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OBJECTIVE--The study was designed to examine the effects of age on sleep and the circadian rhythms during consecutive night shifts. METHODS--Two groups of letter sorters (19-29 (n = 7) and 53-59 (n = 7) years of age were studied in a sleep laboratory under closely controlled conditions. After two baseline days, circadian adjustment to three night shifts was monitored by continuous measurement of rectal temperature, salivary melatonin, and sleep-wakefulness during the night shifts. RESULTS--Age was significantly related to the adjustment to night work of rectal temperature minimum and of self rated sleepiness. Young subjects delayed their temperature phase and decreased sleepiness more than the older subjects. Age was also significantly related to an increase of alertness and to the feeling of being refreshed after the day sleep. Although there were basic differences in sleep duration and structure between the age groups, the latter did not change across the night shifts. CONCLUSION--Aging decreases the ability to recover after several, but not after the first night shift.

There is strong evidence to suggest that circadian psychophysiological adaptation processes are modified by light, depending on its intensity and timing. To characterize such modifications and determine whether they are associated with an alteration in the day/night pattern of melatonin excretion, measurements were obtained around the clock in 14 permanent night workers, each studied over a 48 hr period in the field. The light exposure behavior of these workers was studied with a newly developed light dosimetry by measuring light intensity at eye level. Physical activity was continuously registered and sleep indices were obtained by sleep logs and activity markings. Circadian rhythms of melatonin and cortisol were analysed from salivary samples collected for 24 hr at 2 hr intervals. The interindividual variation of melatonin acrophase determined by cosinor analysis was greater than 180 degrees (from around midnight to noon) and that of cortisol was about 135 degrees (from early morning to afternoon). Hormonal phase positions coincided significantly with light exposure: the more bright light pulses in the morning (maximum lux between 0600 and 0900), the less were the melatonin and cortisol acrophases shifted into the day. There was also a negative correlation between melatonin acrophase shift and duration of the overall light exposure above 1500 lux. Morning light maximum and sleep onset correlated highly significantly. Night workers were divided into those with less than ('non-shifters', n = 9) and more than 6 hr deviation from midnight ('shifters', n = 5) of the melatonin acrophase. The group comparison revealed a marked difference of the mean melatonin concentrations at night, and at 0700.(ABSTRACT TRUNCATED AT 250 WORDS)

OBJECTIVES--The aim of the present study was to define the effect of masking on the estimation of circadian adjustment of and interindividual differences between nurses on a rapidly rotating shift schedule. METHODS--The phase shift of the circadian rhythm of rectal temperature was studied in 17 subjects. The following three different methods for estimating the circadian phase shift were compared: (i) cosinor analysis, (ii) a method using normative endogenous data in which the masking effects are removed ("purification"), and (iii) a method using normative endogenous data in which the masking effects are not removed. RESULTS--The mean phase delay during the second night shift (compared with the morning shift) was 6.3 h according to the cosinor analyses of the raw data and 6.2 h according to the cross-correlation method of the raw data. When the masking effects were removed ("purification"), the phase shift was only 1.7 h. Diurnal type did not significantly explain the differences between individuals in the amount of phase shift of the raw data but was the only significant factor, explaining 32% of the variation between individuals in the phase shift of the purified data. CONCLUSIONS--Masking effects on body temperature should be taken into account before any definite conclusions can be drawn about the relation between individual factors and the adjustment of the circadian rhythm of body temperature.

