Shift work disorder : prevalence, manifestation, and recovery

BACKGROUND Approximately 20% of the workforce is exposed to shift work in Finland. A significant proportion of these workers experience insomnia and/or excessive sleepiness related to their shift work schedule, a phenomenon called shift work disorder (SWD). The International Classification of Sleep Disorders (ICSD) criteria for SWD were updated in the third edition (ICSD-3) in 2014, but scientific publications on SWD prevalence are still mainly based on the ICSD-2 criteria. Furthermore, SWD screening instruments vary significantly and are based on self-reports. Regardless of its prevalence among shift workers, little is known about the manifestation of SWD in real life. Similarly, it is not known whether those with SWD recover from their symptoms on days off. Accordingly, the aim of this thesis is to elucidate how the composition of work shifts and the SWD definitions applied associate with the SWD prevalence estimate, and how SWD manifests in relation to work shifts and free time. METHODS This study includes two independent sets of data; 1) cross-sectional survey data from the ongoing longitudinal Working Hours in the Finnish Public Sector (WHFPS) cohort 2015 study, linked to registry data on working hours among hospital employees, and 2) questionnaires and three-week field data from an SWD study of ground staff at a Finnish airport. Based on the objective working-hour data, 4 831 hospital employees were classified as shift workers without night shifts, shift workers with night shifts, or permanent night workers. To screen individuals for SWD on the basis of different criteria, the SWD survey responses were linked to working-hour registry data. SWD prevalence was estimated among groups with ≥ 1, ≥ 3, ≥ 5, and ≥ 7 non-day shifts (working hours outside 06:00–18:00 hours) per month. In addition, employees responded to questions about insomnia on weekly days off, excessive sleepiness on weekly days off, and their 24-hour sleep length. The ground staff members were allocated to either the SWD (n = 22) or reference (n = 9) group by a questionnaire. Measurements included questionnaires and a three-week sleep diary and actigraphy monitoring. In addition, during the three-week field study, the participants assessed themselves using the Karolinska Sleepiness Scale (KSS), took Psychomotor Vigilance Tests (PVT), and carried out EEG-based sleep recordings on pre-selected morning shift days, night shift days, and days off. RESULTS The ICSD-3-based SWD prevalence estimate varied between 3% and 4% among hospital shift workers without night shifts, between 3% and 10% among those with night shifts, and was 6% among permanent night workers, according to the cut-off of non-day shifts. The ICSD-2 criteria produced higher SWD prevalence estimates: 7%–9%, 6%–34%, and 17%, respectively. SWD was more prevalent among shift workers with night shifts than among those without night shifts when cut-offs of ≥ 1–3 non-day shifts were applied. Among the hospital employees, ICSD-2-based SWD was positively related to excessive sleepiness on days off and negatively related to insomnia on days off. In addition, SWD characterised by shift-related insomnia (but not excessive sleepiness) was positively related to excessive sleepiness on days off and to shorter 24-hour sleep length. When using subjective field measures, the ground staff members with SWD had a shorter total sleep time and longer sleep debt prior to morning shifts than the reference group. Unlike the reference group, the SWD group appeared to have little compensatory