Cognitive Ability in Midlife and Labor Market Participation Among Older Workers: Prospective Cohort Study With Register Follow-up.

BACKGROUND: The study aimed to determine the association of individual cognitive ability in late midlife with labor market participation among older workers. METHODS: This prospective cohort study estimates the risk of long-term sickness absence, disability pension, early retirement, and unemployment from scores on the Intelligenz-Struktur-Test 2000R by combining data from 5076 workers from the Copenhagen Aging and Midlife Biobank with a register on social transfer payments. Analyses were stepwise adjusted for age, gender, physical and psychosocial work environment, health behaviors, occupational social class, education, and chronic diseases. RESULTS: In the fully adjusted model, low cognitive ability (≥1 standard deviation below the mean for each gender) and high cognitive ability (≥1 standard deviation above the mean for each gender) were not associated with risk of any of the four labor market outcomes. CONCLUSION: Individual cognitive ability in late midlife was not associated with risk of long-term sickness absence, disability pension, early retirement, and unemployment in the fully adjusted model. Thus, no direct effect of individual cognitive ability in late midlife was observed on the risk of permanently or temporarily leaving the labor market.

Onset of Workplace Bullying and Risk of Weight Gain: A Multicohort Longitudinal Study.

OBJECTIVE: This study aimed to examine the onset of workplace bullying as a risk factor for BMI increase. METHODS: Repeated biennial survey data from three Nordic cohort studies were used, totaling 46,148 participants (67,337 participant observations) aged between 18 and 65 who did not have obesity and who were not bullied at the baseline. Multinomial logistic regression was applied for the analysis under the framework of generalized estimating equations. RESULTS: Five percent reported onset of workplace bullying within 2 years from the baseline. In confounder-adjusted models, onset of workplace bullying was associated with a higher risk of weight gain of ≥ 1 BMI unit (odds ratio = 1.09; 95% CI: 1.01-1.19) and of ≥ 2.5 BMI units (odds ratio = 1.24; 95% CI: 1.06-1.45). A dose-response pattern was observed, and those exposed to workplace bullying more frequently showed a higher risk (Ptrend = 0.04). The association was robust to adjustments, restrictions, stratifications, and use of relative/absolute scales for BMI change. CONCLUSIONS: Participants with exposure to the onset of workplace bullying were more likely to gain weight, a possible pathway linking workplace bullying to increased long-term risk of type 2 diabetes.

Objective and subjective stress, personality, and allostatic load.

INTRODUCTION: Despite the understanding of allostatic load (AL) as a consequence of ongoing adaptation to stress, studies of the stress-AL association generally focus on a narrow conceptualization of stress and have thus far overlooked potential confounding by personality. The present study examined the cross-sectional association of objective and subjective stress with AL, controlling for Big Five personality traits. METHODS: Participants comprised 5,512 members of the Copenhagen Aging and Midlife Biobank aged 49-63 years (69% men). AL was measured as a summary index of 14 biomarkers of the inflammatory, cardiovascular, and metabolic system. Objective stress was assessed as self-reported major life events in adult life. Subjective stress was assessed as perceived stress within the past four weeks. RESULTS: Both stress measures were positively associated with AL, with a slightly stronger association for objective stress. Adjusting for personality traits did not significantly change these associations. CONCLUSIONS: The results suggest measures of objective and subjective stress to have independent predictive validity in the context of personality. Further, it is discussed how different operationalizations of stress and AL may account for some of the differences in observed stress-AL associations.

Night work during pregnancy and preterm birth-A large register-based cohort study.

