Night work during pregnancy and small for gestational age: a Danish nationwide register-based cohort study.

OBJECTIVE: The aim was to investigate the association between night work during pregnancy and risk of having a small for gestational age (SGA) child. METHODS: This cohort study had payroll data with detailed information on working hours for employees in all Danish administrative regions (primarily hospital employees) between 2007 and 2015, retrieved from the Danish Working Hour Database. Pregnancies, covariates and outcome were identified from the national birth registry. We used logistic regression to investigate the association between intensity and duration of night work during the first 32 pregnancy weeks and SGA. The adjusted model included age, body mass index, socioeconomic status and smoking. Using quantitative bias analysis and G-estimation, we explored potential healthy worker survivor bias (HWSB). RESULTS: The final cohort comprised 24 548 singleton pregnancies in 19 107 women, primarily nurses and medical doctors. None of the dimensions of night work were associated with an increased risk of SGA. We found a tendency towards higher risk of SGA in pregnancies where the women stopped having night shifts during pregnancy. Using G-estimation we found an OR<1 for the association between night work and SGA if all workers continued having night work during pregnancy compared with daywork only. CONCLUSION: We found no increased risk of SGA in association with night work during pregnancy among healthcare workers. G-estimation was not precise enough to estimate the observed indication of HWSB. We need better data on pregnancy discomforts and complications to be able to safely rule out HWSB.

Data management and protection in occupational and environmental exposome research - A case study from the EU-funded EXIMIOUS project.

Within collaborative projects, such as the EU-funded Horizon 2020 EXIMIOUS project (Mapping Exposure-Induced Immune Effects: Connecting the Exposome and the Immunome), collection and analysis of large volumes of data pose challenges in the domain of data management, with regards to both ethical and legal aspects. However, researchers often lack the right tools and/or accurate understanding of the ethical/legal framework to independently address such challenges. With the guidance and support within and between the partner institutes (the researchers and the ethical and legal teams) in the EXIMIOUS project, we have been able to understand and solve most challenges during the first two project years. This has fed into the development of a Data Management Plan and the establishment of data management platforms in accordance with the ethical and legal framework laid down by the EU and the different national regulations of the partners involved. Through this elaborate exercise, we have acquired tools which allow us to make our research data FAIR (Findable, Accessible, Interoperable, and Reusable), while at the same time ensuring data privacy and security (GDPR compliant). Herein we share our experience of creating and managing the data workflow through an open research communication, with the aim of helping other researchers build their data management framework in their own projects. Based on the measures adopted in EXIMIOUS to ensure FAIR data management, we also put together a checklist "DMP CHECK" containing a series of recommendations based on our experience.

Ergonomic risk factors in the working environment of pregnant women.

The majority of Danish women are working, and many are standing/walking or lifting heavy objects at work. It is important for employers and employees to assess ergonomic risk factors in the work environment during pregnancy to avoid potential negative effects on the pregnancy. Studies show that walking/standing > 3-4 h/d may increase the risk of preterm delivery. It is difficult to set specific limits due to heterogenous exposures regarding heavy lifting. Though, results suggest that women should avoid lifting >10 kg repeatedly at work during pregnancy to avoid adverse effects of the pregnancy.

Professional cleaning and risk of asthma - a Danish nationwide register-based study.

OBJECTIVE: This study aimed to investigate the risk of asthma among professional cleaners in a nationwide population-based study. METHODS: Professional cleaners, aged 16-50 years, were identified according to the yearly assigned administrative job and industrial codes in a register-based, matched cohort study with other manual workers as references (1995-2016). Asthma was defined from national registers based on hospitalization and medication. Associations between recent and cumulative cleaning years and risk of asthma were estimated using Poisson regression, first in a full cohort and then in an inception cohort, among workers aged 16-20 years at the start of follow-up. RESULTS: The risk of asthma was not increased for recent cleaning compared to references [adjusted incidence rate ratio (IRRadj) 1.02 [95% confidence interval (CI) 0.99-1.04]. Similar results were seen for the inception cohort, where cumulative years of cleaning were associated with increased risk of asthma, more prominent for the group with the maximum of six years of cleaning IRRadj 2.53 (95% CI 1.38-4.64). Cumulative years of cleaning were associated with decreased risk of asthma, more pronounced for the maximum of ten compared to one year of cleaning [IRRadj 0.74 (95% CI 0.63-0.88)]. CONCLUSIONS: Asthma risk was increased in the inception cohort for cumulative years of cleaning but decreased in the full cohort. We could not confirm that recent work within cleaning was associated with increased risk of asthma. This may be due to healthy worker bias. Thus, we cannot rule out that long-term professional cleaning may be associated with increased risk of asthma.

