Sleep/Wake Cycle Parameters and Sleep/Fatigue Complaints in Female Night Workers

Adaptation to shift-work is influenced by the way workers schedule their lives, including allocation of sleep episodes. Female workers (n = 29) engaged at an assembly line were studied as to individual differences in sleep parameters in order to verify whether those differences could be related to the manifestation of sleep and fatigue complaints. The sample was composed of women (20–40 y) working at night from Monday to Friday. Sleep data were based on daily sleep logs which were filled out by the workers for 10 consecutive weeks. In the analyses of sleep data both diurnal episodes between consecutive night shifts and noctural sleep episodes preceding working nights were taken into account. Worker's complaints were analyzed through questions extracted from an interview form encompassing questions on fatigue associated with the work schedule and on dissatisfaction with sleep on weekdays and weekends. The analysis of diurnal episodes showed no significant correlation between the total amount of sleep per day and the total number of complaints. Nevertheless, the latter was correlated to the length of the first sleep episode on a day, which usually began in the morning. As to sleep onset times, significant correlations were not detected concerning the first diurnal episodes. The analysis of nocturnal episodes did not reveal any significant correlation between sleep parameters and complaints. Results indicate that workers whose sleep onsets were allocated to the morning and were able to sleep for many consecutive hours, tended to show less complaints, suggesting that the temporal allocation of diurnal sleep and its length are relevant in the determination of how these workers perceive fatigue and sleep quality.     

Time Periods in the Nasal Cycle During Night Sleep

The periodic congestion and decongestion of nasal venous sinuses and the alternation of airflow from one side of the nose to the other are referred to as a 'nasal cycle' in the literature. The aim of this study was to detect the nasal cycle during sleep in normal subjects and describe existing time periods and their sequence and patterns. We studied 58 records of the nasal cycle over 6-9 hours of sleep in six healthy volunteers and revealed that the cycle could be described as a combination of 1 to 4 discrete ultradian periods with various length: 1.0-1.5 h (mean 78.6min), 2.5-3.0 h (168.3 min), 4.0-4.5 h (260.3 min) or 5.5-6.0 h (347.5 min). The distribution of the discrete time periods was multi-modal and the mean lengths of periods were 'multiples' of a basic period of 85.4 min (~1.5 h) which was very close to the mean length of the sleep cycle (~1.5 h). In all subjects, during any of the REM stages of the sleep, an alternation of the airflow through the nostrils was observed. In about 75% of all cases, the switch of the flow between the nostrils occurred during the second or following REM stages of the sleep thus shaping a nasal cycle that contained mainly periods of 3.0 or 4.5 hours. We suggest a novel classification of the nocturnal nasal cyclicity and hypothesis that there is a relationship between the nasal cycle and the sleep cycle which, like other cyclic physiological phenomena with ultradian rhythmicity, expresses a pattern of 'lateralisation' that is synchronous with changes in the sleep cycle.     

Time Periods in the Nasal Cycle During Night Sleep

The periodic congestion and decongestion of nasal venous sinuses and the alternation of airflow from one side of the nose to the other are referred to as a ‘nasal cycle’ in the literature. The aim of this study was to detect the nasal cycle during sleep in normal subjects and describe existing time periods and their sequence and patterns. We studied 58 records of the nasal cycle over 6–9 hours of sleep in six healthy volunteers and revealed that the cycle could be described as a combination of 1 to 4 discrete ultradian periods with various length: 1.0–1.5 h (mean 78.6min), 2.5–3.0 h (168.3 min), 4.0–4.5 h (260.3 min) or 5.5–6.0 h (347.5 min). The distribution of the discrete time periods was multi-modal and the mean lengths of periods were ‘multiples’ of a basic period of 85.4 min (?1.5 h) which was very close to the mean length of the sleep cycle (?1.5 h). In all subjects, during any of the REM stages of the sleep, an alternation of the airflow through the nostrils was observed. In about 75% of all cases, the switch of the flow between the nostrils occurred during the second or following REM stages of the sleep thus shaping a nasal cycle that contained mainly periods of 3.0 or 4.5 hours. We suggest a novel classification of the nocturnal nasal cyclicity and hypothesis that there is a relationship between the nasal cycle and the sleep cycle which, like other cyclic physiological phenomena with ultradian rhythmicity, expresses a pattern of ‘lateralisation’ that is synchronous with changes in the sleep cycle.     

