Effects of light interventions for adaptation to night work : Simulated night work experiments

In modern society, the need for 24-hr operation and services requires some people to work outside normal daytime work hours (i.e. shift work), including the night. For instance, healthcare, police, and transportation, are sectors where night work is common. Exposure to shift work, and particularly night work, can have negative impact on the workers’ health. Especially, sleep is reported to be disturbed among night workers, as they must be awake at times they would normally be sleeping, and sleep at times they would normally be awake. This circadian misalignment of the sleep-wake rhythm may in a long-term perspective lead to ill health and diseases. Also, in a short-term perspective night work may cause adverse effects. Night workers experience increased sleepiness and performance deterioration during night shifts, and especially in the early morning hours, the sleep propensity and performance decrements are high. As such, night work has also been associated with increased risk of accidents and injuries. Several countermeasures to reduce the adverse impact of night work have been suggested. Common strategies involve scheduled naps and caffein use. However, there is increasing interest in the use of light interventions for eliciting beneficial effects for night workers. Light exposure has the potential to entrain the biological circadian rhythm in humans, and as such can be used to produce circadian adaptation to a night work schedule. In addition, light has acute alerting effects which can reduce alertness deficits and improve performance during the night shift. Such effects rely on several characteristics of the light, such as timing, intensity, and wavelengths (spectral distribution). With the development of light emitting diode (LED) technology, new strategies for illumination of workplaces have emerged. This thesis is based on three papers using standard ceiling mounted LED-luminaires to administer different light conditions during simulated night shift experiments. The main aim has been to investigate and elucidate how such LED lighting strategies can be used to facilitate adaptation to night work on measures of sleepiness, performance, and circadian rhythm. In paper 1, the objective was to investigate how a full spectrum (4000 K) bright light (~ 900 lx), compared to a standard light (~ 90 lx), affected alertness and performance during three consecutive simulated night shifts (23:00–07:00 hrs), as well as circadian phase shift after the simulated night shifts. Results indicated that bright light effectively reduces sleepiness, and improves performance during three consecutive night shifts, compared to standard light. Bright light seems to be beneficial in the later parts of the shifts, when sleep propensity is particularly high. For instance, in the later parts of night 2 and 3 it was found that the number of lapses of attention on a vigilance task revealed half as many lapses with bright light, compared to standard light. Furthermore, bright light induced a larger phase delay as compared with standard light, although data were incomplete, hence validation of these findings are needed. The objective in the second paper was to investigate how short-wavelength monochromatic blue light (λmax = 455 nm), compared to red light (λmax = 625 nm) with similar photon density (~ 2.8 x 1014 photons/cm2/s), affected alertness and task performance during one simulated night shift (23:00–06:45 hrs), as well as circadian phase shift following the night shift. The results in paper 2 suggest that monochromatic blue light reduces sleepiness and improves performance in the later parts of the night shift. Similar to the findings in paper 1, the number of attentional lapses with blue light was half of that seen with red light. Blue light also led to a larger phase delay of the circadian rhythm. There were indications of improved visual comfort with blue light, although both light conditions overall produced visual discomfort. In the third paper the main aims were to investigate how polychromatic blue-enriched white light (7000 K; ~ 200 lx), compared to warm white light (2500 K) of similar photon density (~ 1.6 x 1014 photons/cm2/s), affected alertness and performance during three consecutive simulated night shifts (23:00–06:45 hrs), as well as circadian adaptation to the night work schedule. The results indicated minor, yet beneficial effects of 7000 K light compared to 2500 K light, mainly in terms of fewer performance errors on a vigilance task in the end of night 1 and 2. No significant difference in terms of circadian phase shifts were found between these two light conditions. In conclusion, the papers suggest that standard ceiling mounted LED-luminaires have the potential to produce light conditions that may facilitate adaptation to night work. Paper 1 suggests that bright light improves performance and reduces sleepiness during three consecutive simulated night shifts. Results from paper 2 indicate that short-wavelength blue light improves performance, reduces sleepiness, and causes a larger phase delay than long-wavelength red light during one simulated night shift. Paper 3 indicates that using polychromatic blue-enriched white light has minor, yet beneficial effects on performance measures, compared to warm white light during three consecutive simulated night shifts. Further research is needed to validate and support the findings and investigate the impact and feasibility of similar light conditions in real-life workplaces. Future research should also explore more light conditions that can be favourable for night workers, in order to develop recommendations for illumination of night workers workplaces. Moreover, there is a need to elucidate potential long-term adverse health impacts of exposure to LED lighting.Doktorgradsavhandlin

