Shift work influences multiple sclerosis risk.

BACKGROUND: An association between working shift at a young age and subsequent risk for multiple sclerosis (MS) has been observed. OBJECTIVE: To investigate whether this finding could be replicated, and to further explore the influence of age at first exposure to shift work. METHODS: Using a Swedish population-based, case-control study (2337 cases and 4904 controls), the incidence of MS among subjects whom had worked shifts was compared with that of those whom had not, by calculating odds ratios (ORs) with 95% confidence intervals (CIs) by means of logistic regression. RESULTS: The OR of developing MS was 1.5 (95% CI 1.2-1.8) among those whom started working shifts before age 20, whereas a less pronounced association was observed among those whom started working shifts at age 20 or later (OR 1.2; 95% CI 1.1-1.4). The effect of shift work was more pronounced among subjects whom had been exposed at a young age, regardless of the duration between the start of shift work and disease onset. CONCLUSION: Some aspects of adolescence seem to be of great importance, regarding the impact of shift work on MS risk. Circadian disruption and sleep deprivation may contribute towards explaining the association; however, the exact mechanisms behind our observations remain to be elucidated.

The impact of work time control on physicians' sleep and well-being.

Physicians' work schedules are an important determinant of their own wellbeing and that of their patients. This study considers whether allowing physicians control over their work hours ameliorates the effects of demanding work schedules. A questionnaire was completed by hospital physicians regarding their work hours (exposure to long shifts, short inter-shift intervals, weekend duties, night duties, unpaid overtime; and work time control), sleep (quantity and disturbance) and wellbeing (burnout, stress and fatigue). Work time control moderated the negative impact that frequent night working had upon sleep quantity and sleep disturbance. For participants who never worked long shifts, work time control was associated with fewer short sleeps, but this was not the case for those who did work long shifts. Optimizing the balance between schedule flexibility and patient needs could enhance physicians' sleep when working the night shift, thereby reducing their levels of fatigue and enhancing patient care.

Immigrant girls perceive less stress.

AIM: To develop a new stress scale and use it for investigating impact of ethnicity on perception of stress. SUBJECTS AND METHODS: One thousand one hundred and twenty-four students (grades 6-9) from 14 schools filled in a questionnaire at school with questions about age, sex, use of language at home (proxy for cultural background), stress and stressors. Factor analysis and analysis of variance were used to analyze the data. RESULTS: Two-stress dimensions were identified, 'pressure'(7 items, Cronbach's alpha 0.862) and 'activation'(4 items, Cronbach's alpha 0.767). Scores on the two scales and a separate 'stress' item were higher in girls and increased with grade. Use of another language than Swedish at home showed a significant effect only for activation, with lower scores in girls. The interaction effect between sex and language was significant for all variables and was due mainly to lower stress in girls using another language than Swedish at home. CONCLUSION: This new stress scale has some promising qualities like a condensed format, basis in a specific stress concept and formulated to be as age and culture independent as possible. Immigrant girls seem to perceive less stress than Swedish born girls, which opens up for questions about protective mechanisms.

The impact of free-time activities on sleep, recovery and well-being.

We compared the effects of different types of free-time activity on subjective and objective indices of sleep, recovery and well-being in an experimental field study. Twelve participants spent four consecutive evenings after work in each of three conditions: pursuing quiet leisure activities at home; undertaking active leisure pursuits; doing additional work. Ratings of rest and recuperation, and of satisfaction, were lowest in the additional work condition. There were few other differences between conditions. However, being satisfied with one's evening activities (regardless of which experimental condition was being undertaken) was associated with improved subsequent sleep (self-reported). Evening activities involving lower mental effort were also associated with better-rated sleep, as well as improved recuperation and fatigue the next day. It is concluded that the nature of activity per se may be less important than (1) whether the activity accords with individual preference and (2) the cumulative demands of daytime and evening activities.

Mental fatigue, work and sleep.