Self-Reported Health and Sleep Complaints Among Nursing Personnel Working Under 12 h Night and Day Shifts

This cross-sectional exploratory study involved health care workers of various skill types and levels. We tested the hypothesis that the prevalence of diseases, sleep complaints, and insufficient time for nonprofessional activities (family, leisure, and rest) are higher among night than day workers. Data collection was carried out in two public hospitals using questionnaires and other forms. Night work was explored as a risk factor, considering a night worker as one who had at least one night job on the occasion of the research. Data were assessed by a univariate analysis. The association between work schedule and the dependent variables—health conditions, sleep complaints, and insufficient time for nonprofessional activities—was evaluated through the estimation of the prevalence ratio, with a confidence interval of 95%. Two hundred and fifty-eight female nursing personnel participated; 41.5% were moonlighters, and only 20 worked a shift of less than 12 h in length. Reports of migraine and need of medical care the 2 weeks before the survey were more prevalent among day than night workers (PR = 0.71; CI = 0.55–0.92 and PR = 0.71; CI = 0.52–0.95, respectively). Migraine headaches occurred less frequently among night than day workers as confirmed by comparing the reports of the night workers and day workers whose work history was always day shifts (PR = 0.74; CI = 0.57–0.96). Reports of mild emotional disorders (mild depression, tension, anxiety, or insomnia) were less frequent among night (PR = 0.76; CI = 0.59–0.98) and ex-night workers (PR = 0.68; CI = 0.50–0.91) than day workers who never had worked a night job. The healthy worker effect does not seem to explain the results of the comparisons between day and night workers. The possible role of exposure by day workers to some risk factors, such as stress, was suggested as an explanation for these results. No significant difference was observed between night and day workers as to sleep complaints, a result that may have been influenced by the nature of the shift-work schedule (no successive night shifts) and possibly nap taking during the night shift. Moreover, the long work hours and moonlighting of the healthcare workers, which is common in Brazil, may have masked other possible differences between the day and night workers. Among night workers, a significant relation was found between years working nights (more than 10 yrs) and high cholesterol values (PR = 2.58; CI = 1.07–6.27), a result that deserves additional study. Working nights more than four times per 2-week span was related to complaints about insufficient time for children (PR = 1.96; CI = 1.38–2.78) and rest/leisure (PR = 1.54; CI = 1.20–1.99). These results can be related to the “social value of time,” as evenings and nights are when families usually spend time together. The complexity of the professional life and the consequent heterogeneity of the group of workers under shift-work schemes confound the results. More in-depth study of the questions raised here demands a more sophisticated epidemiological treatment and larger sample size.     

Sleep Complaints and Polysomnographic Findings: A Study of Nuclear Power Plant Shift Workers

The literature widely recognizes that shift workers have more health complaints than the general population. The objective of this study was to describe the prevalence of sleep complaints and verify the polysomnographic (PSG) variables of shift workers in two Brazilian nuclear power plants. We carried out a subjective evaluation with a sleep questionnaire. Based on these results, the interviewees that reported sleep‐related complaints were referred for polysomnographic evaluation. Of the 327 volunteers initially evaluated by the sleep questionnaire, 113 (35%) reported sleep complaints; they were significantly older, had higher body mass index (BMI), and worked more years on shifts than those without sleep complaints. Of these 113, 90 met criteria for various sleep disorders: 30 (9%) showed obstructive sleep apnea (OSA), 18 (5.5%) showed limb movement, and 42 (13%) evidenced both sleep problems and had a significantly higher proportion of sleep stage 1 and arousals compared with the 23 shift workers that had no indices of sleep problems. The present study found that 90 (27.5%) of the evaluated participants met the PSG criteria of some type of clinical sleep disorder. This high proportion should be investigated for associations with other aspects of work, such as working hours, working schedule, years performing shift work, and access to health services. Due to the strong association between sleep disorders and the incidence of fatigue and sleepiness, the evaluation of the sleep patterns and complaints of shift workers is essential and should be considered to be one of the basic strategies of industry to prevent accidents.     