Physical activity programs have become common at worksites during the last few decades. It is difficult to find a health promotion program at a worksite without an option to join organized physical activity. In this issue of the Scandinavian Journal of Work, Environment & Health, a systematic review is published on the effectiveness of physical activity programs at worksites with respect to work-related outcomes (1). Although the earlier literature on the effects of physical activity on health is extensive, no earlier reviews seem to exist in which the effect of physical activity programs at work on work-related outcomes has been studied simultaneously with the methodological quality of the individual studies. Considering the accepted role of physical activity programs at worksites, it is surprising that the review found only limited evidence for an effect on absenteeism from work, inconclusive evidence for an effect on job satisfaction, job stress and employee turnover, and no evidence for an effect on productivity. The rather upsetting result seems to be due to the lack of randomized control trials - giving always the highest rating for evidence - and shortcomings or a lack of the description of randomization, intention-to-treat analysis, inclusion criteria, compliance, methodological issues, and the like. The limited evidence for an effect of physical activity programs at worksites shows that there is a gap between the "scientific" and "practical" truth. It is not probable that any practical guidebook on worksite health promotion would state that there is "no evidence" that worksite physical exercise influences effectiveness and productivity at work. However, this is the case in strict scientific terms. The conclusion, therefore, offers a challenge to the designers of new studies on this topic. Luckily, the review found some evidence that physical activity is related to lower absenteeism. Considering the expanding evidence on the strong beneficial effects of physical exercise on health, any other result would have been improbable. According to an extensive consensus report of the United States Department of Health and Human Services (2), physical activity has numerous beneficial effects on the cardiovascular and musculoskeletal systems, and the benefits on the functioning of the metabolic, endocrine, and immune systems are considerable. There is sufficient evidence that physical activity is associated with a decrease in the risk of cardiovascular disease, mortality, colon cancer, and noninsulin-dependent diabetes mellitus (2). Furthermore, physical activity appears to relieve symptoms of depression and anxiety and improve employees` psychological health, sleep, and alertness (2, 3, 4). In another paper of this issue (5), a randomized controlled trial evaluated the effectiveness of a worksite exercise program with respect to perceived work ability and sick leaves. Since the participants did physically demanding laundry work, intervention involving physical resources was selected. The effects on work ability were, however, modest, and no effects were found on job satisfaction or sick leaves. Considering the high expectations of the employees and the company, the very minor positive results with respect to work ability must have been disappointing. Work ability is, however, an extremely wide concept that includes such items as the number of current diseases, work impairment, sick leaves, and even mental resources (6). Exercise once a week - without other action - will probably not affect such a large entity. However, as the authors point out, the idea behind the intervention was to promote self-directed physical activity. Actions concerning organizational and professional competence and improvements in the work environment are probably needed simultaneously to produce a more substantial impact on work ability. If conducted well, worksite physical exercise can still be the initiator and trick through which to start face-to-face discussions and prepare the occupational atmosphere for open-type discussions and development. On the individual level, even the perceived effect on well-being can be useful. Physical activity has a positive effect on self-confidence and the perception of balance between word demands and resources (3). The ability to cope well with stress is a handy tool in current worklife.

The aim of the study was to analyse the effects of rapid time zone changes on the circadian rhythms of flight attendants. The mean age of the 40 female subjects was 30.0 (SD = 6.9) years. Measurements of oral temperature, alertness, and visual search were performed at two hour intervals two days before the flight from Helsinki to Los Angeles, during the second and the fourth day in the USA and during the second and fourth day after the return flight to Finland. The body temperature desynchronized and the phases of the alertness and visual search rhythms shifted rapidly in the USA. After the return flight, the acrophases of the circadian rhythms delayed during the second and fourth day in Finland. During the fourth day the acrophase of alertness was 35 min and the acrophases of body temperature and visual search were 2 h 2 min and 3 h 8 min delayed, respectively. The mathematical model based on the C-, S- and W-process theory of alertness explained 25-96% of the variation of observed mean alertness of the subjects in different conditions. It is concluded that the duration of the de- and resynchronization process of the flight attendants' circadian rhythms is on the average longer than 9 days during and after round flights over ten time zones. The mean alertness of the subject can be predicted with considerable accuracy using the mathematical model.