OBJECTIVE: The study examined the multivariate relationship between mental fatigue and different work-related (work load, work hours) and background/life style factors, as well as disturbed sleep. METHODS: A total of 5720 healthy employed men and women living in the greater Stockholm area participated in a questionnaire study on cardiovascular risk factors. The data were analysed using a multiple logistic regression analysis with self-rated fatigue as the dependent variable. RESULTS: Fatigue was predicted by disturbed sleep (4.31; 3.50-5.45, high immersion in work (4.17; 2.93-5.94), high work demands (2.39; 1.54-3.69), social support, being a female, being a supervisor and high age. Shift work, work hours (including overtime) and influence at work did not become significant predictors. With control for work demands a high number of work hours was associated with lower fatigue. CONCLUSION: Disturbed sleep is an important predictor of fatigue, apparently stronger than previously well-established predictors such as work load, female gender, lack of exercise, etc.

Sleep as restitution: an introduction.

This paper summarizes a symposium that has shown that sleep is a state of altered metabolism, and that disturbances and curtailing of sleep have far-reaching effects on endocrinology, immunology and metabolism, changes that may be linked to disease. As yet, the entire causal chain is weak but there are indications that, in particular, the risk of type 2 diabetes and cardiovascular disease may result from disturbed sleep. It is hypothesized that both insulin resistance and chronic low-grade inflammation may be involved.

Sleep disturbances, work stress and work hours: a cross-sectional study.

OBJECTIVE: The study examined the multivariate relationship between disturbed sleep and different work-related and background/life style factors. METHODS: 5720 healthy employed men and women living in the greater Stockholm area participated. A factor analysis of eight items provided one main factor: "disturbed sleep." The data were analyzed using a multiple logistic regression analysis against the index disturbed sleep as well as the separate items "not well rested" and "difficulties awakening." RESULTS: The results showed that high work demands [odds ratio (OR) = 2.15] and physical effort at work (OR = 1.94) are risk indicators for disturbed sleep, while high social support is associated with reduced risk (OR = 0.44). In addition, higher age (45+), female gender, a high body mass index (BMI) and lack of exercise are background/life style risk indicators. Introducing into the model an item representing inability to stop thinking about work during free time yielded the highest OR (3.20) and forced work demands out of the regression. With regard to not feeling well rested, the same significant predictors, except physical effort, were obtained, as well as for having night work and being married. In addition, the age effect was reversed--high age predicted reduced risk of not feeling well rested. Difficulties awakening was predicted by high work demands, low social support, being male, low age and smoking. It is notable that, whereas subjective sleep quality decreased with age, the difficulties awakening and feelings of not being well rested after sleep increased with age. CONCLUSION: It was concluded that stress and the social situation at work are strongly linked to disturbed sleep and impaired awakening, that gender and, even more so, age may modify this and that the inability to stop worrying about work during free time may be an important link in the relation between stress and sleep.

A prospective study of fatal occupational accidents -- relationship to sleeping difficulties and occupational factors.

Very little is known about the association between sleep and (fatal) occupational accidents. This study investigated this relationship using register data of self-rated sleep difficulties, together with occupational and demographic characteristics. The variables were related to subsequent occupational fatal accidents. A national sample of 47,860 individuals was selected at regular intervals over a period of 20 years, and interviewed over the phone on issues related to work and health. The responses were linked to the cause of death register (suicides excluded) and the data set was subjected to a (multivariate) Cox regression survival analysis. One hundred and sixty six fatal occupational accidents occurred, and the significant predictors were: male vs. female: relative risk (RR)=2.30 with a 95% confidence interval (CI) of 1.56-3.38; difficulties in sleeping (past 2 weeks): RR=1.89 with CI=1.22-2.94; and non-day work: RR=1.63 with CI=1.09-2.45. No significant effect was seen for age, socio-economic group, hectic work, overtime (>50 h per week), or physically strenuous work. It was concluded that self-reported disturbed sleep is a predictor of accidental death at work, in addition to non-day work and male gender.