Sleep/Wake Dynamics Changes during Maturation in Rats

Objectives

Conventional scoring of sleep provides little information about the process of transitioning between vigilance states. We applied the state space technique (SST) using frequency band ratios to follow normal maturation of different sleep/wake states, velocities of movements, and transitions between states of juvenile (postnatal day 34, P34) and young adult rats (P71).

Design

24-h sleep recordings of eight P34 and nine P71 were analyzed using conventional scoring criteria and SST one week following implantation of telemetric transmitter. SST is a non-categorical approach that allows novel quantitative and unbiased examination of vigilance-states dynamics and state transitions. In this approach, behavioral changes are described in a 2-dimensional state space that is derived from spectral characteristics of the electroencephalography.

Measurements and Results

With maturation sleep intensity declines, the duration of deep slow wave sleep (DSWS) and light slow wave sleep (LSWS) decreases and increases, respectively. Vigilance state determination, as a function of frequency, is not constant; there is a substantial shift to higher ratio 1 in all vigilance states except DSWS. Deep slow wave sleep decreases in adult relative to juvenile animals at all frequencies. P71 animals have 400% more trajectories from Wake to LSWS (p = 0.005) and vice versa (p = 0.005), and 100% more micro-arousals (p = 0.021), while trajectories from LSWS to DSWS (p = 0.047) and vice versa (p = 0.033) were reduced by 60%. In both juvenile and adult animals, no significant changes were found in sleep velocity at all regions of the 2-dimensional state space plot; suggesting that maturation has a partial effect on sleep stability.

Conclusions

Here, we present novel and original evidence that SST enables visualization of vigilance-state intensity, transitions, and velocities that were not evident by traditional scoring methods. These observations provide new perspectives in sleep state dynamics and highlight the usefulness of this technique in exploring the development of sleep-wake activity.     

A Compromise Phase Position for Permanent Night Shift Workers: Circadian Phase after Two Night Shifts with Scheduled Sleep and Light/Dark Exposure

Night shift work is associated with a myriad of health and safety risks. Phase‐shifting the circadian clock such that it is more aligned with night work and day sleep is one way to attenuate these risks. However, workers will not be satisfied with complete adaptation to night work if it leaves them misaligned during days off. Therefore, the goal of this set of studies is to produce a compromise phase position in which individuals working night shifts delay their circadian clocks to a position that is more compatible with nighttime work and daytime sleep yet is not incompatible with late nighttime sleep on days off. This is the first in the set of studies describing the magnitude of circadian phase delays that occurs on progressively later days within a series of night shifts interspersed with days off. The series will be ended on various days in order to take a “snapshot” of circadian phase. In this set of studies, subjects sleep from 23:00 to 7:00 h for three weeks. Following this baseline period, there is a series of night shifts (23:00 to 07:00 h) and days off. Experimental subjects receive five 15 min intermittent bright light pulses (～3500 lux; ～1100 µW/cm²) once per hour during the night shifts, wear sunglasses that attenuate all visible wavelengths—especially short wavelengths (“blue‐blockers”)—while traveling home after the shifts, and sleep in the dark (08:30–15:30 h) after each night shift. Control subjects remain in typical dim room light (<50 lux) throughout the night shift, wear sunglasses that do not attenuate as much light, and sleep whenever they want after the night shifts. Circadian phase is determined from the circadian rhythm of melatonin collected during a dim light phase assessment at the beginning and end of each study. The sleepiest time of day, approximated by the body temperature minimum (T_min), is estimated by adding 7 h to the dim light melatonin onset. In this first study, circadian phase was measured after two night shifts and day sleep periods. The T_min of the experimental subjects (n=11) was 04:24±0.8 h (mean±SD) at baseline and 7:36±1.4 h after the night shifts. Thus, after two night shifts, the T_min had not yet delayed into the daytime sleep period, which began at 08:30 h. The T_min of the control subjects (n=12) was 04:00±1.2 h at baseline and drifted to 4:36±1.4 h after the night shifts. Thus, two night shifts with a practical pattern of intermittent bright light, the wearing of sunglasses on the way home from night shifts, and a regular sleep period early in the daytime, phase delayed the circadian clock toward the desired compromise phase position for permanent night shift workers. Additional night shifts with bright light pulses and daytime sleep in the dark are expected to displace the sleepiest time of day into the daytime sleep period, improving both nighttime alertness and daytime sleep but not precluding adequate sleep on days off.     