Bright light exposure during simulated night work improves cognitive flexibility

Under embargo until: 2023-03-28Night work leads to sleepiness and reduced vigilant attention during work hours, and bright light interventions may reduce such effects. It is also known that total sleep deprivation impairs cognitive flexibility as measured by reversal learning tasks. Whether night work impairs reversal learning task performance or if bright light can mitigate reversal learning deficits during night work is unclear. In this counterbalanced crossover study (ClinicaTrials.gov Identifier NCT03203538), young healthy individuals completed a reversal learning task twice during each of three consecutive simulated night shifts (23:00–07:00 h). The night shifts were performed in a laboratory under a full-spectrum (4000 K) bright light (~900 lx) and a standard light (~90 lx) condition. Reversal learning task performance was reduced towards the end of the night shifts (04:50 h), compared to the first part of the night shifts (00:20 h) in both light conditions. However, with bright light, the reversal learning task performance improved towards the end of the night shifts, compared to standard light. The study shows that bright light may mitigate performance deficits on a reversal learning task during night work and implies that bright light interventions during night work may be beneficial not only for vigilant attention but also for cognitive flexibility.acceptedVersio

Blue-enriched white light improves performance but not subjective alertness and circadian adaptation during three consecutive simulated night shifts

Use of blue-enriched light has received increasing interest regarding its activating and performance sustaining effects. However, studies assessing effects of such light during night work are few, and novel strategies for lighting using light emitting diode (LED) technology need to be researched. In a counterbalanced crossover design, we investigated the effects of a standard polychromatic blue-enriched white light (7000 K; ∼200 lx) compared to a warm white light (2500 K), of similar photon density (∼1.6 × 1014 photons/cm2/s), during three consecutive simulated night shifts. A total of 30 healthy participants [10 males, mean age 23.3 (SD = 2.9) years] were included in the study. Dependent variables comprised subjective alertness using the Karolinska Sleepiness Scale, a psychomotor vigilance task (PVT) and a digit symbol substitution test (DSST), all administered at five time points throughout each night shift. We also assessed dim-light melatonin onset (DLMO) before and after the night shifts, as well as participants’ opinion of the light conditions. Subjective alertness and performance on the PVT and DSST deteriorated during the night shifts, but 7000 K light was more beneficial for performance, mainly in terms of fewer errors on the PVT, at the end of the first- and second- night shift, compared to 2500 K light. Blue-enriched light only had a minor impact on PVT response times (RTs), as only the fastest 10% of the RTs were significantly improved in 7000 K compared to 2500 K light. In both 7000 and 2500 K light, the DLMO was delayed in those participants with valid assessment of this parameter [n = 20 (69.0%) in 7000 K light, n = 22 (78.6%) in 2500 K light], with a mean of 2:34 (SE = 0:14) and 2:12 (SE = 0:14) hours, respectively, which was not significantly different between the light conditions. Both light conditions were positively rated, although participants found 7000 K to be more suitable for work yet evaluated 2500 K light as more pleasant. The data indicate minor, but beneficial, effects of 7000 K light compared to 2500 K light on performance during night work. Circadian adaptation did not differ significantly between light conditions, though caution should be taken when interpreting these findings due to missing data. Field studies are needed to investigate similar light interventions in real-life settings, to develop recommendations regarding illumination for night workers.publishedVersio