Occupational exposure and markers of genetic damage, systemic inflammation and lung function: a Danish cross-sectional study among air force personnel.

Air force ground crew personnel are potentially exposed to fuels and lubricants, as raw materials, vapours and combustion exhaust emissions, during operation and maintenance of aircrafts. This study investigated exposure levels and biomarkers of effects for employees at a Danish air force military base. We enrolled self-reported healthy and non-smoking employees (n = 79) and grouped them by exposure based on job function, considered to be potentially exposed (aircraft engineers, crew chiefs, fuel operators and munition specialists) or as reference group with minimal occupational exposure (avionics and office workers). We measured exposure levels to polycyclic aromatic hydrocarbons (PAHs) and organophosphate esters (OPEs) by silicone bands and skin wipes (PAHs only) as well as urinary excretion of PAH metabolites (OH-PAHs). Additionally, we assessed exposure levels of ultrafine particles (UFPs) in the breathing zone for specific job functions. As biomarkers of effect, we assessed lung function, plasma levels of acute phase inflammatory markers, and genetic damage levels in peripheral blood cells. Exposure levels of total PAHs, OPEs and OH-PAHs did not differ between exposure groups or job functions, with low correlations between PAHs in different matrices. Among the measured job functions, the UFP levels were higher for the crew chiefs. The exposure level of the PAH fluorene was significantly higher for the exposed group than the reference group (15.9 ± 23.7 ng/g per 24 h vs 5.28 ± 7.87 ng/g per 24 h, p = 0.007), as was the OPE triphenyl phosphate (305 ± 606 vs 19.7 ± 33.8 ng/g per 24 h, p = 0.011). The OPE tris(1,3-dichlor-2-propyl)phosphate had a higher mean in the exposed group (60.7 ± 135 ng/g per 24 h) compared to the reference group (8.89 ± 15.7 ng/g per 24 h) but did not reach significance. No evidence of effects for biomarkers of systemic inflammation, genetic damage or lung function was found. Overall, our biomonitoring study show limited evidence of occupational exposure of air force ground crew personnel to UFPs, PAHs and OPEs. Furthermore, the OH-PAHs and the assessed biomarkers of early biological effects did not differ between exposed and reference groups.

Adverse childhood experiences and asthma: trajectories in a national cohort.

OBJECTIVE: Research has linked early adverse childhood experiences (ACEs) with asthma development; however, existing studies have generally relied on parent report of exposure and outcome. We aimed to examine the association of early life ACEs with empirically determined trajectories of childhood asthma risk, using independent register information on both exposures and outcome. METHODS: Based on nationwide registries, we established a study cohort of 466 556 children born in Denmark (1997-2004). We obtained information on ACEs during the first 2 years of life (bereavement, parental chronic somatic and/or mental illness) and childhood asthma diagnosis or medication use from birth through age 10 years from the Danish National Patient and Prescription Registries, respectively. We identified asthma phenotypes using group-based trajectory modelling. We then used multinomial logistic regression to examine the association between early ACEs and asthma phenotypes. RESULTS: We identified four asthma phenotypes: non-asthmatic, early-onset transient, early-onset persistent and late-onset asthma. Girls with early-onset transient asthma (OR 1.13, 95% CI 1.04 to 1.24), early-onset persistent asthma (1.27, 95% CI 1.08 to 1.48) or late-onset asthma (OR 1.28, 95% CI 1.11 to 1.48) vs no asthma were more likely to have early life ACE exposure compared with girls without ACE exposure. Results were similar for boys who also had experienced early life ACEs with ORs of 1.16 (95% CI 1.08 to 1.25), 1.34 (95% CI 1.20 to 1.51) and 1.11 (95% CI 0.98 to 1.25), respectively. CONCLUSION: In a nationwide-population study, we identified three childhood onset asthma phenotypes and found that ACEs early in life were associated with increased odds for each of these asthma phenotypes among both girls and boys.