The aim of the study was to find out which factors could explain individual differences in the resynchronization speed of circadian rhythms of salivary melatonin and subjective alertness after transmeridian flights over 10 time zones. The mean age of the 40 female subjects was 33.0 +/- 6.9 years. The data were gathered by measurements of the circadian rhythms of melatonin excretion and altertness at 2 h intervals in Helsinki (Finland) two days before westward flight to Los Angeles (USA), where the measurements were repeated on the 2nd day after the flights and on the 2nd day in Finland after return flight. This shift in the acrophases of the two circadian rhythms were used as dependent variables in regression analyses. The predictors used were length of day, marital status, amount of physical exercise, age, neuroticism, extroversion, and eveningness. Age, day length, marital status, and physical exercise explained the acrophase adaptation of the melatonin rhythm after westward flight, and day length, neuroticism, and extroversion after eastward flight. Marital status, neuroticism, and physical exercise explained the variation of the acrophase adjustment of the alertness rhythm after westward flight, and age and eveningness after eastward flight. It is concluded that the amount of daylight and personality are the best predictors of the circadian rhythm adaptation after transmeridian flights.

Individual differences in the subjective health effects of shiftwork are reviewed. Circadian regulation and brain restitution (sleep) are the crucial mechanisms by which inter-individual factors can affect tolerance to shiftwork. On the other hand, shiftworkers can use different coping mechanisms by trying to schedule their lives and especially their sleeping habits to work at unusual hours. Individual factors related to shiftwork tolerance are discussed in two groups; first, the factors which affect primarily the circadian adjustment; and, second, the factors which mainly relate to the ability to sleep at unusual hours. The significance of circadian adjustment in shiftwork tolerance is outlined.

Under normal circumstances, masking effects due to an individual's lifestyle and environment give misleading information when the phase of the endogenous oscillator(s) is inferred from overt circadian rhythms. Methods to overcome this problem are often not feasible in field studies. However, we have developed a series of methods that can be used in such conditions and which give a better estimate of the endogenous oscillator than using raw, masked data. These methods have been assessed for validity in laboratory-based studies and also used in several studies in the field where the amount and quality of data collected can be less. Results confirm the view that the use of masked data leads to an overestimate of the rate of adjustment of the endogenous oscillator to time-zone transitions and shiftwork. They also indicate that masking factors might contribute to the phase stability that normally is measured in nychthemeral circumstances. The methods require further testing but open up the possibility of assessing more accurately than before the process of adjustment of the body clock to changes in the field.

