Internal locus of control and choice in health service shift workers.

This study examined the relationship between shift work-specific locus of control (SH-LOC), active choice of work schedule and health outcomes, personal initiatives and coping behaviours in 1611 Danish Health Service shift workers. The 20-item SH-LOC scale was administered as part of a battery of measures. Multivariate analysis of covariance (controlling for age, workplace experience and weekly work hours) tested for differential responses to shift working and coping strategies. Interactive effects of internality and type of work rota were examined. Higher internality was linked to better tolerance to shift work. This did not appear to be a result of greater personal action in higher internals. The importance of control as a potential moderating factor to shift work exposure and the possible use of this measure in the process of shift worker monitoring is highlighted.

Intervention in shift scheduling and changes in biomarkers of heart disease in hospital wards.

OBJECTIVES: The effect of introducing regularity, few consecutive night shifts, more weekends off, and only 2 different types of shifts (day-evening or day-night) into shift scheduling on biomarkers of heart disease was studied. METHODS: Ergonomic shift criteria were introduced in a quasi-experimental controlled intervention in 4 hospital wards. Six wards participated as controls. Altogether 101 nurses and nurses' aides were followed for 6 months with measurements of cholesterol and triglycerides. The intervention led to more regular schedules and more staff having 2 shifts in 2 of the intervention wards 1 year after the intervention. The schedules among the controls became less regular and less predictable. The number of consecutive night shifts remained unchanged. RESULTS: After 6 months the high-density lipoprotein (HDL) cholesterol level had increased in the intervention group, and the total cholesterol and low-density lipoprotein (LDL) cholesterol levels and the total:HDL cholesterol ratio had decreased. Regardless of the intervention, changes in regularity were associated with the triglyceride and HDL cholesterol levels and also with the total:HDL cholesterol ratio. More ergonomic changes were associated with lower LDL cholesterol levels, a lower total:HDL cholesterol ratio, and higher HDL cholesterol levels. CONCLUSIONS: Increased ergonomic scheduling was possible. Lipids and lipoproteins changed as predicted, both when the changes were assessed in respect to the changes in schedules that resulted from the intervention and the changes that occurred regardless of the intervention. The study suggests that scheduling based on ergonomic criteria is a possible means for reducing the risk of heart disease among shift workers.

Work environment of Danish shift and day workers.

OBJECTIVES: Both shift work and other work environment factors have been shown to be related to heart disease. This study examined whether shift work is associated with other work environment factors related to heart disease in a random sample of the population. If so, shift work could be acting as a proxy for work environment differences. METHODS: Data on 5940 employees in the Danish Work Environment Cohort Study from 1990 were reanalyzed. The information included work schedules [permanent day work, irregular workhours (including morning work), 2-shift or fixed evening and 3-shift or fixed night], length of workweek, physical factors (noise, heat, dust, passive smoking, walking, standing and monotonous repetitive tasks), and psychosocial factors (including demands and control dimensions, social support, conflicts and job insecurity). RESULTS: At least 1 group of shift workers had a higher prevalence of nearly every unfavorable work environment factor investigated. Exceptions were dust exposure and quantitative demands. Especially conflicts at work and low decision latitude were higher among all the groups of shift workers, and all-day walking or standing work and part-time jobs were more often found among female shift workers. The 3 different shiftwork groups were exposed to different parts of the work environment, and also men and women in shift work differed in relation to the work environment. Age and social class influenced the relationship, but not in any particular pattern. CONCLUSIONS: In a heterogenous population shift work was found to be associated with other work environment factors suspected to cause heart disease.

Management of health and safety in the organization of worktime at the local level.

OBJECTIVES: This study examined the consideration of health and safety issues in the local process of organizing worktime within the framework of regulations. METHODS: The study encompassed all 7 hospitals in one region of Denmark. Twenty-three semi-structured interviews were carried out with 2 representatives from the different parties involved (management, cooperation committees, health and safety committees from each hospital, and 2 local unions). Furthermore, a questionnaire was sent to all 114 wards with day and night duty. The response rate was 84%. Data were collected on alterations in worktime schedules, responsibilities, reasons for the present design of schedules, and use of inspection reports. RESULTS: The organization of worktime takes place in single wards without external interference and without guidelines other than the minimum standards set in regulations. At the ward level, management and employees were united in a mutual desire for flexibility, despite the fact that regulations were not always followed. No interaction was found in the management of health and safety factors between the parties concerned at different levels. CONCLUSIONS: The demands for flexibility in combination with the absence of guidelines and the missing dynamics between the parties involved imply that the handling of health and safety issues in the organization of worktime may be accidental and unsystematic. In order to consider the health and safety of night and shift workers within the framework of regulations, a clarification of responsibilities, operational levels, and cooperation is required between the parties concerned.

Shift work and sick leave.