The Amount of Diurnal Sleep, and Complaints of Fatigue and Poor Sleep, in Night-Working Women: The Effects of Having Children

This study deals with female industrial night workers. There is little scientific literature on this topic since, until recently, such shift systems have in most countries been restricted to men. The amount of diurnal sleep, as well as complaints about fatigue and poor sleep, were compared in women who were (n = 17) or were not (n = 26) caring for children. The women were engaged at an assembly line, working nights (22:00-06:00) from Monday to Friday. They filled out sleep logs for 10 consecutive weeks and were interviewed about complaints concerned with fatigue and poor sleep. A comparison of the diurnal sleeps taken between consecutive night shifts showed that the average total length of daily sleep, as well as the time of onset of the first sleep, did not differ between the groups; however, workers who had children tended to show, in comparison with their childless colleagues, more sleep episodes per day and a shorter first sleep. The total number of complaints about poor sleep and fatigue did not differ between the groups; nevertheless, workers with children complained more of difficulty in falling asleep, had a greater dissatisfaction with the amount of sleep on weekdays, and tended to show an increasing fatigue as the week progressed. We conclude that there are social pressures in women who care for children that are in addition to those that are a general consequence of night work. These results reinforce a need for the implementation of measures that organise child care, so helping a mother who wishes to work also outside the home.     

The Amount of Diurnal Sleep,and Complaints of Fatigue and Poor Sleep,in Night-Working Women: The Effects of Having Children

This study deals with female industrial night workers. There is little scientific literature on this topic since, until recently, such shift systems have in most countries been restricted to men. The amount of diurnal sleep, as well as complaints about fatigue and poor sleep, were compared in women who were (n = 17) or were not (n = 26) caring for children. The women were engaged at an assembly line, working nights (22:00-06:00) from Monday to Friday. They filled out sleep logs for 10 consecutive weeks and were interviewed about complaints concerned with fatigue and poor sleep. A comparison of the diurnal sleeps taken between consecutive night shifts showed that the average total length of daily sleep, as well as the time of onset of the first sleep, did not differ between the groups; however, workers who had children tended to show, in comparison with their childless colleagues, more sleep episodes per day and a shorter first sleep. The total number of complaints about poor sleep and fatigue did not differ between the groups; nevertheless, workers with children complained more of difficulty in falling asleep, had a greater dissatisfaction with the amount of sleep on weekdays, and tended to show an increasing fatigue as the week progressed. We conclude that there are social pressures in women who care for children that are in addition to those that are a general consequence of night work. These results reinforce a need for the implementation of measures that organise child care, so helping a mother who wishes to work also outside the home.     