Half of patients with coronary heart disease do not have any of the established risk factors (1). When the significance of work with respect to personal life is taken into account, it is not surprising that researchers are continually trying to identify new risk factors from the psychosocial work environment. Half of patients with coronary heart disease do not have any of the established risk factors (1). When the significance of work with respect to personal life is taken into account, it is not surprising that researchers are continually trying to identify new risk factors from the psychosocial work environment. Shift work is one of the factors under debate. On the basis of a review of 17 studies dealing with shift work and cardiovascular disease (2), Boggild & Knutsson concluded, in 1999, that shift workers have a 40% increase in risk when compared with day workers. A new case-referent study controlling for job strain, age, education level, and smoking also supports the conclusion of an increased risk for shift workers (3). However, some of the published studies contained in the earlier review and a later paper (4) did not find an association between shift work and cardiovascular disease; therefore the relationship does not seem to be consistent. In this issue of the Scandinavian Journal of Work, Environment & Health a straightforward paper shows that, in a random sample of employees, shift workers reported high exposure to work environment factors like noise, heat, passive smoking, walking, standing, and psychosocial stress - most of which can be related to cardiovascular disease (5). The paper adds to the discussion on the methodological problems faced by studies investigating shift work and cardiovascular disease. Shiftwork populations are often self-selected (6, 7), and the observed weak associations allow the possibility for unaccounted confounding. Twenty-four hour operations have characteristic jobs that also vary according to the time of day. Great differences in shift workers` and day workers` work environment and stress, social class, or living habits make the interpretation of even good follow-up studies difficult. The existing evidence for a causal relationship between shift work and cardiovascular disease seems to lack experimental evidence, dose-response studies with exact exposure information, and - perhaps most importantly - strong evidence for biological mechanisms indicating how shift work could actually increase the risk of cardiovascular disease. Since etiologic intervention studies of cardiovascular disease need large study populations and exposure contrasts (8), a clever approach has been to conduct intervention studies focusing on biomarkers for atherosclerosis or thrombosis instead of morbidity (9, 10). This issue of the Scandinavian Journal of Work, Environment & Health contains the report of an intervention study aimed at examining whether ergonomic shift scheduling changes the biomarkers of heart disease (11). The changes related to higher regularity, few consecutive night shifts, and more weekends off led to favorable changes in risk factors for ischemic heart disease. In the group with the highest number of ergonomic changes, an 8% decrease in total cholesterol, a 15% decrease in low-density lipoprotein (LDL) cholesterol, a 9% increase in high-density lipoprotein (HDL) cholesterol, and a 14% decrease in the total:HDL cholesterol ratio were observed. When changes in the principles of shift scheduling were analyzed across the data, higher regularity and a reduction in the number of consecutive night shifts were positively related to the biomarkers. The study shows that the timing of work can change risk factors for cardiovascular disease. Even more important, we are informed how work schedules should be improved to reduce biomarkers for atherosclerosis, and perhaps the incidence of ischemic heart disease in the long run. However, the question concerning mechanisms remains open. The observed changes in biomarkers were not related to changes in smoking, alcohol consumption, or exercise levels at the beginning of the study. However, possible changes in diet were not measured. Meal timing has been shown to influence postprandial levels of lipids and glucose (12, 13). The present intervention resulted in only slight changes in sleep and perceived stress. The recently found effects of sleep loss on lipid metabolism, glucose tolerance, autonomous nervous activity, and cortisol patterns (14) may thus not have been the key mechanism either. We do not know why shift work increases the risk of cardiovascular disease. There are probably many reasons, changes in circadian rhythms, life-style factors and psychosocial stress being mentioned the most frequently. Since factors like smoking, physical activity, or psychosocial stress are not "new" risk factors, only changes in circadian rhythms or factors related to sleep loss influencing the formation of atheroma or a clot of the artery wall would be really specific heart disease mechanisms for shift workers. The current study (11) shows that regularity in shifts decreased ischemic heart disease biomarkers. We still need information, however, on whether the regularity in meal patterns, sleep, physical activity, or some other circadian functions were the key factors leading to the improvement. The answers would help us to provide better recommendations for optimum schedules. Increasing demands for flexibility in workhours is a topical issue in many firms. With respect to sleep-wakefulness and job satisfaction, numerous studies indicate that regularity, predictability, a low number of consecutive night shifts, and sufficient time-off between shifts are advantageous (15). Putting cardiovascular disease and its biomarkers on the list of outcomes of future intervention studies of shift work would be welcomed.

The amplitude and phasing of circadian rhythms are under discussion as possible predictors of tolerance to night work. In a field study, subjective sleepiness and oral temperature of 147 female nurses were measured at 2-hour intervals during a period with one morning shift and two consecutive night shifts. The nurses also filled out a questionnaire. Two types of tolerance indices were constructed: The "health index" was based on questions referring to general fatigue, gastrointestinal symptoms, and sleep disturbances, and the "sleepiness index" on the actual subjective ratings of sleepiness. According to the health index, the group with good tolerance had a larger circadian amplitude of the oral temperature rhythm on the day of the morning shift than the group with poor tolerance. However, with regard to the sleepiness index, the corresponding difference between the groups with good or poor tolerance was not significant. The data did not confirm the hypothesis that predicts a quick adjustment of the circadian rhythm when the circadian amplitude is small before the change to night work. The contradictory results found in this and in other studies do not yet permit prediction of tolerance to night work.

