This dedicated issue of Chronobiology International is devoted to the selected proceedings of the 20th International Symposium on Shift Work and Working Time held in Stockholm, Sweden, 28 June to 1 July 2011. It constitutes the fifth such issue of the journal since 2004 dedicated to the selected proceedings to the meetings of the Working Time Society. The key theme of the 20th Symposium was "Biological Mechanisms, Recovery, and Risk Management in the 24-h Society." The collection of papers of this dedicated issue represents the best of contemporary research on the effects of night and rotating shift schedules on worker health and safety. The contents cover such topics as sleep restriction, injuries, health, and performance of night work and rotating shiftwork, plus light treatment as a countermeasure against the circadian disruption of shiftwork. The majority of the papers are observational field studies, including some of large sample size, and three studies are well-designed laboratory experiments.
Human pregnancy is associated with increased requirements for dietary energy and this increase may be partly offset by reductions in physical activity during gestation. Studies in well-nourished women have shown that the physical activity level (PAL), obtained as the total energy expenditure (TEE) divided by the BMR, decreases in late pregnancy. However, it is not known if this decrease is really caused by reductions in physical activity or if it is the result of decreases in energy expenditure/BMR (the so-called metabolic equivalent, MET) for many activities in late pregnancy. In the present study activity pattern, TEE and BMR were assessed in twenty-three healthy Swedish women before pregnancy as well as in gestational weeks 14 and 32. Activity pattern was assessed using a questionnaire and heart rate recording. TEE was assessed using the doubly labelled water method and BMR was measured by means of indirect calorimetry. When compared to the pre-pregnant value, there was little change in the PAL in gestational week 14 but it was significantly reduced in gestational week 32. Results obtained by means of the questionnaire and by heart rate recording showed that the activity pattern was largely unaffected by pregnancy. The findings support the following conclusion: in a population of well-nourished women where the activity pattern is maintained during pregnancy, the increase in BMR represents approximately the main part of the pregnancy-induced increase in TEE, at least until gestational week 32.
The adjustment of sleep-wake patterns and the circadian temperature rhythm was monitored in nine Royal Norwegian Air-force volunteers operating P-3 aircraft during a westward training deployment across nine time zones. Subjects recorded all sleep and nap times, rated nightly sleep quality, and completed personality inventories. Rectal temperature, heart rate, and wrist activity were continuously monitored. Adjustment was slower after the return eastward flight than after the outbound westward flight. The eastward flight produced slower readjustment of sleep timing to local time and greater interindividual variability in the patterns of adjustment of sleep and temperature. One subject apparently exhibited resynchronization by partition, with the temperature rhythm undergoing the reciprocal 15-h delay. In contrast, average heart rates during sleep were significantly elevated only after westward flight. Interindividual differences in adjustment of the temperature rhythm were correlated with some of the personality measures. Larger phase delays in the overall temperature waveform (as measured on the 5th day after westward flight) were exhibited by extraverts, and less consistently by evening types.
OBJECTIVE: To determine the contribution of prone sleeping, bed sharing, and sleeping outside an infant crib to sudden infant death syndrome (SIDS). METHODS: We conducted a retrospective descriptive study of all SIDS cases in Alaska from January 1, 1992, through December 31, 1997. Reviewed data sources included maternal and infant medical records, autopsy reports, birth and death certificates, police and state trooper death scene investigations, and occasionally home interviews. RESULTS: The death certificate identified SIDS as a cause of death for 130 infants (cause-specific infant mortality rate: 2.0 per 1000 live births). Among infants for whom this information was known, 113 (98%) of 115 were found in the prone position, sleeping outside an infant crib, or sleeping with another person. By contrast, 2 (1.7%) were found alone and supine in their crib (1 of whom was found with a blanket wrapped around his face). Of 40 infants who slept with a parent at the time of death, only 1 infant who slept supine with a non-drug-using parent on an adult nonwater mattress was identified. CONCLUSION: Almost all SIDS deaths in Alaska occurred in association with prone sleeping, bed sharing, or sleeping outside a crib. In the absence of other risk factors, SIDS deaths associated with parental bed sharing were rare.
Associations between seasonal variations in day length (photoperiod), sleep timing, sleep quality and mood: a comparison between Ghana (5°) and Norway (69°).
The hypothesis of whether day length (photoperiod) is an important zeitgeber (time-giver) for keeping the circadian rhythm entrained to a 24-hour cycle was examined, as was its association with sleep patterns and mood problems. Data were collected prospectively from a site with very large differences in daylight duration across seasons (Troms? in Norway, 69?39'N) and a site with very small seasonal differences in daylight duration (Ghana in Accra, 5?32'N). Two hundred subjects were recruited from both sites in January. At the follow-up in August, 180 and 150 subjects in Ghana and Norway participated, respectively. Use of a weekly sleep diary indicated low to moderately strong seasonal changes in rise- and bedtime, sleep efficiency and sleep onset latency only in the northern latitude. No seasonal changes in sleep duration or night awakenings were observed. The self-report measures indicated moderate to strong seasonal differences in insomnia and fatigue, and weaker differences in depressed mood in Norway, but small to non-existing seasonal differences in Ghana. Lack of daylight was related to phase-delayed rise- and bedtimes, increased problems falling asleep, daytime fatigue and depressive mood. However, total sleep duration and sleep quality appeared unaffected.