Work and rest sleep schedules of 227 European truck drivers.

OBJECTIVE: To investigate the sleep-wake behavior and performance of a random sample of European truck drivers. METHODS: The drivers completed a questionnaire concerning sleep-wake habits and disorders experienced during the previous 3 months. In addition, they were asked to complete a sleep and travel log that included their usual work and rest periods during the previous two days. They answered questions concerning working conditions and reported their caffeine and nicotine intake during their trips. RESULTS: A total of 227 drivers, mean age 37.7+/- 8.4 years (96.2% acceptance rate), participated in the study. The drivers were found to have a fairly consistent total nocturnal sleep time during their work week, but on the last night at home prior to the new work week there was an abrupt earlier wake-up time associated with a decrease in nocturnal sleep time. Of the drivers, 12.3% had slept less than 6 h in the 24 h previous to the interview and 17.1% had been awake more than 16 h. CONCLUSIONS: Shifting sleep schedules between work and rest periods can generate long episodes of wakefulness. This type of sleep deprivation is rarely investigated. Its is usually not taken into consideration when creating work schedules, but affects the performance of drivers. Unsuspected shifts occur at the onset of a new workweek. Sleep hygiene education for professional drivers is still far from perfect.

The biological effects of solar activity.

The synchronization of biological circadian and circannual rhythms is broadly viewed as a result of photic solar effects. Evidence for non-photic solar effects on biota is also slowly being recognized. The ultrastructure of cardiomyocytes from rabbits, the time structure of blood pressure and heart rate of neonates, and the heart rate variability of human adults on earth and in space were examined during magnetically disturbed and quiet days, as were morbidity statistics. Alterations in both the about-daily (circadian) and about-weekly (circaseptan) components are observed during disturbed vs. quite days. The about-weekly period of neonatal blood pressure correlates with that of the local geomagnetic disturbance index K. Circaseptans which are seen early in human life and in various other forms of life, including unicells, may provide information about the possible site(s) of life's origins from an integrative as well as adaptive evolutionary perspective.

[International consensus meeting on fatigue and the risk of traffic accidents. The significance of fatigue for transportation safety is underestimated]. / Internationellt konsensusmöte om trötthet och olycksrisk i trafiken. Trötthet har underskattad betydelse för transportsäkerheten.

Recently there has been a sizeable increase in research on fatigue and accidents in transportation. Therefore a meeting was convened last year to discuss prevalence, mechanisms and countermeasures, with the intention to produce an international consensus document. It was concluded that official statistics strongly underestimate prevalence, and that a reasonable estimate, based on research, lies between 10 and 20% for accidents on the road, in the air and at sea. The main causes are disturbed sleep and work at the circadian low, caused by night work, morning work, sleep/wake disorders (including sleep apnea) or social obstacles to sleep. Suggested countermeasures include information/education of the public and of transportation companies, as well as enforcement of existing work hour regulation. Additional countermeasures include strategic use of napping and caffeine, as well as implementation of rumble strips and--possibly--electronic devices for drowsiness detection.

[Drowsiness--greater traffic hazard than alcohol. Causes, risks and treatment]. / Vakenhetsstörning--en större trafikfara än alkohol. Orsaker, risker och behandling.