Maternal exposure to psychosocial job strain during pregnancy and behavioral problems in the 11-year-old children: a Danish cohort study.

Maternal psychosocial stress may impact child neurodevelopment, but little is known regarding psychosocial job strain. We hypothesized high psychosocial job strain during pregnancy was associated with behavioural problems in the 11-year-old children. Mothers in the Danish National Birth Cohort (1996-2002) were included if they worked, provided information on job strain [Karasek's model: high job strain (often job demand/seldom job control) and passive (seldom or sometimes job demands/seldom job control)] during early pregnancy. At the 11-year follow-up, children (N = 30,592), mothers (N = 30,993), and teachers (N = 12,810) responded to the Strength and Difficulties Questionnaire (SDQ), a screening tool for child behaviour. Scores for hyperactivity, conduct, emotional and peer problems were dichotomised [80% (no) vs. 20% (yes)] according to Danish norms (yes/no). Maternal job strain was not associated with behavioural problems with teachers as informants. When assessed by child or mother, high maternal job strain increased risk of child behavioural problems, but risks were more pronounced for mothers in passive jobs [maternal assessment of total difficulties/odds ratio (95% confidence interval): high strain-girls: 1.16 (0.97-1.40); boys: 1.24 (1.02-1.50). Passive girls: 1.43 (1.21-1.68); boys: 1.25 (1.05-1.49)]. This is one of the first studies on this topic. The different types of maternal job strain were partly associated with child behavioural problems at 11 years; more so if mothers worked in passive rather than the hypothesized high strain jobs. Findings showing dependency on informant could not only indicate unmeasured confounding or rater's bias, but also selection in the smaller numbers of teacher informants or different environments of interaction with the children.

Exposure to psychosocial work strain and changes in smoking behavior during pregnancy - a longitudinal study within the Danish National Birth Cohort.

Objective Knowledge of the relationship between psychosocial strain in the work environment and smoking during pregnancy is scarce. This study aimed to examine the association between psychosocial job strain and change in smoking behavior during pregnancy. Methods The cohort included 65 645 pregnancies from the Danish National Birth Cohort (1996-2002), where pregnant women were interviewed on job factors and lifestyle during the first and third trimesters. Smoking was categorized into non-, non-daily, and daily smoking at each interview. Psychosocial job strain was categorized into four groups based on the concept of Karasek's demand-control model: low strain (reference), passive, active and high strain. Associations between psychosocial strain and change in smoking status between the first and second interviews were analyzed by multinomial logistic regression, separately for each smoking category at first interview. Results Non-smoking women exposed to high strain work were more likely to become daily smokers [adjusted odds ratio (OR adj) 1.41, (95% confidence interval (CI) 1.08-1.83)] compared to non-smoking women exposed to low strain work. Non-smoking women exposed to passive work were more likely to become both non-daily and daily smokers [OR adj1.59 (95% CI 1.21-2.08) and OR adj1.32 (95% CI 1.03-1.70), respectively]. Daily smoking women exposed to high strain work were less likely to decrease their smoking [OR adj0.57 (95% CI 0.32-0.99)] compared to daily smoking women exposed to low strain work. Conclusions Psychosocial strain influenced the women's smoking behavior during pregnancy, especially in job types with low control.

Maternal life and work stressors during pregnancy and asthma in offspring.

BACKGROUND: Maternal stressors during pregnancy are potential risk factors for asthma in offspring. However, previous studies have been limited by the use of self-reported data focusing on stressors either in private life or at work. This study examined the association between maternal stressors both in private life and at work during pregnancy and asthma in offspring. METHODS: In the Danish National Birth Cohort, 75 156 live-born singletons born during 1996-2002 were identified. Maternal information on job title were available around weeks 12-16 of gestation. Data on maternal bereavement, life-threatening illness, suicide attempt and alcohol or drug abuse of a close relative and offspring childhood asthma (3-10 years of age) were obtained from Danish nationwide registers. Maternal psychosocial work stressors (job control, psychological job demands, emotional job demands, work-related violence and threats of work-related violence) were estimated by the use of job-exposure matrices. The association between maternal stress and childhood asthma was analysed in Cox models adjusted for maternal age, comorbidity and parity. RESULTS: Neither private-life nor work stressors were related to onset of asthma in offspring. Separate analyses by parental atopy or onset of asthma in offspring supported the main findings. CONCLUSIONS: This study does not support an elevated risk of childhood asthma related to exposure to stress during pregnancy.

