Prospective, population-based study of occupational movements and postures of the neck as risk factors for cervical disc herniation.

OBJECTIVE: We studied the associations between objectively measured occupational neck exposures in a job exposure matrix (JEM) and cervical disc herniation (CDH). DESIGN: A cohort study of Danish workers who ever held at least one of 29 jobs (eg, dentists, hairdressers, childcare, carpenters) from 1981 to 2016 was formed. Representative whole work-day inclinometric measurements from previous studies using triaxial accelerometers measuring neck angular velocity and posture of the neck were used as exposure in a JEM. Job titles were retrieved from the Danish Occupational Cohort with eXposure data database. The risk of CDH by quintiles of cumulated exposure was assessed by incidence rate ratios (IRR), adjusted for age, sex, calendar-year, previous lumbar disc herniation and educational level, using Poisson regression models. SETTING: Nationwide Danish registers. PARTICIPANTS: 852 625 Danish workers within 29 different job-titles. OUTCOME MEASURES: First diagnosis of CDH was retrieved from the Danish National Patient Register. RESULTS: We found 14 000 cases of CDH during 20.2 million person-years of follow-up. Increasing levels of neck angular velocity showed a decreasing risk with IRR 0.90 (95% CI 0.86 to 0.95) when the highest level of cumulative exposure (dynamic work) was compared with the lowest (static work). Similar results were found for extension and flexion of the neck, though not statistically significant for extension. Multiple sensitivity analyses did not change the results. CONCLUSION: In this large register-based study based on a JEM, we found no evidence of an increased risk of CDH with increasing cumulated angular velocity, flexion or extension of the neck. Factors other than occupational dynamic neck movements and bent neck position seem to be important in the development of CDH.

Hospital admissions for neurological and renal diseases among dentists and dental assistants occupationally exposed to mercury.

OBJECTIVES: For many years an amalgam containing metallic mercury, which has been associated with neurological and renal diseases, has been used in dentistry. In this nationwide study we compared hospital admissions due to neurological and renal diseases among dentists and dental assistants to admissions in controls. METHODS: This register-based cohort study included all Danish workers employed in dental clinics, general practitioners' clinics or lawyers' offices between 1964 and 2006. We compared dentists with general practitioners and lawyers, and dental assistants with medical secretaries, nurses and legal secretaries. We also compared dentists and dental assistants employed during periods with high occupational mercury exposure with dentists and dental assistants employed during periods with less mercury exposure. We followed all subjects in a nationwide register of hospital admissions. We analysed risk of neurological diseases, Parkinson's disease and renal diseases using a Cox regression model. RESULTS: The cohort consisted of 122,481 workers including 5371 dentists and 33,858 dental assistants. For neurological diseases, no association was observed for dental assistants, while for dentists an increasing risk for periods with less mercury exposure was observed. Among dental assistants, a negative association between employment length and risk of neurological disease was observed. Admissions for renal disease among dental assistants were increased during periods with less mercury exposure compared with controls. For dentists a non-significant increased risk was observed between employment length and renal disease risk. CONCLUSIONS: Our nationwide study does not indicate that occupational exposure to mercury increases the risk of hospital admissions for neurological, Parkinson's or renal diseases.

Work-unit social capital and incident purchase of psychotropic medications: A longitudinal cohort-study of healthcare workers.

BACKGROUND: Whether workplace social capital affects employees' mental health is debated. We examined the association between work-unit aggregated social capital and incident purchase of psychotropic medications among employees. METHODS: We used data from the WHALE (Well-being in Hospital Employees) cohort study. The study population comprised 21,711 employees without recent psychotropic purchase-history nested within 2283 work units in the Capital Region of Denmark. Employees were invited to participate in a survey in March 2014 (86% response). We assessed workplace social capital by eight items (covering trust/justice and collaboration) and aggregated the mean of responses up to each work unit and categorized the scores into quartiles. Data on psychotropic purchases (antidepressants and anxiolytics/hypnotics/sedatives) were extracted via linkage to national registers. Using two-level mixed-effects survival models, we analyzed the association between work-unit social capital and psychotropic purchases during a one-year follow-up period adjusting for individual-level workplace social capital. RESULTS: Low work-unit social capital was associated with higher purchases of overall psychotropic medications in a dose-response manner (low-versus-high: HR=1.32, 95% CI=1.05-1.65), but this effect attenuated after adjusting for individual-level workplace social capital (HR=1.14, 95% CI=0.88-1.46). Low work-unit social capital was associated with higher purchases of antidepressants (HR=1.78, 95% CI=1.16-2.73) even after adjusting for individual-level workplace social capital (HR=1.69, 95% CI=1.05-2.73). LIMITATIONS: Medical doctors/dentists were underrepresented in the data on workplace social capital. CONCLUSIONS: Low work-unit social capital may be associated with higher use of antidepressants among healthcare employees. Interventions to improve social capital could potentially promote mental health at work in the healthcare setting.