The use of visual display screens and handheld mobile phones, or cellular phones as they are called, has increased dramatically in recent years. In Finland, 70% of the population has a mobile telephone, and almost everyone is daily exposed to the weak electromagnetic fields emitted by the video displays of televisions, personal computers, and other such devices. In addition, the users of mobile phones - and especially the users of video-screen-based devices - are younger than ever. At work, the amount of new technology has increased steeply, and mobile technology has made it possible to work without limitations. It is understandable that the extensive use of new equipment and the exposure to electromagnetic fields have increased concerns about the possible biological or adverse effects. The radiofrequency (RF) power emitted by mobile phones is too low to cause significant warming of absorbing tissues (1). As a consequence, increasing interest has focused on the nonthermal effects of RF radiation, especially on the possible functional disturbances of the brain. Thus far, only a few studies have been published concerning the possible effects of cellular phones on the electroencephalographic (EEG) activity of humans. In this issue, Hietanen and her co-workers (2) studied the effects of RF electromagnetic fields emitted from cellular phones on the EEG activity of humans while awake. A single-blind, placebo-controlled experiment was used. To everyone's relief, the findings suggest that exposure to RF fields emitted by 5 different cellular phones, operating at 900 MHz or 1800 MHz, had no abnormal EEG effects on humans. "Hypersensitivity" to electricity is a separate and controversial condition. Many workers complain of its symptoms, such as redness and burning of the skin and face, pricking, pain or dryness of the throat and mouth, abdominal pain, lack of concentration, and headache, mainly from exposure to video screens. The persons suffering from the condition are very difficult to treat, and many of them are often on sick leave even though "hypersensitivity to electricity" is not an accepted diagnosis. Most earlier double-blind provocation studies have shown that such patients have not been able to determine whether or not they have been subject to a field or sham exposure. However, most of the studies have been performed in the laboratory and may not have been representative of normal living conditions. In this issue, Flodin and his co-workers (3) performed a double-blind provocation study in the homes or workplaces of patients, rather than in the laboratory, while also taking into consideration the long possible latency of "electric hypersensitivity" symptoms. However, the patients, selected for study because of distinct reactions from electric equipment, were no better than their control group in deciding whether or not they were exposed to electric and magnetic fields. The new studies offer us some relief, but they also point out the need for new and objective information. Vast economic interests are related to the production and use of new technology. Any doubts or hints of possible health or "brain" effects need urgent research, which also should not have any conflict of interest with the manufacturers of such technology. From the point of view of technology producers, early and objective data on the safety of new products help to respond to the resistance and prejudices against the distribution of new technology, for example, the rapid installation of antennas for cellular phone base stations, which are already being opposed by new groups of activists. Research on the biological effects of electromagnetic or electric fields also places high requirements on the quality of experimental research. The observed negative results should not raise any methodological speculations. On the other hand, the used methods and exposure parameters vary widely (4) and minor biological and neurophysiological effects are always difficult to detect. The lack of knowledge on biological mechanisms and the lack of information on the biologically "significant" effects of the selected output measures make adequate power estimations extremely difficult. These estimations would be badly needed to aid the selection of correct designs and sample sizes and to hinder later speculations on the quality of the mostly "negative" studies. Biological research on electromagnetic fields keeps us alert. Recently, a well-done experimental study suggested that the RF fields emitted by GSM telephones have a facilitating effect on cognitive processing, especially in tasks that require attention or cognitive manipulation in working memory (5). At the same time, the European Union parlament arranged a discussion forum with the title "Are Wireless Waves Scrambling Our Brains?" Both examples indicate the urgent need for objective scientific data on the short- and long-term effects of electromagnetic fields on human brain function and health.

A physical training intervention was carried out on 75 nurses and nursing aides working irregular shifts to determine the effects of such an intervention on health, sleep-wakefulness and adaptation to shiftwork. The study design and changes in physical fitness, fatigue, sleep and psychosomatic symptoms are examined. Training (T) and control (C) groups were built randomly from matched sets of subjects. Questionnaire, laboratory and field studies were done before and after a controlled physical training programme lasting four months. Maximal oxygen consumption and muscle strength increased and heart rates at rest and at work decreased significantly in the T but not in the C group. General fatique during the shift cycle, and fatigue during the night shifts were reduced, whereas fatigue during the evening shifts increased owing to the intervention. Sleep length increased slightly and musculoskeletal symptoms were reduced. The results suggest that moderate physical training increases the physical fitness of fe...