sleep on days off. Furthermore, the SWD group had poorer sleep efficiency and longer sleep latency on most days than the reference group. The SWD group reported lower sleep quality and less relaxation at bedtime across all days. KSS sleepiness was greater in the SWD group than in the reference group at the beginning of morning shifts, at the end of morning shifts, and at the end of night shifts. The SWD group also showed more PVT lapses at the beginning of night shifts than the reference group. CONCLUSIONS The ICSD-3 criteria produced lower SWD prevalence estimates than the ISCD-2 criteria. Many employees only sporadically experienced primary symptoms of SWD, which is not consistent with ICSD criteria. To reduce the amount of false positive SWD cases, future studies should not diagnose these individuals as having SWD. In addition to night shifts, sleep and alertness are also disturbed in SWD related to morning shifts. On days off, SWD was associated with less compensatory sleep and higher prevalence of excessive sleepiness, which implies that individuals with SWD may have reduced capacity to recover from shift work. Further studies are needed to determine whether longer recovery periods could alleviate SWD symptoms.Työnteko normaaliin nukkuma-aikaan aiheuttaa monelle vuorotyöntekijälle unettomuutta tai voimakasta väsymystä. Oireet voivat pitkään toistuessaan kehittyä vuorotyöunihäiriöksi (VTH). VTH:n yleisyys vaihtelee tutkimuksittain 3–63 %:n välillä, kuvastaen kohdepopulaatioiden, vuorojärjestelmien ja VTH:n seulontamenetelmien eroja eri tutkimuksissa. Aiempien julkaisujen VTH-määritelmät perustuvat pääosin vanhoihin Kansainvälisen unihäiriöluokituksen kriteereihin, joissa oireita ei sidottu unen määrän vähenemiseen toisin kuin uusissa (v. 2014 päivitetyissä) kriteereissä. Tässä työssä tutkittiin kuinka uudet ja vanhat VTH-kriteerit sekä erilaiset VTH:n seulontamenetelmät ja vuorotyöaikataulut vaikuttavat arvioihin VTH:n yleisyydestä. Koska sekä VTH:n näyttäytyminen arjessa että VTH:n oireista palautuminen tunnetaan huonosti, väitöstyössä kartoitettiin VTH:n ilmenemistä eri työvuorojen ja vapaapäivien yhteydessä. Sairaalahenkilöstön työaikarekisterin käytön ansiosta tämä on ensimmäinen työ VTH:n yleisyydestä, jossa vuorotyölle altistuminen voitiin arvioida tarkasti. VTH:n oireita harvoin kokevien ja vuorotyölle harvoin altistuvien mukanaolo johti VTH:n yleisyyden yliarviointiin. Vanhoihin kriteereihin verrattuna uusien VTH-kriteerien käyttö taas tiputti arvion VTH:n yleisyydestä vähintään puoleen. Toisessa aineistossa lentokenttähenkilöstön kolmiviikkoisen seurannan aikana VTH-ryhmän rentoutuminen oli nukkumaan mennessä vähäisempää, nukahtaminen kesti kauemmin ja uni oli heikompilaatuista kuin vertailuryhmässä. VTH-ryhmä oli vertailuryhmää uneliaampi sekä yö- että aamuvuorossa. Lisäksi VTH-ryhmällä oli lyhyempi uni ja pidempi univaje ennen aamuvuoroja. Toisin kuin vertailuryhmä, VTH-ryhmä nukkui vapaapäivinä vain vähän yli unentarpeensa, kun taas sairaalahenkilöstössä VTH oli vapaapäivinä yhteydessä voimakkaaseen väsymykseen. Tulosten perusteella vanhoista kriteereistä uusiin siirtyminen pienensi arviota VTH:n yleisyydestä noin 3–6 %:iin. Väärien VTH-positiivisten ja VTH:n yleisyyden yliarvioinnin välttämiseksi tulevissa tutkimuksissa harvakseltaan oirehtiville työntekijöille ei pitäisi diagnosoida VTH:tä. Paljon tutkittujen yövuorojen lisäksi uni ja vireys häiriintyivät VTH:ssä myös aamuvuorojen yhteydessä. Vapaapäivinä VTH oli yhteydessä vähäisempään korvausuneen ja yleisempään väsymykseen, mikä voi kieliä heikommasta kyvystä palautua vuorotyöstä

