14:00--19:59?h (p.F)?=?0.0349) and 20:00--01:59?h (p.F)?=?0.0379). Sleepiness and fatigue ratings pre-flight and at TOD did not change across days in Asia. TST on post-trip day 1 was longer than baseline (estimated mean extension?=?1.68?h; adjusted p(t)?<?0.0001). On all post-trip days, sleep efficiency was comparable to baseline. Sleep propensity distribution phase markers and chi-square periodogram analyses suggest complete readaptation in 12?d. Two opposing influences appeared to affect sleep and PVT performance across days in Asia: progressive circadian adaptation to local time and increasing duty during local night, which displaced sleep from the optimal physiological time. Cumulative sleep restriction across the return flight may explain the large rebound in TST on day 1 post-trip. Thereafter TST, sleep efficiency, and sleep timing suggest that readaptation was complete. Rapid post-trip readaptation may be facilitated by pilots having unconstrained nocturnal sleep opportunities, coupled with stronger patterns of family and social cues than in Asia.     

Sleep length as a function of morning shift-start time in irregular shift schedules for train drivers: self-rated health and individual differences

Forty-six male train drivers (mean age = 46.5, SD = 5.1) were recruited to participate in a diary study for 14 consecutive days with questions about their sleep and working hours. A polynomial mixed-effect regression model showed a curvilinear relation ( p < .001) between shift-start time and sleep duration for shifts starting at 03:00-12:00 hand with a near linear increase for ones starting between 04:30 and 09:00 h of approximately 0.7 h for every 1 h the shift was delayed. The longest sleeps were estimated at approximately 8 h before shifts that started at approximately 10:00 h. The shortest sleeps were found for shifts that started before 04:30 h and were estimated at approximately 5 h. Individual differences were estimated with a random-effect standard deviation of 0.51 h, independent of shift start time ( p = .005). One-half of the between-subject variance was explained by subjective health. A one-step decrease in health was associated with a 26 min increase in sleep length. The results have practical implications for constructing shift schedules. Early morning shifts reduced sleep length substantially and should be mixed with later start hours to avoid the accumulation of sleep dept. Delaying the shift-start past 10:00 h had little effect on sleep opportunity; however, delaying shift-start to between 04:30 and 9:00 h had a strong impact on sleep length, with 70% of the extra time used for sleep, suggesting large positive effects for this range of shift-start times.     

Differences in sleep, light, and circadian phase in offshore 18:00-06:00 h and 19:00-07:00 h shift workers

Complaints concerning sleep are high among those who work night shifts; this is in part due to the disturbed relationship between circadian phase and the timing of the sleep-wake cycle. Shift schedule, light exposure, and age are all known to affect adaptation to the night shift. This study investigated circadian phase, sleep, and light exposure in subjects working 18:00-06:00 h and 19:00-07:00 h schedules during summer (May-August). Ten men, aged 46+/-10 yrs (mean+/-SD), worked the 19:00-07:00 h shift schedule for two or three weeks offshore (58 degrees N). Seven men, mean age 41+/-12 yrs, worked the 18:00-06:00 h shift schedule for two weeks offshore (61 degrees N). Circadian phase was assessed by calculating the peak (acrophase) of the 6-sulphatoxymelatonin rhythm measured by radioimmunoassay of sequential urine samples collected for 72 h at the end of the night shift. Objective sleep and light exposure were assessed by actigraphy and subjective sleep diaries. Subjects working 18:00-06:00 h had a 6-sulphatoxymelatonin acrophase of 11.7+/-0.77 h (mean+/-SEM, decimal hours), whereas it was significantly later, 14.6+/-0.55 h (p=0.01), for adapted subjects working 19:00-07:00 h. Two subjects did not adapt to the 19:00-07:00 h night shift (6-sulphatoxymelatonin acrophases being 4.3+/-0.22 and 5.3+/-0.29 h). Actigraphy analysis of sleep duration showed significant differences (p=0.03), with a mean sleep duration for those working 19:00-07:00 h of 5.71+/-0.31 h compared to those working 18:00-06:00 h whose mean sleep duration was 6.64+/-0.33 h. There was a trend to higher morning light exposure (p=0.07) in the 19:00-07:00 h group. Circadian phase was later (delayed on average by 3 h) and objective sleep was shorter with the 19:00-07:00 h than the 18:00-06:00 h shift schedule. In these offshore conditions in summer, the earlier shift start and end time appears to favor daytime sleep.     