The effects of a physical training intervention on the circadian rhythms of alertness, short-term memory performance (SAM-test) and oral temperature (t 0) were studied in 75 nurses and nursing aides working irregular shifts in a hospital. Measurements were made every two hours during the days of one morning and two night shifts. In the training group (T), fatigue decreased significantly during the night but not during the day compared to the control group (C). No significant changes were found in the circadian rhythms of the SAM-test and t 0 between the groups, but inside the T group, performance in the SAM-test improved significantly during the day and night shifts, and the mesor and amplitude of t 0 decreased during the day of a morning shift. The results suggest that physical training can induce changes in the circadian rhythms of shift workers which may be interpreted as an adaptation to shift work.

Daytime napping and its effects on 145 female shiftworkers were studied by comparing the individual characteristics, alertness, and short-term memory performance of subjects who took or did not take naps. Of the subjects 56% (n = 82) took a nap before a night shift and 21% (n = 30) after a morning shift. After a morning shift, napping was more frequent among evening types and subjects living alone (not married). Before a night shift, daytime napping was not connected to individual characteristics, but the total sleep time of nappers during the preceding night was shorter than that of non-nappers. At 10.00 and at 04.00-08.00, at the end of the night shift, nappers were significantly more alert than subjects who had not taken naps. The length and timing of the daytime nap did not correlate to either alertness or performance during the following night. In a questionnaire, nappers before a night shift had less sleep disturbances than non-nappers.

Maximal oxygen consumption (VO2max), muscle strength (MS) and physical activity were compared to age, shiftwork experience, morningness, personality traits and social factors intervening in the shiftwork tolerance of 128 women. The subjects were nurses and nursing aids working irregular shifts in a hospital. Neuroticism was the most powerful negative factor connected to higher fatigue and various symptoms of the subjects. High VO2max and good MS were, on the other hand, the most important positive factors connected to lower fatigue and musculoskeletal symptoms and better sleep quality of the subjects. In different shifts, fatigue, sleep length and quality were influenced most by morningness. It is concluded that physical fitness is an important individual factor explaining the variations of shiftwork tolerance in women.

SummaryTwelve outpatients with seasonal affective disorder were treated by 1-h morning bright light exposure for 5 days. The light treatment intervention produced a significant phase advance of self-rated sleepiness rhythm, a significant decrease of the mean level of subjective sleepiness, and a significant reduction of depression scores. No significant objective circadian rhythm phase shift nor amplitude changes would account for the antidepressant effect.

Study Design: A prospective cohort study. Objective: To study the relationship of sleep disturbances with severe back disorders leading to hospitalization. Summary of Background Data: Sleep disturbances are associated with persistent pain syndromes, but little is known about their relationship with back disorders. Methods: The first hospital admission for back disorders from 1973 to 2000 was studied in a cohort of metal industry workers (n = 902). The occurrence of sleep disturbances at baseline was categorized as: none; 1 type (either difficulties in falling asleep/waking up at night or nightmares); or both types. Cox proportional hazards regression was used to estimate the time between the assessment of risk factors and first hospital admission for back disorders. Results: Those individuals who had 1 type of sleep disturbance had a 2.1-fold (95% confidence interval 1.1-3.8) risk of back-related hospitalization, and those with both types of disturbance a 2.4-fold (1.2-4.6) risk, compared with those with no sleep disturbances. The hazard ratios were 2.1; 1.0-4.6 and 2.9; 1.2-7.1, respectively, when patients with chronic back disease or recurrent back symptoms at baseline were excluded from the analyses. Conclusion: These findings suggest that sleep disturbances are predictive of hospitalization for back disorders. The mechanism underlying this association warrants further study.