Workplace-level interventions and trials of working time reduction: A Scoping review

The potential impact of working time reduction on well-being and productivity has been the subject of debate. The aim of this scoping literature review was to investigate the effects of workplace-level interventions and experiments in reducing working time on health, well-being at work and productivity. The results show that reduced working hours were generally associated with improved job satisfaction but also with experiences of work intensification. Reducing working hours by 20– 25% without reducing pay improved perceived sleep quality, work-life balance and reduced musculoskeletal disorders. Some trials have been able to reduce working hours without reducing productivity, but there are still very few studies focusing on sickness absence or productivity. High-quality research of the effects of reduced working hours would require a controlled follow-up study with a sufficiently large and representative sample, and the use of a wide range of measurements, including those of productivity

Työajan lyhentämisen työpaikkatason interventiot ja kokeilut : kirjallisuuskatsaus

tuottavuusvaikutukset ovat herättäneet keskustelua. Tämän kartoittavan kirjallisuuskatsauksen tavoitteena oli selvittää työpaikkatason työajan lyhentämisen interventioiden ja -kokeilujen vaikutuksia terveyteen, työhyvinvointiin ja tuottavuuteen. Tulosten mukaan lyhennetty työaika oli yleensä yhteydessä parempaan työtyytyväisyyteen mutta myös kokemuksiin työn tiivistymisestä. Työajan lyhentäminen 20–25 prosenttia ilman palkan alennusta paransi koettua unen laatua, työn ja muun elämän yhteensovittamista sekä vähensi tuki- ja liikuntaelinoireita. Joissakin kokeiluissa työajan lyhentäminen ilman tuottavuuden laskua oli mahdollista, mutta sairauspoissaolo- tai tuottavuustutkimuksia on vielä hyvin vähän. Lyhennetyn työajan vaikutusten tieteellinen selvittäminen edellyttäisi kontrolloitua seurantatutkimusta riittävän suurella ja edustavalla otoksella, sekä laaja-alaisten, myös työn tuottavuuteen kohdistuvien seurantamittareiden käyttöä

Do holidays change subjective sleep length or sleep debt in shift work disorder?

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Well-being at work among helicopter emergency medical service personnel in Finland

Personnel engaged in emergency medical services (EMS) and in helicopter emergency medical services (HEMS) perform challenging missions 24/7. This underlines the importance of overall well-being at work among these personnel. Only healthy personnel can successfully perform challenging HEMS missions in the long run. Fatigue due to an imbalance between overall strain and recovery is an occupational hazard that may compromise both well-being at work and operational and patient safety in HEMS settings. However, there are no evidence-based recommendations available on how to mitigate fatigue at HEMS work. For this reason, it is important to create a comprehensive picture of HEMS personnel’s overall well-being at work, including on-duty fatigue, at the national level. The research aim of the present study was to assess the overall well-being at work among HEMS personnel in Finland, with the main emphasis on fatigue and the balance between strain and recovery. To make the results as useful as possible for development actions, different occupational groups, duties, and task load levels were considered in the assessment. The development aim of the present study was to a) identify the main development needs to promote the overall balance between strain and recovery in HEMS professionals and b) introduce a future improvement plan to achieve this goal

Inhibition of Homophilic Interactions and Ligand Binding of the Receptor for Advanced Glycation End Products by Heparin and Heparin-Related Carbohydrate Structures

Background: Heparin and heparin-related sulphated carbohydrates inhibit ligand binding of the receptor for advanced glycation end products (RAGE). Here, we have studied the ability of heparin to inhibit homophilic interactions of RAGE in living cells and studied how heparin related structures interfere with RAGE–ligand interactions. Methods: Homophilic interactions of RAGE were studied with bead aggregation and living cell protein-fragment complementation assays. Ligand binding was analyzed with microwell binding and chromatographic assays. Cell surface advanced glycation end product binding to RAGE was studied using PC3 cell adhesion assay. Results: Homophilic binding of RAGE was mediated by V1- and modulated by C2-domain in bead aggregation assay. Dimerisation of RAGE on the living cell surface was inhibited by heparin. Sulphated K5 carbohydrate fragments inhibited RAGE binding to amyloid β-peptide and HMGB1. The inhibition was dependent on the level of sulfation and the length of the carbohydrate backbone. α-d-Glucopyranosiduronic acid (glycyrrhizin) inhibited RAGE binding to advanced glycation end products in PC3 cell adhesion and protein binding assays. Further, glycyrrhizin inhibited HMGB1 and HMGB1 A-box binding to heparin. Conclusions: Our results show that K5 polysaccharides and glycyrrhizin are promising candidates for RAGE targeting drug development.Peer reviewe

