We conducted this study to examine the relationship between shift work duration and the metabolic risk factors of cardiovascular disease among shift workers. The study population consisted of 226 female hospital nurses and 134 male workers at a firm manufacturing diapers and feminine hygiene materials, whose mean ages were 28.5 yr for the nurses and 29.1 yr for the male workers. The fasting blood sugar level, serum cholesterol, blood pressure, height and weight, waist and hip circumferences (only for the nurses), and numbers of walks during work (as a measure of physical activity) were measured. Using the Karasek's job contents questionnaire, job stress was assessed. Information about the years of work, shift work duration, past medical and behavioral history, including smoking, was obtained by a self-administered questionnaire. With definitions of hypertension as systolic blood pressure (SBP) ≥160 or diastolic blood pressure (DBP) ≥90 mmHg occurring at least once, hypercholesterolemia as serum total cholesterol ≥240 mg/dl, obesity as body mass index (BMI) ≥25 kg/m² and as waist to hip ratio (WHR) ≥0.85, we examined the prevalences of metabolic risk factors among subjects. Regression analyses to show the relationships between shift work duration and metabolic risk factors were performed using simple and multivariate models stratified by age, and adjusted for smoking, drinking, job strain and physical activity. Duration of shift work was significantly associated with SBP or cholesterol level among male workers aged 30 or more. Among female nurses, it was inversely associated with DBP (in those who were below 30 yr old) and cholesterol (in those who were aged 30 or more). BMI was non-significantly associated with the duration of shift work in both male workers and female nurses who were 30 yr old or more. WHR in female nurses increased slightly according to increasing duration of shift work. Fasting blood sugar was not significantly associated with the duration of shift work in either sex regardless of age-group. These results suggest an association between shift work duration and the metabolic risk factors of cardiovascular disease.

View full abstract

The changes of N-methyl-D-aspartate (NMDA) receptor and protective efficacy of memantine (MEM) in rats poisoned with dichlorvos were studied. Dichlorvos evoked down-regulation of the affinity and density of [³H]MK-801 binding to NMDA receptor in the brain of rats receiving dichlorvos (15 and 25 mg/kg bw, i.p.). The binding capacity of NMDA receptor and acetylcholinesterase activity were determined at 4 h, 8 h, 16 h, 24 h and 48 h after treatment. When rats were given a different doses of MEM (5, 15 and 45 mg/kg bw) after poisoning (dichlorvos 25 mg/kg bw), the latency of onset of signs was postponed and the magnitude of muscular fasciculation was alleviated as the dose of MEM increased. The lower doses of MEM (5 and 15 mg/kg bw) could antagonize the dichlorvos-evoked down-regulation of NMDA receptor, while the highest dose (45 mg/kg bw) decreased the Bmax and Kd values of NMDA receptors. These results show the dichlorvos-evoked down-regulation of NMDA receptor might be self-regulation by the body to protect the central nervous system. MEM could antagonize the down-regulation of NMDA receptors, and alleviated signs of poisoning, especially reducing the magnitude of muscular fasciculation. We suggest that the role of NMDA receptor in organophosphates (OP) poisoning should receive more attention, and, that MEM treatment in acute OP poisoning, as a supplement to atropine and oxime, should be considered.

View full abstract

In Japan, Karoshi, which means `death from overwork', has become a focus of social concern. However, no previous study has examined long working hours and job strain simultaneously in relation to incidence of cardiovascular events (CVE) in Japanese workers. We prospectively evaluated the relation between job strain or long working hours and risk of CVE in treated hypertensives during the years 1994-2000. In this study, we followed a sample of 1,615 participants (908 men and 707 women) aged 40-65 yr who were working more than 5 working hours per day. Participants completed questions about work-related conditions and lifestyle variables at baseline, and were free of diagnosed cardiovascular disease, stroke or cancer. Job strain (the combination of job demands and job control) was assessed using a simple questionnaire developed with reference to Karasek's model. The main outcome measure was incidence of CVE. During the mean follow-up period of 5.6 yr, we documented 38 cases of initial CVE. Analyses were conducted using the Cox proportional hazard model. We found a significant association between incidence of CVE and job strain categories, but not long working hours. Multivariate relative risks for CVE in active jobs and high strain jobs overall were 2.89 (95% CI: 1.33-6.28) and 2.45 (95% CI: 0.87-6.93); for men 2.94 (95% CI: 1.29-6.73) and 1.86 (95% CI: 0.51-6.75), and for women 3.97 (95% CI: 0.34-46.88) and 9.05 (95% CI: 1.17-69.86), respectively. In conclusion, active jobs and high strain jobs were associated with increased risk of CVE for treated hypertensive workers.