Stress and shortage of sleep may cause daytime somnolence and impaired vigilance at the wheel, especially among those suffering from sleep disturbances. According to the international consensus meeting in Stockholm in May of 2000 on "The sleepy driver and pilot--causes, risks and countermeasures", drowsy driving is an underestimated risk factor in official statistics, and as many as 15-30 percent of today's traffic accidents are related to drowsiness; thus it is an even greater risk factor than alcohol. Drowsy drivers suffer from inattention, impaired concentration and may even fall asleep at the wheel. Accidents during dozing result in three times as many fatalities as other accidents. There are a number of reasons for habitual drowsiness at the wheel aside from sleep deprivation, including rhonchopathy, shift work and jet lag, mental depression, insomnia, narcolepsy, endocrinological diseases, periodic limb movement disorder, medication, pain-disordered sleep, and heart disease. Among the most active drivers, i.e. middle aged men, obstructive sleep apnea syndrome (OSAS) has been found to be the most common reason for habitually drowsy driving. OSAS causes a 2-3 fold increased risk of traffic accidents, and it impairs simulated driving. Palatoplasty as well as nasal CPAP have been shown to improve vigilance and driving performance to an extent that the increase in risk is eliminated. Drivers suffering from habitual drowsiness and micro-sleep attacks forcing them to take repeated rests are at special risk. Even if they are as dangerous as drivers with unlawful blood alcohol levels they cannot be caught in a police checkpoint. However they often seek medial advice, and properly treated they may often return safely to traffic. If not, there could be a need to report them to the authorities so as to limit or prohibit their driving.

Age, gender and early morning highway accidents.

Accident register data, time budget studies and road traffic flow data were used to compute the age and gender-dependent relative risk [odds ratio (OR)] of being involved in a driving accident in which the driver was injured or killed. Alcohol-related accidents were excluded from the analysis. The results showed that the night-time risk, compared with that of the forenoon, was dramatically increased (OR=5) for young drivers (18--24 years) and reduced for old (65+) drivers. In direct comparison, the young drivers had 5-10 times higher risk of being involved in an accident during late night than during the forenoon, with the excess risk during the daytime being considerably lower. Women had a less pronounced night-time peak than men. In direct comparison, men had twice as high a risk as women during the late night hours. The results clearly demonstrate a strong effect of young age on night-time accident risk, together with a moderate effect of (male) gender.

Night driving, season, and the risk of highway accidents.

Official accident and traffic density statistics on Swedish highways were used to compute the relative risk (Odds Ratio - OR) of being injured or killed in a traffic accident at different times of day. After removing accidents due to alcohol 10344 accidents remained for computations, and the period 10:00h-11:00h was used as the reference point. The highest total risk was seen at 0400h (OR=5.7, Confidence interval = 5.6-5.8), with an OR of 11.4 (Ci=10.3-12.5) for fatal accidents at the same point. The same pattern was exhibited by single vehicle, head-on, and "other" (e.g., turning off the road) accidents, whereas overtaking and rear-end accidents did not show clear 24 hour patterns. Retaining alcohol-related accidents approximately doubled the nighttime peak for total accidents. During the winter, the peak of total accidents occurred at 03:00h (OR=3.8, Ci=3.5-4.0), five hours before sunrise, whereas the summer peak occurred at 04:00h (OR=11.6, Ci=11.3-11.9), shortly after the early summer sunrise and with consistently higher nighttime risk than for winter driving. It was concluded that early morning driving is several times more dangerous than driving during the forenoon. Apart from alcohol the effect seems related to sleepiness, but not to darkness.

Time of day type of food--relation to mood and hunger during 24 hours of constant conditions.

A six-day high-carbohydrate meal (HC; 65 E% (energy percent) carbohydrates, 20 E% fat and 15 E% protein) and a six-day high-fat meal (HF; 40 E% carbohydrates, 45 E% fat and 15 E% protein) were given to seven healthy subjects in a crossover design. On the last day subjects were kept awake for 24 hours in a metabolic laboratory while substrate utilisation and energy expenditure were measured by indirect calorimetry. The subjects were given isocaloric meals every four hours. Results showed that hunger decreased at night (F = 4.2, p < 0.05) and linearly increased after meal intake. Macronutrient composition (fat/carbohydrates) seemed to be of less importance for hunger. Hunger and thirst were found to be strongly associated with gastrointestinal substances, for hunger the strongest being a negative correlation with triacylglycerol (partial correlation = -0.39). It is suggested that it might not be necessary for shift workers to eat full portions at night but that satiation will occur with less food. Possibly lack of adjustment of nocturnal food intake might be one reason why overweight is common in shift work populations.