BACKGROUND: Melatonin stimulates the production of progesterone, which is essential for the maintenance of pregnancy. Since melatonin in blood is reduced due to work under illuminated conditions during night work, it has been hypothesized that night work may increase the risk of preterm birth. Previous meta-analyses have not revealed increased risk of preterm birth in women working night shifts during pregnancy. Still, these studies might have been limited by inaccurate self-reports of timing, intensity and duration of night work most likely causing bias towards the null. The aim of this is study was to investigate if the frequency and duration of night work during the first (week 1-12) and second (week 13-22) trimester of pregnancy were associated with risk of preterm birth when objective and prospective data on night work are used. METHOD: In a register-based prospective cohort study, we obtained individual day-to-day information on working hours from The Danish Working Hour Database (DWHD, a payroll database including all public service employees in administrative Danish Regions from 2007-2013) and information on preterm birth from the Danish Medical Birth Registry. Night-shift was defined as at least three working hours between 23:00 and 06:00. Preterm birth was defined as giving birth during gestational weeks 23-37. Odds of preterm birth according to working night shifts were analysed by logistic regression. RESULTS: We identified 16,501 pregnant women eligible for the study, of which 10,202 women (61.8%) had at least one night-shift during the first 22 gestational weeks. The risk of preterm birth was not elevated among women working night shifts compared to women working only day shifts during either the first or second trimester. Within night-shift workers, the risk was not related to the number of night shifts, the duration of night shifts, consecutive night shifts or quick returns defined as short intervals between shifts. Odds of preterm birth was not related to change of working schedule from the first to second trimester, although women changing from night shifts in the first trimester to day work only in the second trimester displayed a weak increased odds of preterm birth (OR 1.21, 95%CI 0.98-1.49) compared to women working night shifts in both trimesters. CONCLUSION: Our results, which are without bias from self-report of either exposure or outcome, are in line with the results of previous meta-analyses. Due to the detailed information on hours worked during pregnancy, we were able to investigate several dimensions of night work not previously investigated, of which none were associated with elevated risk of preterm birth.

Workplace bullying and workplace violence as risk factors for cardiovascular disease: a multi-cohort study.

AIMS: To assess the associations between bullying and violence at work and cardiovascular disease (CVD). METHODS AND RESULTS: Participants were 79 201 working men and women, aged 18-65 years and free of CVD and were sourced from three cohort studies from Sweden and Denmark. Exposure to workplace bullying and violence was measured at baseline using self-reports. Participants were linked to nationwide health and death registers to ascertain incident CVD, including coronary heart disease and cerebrovascular disease. Study-specific results were estimated by marginal structural Cox regression and were combined using fixed-effect meta-analysis. Nine percent reported being bullied at work and 13% recorded exposure to workplace violence during the past year. We recorded 3229 incident CVD cases with a mean follow-up of 12.4 years (765 in the first 4 years). After adjustment for age, sex, country of birth, marital status, and educational level, being bullied at work vs. not was associated with a hazard ratio (HR) of 1.59 [95% confidence interval (CI) 1.28-1.98] for CVD. Experiencing workplace violence vs. not was associated with a HR of 1.25 (95% CI 1.12-1.40) for CVD. The population attributable risk was 5.0% for workplace bullying and 3.1% for workplace violence. The excess risk remained similar in analyses with different follow-up lengths, cardiovascular risk stratifications, and after additional adjustments. Dose-response relations were observed for both workplace bullying and violence (Ptrend < 0.001). There was only negligible heterogeneity in study-specific estimates. CONCLUSION: Bullying and violence are common at workplaces and those exposed to these stressors are at higher risk of CVD.

Short time between shifts and risk of injury among Danish hospital workers: a register-based cohort study.

Objectives Short time between consecutive work shifts (quick returns, ie, ≤11 hours between shifts) is associated with sleepiness and fatigue, both of which have been linked to risk of injury. This paper aims to study quick returns between work shifts and risk of injury among Danish hospital workers. Method The study population included 69 200 employees, primarily working at hospitals, corresponding to 167 726 person years at risk between 2008-2015. Information on working hours was obtained from payroll data in the Danish Working Hour Database and linked, at an individual level, with data on 11 834 injury records identified in the National Patient Register and the Danish Register of Causes of Death. Multivariate Poisson regression models were used to calculate incidence rate ratios (IRR) with 95% confidence intervals (CI). Results Results showed the shorter the time between shifts, the higher the risk of injury. Thus, an elevated risk of injury was observed after quick returns compared with the standard 15-17 hours between shifts (IRR 1.39, 95% CI 1.23-1.58). Furthermore, when assessing the number of days since a quick return, the risk of injury was especially high within the first two days (day 1: IRR 1.39, 95% CI 1.23-1.58; day 2: IRR 1.39, 95% CI 1.21-1.58) following a quick return. Conclusions Our results suggest that quick returns increased the risk of injury, in particular within the first two days following a quick return. These findings point towards avoiding or reducing the number of quick returns in order to lower employees' risk of injury.