View full abstract

Occupational asthma has been found to be associated with lowered socio-economic outcomes, an increased unemployment rate and a decreased quality of life. The compensation of occupational diseases is comparatively favourable in Finland. Our aim was to follow-up the working status and life satisfaction of patients with diisocyanate-induced asthma in 245 cases diagnosed during 1976-1992. A questionnaire was sent out on average 10 (3-19) yr after the diagnosis to the surviving 235 patients. The questionnaire was validated by re-examining 91 of them clinically, and with spirometry, histamine challenge test and peak flow surveillance. Of the 213 responding patients, 14% were unemployed, and for 50% of them unemployment was caused by asthma. Unemployment was associated with nocturnal asthma symptoms (OR 10.93; CI 2.69-44.452), increased PEF variability (OR 8.46; CI 1.52-46.97) and with the use of short-acting β-sympathomimetic medication (p=0.045). Satisfaction with life was associated with present working (OR 3.50; CI 1.73-7.06) and with good condition of asthma as assessed by the use of asthma medication (OR 0.49; CI 0.27-0.89) and objective measurements of the asthma condition, e.g. PEF variability (OR 0.21; CI 0.08-0.59). As a conclusion, unemployment was remarkably low as compared with earlier reports and related to the period of simultaneous economic recession. Unemployment, as well as dissatisfaction with life were associated with poor conditions of asthma. Unemployment was associated with improper asthma care favouring the use of short-acting β-sympathomimetic medication. Proper follow-up of asthma is essential for minimizing the social complaints of occupational asthma, as well as for enhancing life satisfaction.

View full abstract

This study sought to determine the relationship of job type differences to burnout level, the details of job characteristics for each job type, and the association between burnout and job factors in 189 social workers at all social welfare offices in a prefecture in Japan. Among the three job types, 32.9% of social workers involved with public assistance, 29.0% of social workers involved with public assistance, the elderly, the disabled and single mothers, and 15.2% of social workers involved with the elderly, the disabled and single mothers were scored in the "high burnout" category (p<.05). Job type differed significantly with respect to the job characteristics of percentage of time spent on home visits per typical working day, job satisfaction, aversion to the job, and social support. The job type of public assistance work had a higher percentage of time spent on home visits per typical working day, aversion to the job, lower job satisfaction, and less social support than the job type involving no public assistance work. Multiple regression analyses showed the associations between job factors and burnout for each job type. Aversion to the job had a primary positive association with burnout for all social worker job types. Social support had a negative association with burnout in social workers whose clients included public assistance cases. The number of years in social work had a negative association with burnout, while percentage of time spent doing interviews per typical working day had a positive association with burnout in social workers who were involved with public assistance, the elderly, the disabled and single mothers. These results suggest that the job type of public assistance work may carry a higher risk of burnout than job types involving no public assistance work. To ameliorate this risk, it was thought to be important to improve aversion to the job as well as having a social support network for public assistance social workers.

View full abstract

A clustering of insulin resistance, hypertension and dyslipidemia has been labeled as the metabolic syndrome. Asians have a lower frequency of obesity than do Caucasians, but have an increasing tendency toward metabolic syndrome. Most data on metabolic syndrome are based on studies from Western countries with only limited information derived from Asian populations. We conducted a cross-sectional study of individuals aged 30-60 yr in workplace settings. We examined and analyzed the health data of 1,384 Japanese, Koreans and Mongolians for metabolic syndrome based on the modified definitions of the working definition proposed by the Third Report of the National Cholesterol Educational Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP III definition). The prevalence of metabolic syndrome using the ATP III-BMI30 and ATP III-BMI25 definitions was 7% and 12% for Japanese, 7% and 13% for Koreans, and 12% and 16% for Mongolians, respectively. With the exception of obesity, the prevalences of individual metabolic abnormalities within each of the three Asian groups were similar to each other and to reported rates of prevalence in the U.S.A. Nevertheless, the values of sensitivity and specificity by the metabolic syndrome definitions are remarkably different relative to ethnicity. A universal metabolic syndrome definition is inappropriate for comparisons of metabolic syndrome among Asian ethnic groups. We believe that the ATP III-BMI25 definition is suitable for the determination of metabolic syndrome among Japanese and Koreans, and that the ATP III-BMI30 is more appropriate for Mongolians.