Polyphasic Wake/Sleep Episodes in the Fire Ant, Solenopsis Invicta

Sleep is a well-studied biological process in vertebrates, particularly birds and mammals. Less is know about sleep in solitary and social invertebrates, particularly the ants. This paper reports a study of light/dark periods on worker activity as well as sleep location, posture and the wake/sleep cycles of fire ant workers and queens located in an artificial nest chamber. Workers slept in one of three locations: on the ceiling, against the chamber wall or in the center of the chamber floor. Workers on the ceiling or against the chamber wall slept for longer periods than those at the center of the chamber floor where most grooming and feeding activity occurred. When sleeping, queens huddled together. Their close contact generated synchronized wake/sleep cycles with each other. Sleep posture was distinctly different than wake posture. During deep sleep, queens and workers folded their antennae and were non-responsive to contact by other ants. Another indicator of deep sleep was rapid antennal movement (RAM sleep). Sleep episodes were polyphasic. Queens averaged ~92 sleep episodes per day, each episode lasting ~6 min, for a total of ~9.4 h of sleep per day. Workers averaged ~253 sleep episodes lasting 1.1 min each for a total of ~4.8 h of sleep per day. Activity episodes were unaffected by light/dark periods. Workers were hypervigilant with an average of 80% of the labor force completing grooming, feeding or excavation tasks at any given time. These findings reinforce the parental exploitation hypothesis—sterile workers are a caste of disposable, short-lived helpers whose vigilance and hyperactivty increases the queen’s fitness by buffering her and her fertile offspring from environmental stresses.     

Twenty-Four-Hour Prolactin Profiles in Night Workers

In addition to sleep processes, it has been suggested that an intrinsic circadian rhythmicity is involved in the temporal organization of prolactin (PRL) secretion. Eight night workers were studied to determine whether the PRL rhythm is adapted to their rest-activity schedule and whether this provides evidence in favor of an endogenous clock-driven component. Ten day-active subjects, sleeping once during the night and once after an 8-h delay in their sleep period, were used as a control group. Plasma PRL, body temperature, and plasma melatonin were measured at 10-min intervals. Twenty-four-hour PRL profiles did not differ between night workers sleeping as usual during the daytime and day-active subjects submitted to an abrupt sleep shift to daytime. For the two groups of subjects a transient PRL peak, similar in size and time of occurrence, was observed during the night. Melatonin, a strong marker of the primary circadian oscillator, displayed a phase shift that differed widely among night workers. Body temperature, on the other hand, was found to be more regularly adapted despite the persistence of a small decrease or leveling off during the night. Although no relationship was found between the melatonin increase and the nocturnal PRL peak, a concomitance with this transient temperature decrease could be demonstrated. The persistence of this PRL peak in night workers raises the question of its significance. (Chronobiology International, 13(4), 283-293, 1996)     

Metabolic Syndrome in Permanent Night Workers

Night and shift work might be risk factors for metabolic and cardiovascular disorders due to interference with diet, circadian metabolic rhythms, and lifestyle. The relationship between permanent night work and metabolic and cardiovascular risk factors was explored in a retrospective longitudinal study of workers employed in a large municipal enterprise in charge of street cleaning and domestic waste collection. All subjects who had worked night shifts between 1976 and 2007 as hand sweepers, motor sweepers, and delivery tricar drivers were compared with subjects who always worked the same jobs but on day shifts. From the periodical medical surveillance files, we identified 488 male workers who had been examined on average five times (minimum 2, maximum 14) during the study period, for a total of 2,328 medical examinations; 157 always had worked day shifts, 12 always the night shift, and 319 both (initially day and subsequently night shifts). Their age ranged from 22 to 62 yrs, and work experience varied from 1 to 28 yrs. Lifestyle habits (smoking, alcohol consumption), body mass index, serum glucose, total cholesterol, tryglicerides, hepatic enzymes, blood pressure, resting electrocardiogram, diabetes, coronary heart disease, hypertension, and related drugs were taken into consideration for the analysis. We used generalized estimating equations (GEE) models (exchangeable correlation matrix) to analyze the relationship between night work and health effects while accounting for within‐subject correlations and adjusting for study period, job, age, and lifestyle variables. As a whole, night workers smoked more and had significantly higher BMI, serum total cholesterol, and triglycerides than day workers. Both the inter‐individual comparison between day and night workers and the intra‐individual comparison among the workers, who were day workers at the beginning of their employment and later became night workers, showed a significant increase in BMI, total cholesterol, and tryglicerides associated with night work. No consistent effect was seen on fasting glucose, hepatic enzymes, and blood pressure, whereas a higher incidence of coronary heart disease was recorded in night workers.     