Parental socioeconomic position and midlife allostatic load: a study of potential mediators.

BACKGROUND: The mechanisms underlying the association of parental socioeconomic position with later life allostatic load remain unclear. The present study aims to examine potential pathways underlying this association: personality, social relations, intelligence and education. METHODS: The study comprised 361 members of the Copenhagen Perinatal Cohort who participated in two subsequent follow-ups: the Prenatal Development Project (mean age 27 years) and the Copenhagen Aging and Midlife Biobank study (mean age 50 years). Allostatic load was based on 14 biomarkers representing the inflammatory, metabolic and cardiovascular system measured at midlife. Information on potential mediators was collected in young adulthood, and their role in the association of parental socioeconomic position with midlife allostatic load were examined in linear regression path analyses. RESULTS: Parental socioeconomic position at one year was inversely associated with midlife allostatic load (ß = - 0.238, p < .001). No mediation effects were found for personality or social relations. In a model including intelligence and education, a significant indirect effect was found for education (ß = - 0.151, p < .001). A significant direct effect remained (ß = - 0.111, p = .040). CONCLUSIONS: Parental socioeconomic position was inversely associated with allostatic load in midlife. Results suggest that part of this association was mediated by education. A better understanding of the non-cognitive pathways related to education is an important prerequisite for the development of effective intervention strategies.

Indoor, outdoor, and night work and blood concentrations of vitamin D and parathyroid hormone.

Objectives The aim of this study was to examine blood concentrations of 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) among indoor, outdoor, permanent and rotating night workers and the association with hours spent outdoors on and off work days. Methods Blood samples were collected from 425 workers (162 indoor, 112 outdoor, 118 rotating night and 33 permanent night workers) throughout all seasons. Serum concentrations of 25-hydroxyvitamin D (25OHD) and parathyroid hormone (PTH) were analyzed by isotope dilution liquid chromatography-tandem mass spectrometry (LC MS/MS) and an automated immune analyzer, respectively. Personal light exposure levels were continuously recorded and used to estimate hours spent outdoors (all workers). Results Permanent night workers had 25.3% (95% CI 11.9-36.6) lower 25OHD concentration, 4.55 (95% CI 1.39-14.94) higher odds of vitamin D insufficiency (<50 nmol/L) and 14.5% [95% confidence interval (CI) 0.1-31.1] higher PTH concentration than indoor workers. Outdoor workers had similar 25OHD concentrations but 7.5% (95% CI -0.5-14.9) lower PTH concentration compared to indoor workers. Rotating night workers 25OHD and PTH concentrations did not differ from indoor workers. Concentration of 25OHD increased by 5.2% (95% CI 1.1-9.5) per hour spent outdoor at workdays in the summer. Conclusion Clinicians should be aware that vitamin D insufficiency may be more prevalent among permanent night workers and human resources should consider the positive effect of allowing workers to spend time outdoor during work hours.

Occupational Social Class and Personality Traits in Relation to Leisure-Time Physical Activity Level: Cross-Sectional Results From the Copenhagen Aging and Midlife Biobank.

OBJECTIVE: To investigate separate and combined associations of occupational social class and personality traits with late midlife leisure-time physical activity duration and intensity. METHOD: Cross-sectional data from the Copenhagen Aging and Midlife Biobank ( N = 4,649) were analyzed using linear regression models with leisure-time physical activity (metric equivalence) as outcome. RESULTS: Low versus high occupational social class was associated with 4% (95% confidence interval [CI] = [3%, 5%]) greater leisure-time physical activity duration, but 2% (CI = [1%, 3%]) lower intensity. Each 10-unit increase in extraversion was associated with 5% (CI = [2%, 8%]) greater duration. Intensity increased by each 10-unit increase in conscientiousness (6%, CI = [4%, 7%]), openness (3%, CI = [1%, 4%]), neuroticism (3%, CI = [1%, 4%]), and extraversion (5%, CI = [4%, 7%]). Conscientiousness was positively associated with duration in low, but not in high, occupational social class (interaction p value = .002). DISCUSSION: Higher occupational social class was associated with lower leisure-time physical activity duration, but higher intensity. Extraversion was positively associated with duration and intensity. Conscientiousness, openness, and neuroticism were positively associated with intensity. Overall, interactions were not consistent.