Flexible work hours, health and well-being in the European Union: preliminary data from a SALTSA project.

Demand for flexible work hours (FWH) is increasing in Europe aimed at increasing the number of production hours on one hand, and, on the other, reducing individual working hours and/or increasing autonomy and control on them. In view of the lack of knowledge of the effects of FWH on health and safety, we started a pilot project, funded by the Joint Programme for Working Life Research in Europe (SALTSA), aimed at: a) comparing the most relevant national legislation and how the EU Directive 93/104 "concerning certain aspects of working time" has been implemented in the member States; b) reporting prevalence and trend of FWH in Europe according to the three EU Surveys on Working Conditions carried out in the last decade; c) collecting practical examples of innovative FWH; d) evaluating their impact on health and safety in relation to work sectors, job demands, social life, aging and gender. Consequent actions are going to include information and consultancy for pertinent authorities and social parties involved, as well as training programmes for Union officials and similar groups concerning the organisation of FWH according to ergonomic principles.

The effects of double-shifts (15.5 hours) on sleep, fatigue and health.

The aim of the present study was to investigate how "double-shifts" (15.5 hours) affects sleep, fatigue and self-rated health. The study was carried out on male construction workers of which 80% were long-distance commuters. The schedule involved two work periods and each work period involved two double shifts in a row. The subjects filled in a sleep/wake diary at 8 times across a year and a questionnaire at 3 times. They also wore an actigraph during one shift cycle. The results showed that sleepiness, and to a certain extent, mental fatigue increased during double shifts and accumulated across days. The short rest time (8.5 hours) between days caused insufficient sleep and approximately 5.5 hours of sleep was obtained between double shifts. Questionnaire data showed that complaints of insufficient sleep, exhaustion on awakening and pain symptoms increased across the year. It was concluded that a shift system involving double shifts has a negative effect on fatigue, recovery and health-related well-being.

A 6-hour working day--effects on health and well-being.

The effect of the total amount of work hours and the benefits of a shortening is frequently debated, but very little data is available. The present study compared a group (N = 41) that obtained a 9 h reduction of the working week (to a 6 h day) with a comparison group (N = 22) that retained normal work hours. Both groups were constituted of mainly female health care and day care nursery personnel. The experimental group retained full pay and extra personnel were employed to compensate for loss of hours. Questionnaire data were obtained before and 1 year after the change. The data were analyzed using a two-factor ANOVA with the interaction term year*group as the main focus. The results showed a significant interaction of year*group for social factors, sleep quality, mental fatigue, and heart/respiratory complaints, and attitude to work hours. In all cases the experimental group improved whereas the control group did not change. It was concluded that shortened work hours have clear social effects and moderate effects on well-being.

Bright light treatment used for adaptation to night work and re-adaptation back to day life. A field study at an oil platform in the North Sea.

Night workers complain of sleepiness, reduced performance and disturbed sleep due to lack of adjustment of the circadian rhythm. In simulated night-work experiments scheduled exposure to bright light has been shown to reduce these complaints. Here we studied the effects of bright light treatment on the adaptation to 14 days of consecutive night work at an oil platform in the North Sea, and the subsequent readaptation to day life at home, using the Karolinska sleep/wake diary. Bright light treatment of 30 min per exposure was applied during the first 4 nights of the night-shift period and the first 4 days at home following the shift period. The bright light exposure was scheduled individually to phase delay the circadian rhythm. Bright light treatment modestly facilitated the subjective adaptation to night work, but the positive effect of bright light was especially pronounced during the re-adaptation back to day life following the return home. Sleepiness was reduced and the quality of day was rated better after exposure to bright light. The modest effect of bright light at the platform was, possibly, related to the finding that the workers seemed to adapt to night work within a few days even without bright light. These results suggest that short-term bright light treatment may help the adaptation to an extended night-work period, and especially the subsequent re-adaptation to day life.