Aging in Mice Reduces the Ability to Sustain Sleep/Wake States

One of the most significant problems facing older individuals is difficulty staying asleep at night and awake during the day. Understanding the mechanisms by which the regulation of sleep/wake goes awry with age is a critical step in identifying novel therapeutic strategies to improve quality of life for the elderly. We measured wake, non-rapid eye movement (NREM) and rapid-eye movement (REM) sleep in young (2–4 months-old) and aged (22–24 months-old) C57BL6/NIA mice. We used both conventional measures (i.e., bout number and bout duration) and an innovative spike-and-slab statistical approach to characterize age-related fragmentation of sleep/wake. The short (spike) and long (slab) components of the spike-and-slab mixture model capture the distribution of bouts for each behavioral state in mice. Using this novel analytical approach, we found that aged animals are less able to sustain long episodes of wakefulness or NREM sleep. Additionally, spectral analysis of EEG recordings revealed that aging slows theta peak frequency, a correlate of arousal. These combined analyses provide a window into the mechanisms underlying the destabilization of long periods of sleep and wake and reduced vigilance that develop with aging.     

Chronic Upper Airway Obstruction Induces Abnormal Sleep/Wake Dynamics in Juvenile Rats

Objectives

Conventional scoring of sleep provides little information about the process of transitioning between vigilance-states. We used the state space technique to explore whether rats with chronic upper airway obstruction (UAO) have abnormal sleep/wake states, faster movements between states, or abnormal transitions between states.

Design

The tracheae of 22-day-old Sprague-Dawley rats were surgically narrowed to increase upper airway resistance with no evidence for frank obstructed apneas or hypopneas; 24-h electroencephalography of sleep/wake recordings of UAO and sham-control animals was analyzed using state space technique. This non-categorical approach allows quantitative and unbiased examination of vigilance-states and state transitions. Measurements were performed 2 weeks post-surgery at baseline and following administration of ritanserin (5-HT2 receptor antagonist) the next day to stimulate sleep.

Measurements and Results

UAO rats spent less time in deep (delta-rich) slow wave sleep (SWS) and near transition zones between states. State transitions from light SWS to wake and vice versa and microarousals were more frequent and rapid in UAO rats, indicating that obstructed animals have more regions where vigilance-states are unstable. Ritanserin consolidated sleep in both groups by decreasing the number of microarousals and trajectories between wake and light SWS, and increasing deep SWS in UAO.

Conclusions

State space technique enables visualization of vigilance-state transitions and velocities that were not evident by traditional scoring methods. This analysis provides new quantitative assessment of abnormal vigilance-state dynamics in UAO in the absence of frank obstructed apneas or hypopneas.     

Personal Light Dosimetry in Permanent Night and Day Workers

Light exposure was measured in six day and six night watches (working 12-hour shifts five days in a row) during 48 h on work days and 48 h on days off using a photocell with a sensitivity corresponding to photopic vision. The photocell was mounted on a frame of spectacles, thus measuring in viewing direction. Light exposure was low both in night and day watches; however, in night watches exposures were significantly lower: On work days, night watches spent a mean of 13 min above 1,500 lx, day watches 52 min; on days off, night watches spent 3 min above 1,500 lx but day watches 89 min. Unexpectedly, night watches had no higher exposure during days off. We suspect that this is due to a light avoidance tendency in permanent night workers. High negative correlations between the acrophases of subjective state (e.g., alertness and mood) and light exposure in night watches indicate that bright light would probably increase desynchroniza-tion between subjective state, sleep, and activity.     