Workplace bullying and violence as risk factors for type 2 diabetes: a multicohort study and meta-analysis.

AIMS/HYPOTHESIS: The aim of this multicohort study was to examine whether employees exposed to social stressors at work, such as workplace bullying and violence, have an increased risk of type 2 diabetes. METHODS: The study included 45,905 men and women (40-65 years of age and free of diabetes at baseline) from four studies in Sweden, Denmark and Finland. Workplace bullying and violence were self-reported at baseline. Incident diabetes was ascertained through national health and medication records and death registers. Marginal structural Cox models adjusted for age, sex, country of birth, marital status and educational level were used for the analyses. RESULTS: Nine per cent of the population reported being bullied at work and 12% were exposed to workplace violence or threats of violence. Bullied participants had a 1.46 (95% CI 1.23, 1.74) times higher risk of developing diabetes compared with non-bullied participants. Exposure to violence or threats of violence was also associated with a higher risk of diabetes (HR 1.26 [95% CI 1.02, 1.56]). The risk estimates attenuated slightly when taking BMI into account, especially for bullying. The results were similar for men and women, and were consistent across cohorts. CONCLUSIONS/INTERPRETATION: We found a higher risk of incident type 2 diabetes among employees exposed to bullying or violence in the workplace. Further research is needed to determine whether policies to reduce bullying and violence at work may reduce the incidence of type 2 diabetes in working populations. Research on the mechanisms is also highly warranted.

Noise-Induced Hearing Loss - A Preventable Disease? Results of a 10-Year Longitudinal Study of Workers Exposed to Occupational Noise.

AIMS: To survey current, Danish industrial noise levels and the use of hearing protection devices (HPD) over a 10-year period and to characterise the association between occupational noise and hearing threshold shift in the same period. Furthermore, the risk of hearing loss among the baseline and the follow-up populations according to first year of occupational noise exposure is evaluated. MATERIALS AND METHODS: In 2001-2003, we conducted a baseline survey of noise- and hearing-related disorders in 11 industries with suspected high noise levels. In 2009-2010, we were able to follow up on 271 out of the 554 baseline workers (49%). Mean noise levels per industry and self-reported HPD use are described at baseline and follow-up. The association between cumulative occupational noise exposure and hearing threshold shift over the 10-year period was assessed using linear regression, and the risk of hearing loss according to year of first occupational noise exposure was evaluated with logistic regression. RESULTS: Over the 10-year period, mean noise levels declined from 83.9 dB(A) to 82.8 dB(A), and for workers exposed >85 dB(A), the use of HPD increased from 70.1 to 76.1%. We found a weak, statistically insignificant, inverse association between higher ambient cumulative noise exposure and poorer hearing (-0.10 dB hearing threshold shift per dB-year (95% confidence interval (CI): -0.36; 0.16)). The risk of hearing loss seemed to increase with earlier first year of noise exposure, but odds ratios were only statistically significant among baseline participants with first exposure before the 1980s (odds ratio: 1.90, 95% CI: 1.11; 3.22). CONCLUSIONS: We observed declining industrial noise levels, increased use of HPD and no significant impact on hearing thresholds from current ambient industrial noise levels, which indicated a successful implementation of Danish hearing conservation programs.

School education, physical performance in late midlife and allostatic load: a retrospective cohort study.

BACKGROUND: The mechanisms underlying the social gradient in physical functioning are not fully understood. Cumulative physiological stress may be a pathway. The present study aimed to investigate the association between highest attained school education and physical performance in late midlife, and to determine to what extent cumulative physiological stress mediated these associations. METHODS: The study is based on data from the Copenhagen Aging and Midlife Biobank (CAMB; n=5467 participants, aged 48-62 years, 31.5% women). School education was measured as highest examination passed in primary or secondary school (3 categories). Cumulative stress was operationalised as allostatic load (AL), and measured as the number of biological parameters (out of 14) in which participants scored in the poorest quartile. Physical performance included dynamic muscle performance (chair rise ability, postural balance, sagittal flexibility) and muscle strength (jump height, trunk extension and flexion, and handgrip strength). RESULTS: Among women, higher school education was associated with better performance in all physical performance tests. Among men, higher school education was associated with better performance only in chair rise and jump height. AL partially mediated the association between school education and physical performance, and accounted only for 2-30% of the total effect among women. Similar results were observed among men for chair rise and jump height. CONCLUSIONS: These results might indicate that AL plays a minor role in the association between school education and late midlife dynamic muscle performance in both men and women, and in muscle strength among women.