The influence of multiple occupational exposures on absence from work in pregnancy: a prospective cohort study.

Objectives Many women experience absence periods from work during pregnancy. Several single risk factors for absence are identified, whereas the impact of multiple concurrent exposures has been sparsely studied. We hypothesized that the presence of multiple occupational exposures would be associated with an increased risk of absence from work during pregnancy. Methods We included women from the Danish National Birth Cohort (1996-2002), pregnant with one child and working ≥30 hours/week at interview (mean gestational week 17 (standard deviation 4.0); N=50 142). Information about five occupational exposures (job demands, job control, work posture, work shift, lifting) were retrieved from the interview, each assigned values of 0/1, and summed into an index (0-5). The woman's first absence from work (both regular and related to pregnancy) after the interview was available from a nationwide administrative register. We analyzed data with Cox regression using gestational age as the underlying time-variable. Results Few women experienced none of the occupational exposures (3.6%) and most experienced two exposures (34.7%). Only 24.3% of the women were absent from work before gestational week 31. The number of occupational exposures was associated with an increasing risk of absence. The adjusted hazard ratio for absence increased from 1.3 [95% confidence interval (CI) 1.1-1.5] for one exposure to 2.9 (95% CI 2.5-3.3) for four to five exposures compared to no occupational exposure. Conclusion The higher the number of potentially adverse occupational exposures pregnant women experienced, the higher the risk for absence from work during pregnancy.

Risk of childhood asthma following prenatal exposure to negative life events and job stressors: A nationwide register-based study in Denmark.

Objectives This study aimed to examine the association between negative life events, job stressors (low job control or high psychosocial job demands) and offspring asthma phenotypes (early-onset transient, early-onset persistent and late-onset asthma). Methods In a population-based cohort study comprising 547 533 liveborn singletons, we determined negative life events and offspring asthma at age six years using data from Danish nationwide registers. We assessed job demands and job control from gender-specific job exposure matrices. Prevalence ratios (PR) of each asthma phenotype were estimated using log-binomial regression. Results Maternal exposure to negative life events prenatally was not significantly associated with offspring asthma. Among mothers with low job demands, low job control was associated with increased risk for early-onset transient asthma [PR=1.14, 95% confidence interval (CI) 1.09-1.19], early-onset persistent asthma (PR=1.17, 95% CI 1.11-1.23), and late-onset asthma (PR=1.06, 95% CI 1.00-1.14). Among mothers with high job demands, low job control was not associated with offspring asthma apart from a reduced risk of early-onset persistent asthma (PR=0.94, 95% CI 0.90-0.97). These associations were independent of child sex and parental atopic history. Conclusions Maternal stressors in private life do not seem to influence offspring asthma significantly. Low job control is associated with offspring asthma, which is modified by maternal psychosocial job demands. Our findings warrant further exploration.

Combined exposure to lifting and psychosocial strain at work and adverse pregnancy outcomes-A study in the Danish National Birth Cohort.

BACKGROUND: Previous studies have investigated physical and psychosocial job exposures separately in relation to foetal growth. We therefore investigated if occupational lifting and psychosocial job strain interact to affect foetal growth and gestational length. We hypothesised that heavy lifting and high job strain would increase the risk of impacted foetal growth (small or large for gestational age) and preterm birth. METHODS: The cohort included 47,582 pregnancies from the Danish National Birth Cohort (1996-2002), where the woman was pregnant at 22 gestational weeks (GW), expected one child and worked ≥30 hours/week. Information on occupational lifting and psychosocial job strain was derived from an interview (16±3.0 GW). Data to calculate small and large for gestational age (SGA/LGA) and gestational length was retrieved from the Medical Birth Register. Interaction between lifting and job strain (Karasek's model) was analysed by multinomial logistic regression. RESULTS: Overall, the adjusted regression analysis showed statistically significant interaction between lifting and job strain for SGA and LGA. For each additional 250 kg lifted/day, high strain women (high Demand/low Control) had increased odds of giving birth to a LGA-child (OR = 1.15; 95% CI 1.06-1.26), whereas women in the active group (high Demand/high Control) had increased odds of giving birth to a SGA child (OR = 1.12; 95% CI 1.03-1.23). When women lifting ≤1000 kg/day were excluded in the sensitivity analyses the interaction between lifting and job strain became insignificant. No interaction of lifting and job strain was found for gestational length. CONCLUSIONS: The main findings may give some support to our hypothesis, as lifting in combination high with job strain increased the risk of giving birth to a LGA child. This finding was, however, not supported in the sensitivity analysis and no association of the interaction was found relative to gestational length.