Velferdsholdninger og sosiale verdier i europeiske velferdsregimer: En tverrnasjonal undersøkelse av sosiale verdiers betydning for holdninger til velferdsstaten i tre ulike velferdsregimer

Background: Welfare states and the welfare policies in practice in welfare states have implications for population health. Studies have shown that attitudes towards welfare and welfare policies vary between welfare regimes, and that different factors, including social values, matter in the explanation of welfare attitudes. Objectives: The main purpose of this study has been to investigate how social values matter in the explanation of attitudes towards the welfare state's scope and responsibilities, and of attitudes towards taxation and financing in different welfare regimes. A second objective has been to investigate the levels of welfare attitudes and social values in different welfare regimes. Material and method: The analyses were conducted on the basis of data from the European Social Survey Round 4 2008/2009. The sample used consisted of all of the respondents from Germany, Great Britain and Sweden, which are examples of different types of welfare regimes. Descriptive analyses together with analysis of variance and hierarchical multiple regression analysis, were conducted in order to investigate social values and welfare attitudes. Results: The levels of the welfare attitudes and social values varied between the countries. In Sweden, the respondents were more positive to the welfare state's scope and responsibilities as well as to taxation and financing than the respondents in Germany and Great Britain. Social values had implications for welfare attitudes in all three countries; however, the explained variance in the attitudes was relatively low. Conclusion: The differences found in the levels of welfare attitudes and social values indicate that welfare attitudes vary between welfare regimes. Social values matter in the explanation of variance in attitudes towards the welfare state's scope and responsibilities, and in attitudes towards taxation and financing. The somewhat limited explanatory power indicates that more, and more thorough, studies on the mechanisms behind welfare attitudes are needed

Subcutaneous fat accumulation in Norwegian owls and raptors

The mean subcutaneous fat deposition (MFS) found in dead diurnal raptors and owls collected in Norway in 1987-92 was compared to detect possible overall and intra- and interspecific seasonal differences. In general, the relative fat deposition rate was correlated with body size (P < 0.001), and was highest in winter (P = 0.01) and in females (P = 0.02) . After correcting for the size effect, species-specific differences were still present (P = 0.000), but the effect of sex disappeared (P = 0.34) . We propose that the relative rate of fat deposition in northern Palaearctic owls and raptors reflects adaptations to resist starvation balanced against the demands for high agility and low flying costs. This trade-off probably varies between breeding and non-breeding seasons, sexes, and species with different migratory and hunting habits

Bedring av håndhygiene i legekonsultasjoner ved HOP, Ahus

Bakgrunn/emne: Den bakenforliggende hensikten med å gjennomføre ett kvalitetsforbedringsprosjekt ved AHUS Hematologisk/Onkologisk poliklinikk er å redusere risikoen for unngåelige HAI hos kreftpasienter, som på grunn av sin grunnsykdom og/eller behandling er spesielt sårbare for slike infeksjoner. Målsettingen er å vurdere praksis på avdelingen opp mot retningslinjer for håndhygiene, samt innføre tiltak for bedring av håndhygiene om nødvendig, og evaluering av disse. Kunnskapsgrunnlag: Vi gjorde et systematisk litteratursøk for å finne sammenheng mellom sykehusinfeksjoner og immunsupprimerte, og for å finne viktige smittekilder i den sammenheng vårt prosjekt er rettet mot, samt kunnskap om de mest effektive håndhygienemetodene og tiltak for bedring av håndhygienepraksis. Litteraturen viste at immunsupprimerte er ekstra utsatt for HAI og at de har dårligere prognose ved en HAI enn andre pasienter. Søket viste også at stetoskop, penner, telefoner, tastaturer og pc-mus er viktige smittekilder for HAI og at hyppig rengjøring av utstyr og hender vil redusere antall HAI og redusere patogener. Begrunnet tiltak og metode: Vi foreslår tre tiltak: Kursing/ holdningskampanjer for å endre praksis hos leger, observasjon av praksis med tilbakemelding som en del av opplæringen, samt å øke tilgjengeligheten på hygieneartikler for å øke compliance hos leger. For å kontrollere effekt av tiltakene bruker vi følgende to prosessindikatorer: Forbruk av sprit og observert praksis (andel riktig utførte håndhygienerutiner – riktig anledning, riktig teknikk) Organisering: Prosjektet presenteres for legene på avdelingen og det opprettes en tverrfaglig prosjektgruppe. Prosjektgruppen starter opplæring av legene. Etter to og fire uker måler man forbruk av sprit. Den fjerde uka observeres også legene med tilbakemelding på deres utførelse. Etter åtte uker skal prosjektet vurderes og oppsummeres og legene skal få tilbakemelding om resultatene. Etter tolv uker skal man på nytt måle forbruk og legge en plan for om man skal videreføre prosjektet. Etter dette kan man fortsette å måle forbruket etter et halvt år og videre årlig og vurdere også videre observasjon med tilbakemelding, for slik å kunne vurdere om man skal oppregulere prosjektaktiviteten igjen. Vurdering: Dersom tiltakene viser seg å ha effekt, kan man vurdere å opprettholde prosjektaktiviteten over tid, samt å spre resultatene eller prosjektdesignet til andre avdelinger