Cortisol, Health, and Coping in Patients with Nonspecific Low Back Pain.

Subjective health complaints (SHC), including nonspecific low back pain (LBP) as the most common single complaint, are the main reasons for long-term sick leave in many western countries. These complaints are often attributed to "stress". Cortisol has frequently been considered a biomarker reflecting sustained physiological HPA-axis activity, and is characterized by a high cortisol awakening response (CAR) and low evening values. The aim of the study was to investigate whether LBP patients had a normal characteristic cortisol profile, and whether possible deviations were related to coping and health. 305 patients on long-term sick leave for LBP participated in the study, and saliva cortisol profiles were compared to a reference population consisting of Danish workers. Cortisol was measured upon awakening, after 30 min, and in the evening. Additionally, patients answered questionnaires about SHC, fatigue, pain, coping, and social support. The patients showed a seemingly normal cortisol profile. However, CAR was larger among patients compared to the reference population. Patients with low cortisol reactivity had more SHC, pain, and fatigue, and those with higher evening cortisol reported higher scores on coping. The results are discussed in terms of theory, practical considerations, and possible mechanisms for the association between cortisol, health, and coping.

Defective mitochondrial respiration, altered dNTP pools and reduced AP endonuclease 1 activity in peripheral blood mononuclear cells of Alzheimer's disease patients.

AIMS: Accurate biomarkers for early diagnosis of Alzheimer's disease (AD) are badly needed. Recent reports suggest that dysfunctional mitochondria and DNA damage are associated with AD development. In this report, we measured various cellular parameters, related to mitochondrial bioenergetics and DNA damage, in peripheral blood mononuclear cells (PBMCs) of AD and control participants, for biomarker discovery. METHODS: PBMCs were isolated from 53 patients with AD of mild to moderate degree and 30 age-matched healthy controls. Tests were performed on the PBMCs from as many of these participants as possible. We measured glycolysis and mitochondrial respiration fluxes using the Seahorse Bioscience flux analyzer, mitochondrial ROS production using flow cytometry, dNTP levels by way of a DNA polymerization assay, DNA strand breaks using the Fluorometric detection of Alkaline DNA Unwinding (FADU) assay, and APE1 incision activity (in cell lysates) on a DNA substrate containing an AP site (to estimate DNA repair efficiency). RESULTS: In the PBMCs of AD patients, we found reduced basal mitochondrial oxygen consumption, reduced proton leak, higher dATP level, and lower AP endonuclease 1 activity, depending on adjustments for gender and/or age. CONCLUSIONS: This study reveals impaired mitochondrial respiration, altered dNTP pools and reduced DNA repair activity in PBMCs of AD patients, thus suggesting that these biochemical activities may be useful as biomarkers for AD.

Month-to-month variation in sleep among healthy, Scandinavian daytime workers.

BACKGROUND: The overall purpose of the present study was to attain more insight in month-to-month variation of sleep duration and quality in order to improve design and interpretation of, e.g. epidemiological studies using sleep as outcome. METHODS: The study design entailed monthly self-reports from 38 (26 women/12 men) daytime workers, who completed the Karolinska Sleep Diary (KSD) once a month during one year. A subgroup (n = 16) also wore actigraphs on one day every month during a year. Self-reports of bedtime, time of awakening, sleep duration, individual sleep characteristics, disturbed sleep index (DSI, 4 items) and awakening index (AWI, 3 items) were analyzed together with actigraphy-derived measures. Hours of daylight were used to test for circa-annual variation in statistical models adjusted for intake of hypnotics and alcohol, gender, age and within-person variability. RESULTS: Hours of daylight were found to be associated to self-reported bedtime (p = 0.032) and DSI (p = 0.030), thereby indicating a circa-annual variation. Bedtime was delayed by 1.8 min (95% CI: 0.6-2.9 min) per 1 hour increase in length of daylight. Sleep was slightly more disturbed during the winter. CONCLUSION: Only circa-annual variation in self-reports of bedtime and DSI were observed in a healthy daytime working population, and the effects were small. Therefore potential bias due to circa-annuality in the studied parameters appears to be of limited concern in adult daytime working populations.