Vertaisarvioitu. Lähtökohdat : Kansainvälisiäkään rekisteritutkimuksia lääkärien työajoista ei tiettävästi ole. Kyselytutkimusten mukaan lääkärien työajat ovat varsin pitkiä. Menetelmät : Tutkimme sairaalalääkärien toteutuneiden työaikojen vuositason muutoksia suhteessa kokoaikaisuuteen, ikään ja sukupuoleen. Aineistona oli 12 sairaanhoitopiirin työaikatiedot vuosilta 2014–2018 (n =13 543, 58 % naisia). Tulokset : Kokoaikaisiksi luokiteltujen lääkärien viikkotyöaika oli keskimäärin 43 tuntia. Yli neljäsosalla kokonaistyöaika vuodessa oli yli 2 000 tuntia. Selkeimpiä vuositason muutoksia työajoissa olivat alle 13 tunnin päivystysvuorojen osuuden kasvu yli 10 prosenttiyksiköllä 41 %:iin ja päivystys- ¬vuorojen määrän kasvu 4–5 vuorolla. Muutokset olivat samansuuntaisia naisilla ja miehillä, mutta miesten kokonaistyöaika oli keskimäärin noin 70 tuntia vuodessa pidempi kuin naisten. Päivystyksiä oli pääosin enemmän alle 35-vuotiailla, mutta vähintään viikon työvuorojaksoja ja vapaamuotoista päivystystä oli enemmän vanhemmilla lääkäreillä. Päätelmät : Sairaalalääkärien vuosina 2014–2018 toteutuneissa työajoissa näkyi varsin pitkä kokonaistyöaika ja alle 13 tunnin päivystysvuorojen osuuden kasvu. Lisää tutkimusta tarvitaan erikoisaloittain sekä uusien työaikasäännösten ja COVID-19-pandemian vaikutuksista työaikaan.

The present study investigated the effects of five days' cumulative sleep restriction and two nights' recovery sleep on multiple-task performance and subjective sleepiness in a controlled laboratory environment. A total of 21 volunteers participated, thirteen in the experimental group and eight in the control group. Compared to the control group, the sleepiness of the sleep-loss group gradually increased over the five days, but returned to the baseline level after an eight hour recovery sleep period. Multiple-task performance declined selectively in the memory, arithmetic and auditory subtasks, while visual monitoring results were not affected. After the eight hour recovery period, the performance of the sleep-restricted participants in the auditory subtask remained low, although the individuals themselves no longer reported sleepiness. Performance in the rest of the tasks returned to the baseline level. Thus the partial cumulative sleep loss selectively impaired cognitive performance in subtasks of a multiple-task environment, which simulated many ordinary working environments. This may be due to the slowing of the cognitive processing during sleep restriction, as well as decline in attention control.

Shift workers are at increased risk of health problems. Effective preventive measures are needed to reduce the unfavourable effects of shift work. In this study we explored whether use of digital participatory working time scheduling software improves employee well-being and perceived workability by analysing an observational cohort study as a pseudo-experiment. Participants of the Finnish Public Sector cohort study with payroll records available between 2015 and 2019 were included (N = 2427). After estimating the propensity score of using the participatory working time scheduling software on the baseline characteristics using multilevel mixed-effects logistic regression and assigning inverse probability of treatment weights for each participant, we used generalised linear model to estimate the effect of using the participatory working time scheduling software on employees’ control over scheduling of shifts, perceived workability, self-rated health, work-life conflict, psychological distress and short sleep (≤6 h). During a 2-year follow-up, using the participatory working time scheduling software reduced the risk of employees’ low control over scheduling of shifts (risk ratio [RR] 0.34, 95% CI 0.25–0.46), short sleep (RR 0.70, 95% CI 0.52–0.95) and poor workability (RR 0.74, 95% CI 0.55–0.99). The use of the software was not associated with changes in psychological distress, self-rated health and work-life conflict. In this observational study, we analysed as a pseudo-experiment, the use of participatory working time scheduling software was associated with increased employees’ perceived control over scheduling of shifts and improved sleep and self-rated workability.