Depressive symptoms and early retirement intentions among Danish eldercare workers: Cross-sectional and longitudinal analyses.

BACKGROUND: Depression increases the risk of disability pension and represents a health related strain that pushes people out of the labour market. Although early voluntary retirement is an important alternative to disability pension, few studies have examined whether depressive symptoms incur early voluntary retirement. This study examined whether depressive symptoms and changes in depressive symptoms over time were associated with early retirement intentions. METHODS: We used a cross-sectional (n = 4041) and a prospective (n = 2444) population from a longitudinal study on employees of the Danish eldercare sector. Depressive symptoms were measured by the Major Depression Inventory and the impact of different levels of depressive symptoms (severe, moderately severe, moderate, mild and none) and changes in depressive symptoms (worsened, improved, unaffected) on early retirement intentions were analysed with multinomial logistic regression. RESULTS: In the cross-sectional analysis all levels of depressive symptoms were significantly associated with retirement intentions before the age of 62 years. Similar associations were found prospectively. Depressive symptoms and worsened depressive symptoms in the two year period from baseline to follow-up were also significantly associated with early retirement intentions before age 62. The prospective associations lost statistical significance when controlling for early retirement intentions at baseline. CONCLUSIONS: The whole spectrum of depressive symptoms represents a health related strain that can incur intentions to retire early by early voluntary retirement. In order to change the intentions to retire early, the work related consequences of depressive symptoms should be addressed as early in the treatment process as possible.

Psychiatric disorders among women and men in assisted reproductive technology (ART) treatment. The Danish National ART-Couple (DANAC) cohort: protocol for a longitudinal, national register-based cohort study.

INTRODUCTION: There are complex causal associations between mental disorders, fertility treatment, fertility treatment outcome and infertility per se. Eating disorders cause endocrine disturbances, anovulation and thereby infertility, and research has shown that infertility as well as unsuccessful assisted reproductive technology (ART) treatment are potential risk factors for developing a depression on a long-term basis. Despite the fact that worldwide more than 400 000 ART treatment cycles are performed every year, the causal associations between mental disorders, use of medication for mental disorders and ART treatment in both sexes have only been sparsely explored. METHOD AND ANALYSIS: The main objective of this national register-based cohort study is to assess women's and men's mental health before, during, and after ART treatment in comparison with the mental health in an age-matched population-based cohort of couples with no history of ART treatment. Furthermore, the objective is to study the reproductive outcome of ART treatment among women who have a registered diagnosis of a mental disorder or have used medication for mental disorders prior to ART treatment compared with women in ART treatment without a mental disorder. We will establish the Danish National ART-Couple (DANAC) cohort including all women registered with ART treatment in the Danish in vitro fertilisation Register during 1994-2009 (N=42 915) and their partners. An age-matched population-based comparison cohort of women without ART treatment (n=215 290) and their partners will be established. Data will be cross-linked with data from national registers on psychiatric disorders, medical prescriptions for mental disorders, births, causes of deaths and sociodemographic data. Survival analyses and other statistical analyses will be conducted on the development of mental disorders and use of medication for mental disorders for women and men both prior to and after ART treatment.

[The psychosocial consequences of infertility and fertility treatment]. / Psykosociale følger af infertilitet og fertilitetsbehandling.

Infertility and its treatment are severe, chronic, low-control stressors. Among women unsuccessful treatment is associated with increased risk of developing depressive symptoms. Among men infertility is associated with more negative emotional responses. Lifelong involuntary childlessness is associated with reduced mental well-being. It is recommended in the future to integrate mental health professionals at fertility clinics in Denmark in order to secure that also the psychosocial consequences of infertility and fertility treatment are taken care of with the highest professional standard based on scientific knowledge within this field.