Sleep homeostasis and night work: a polysomnographic study of daytime sleep following three consecutive simulated night shifts

Purpose: Millions of people work at times that overlap with the habitual time for sleep. Consequently, sleep often occurs during the day. Daytime sleep is, however, characterized by reduced sleep duration. Despite preserved time spent in deep NREM sleep (stage N3), daytime sleep is subjectively rated as less restorative. Knowledge on how night work influences homeostatic sleep pressure is limited. Therefore, we aimed to explore the effect of three consecutive simulated night shifts on daytime sleep and markers of sleep homeostasis. Patients and Methods: We performed continuous EEG, EMG and EOG recordings in the subjects’ home setting for one nighttime sleep opportunity, and for the daytime sleep opportunities following three consecutive simulated night shifts. Results: For all daytime sleep opportunities, total sleep time was reduced compared to nighttime sleep. While time spent in stage N3 was preserved, sleep pressure at sleep onset, measured by slow wave activity (1– 4 Hz), was higher than nighttime sleep and higher on day 3 than on day 1 and 2. Elevated EEG power during daytime sleep was sustained through 6 h of time in bed. Slow wave energy was not significantly different from nighttime sleep after 6 h, reflecting a less efficient relief of sleep pressure. Conclusion: Adaptation to daytime sleep following three consecutive simulated night shifts is limited. The increased homeostatic response and continuation of sleep pressure relief even after 6 h of sleep, are assumed to reflect a challenge for appropriate homeostatic reduction to occur.publishedVersio

Hearing loss in the royal Norwegian navy: a cross-sectional study

Objectives Prior studies have indicated a high prevalence of noise-induced hearing loss (NIHL) among Navy personnel; however, it is not clear whether this is caused by work on board. The present study aimed to assess the prevalence of hearing loss among Navy personnel in the Royal Norwegian Navy (RNoN), and to investigate whether there is an association between work on board RNoN vessels and occurrence of hearing loss. Methods Navy personnel currently working on board RNoN vessels were recruited to complete a questionnaire on noise exposure and health followed by pure tone audiometry. Hearing loss was defined as hearing threshold levels ≥25 dB in either ear at the frequencies 3,000, 4,000 or 6,000 Hz. Hearing thresholds were adjusted for age and gender using ISO 7029. Results The prevalence of hearing loss among Navy personnel was 31.4 %. The work exposure variables: years of work in the Navy, years on vessel(s) in the Navy and years of sailing in the Navy were associated with reduced hearing after adjusting for age, gender and otitis as an adult. Among the work exposure variables, years of sailing in the Navy was the strongest predictor of reduced hearing, and significantly reduced hearing was found at the frequencies 1,000, 3,000 and 4,000 Hz. Conclusions Our results indicate that time spent on board vessels in the RNoN is a predictor of reduced hearing