An interlaboratory comparison between similar methods for determination of melatonin, cortisol and testosterone in saliva.

An interlaboratory comparison study for melatonin, cortisol and testosterone in saliva in which five laboratories participated is reported in this study. Each laboratory blindly measured eight samples prepared from natural saliva spiked with melatonin, cortisol and testosterone in the range 0-579 pmol/L for melatonin, 0-90 nmol/L for cortisol, and 0-622 pmol/L for testosterone. The recovery of spiked material for melatonin ranged from 91-110%, from 83-100% for cortisol and from 80-94% for testosterone. The content of natural hormone in saliva was estimated to be between 0.278 and 6.90 pmol/L for melatonin, 0.56 and 6.72 nmol/L for cortisol and 11.9 and 73.8 pmol/L for testosterone. This indicates a large interlaboratory variation. The present study emphasizes the importance of external quality control for the analysis of melatonin, cortisol and testosterone in saliva.

Depression and BMI influences the serum vascular endothelial growth factor level.

Recent studies suggest that the angiogenic cytokine vascular endothelial growth factor (VEGF) is involved in the pathogenesis of depression. However, only a few studies have investigated serum VEGF levels in individuals with depression, or the possible association between genetic variants within the VEGF gene and depression. The purpose of the present study was to investigate differences between serum VEGF levels in individuals with depression vs. control individuals, and associations between genetic markers located within VEGF and depression. In addition, determinants of the serum VEGF levels were identified. One-hundred and fifty-five depressed subjects and 280 controls were included in the study. All individuals returned a questionnaire and participated in a semi-structured diagnostic interview. Eleven single nucleotide polymorphisms were successfully analysed. VEGF levels were measured in serum by immunoassay and independent determinants of the serum VEGF level were assessed by generalized linear models.The main findings were that depression, severity of depression, previous depressive episodes, age and body mass index (BMI) were associated with higher serum VEGF levels. The genetic marker rs10434 was significantly associated with depression after correction for multiple testing, but not with the serum VEGF level. Our final model included depression and BMI as predictors of serum VEGF levels. Our study suggests a role for circulating serum VEGF in depression. Furthermore, our data also demonstrate that other factors than a diagnosis of depression influence the serum VEGF level. The importance of these factors should be emphasized when studies are compared.

An association study between the norepinephrine transporter gene and depression.

A potential approach for identification of candidate genes for depression is characterization of chromosomal rearrangements. Through analysis of a chromosome translocation in an individual with recurrent depression, we identified a potential candidate gene: the norepinephrine transporter (NET; SLC6A2 for solute carrier 6 family member 2). The gene is responsible for the reuptake of norepinephrine and dopamine into presynaptic nerve terminals and the norepinephrine system appears to play an important role in depression. We therefore analyzed genetic variants within SLC6A2 for association with depression in 408 affected and 559 control individuals from Denmark. After quality control of the genotypes, 31 of 45 single nucleotide polymorphisms (SNPs) were left for analyses. One SNP showed a nominal association with depression but did not survive correction for multiple testing. The results from our study do not suggest SLC6A2 as a susceptibility gene for depression in the Danish population.

Occupational noise exposure and the risk of stroke.

BACKGROUND AND PURPOSE: Traffic noise <60 dB(A) has been associated with an increased risk of stroke. We investigated this relationship for 80 to 86 dB(A) occupational noise. METHODS: We followed 116,568 industrial and 47,679 financial workers by linkage to Danish registries 2001 through 2007. Full-shift noise levels were estimated from subsets of workers at baseline and end of follow-up. RESULTS: We identified 981 stroke patients and observed a 27% increased confounder-adjusted risk of stroke for industrial compared with financial workers. However, longer duration or higher noise level within the industrial workers were unrelated to the risk of stroke. CONCLUSIONS: Our study did not support an association between occupational noise exposure and stroke, and the higher risk among industrial workers may reflect lifestyle differences.