Differential DNA methylation in recovery from shift work disorder

The human DNA methylome is responsive to our environment, but its dynamics remain underexplored. We investigated the temporal changes to DNA methylation (DNAme) in relation to recovery from a shift work disorder (SWD) by performing a paired epigenome-wide analysis in an occupational cohort of 32 shift workers (25 men, age=43.8 +/- 8.8 years, 21 SWD cases). We found that the effect of vacation on DNAme was more prominent in the SWD-group as compared to controls, with respect to the amount of significantly differentially methylated positions (DMPs; P-unadjPeer reviewe

Sleep and alertness in shift work disorder : findings of a field study

PurposeAlthough shift work disorder (SWD) affects a major part of the shift working population, little is known about its manifestation in real life. This observational field study aimed to provide a detailed picture of sleep and alertness among shift workers with a questionnaire-based SWD, by comparing them to shift workers without SWD during work shifts and free time.MethodsSWD was determined by a questionnaire. Questionnaires and 3-week field monitoring, including sleep diaries, actigraphy, the Karolinska Sleepiness Scale (KSS), EEG-based sleep recordings, and Psychomotor Vigilance Tasks (PVT), were used to study 22 SWD cases and 9 non-SWD workers.ResultsThe SWD group had a shorter subjective total sleep time and greater sleep debt before morning shifts than the non-SWD group. Unlike the non-SWD group, the SWD group showed little compensatory sleep on days off. The SWD group had lower objective sleep efficiency and longer sleep latency on most days, and reported poorer relaxation at bedtime and sleep quality across all days than the non-SWD group. The SWD group's average KSS-sleepiness was higher than the non-SWD group's sleepiness at the beginning and end of morning shifts and at the end of night shifts. The SWD group also had more lapses in PVT at the beginning of night shifts than the non-SWD group.ConclusionsThe results indicate that SWD is related to disturbed sleep and alertness in association with both morning and night shifts, and to less compensatory sleep on days off. SWD seems to particularly associate with the quality of sleep.Peer reviewe

Vuorotyöunihäiriön seulonta- ja diagnoosimenetelmien kehittäminen työterveyshuoltoon

Tämän tutkimuksen tavoitteena oli tuottaa tietoa epäsäännöllisiin työaikoihin liittyvien uni- ja vireyshäiriöiden diagnosoinnin edistämiseksi ja kehittää seulontamenetelmiä siten, että vireystilaongelmat voitaisiin entistä paremmin tunnistaa työterveyshuollossa. Henkilöt, joilla seulontamenetelmän perusteella arvioitiin olevan vuorotyöunihäiriö, eivät kärsineet merkittävästä univajeesta, mutta arvioivat unen tarpeensa suuremmaksi ja unen laadun heikommaksi kuin oireettomat vuorotyöntekijät. Tutkimuksen tulokset osoittivat, että vuorotyöhön liittyvien uni- ja vireystilaongelmien seulontaan voidaan käyttää kyselymenetelmää

A distinctive DNA methylation pattern in insufficient sleep

Short sleep duration or insomnia may lead to an increased risk of various psychiatric and cardio-metabolic conditions. Since DNA methylation plays a critical role in the regulation of gene expression, studies of differentially methylated positions (DMPs) might be valuable for understanding the mechanisms underlying insomnia. We performed a cross-sectional genome-wide analysis of DNA methylation in relation to self-reported insufficient sleep in individuals from a community-based sample (79 men, aged 39.3 +/- 7.3), and in relation to shift work disorder in an occupational cohort (26 men, aged 44.9 +/- 9.0). The analysis of DNA methylation data revealed that genes corresponding to selected DMPs form a distinctive pathway: "Nervous System Development" (FDR P value <0.05). We found that 78% of the DMPs were hypomethylated in cases in both cohorts, suggesting that insufficient sleep may be associated with loss of DNA methylation. A karyoplot revealed clusters of DMPs at various chromosomal regions, including 12 DMPs on chromosome 17, previously associated with Smith-Magenis syndrome, a rare condition comprising disturbed sleep and inverse circadian rhythm. Our findings give novel insights into the DNA methylation patterns associated with sleep loss, possibly modifying processes related to neuroplasticity and neurodegeneration. Future prospective studies are needed to confirm the observed associations.Peer reviewe