Sleepiness and Performance in Response to Repeated Sleep Restriction and Subsequent Recovery during Semi‐Laboratory Conditions

There is an ongoing debate of how best to measure the effects of sleep loss in a reliable and feasible way, partly because well controlled laboratory studies and field studies have come to different conclusions. The aims of the present study were to investigate both sleepiness and performance in response to long‐term sleep restriction and recovery in a semi‐laboratory environment, investigate order effects (i.e., whether levels return to baseline) in a study with seven days of recovery, and characterize individual differences in tolerance to restricted sleep. Nine healthy men (age 23–28 yrs) participated in the protocol, which included one habituation day (sleep 23:00–07:00 h), two baseline days (23:00–07:00 h), five days with restricted sleep (03:00–07:00 h), and seven recovery days (23:00–07:00 h). Participants went outdoors at least twice each day. Reaction‐time tests were performed at 08:00, 14:00, and 20:00 h each day in the laboratory. Sleepiness was self‐rated by the Karolinska Sleepiness Scale (KSS) after each test. The mixed‐effect regression models showed that each day of restricted sleep resulted in an increase of sleepiness by 0.64±.05 KSS units (a nine‐step scale, p<.001), increase of median reaction times of 6.6±1.6 ms (p=.003), and increase of lapses/test of 0.69±.16 ms (p<.001). Seven days of recovery allowed participants to return to the baseline for sleepiness and median reaction time, but not for lapses. The individual differences were larger for performance measures than for sleepiness; the between‐subject standard deviation for the random intercept was in the magnitude of the effects of 1.1 days of restricted sleep for sleepiness, 6.6 days of restricted sleep for median reaction time, and 3.2 days for lapses. In conclusion, the present study shows that sleepiness is closely related to sleep pressure, while performance measures, to a larger extent, appear determined by specific individual traits. Moreover, it is suggested to measure sleepiness in a standardized situation so as to minimize the influences of contextual factors.     

Inhibiting effect of plasma from normal and tumour bearing mice on the mitotic rate of regenerating liver

Plasma from normal mice and from mice bearing the ES2 transplantable malignant tumour was injected intraperitoneally at a dose of 0.01 ml/g body weight in partially hepatectomized mice. Control animals were injected with a solution of sodium citrate in saline. The recipients were killed at the first (14:00 hours/48 h). These times are the time of day and the number of h after partial hepatectomy and second (14:00 hours/72 h) peak times after partial hepatectomy. The number of colchicine metaphases per 1000 nuclei was determined for hepatocytes and litoral cells. A different effect was obtained with plasma from tumour-bearing compared with normal mice. Plasma from both sources when injected 26 h after partial hepatectomy (16:00 hours/26 h) inhibited the mitotic activity of hepatocytes at the next peak of regenerative activity (14:00 hours/48 h). The plasma from tumour-bearing mice also inhibited the peak on the following day (14:00 hours/72 h), whereas plasma from normal mice had no inhibitory effect and, indeed, a compensatory wave was observed at this time. Furthermore, plasma from tumour-bearing mice also showed an inhibitory effect at the first peak (14:00 hours/48 h) when injected at the time of partial hepatectomy (14:00 hours/00 h) or at 22 h before partial hepatectomy (16:00 hours/-22 h) whereas the injection of plasma from normal mice at these times had no inhibitory effect. In the litoral cells the injection of plasma from tumour-bearing mice made 22 h before hepatectomy (16:00 hours/-22 h) led to a stimulation of mitotic activity which was controlled at 14:00 hours/48 h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diurnal changes in psychophysiological variables of school girls: comparison with regard to age and teacher's appreciation of learning.