OBJECTIVE: Shift workers working nights are known to have higher morbidity from certain illnesses than day workers. This study examined episodes of certified sick leaves of day workers and shift workers in a large industrial plant to examine whether slowly rotating shift work leads to increased risk of sick leave. METHODS: In a case-base design more than 11000 episodes of sick leave, lasting more than 3 days, were obtained from the sick-leave files of a chemical plant in Norway. The diagnoses were grouped into 5 categories according to information on their work schedules. The workers included in the study were divided into 3 groups. They worked slowly rotating 3 shifts, 2 shifts without night work, and daytime schedules. RESULTS: For all the diagnoses the shift workers and day workers were evenly distributed among the cases and the referents, the odds ratios ranging from 0.8 to 1.2. The risk of sick leave did not change with the number of years in shift work. There was a higher risk of sick leave with musculoskeletal diagnoses among the 2-shift workers. CONCLUSIONS: In this study shift workers did not have a higher risk of sick leave for diseases that, in previous studies, have been shown to be related to shift and night work. Although bias may be present in the study, the results are in line with those of previous studies, and they suggest that even certified sick leaves are not a valid proxy for morbidity.

Employment status, non-daytime work and gastric ulcer in men.

BACKGROUND: An excess risk of gastric ulcer (GU) (ICD-8: 531) has formerly been found in shift workers and ex-shiftworkers but little is known about the risk of GU associated with other forms of non-daytime work. This study deals with associations between non-daytime work and GU. METHODS: A fixed cohort of 122,116 men in occupations in which at least 20% had non-daytime work and a reference group of 593,281 men in occupations with daytime work only, was followed in the National Inpatient Register for first discharges with GU as the principal diagnosis. RESULTS: For men with daytime work only we found a steep inverse association between GU and employment status. Men in occupational groups with late evening work had a standardized hospitalization ratio (SHR) of 236 (90% confidence interval [Cl]: 184-299), groups working in rosters covering 24-hour services had an SHR of 147 (90% Cl: 116-183). A slightly raised risk of 114 (90% Cl: 101-128) was found in groups having other forms of non-daytime work. For all men in groups with non-daytime work we found a significant SHR of 130 (90% Cl: 118-142). CONCLUSION: We conclude that both low employment status and non-daytime work are associated with an increased risk of GU.

Psychometric tests for assessment of brain function after solvent exposure.

Psychometric testing is a key issue in neuropsychological toxicology assessment. Evaluation of methods for assessing general intellectual impairment is necessary as conventional neurology has been shown to be insensitive to the neurotoxic effects of solvents and metals. This study presents an analysis of a psychometric test battery from an investigation of psycho-organic syndrome in a historical cohort of 96 metal degreasers with long-term exposure to solvents, particularly trichloroethylene. The neuropsychological test battery was a combination of Wechsler Adult Intelligence Scale (WAIS), Luria, and tests developed in Scandinavia. Linear regression analysis showed a significant dose-response relation between increasing cumulative solvent exposure and impaired psychometric test performance in 9 out of 15 tests. Multivariate analysis, however, suggests that much of the variance was due to confounding variables, especially age, and to a lesser degree, primary intellectual function and word blindness. After control for confounding factors the strongest association with solvent exposure occurred for the following three tests: acoustic-motor function, Paced Auditory Serial Addition Test (PASAT), and the visual gestalt test.

Solvent-induced chronic toxic encephalopathy.

Chlorinated solvents, especially trichloroethylene, have been extensively used for metal degreasing since the beginning of this century. There have been case reports of cranial nerve damage and symptoms of acute and reversible encephalopathy. However, another issue during the last decade is the possible existence of a syndrome of chronic cerebral dysfunction. Our study deals with the risk of developing a state of psychoorganic syndrome after long-term exposure to solvents, mainly trichloroethylene. In this historical cohort study, 96 metal degreasers participated in a clinical medical and psychological examination. The risk of developing psychoorganic syndrome was proportional to the exposure duration, to increasing age, and to decreasing primary intellectual level. Using logistic regression analysis, there was a significantly increased risk of developing psychoorganic syndrome from solvent exposure. There was an odds ratio of 5.6 (0.93-34.3) for psychoorganic syndrome in the medium-exposed group. In the most highly exposed group, with a mean full-time exposure duration of 11 years, there was a significantly increased risk of psychoorganic syndrome, the adjusted odds ratio was 11.2 (1.9-66.6). None of four other potential confounders (arteriosclerotic disease, neurologic/psychiatric disease, alcohol abuse, and current solvent exposure) had any significant associations to psychoorganic syndrome.

Psychoorganic syndrome from exposure to fluorocarbon 113--an occupational disease?

A cross-sectional clinical study of 99 workers engaged in degreasing with halogenated hydrocarbons has been carried out. Among 23 cleaners from one factory, all at the time using fluorocarbon 113, we found 3 persons with symptoms and signs of psychoorganic syndrome after heavy exposure to fluorocarbon 113 for 2 1/2-4 1/2 years. The possibility of developing psychoorganic syndrome from occupational exposure to fluorocarbon is discussed by presenting these 3 cases.