The increasing prevalence of overweight and obesity among children is of special concern. Inverse associations between sleep length and overweight have been found in children. Short sleeping hours result in hormonal changes, which increase perceived hunger and appetite. This could affect food intake, and consequently lead to overweight. The aim is to find out whether there is an association between adequate sleep and food consumption among 10-11-year-old school children in Finland. One thousand two hundred and sixty-five children (response rate 79 %), aged 9-11, from thirty-one schools filled in a questionnaire about their health behaviour. Inadequate sleep was measured as short sleeping hours during school nights and weekend nights, difficulties in waking up in the morning and tiredness during the day. Food consumption patterns were measured by two consumption indices, energy-rich foods and nutrient-dense foods, based on a short FFQ (sixteen items). Inadequate sleep is associated with food consumption patterns. Boys with shorter sleep duration during school nights, and who were felt tired during the day, were more likely to consume energy-rich foods. Girls with shorter sleep duration during school nights consumed more likely energy-rich foods and less likely nutrient-dense foods. Adjusting for physical activity and screen time weakened the explored associations. The associations with energy-rich foods were stronger for boys than for girls. Sleeping habits are associated with food consumption patterns. Shorter sleep duration during school nights in school children is associated with higher consumption of energy-rich foods.
Chronotype is an emerging predictor of health and longevity, and understanding its influence on chronic diseases is important for constructing conceptual models of long-term pathways to health. We assessed the associations of chronotype with health status in the general Finnish adult population. Our population-based data were derived from the National FINRISK 2012 study and consisted of 4414 participants, aged 25-74 years, living in Finland. As part of their health examination, participants were asked about their circadian preference to the daily activities (morningness-eveningness) and a diagnosis or treatment for a set of common noncommunicable medical conditions and chronic diseases during the past 12 months. We found that there were 1935 (43.8%) morning types (MTs) and 595 (13.5%) evening types (ETs) and that 1884 (42.7%) were intermediates. As compared with the MTs, the ETs had significantly greater odds for depression (OR = 2.44, 95% CI = 1.52-3.90, p
Attenuation of vagal recovery during sleep and reduction of cortisol/melatonin ratio in late afternoon associate with prolonged daytime sleepiness among media workers with irregular shift work.
Media work is characterized by information flow, deadlines, and 24/7 alertness. Good recovery prevents stress-related disorders.
The standardized questionnaire included items about health, health habits, sleep, work conditions, and work stress. Recordings of 24-hr heart rate variability (HRV) and four salivary samples for cortisol and melatonin levels were analyzed from 70 randomly selected workers with irregular shift work, and 70 workers with normal daytime work.
Irregular shift work increased the risk of insufficient recovery when compared to normal daytime work (OR 2.0; P
PURPOSE: The aim of the study was to describe in detail the electroclinical findings associated with a mutation in the acetylcholine receptor in a Norwegian family with autosomal dominant nocturnal frontal lobe epilepsy (ADNFLE). Furthermore, we compared the clinical features associated with this mutation with those of an Australian family with a different mutation at the same locus, as well as with those of eight Italian families with ADNFLE and without a verified mutation in this gene. METHODS: We obtained medical records from all of the 10 known affected members of the Norwegian family. A personal interview and a clinical neurologic examination were carried out in six of them. Interictal and ictal scalp EEG recordings were obtained in eight and three, respectively, computed tomography/magnetic resonance imaging (CT/MRI) in five, and blood samples for genetic analysis in seven individuals. The clinical features after an insertion of a leucine residue in the alpha4 subunit of the neuronal nicotinic acetylcholine receptor are examined. Furthermore, the clinical features that accompany this insertion and the clinical features associated with a missense mutation (Ser248Phe) in the same gene were compared. RESULTS: All the affected individuals had a seizure semiology consistent with frontal lobe seizures. Their seizures started in childhood (mean age, 8 years) and were often misinterpreted as benign nocturnal parasomnias, nocturnal paroxysmal dystonia, or a psychiatric disorder. The affected family members were of normal intellect and showed no abnormalities at neurologic and neuroradiologic examinations. Interictal scalp EEG registrations were mostly normal, ictal scalp EEG registrations in three individuals revealed left frontal low-voltage epileptiform discharges in two, and only shallow arousal preceding the attack in one. Although the seizure susceptibility varied among the affected individuals, the epilepsy course was mostly benign. CONCLUSIONS: Patients with ADNFLE, either with the 776ins3 mutation or the Ser248Phe mutation, and those without any recognized mutation in the acetylcholine receptor, have strikingly homogeneous phenotypes, and it seems difficult to separate them on clinical grounds.