Ninety-five nonresident girls of a private school volunteered for the study with the teachers' help as well as parental consent. Ages were approximately 8, 9, and 10 years. They were synchronized with diurnal activity from 0730 to 2100 h and nocturnal rest. Fatigue, drowsiness, and attention were self-rated using visual analogue scales; oral temperature was self-measured and a letter cancellation test was performed. Each of these variables was measured at school at 0900, 1100, 1400, and 1600 h on Mondays, Thursdays, Fridays, and Saturdays for two consecutive weeks in 1987 (March 30-April 11) and again in 1989 (March 13-25) when the youngest group had become 10 years old. According to conventional teacher evaluation of learning (learning performance) within each group, three subgroups were formed: top third, middle third, and bottom third. Time series (more than 50,000 data) were analyzed according to several statistical methods, but mainly chronograms with ANOVA. Similar diurnal changes in oral temperature were validated for each group and subgroups. The occurrence of a diurnal change in self-rated variables (fatigue and drowsiness) and score in letter cancellation was age related: no detection in the 8-year-old group (and subgroups) and validation (p less than 0.002) in 9- and 10-year-old groups (and respective subgroups). A good learning performance was associated with a reduced drowsiness in school girls of 9 and 10 years. Age-related, time-of-day differences in drowsiness (when detected) as well as learning performance effect were not associated with observed duration of sleep. Validated changes in self-rated fatigue were close to that of drowsiness. At 0900 h, girls of 9 and 10 years were more tired when belonging to the bottom third than top third subgroup. Whatever the time of day, self-rated attention was greater in the top than in the bottom third for these girls. Differences related to learning performance were validated in each grade. However, best scores were recorded for the bottom third in the 8-year-old group, while best scores were provided by top third subgroups in 10-year-old girls. It seems that in girls around 8 years of age, critical changes can be detected with regard to the (ontogenic?) occurrence of time-of-day differences in a set of psychophysiologic variables as well as influential effects of learning performance on the same variables. Reported finding are compatible with the hypothesis of circadian oscillators working at the level of the cortex of the human brain.     

Effects of Low Doses of Melatonin on Late Afternoon Napping and Mood

The effects of low doses of melatonin (0.1, 0.5 and 1 mg) given at 16:00 h on induction and quality of sleep in the late afternoon (17:00-21:00 h), as well as on subjective fatigue and mood ratings before and after sleep were studied. Ten healthy male volunteers (age 26-30 years) were given on a double-blind crossover basis, tablets containing melatonin, or placebo, with one day washout between treatments. Mood and fatigue were assessed before and after bedtime. Sleep quality was objectively monitored using wrist-worn actigraphs and subjectively by using sleep logs. Data were analysed by means of analysis of variance for repeated measures with a factor of group (placebo and the three melatonin doses). The analysis revealed dose-dependent increase by melatonin in subjective evaluation of fatigue and sleepiness, and decrease in alertness, efficiency, vigor and concentration before the nap. Melatonin did not significantly affect actigraph-measured nap sleep latency and efficiency but reduced wake time after sleep onset and delayed sleep offset time compared to placebo, Melatonin did not significantly affect sleep latency and sleep efficiency in the night following the treatment. These data indicate acute effects of low doses of melatonin given at 16:00h on sleepiness and fatigue but not on sleep efficiency or latency in healthy young individuals.     

Effects of Low Doses of Melatonin on Late Afternoon Napping and Mood

The effects of low doses of melatonin (0.1, 0.5 and 1 mg) given at 16:00 h on induction and quality of sleep in the late afternoon (17:00-21:00 h), as well as on subjective fatigue and mood ratings before and after sleep were studied. Ten healthy male volunteers (age 26-30 years) were given on a double-blind crossover basis, tablets containing melatonin, or placebo, with one day washout between treatments. Mood and fatigue were assessed before and after bedtime. Sleep quality was objectively monitored using wrist-worn actigraphs and subjectively by using sleep logs. Data were analysed by means of analysis of variance for repeated measures with a factor of group (placebo and the three melatonin doses). The analysis revealed dose-dependent increase by melatonin in subjective evaluation of fatigue and sleepiness, and decrease in alertness, efficiency, vigor and concentration before the nap. Melatonin did not significantly affect actigraph-measured nap sleep latency and efficiency but reduced wake time after sleep onset and delayed sleep offset time compared to placebo, Melatonin did not significantly affect sleep latency and sleep efficiency in the night following the treatment. These data indicate acute effects of low doses of melatonin given at 16:00h on sleepiness and fatigue but not on sleep efficiency or latency in healthy young individuals.     