Wearing Blue-Blockers in the Morning Could Improve Sleep of Workers on a Permanent Night Schedule: A Pilot Study

Night shiftworkers often complain of disturbed sleep during the day. This could be partly caused by morning sunlight exposure during the commute home, which tends to maintain the circadian clock on a daytime rhythm. The circadian clock is most sensitive to the blue portion of the visible spectrum, so our aim was to determine if blocking short wavelengths of light below 540 nm could improve daytime sleep quality and nighttime vigilance of night shiftworkers. Eight permanent night shiftworkers (32–56 yrs of age) of Quebec City's Canada Post distribution center were evaluated during summertime, and twenty others (24–55 yrs of age) during fall and winter. Timing, efficacy, and fragmentation of daytime sleep were analyzed over four weeks by a wrist activity monitor, and subjective vigilance was additionally assessed at the end of the night shift in the fall–winter group. The first two weeks served as baseline and the remaining two as experimental weeks when workers had to wear blue-blockers glasses, either just before leaving the workplace at the end of their shift (summer group) or 2 h before the end of the night shift (fall–winter group). They all had to wear the glasses when outside during the day until 16:00 h. When wearing the glasses, workers slept, on average ±SD, 32±29 and 34±60 more min/day, increased their sleep efficacy by 1.95±2.17% and 4.56±6.1%, and lowered their sleep fragmentation by 1.74±1.36% and 4.22±9.16% in the summer and fall–winter group, respectively. Subjective vigilance also generally improved on Fridays in the fall–winter group. Blue-blockers seem to improve daytime sleep of permanent night-shift workers.     

Effects of Transitions into and out of Daylight Saving Time on the Quality of the Sleep/Wake Cycle: an Actigraphic Study in Healthy University Students

The main goal of the present study was to examine the effects of transition into and out of daylight saving time (DST) on the quality of the sleep/wake cycle, assessed through actigraphy. To this end, 14 healthy university students (mean age: 26.86?±?3.25?yrs) wore an actigraph for 7?d before and 7?d after the transition out of and into DST on fall 2009 and spring 2010, respectively. The following parameters have been compared before and after the transition, separately for autumn and spring changes: bedtime (BT), get-up time (GUT), time in bed (TIB), sleep onset latency (SOL), fragmentation index (FI), sleep efficiency (SE), total sleep time (TST), wake after sleep onset (WASO), mean activity score (MAS), and number of wake bouts (WB). After the autumn transition, a significant advance of the GUT and a decrease of TIB and TST were observed. On the contrary, spring transition led to a delay of the GUT, an increase of TIB, TST, WASO, MAS, and WB, and a decrease of SE. The present results highlight a more strong deterioration of sleep/wake cycle quality after spring compared with autumn transition, confirming that human circadian system more easily adjusts to a phase delay (autumn change) than a phase advance (spring transition).     

Relation of Chronotype to Sleep Complaints in the General Finnish Population

Individuals show variation in their preference for the daily timing of activities. In this study the authors analyzed whether chronotypes associate with sleep duration and sleep-related complaints. The authors used the National FINRISK Study 2007 Survey data on 3696 women and 3162 men, representative of the Finnish population aged 25 yrs and older, for the assessment of chronotype and self-reported sleep. Evening types experienced insomnia symptoms, had nightmares, and had used recently hypnotics significantly more often than other chronotypes among both men and women. In a multinominal logistic regression model predicting insufficient sleep, the association of eveningness with insufficient sleep was not abolished after adjustment for sex, age, and sleep duration. The prevalence of short sleepers was significantly higher in evening types among men than among women, whereas that of long sleepers was significantly higher in evening types among both men and women, as compared with the other chronotypes. These results indicate that eveningness predisposes individuals to a range of sleep complaints. (Author correspondence: ilona.merikanto@helsinki.fi)