Explaining Sleep Duration in Adolescents: The Impact of Socio‐Demographic and Lifestyle Factors and Working Status

Previous studies found students who both work and attend school undergo a partial sleep deprivation that accumulates across the week. The aim of the present study was to obtain information using a questionnaire on a number of variables (e.g., socio‐demographics, lifestyle, work timing, and sleep‐wake habits) considered to impact on sleep duration of working (n=51) and non‐working (n=41) high‐school students aged 14–21 yrs old attending evening classes (19:00–22:30 h) at a public school in the city of São Paulo, Brazil. Data were collected for working days and days off. Multiple linear regression analyses were performed to assess the factors associated with sleep duration on weekdays and weekends. Work, sex, age, smoking, consumption of alcohol and caffeine, and physical activity were considered control variables. Significant predictors of sleep duration were: work (p < 0.01), daily work duration (8–10 h/day; p < 0.01), sex (p=0.04), age 18–21 yrs (0.01), smoking (p=0.02) and drinking habits (p=0.03), irregular physical exercise (p < 0.01), ease of falling asleep (p=0.04), and the sleep‐wake cycle variables of napping (p < 0.01), nocturnal awakenings (p < 0.01), and mid‐sleep regularity (p < 0.01). The results confirm the hypotheses that young students who work and attend school showed a reduction in night‐time sleep duration. Sleep deprivation across the week, particularly in students working 8–10 h/day, is manifested through a sleep rebound (i.e., extended sleep duration) on Saturdays. However, the different roles played by socio‐demographic and lifestyle variables have proven to be factors that intervene with nocturnal sleep duration. The variables related to the sleep‐wake cycle—naps and night awakenings—proved to be associated with a slight reduction in night‐time sleep, while regularity in sleep and wake‐up schedules was shown to be associated with more extended sleep duration, with a distinct expression along the week and the weekend. Having to attend school and work, coupled with other socio‐demographic and lifestyle factors, creates an unfavorable scenario for satisfactory sleep duration.     

The impact of shift starting time on sleep duration,sleep quality,and alertness prior to injury in the People’s Republic of China

Early shift start time and night shifts are associated with reduced sleep duration and poor sleep quality that often lead to increased fatigue levels, performance decrements and adverse safety and health outcomes. This study investigates the impact of shift starting time on sleep patterns, including the duration and quality of sleep and alertness/sleepiness at the time of injury, in a large epidemiological field study of hospitalized adults with severe work-related hand injury in the People’s Republic of China (PRC) from multiple industries with severe work-related traumatic hand injury were recruited from 11 hospitals in three industrially-developed cities in the PRC: Ningbo, Liuzhou and Wuxi. Analysis of covariance (ANCOVA) was used to compare sleep duration, sleep quality and alertness/sleepiness across 3?h increments of shift start time, while adjusting for age, gender, work hours, shift duration, day of injury and several transient work-related factors. Effect modification by gender was also evaluated. Seven-hundred and three hospitalized adults (96.4%) completed a face-to-face interview within 4 days of injury; 527 (75.0%) were male, with a mean (±SEM) age of 31.8?±?0.4 years. Overall, these adults worked relatively long weekly (55.7?±?0.6?h) and daily hours (8.6?±?0.07?h). Average sleep duration prior to injury was 8.5?h (±0.07), and showed significant variations (p value <0.05) across shift starting time increments. Overall mean prior sleep duration was shortest for individuals starting shifts from “21:00–23:59” (5.6±0.8?h) followed by midnight “00:00–02:59” (6.1?±?0.6?h). However, a statistically significant interaction (p?<?0.05) was observed between gender and shift starting time on mean sleep duration. For males the shortest sleep duration was 5.6?h (“21:00–23:59”) and for females the shortest was 4.3?h (“24:00–02:59” and “15:00–17:59”). Sleep quality (generally quite well) and alertness/sleepiness based on the KSS (generally alert) did not vary significantly across shift starting time. Results suggest that sleep duration is shortest among injured PRC adults starting shifts late night and early morning. However, with more than 8.5?h of sleep on average work days, Chinese slept much longer than typical US day workers (Sleep in America Poll, 2012, 6:44 on workdays, 7:35 on free days), and this may help to explain higher than expected alertness/sleepiness scores at the time of injury.