View full abstract

Employees of two large companies in Switzerland took part in a nationwide health information and promotion campaign at work, which included various physical examinations. A total of 5,849 consecutive participants were sent a questionnaire to determine whether changes had been made in their lifestyles and if they had benefited from participation; 2,361 (40.4%) responded. The campaign was rated highly at 8.3 on a scale from 1 to 10. Respondents reported benefiting most from the personal examination results, in particular the measurement of bone density, examination of the carotid arteries and discussions with the staff. Of the respondents, 921 stated they changed their lifestyle in the area of physical activity (64.4%) and nutrition (63.6%). Multiple logistic regression analysis showed the variables predictive of responding were age, hierarchy, diet and smoking. Health promotion at work and the choice of offered examinations may influence the effects of health care promotion at the workplace and the readiness of participants to improve their attitudes to health. Health promotion at work is highly regarded by employees who pay more attention to diet, smoke less and in particular those over 50 yr of age. High-tech equipment in a mobile unit may attract employers and employees may profit most from the individual examination results; 39% of the respondents stated they changed their lifestyle as a consequence of the Check Bus campaign.

View full abstract

To clarify the neuromotor effects of long-term exposure to mixed organic solvents, postural sway and tremor were measured in 62 solvent workers of four Buddhist altar manufacturing factories who had worked for 1-46 (mean 12) yr. By using the passive gas sampler, 8-h time-weighted average concentrations in the workers were estimated to be 0.02-8.7 ppm for toluene, 0.02-7.7 ppm for xylene, 0.02-5.5 ppm for styrene and 0.02-40.5 ppm for n-hexane. Sagittal sway and sway area of the posturography with eyes closed were significantly larger in the solvent workers than in 35 age-matched controls (p<0.05), and there was a significant difference in Romberg quotient of sagittal sway between the two groups (p<0.05). Also, tremor intensities at 1.0-5.9 Hz, 6.0-9.9 Hz and 10.0-13.9 Hz with the right hand, and at 6.0-9.9 Hz with the left hand were significantly stronger in the solvent workers than in the controls. Among the solvent workers, transversal and sagittal sways with eyes open and tremor intensity at 10.0-13.9 Hz were significantly related to toluene exposure (p<0.05), which may have been due to the acute effects of such solvents. These findings suggest that long-term exposure to mixed organic solvents may impair neuromotor functions as measured by postural sway and tremor.

View full abstract

This study was aimed at understanding the relationship among menstrual pattern, dysmenorrhea, life style and working conditions in nurses. The nurses were randomly selected from a medical center in Northern Taiwan. Each subject completed daily records including life and working conditions during the study period. The study showed that there were statistically significant differences in work years, daily working hours and type of work shift among nurses that worked at different units in the hospital. In the perceived regular cycle group, nurses that worked the night shift only exhibited the shortest menstrual cycles, less than 25 d. There was a significant difference (p<0.05) among the nurses' menstrual cycles. Many life factors (such as passive tobacco smoke exposure, perceived life satisfaction and perceived life stress) and working factors (such as work years, perceived work satisfaction and perceived work stress) were not significantly related to menstrual cycle regularity. In addition, 30% of the nurses complained of dysmenorrhea. Some factors including age, marital status and perceived life satisfaction were significantly related to dysmenorrhea. However, other life factors (such as passive tobacco smoke exposure, smoking, coffee, alcohol, cold drink habits, exercise and perceived life stress) and working factors (such as working places, type of work shift, daily work hours, perceived work satisfaction and perceived work stress) showed no correlation with dysmenorrhea. This study indicates that women should pay attention to their menstrual function and dysmenorrhea phenomenon.

View full abstract

With the rapidly increasing number of work-related suicides in Japan (Karojisatsu, in Japanese), both applications for worker's compensation insurance and civil suits are proliferating. The phenomenon of work-related suicide is examined along with the process and related factors. With informed consent from bereaved families, two certified psychiatrists independently reviewed and summarized 22 insurance and legal reports filed by psychiatrists on employee suicides that were related to heavy workloads. A clinical epidemiologist participated in discussions with psychiatrists to reach a consensus concerning the cause of the suicides. Only one case involved a female. Seventeen had experienced personnel changes, such as a promotion or transfer. Low social support was recognized in 18, high psychological demand in 18, low decision latitude in 17, and long working hours in 19 cases (more than 11 hours per day for 3 months or more, and without a day off in 9). The subjects had depressive episodes by the ICD-10 criteria and showed suicidal signs. Ten of them saw a general practitioner because of unspecified somatic complaints, but no effective measures were taken. None of them had a history of psychiatric consultation or had received mental health education dealing with job stress management. Although causality cannot be made from this case series report, we hypothesize that long working hours, heavy workloads, and low social support may cause depression, which can lead to suicide. Appropriate countermeasures are urgently needed and the present findings suggest some of them are possible.

View full abstract

Few studies have focused on the health effects of vibrating tools on workers in the tropical area. Work conditions and health effects related to rock drill operation were studied in 102 quarry workers, including 73 rock drill operators in Vietnam. We aimed to clarify (1) risk of vibration exposure, (2) occurrence of vibration-induced white finger (VWF), and (3) characteristics of hand-arm vibration syndrome (HAVS). Total weighted r.m.s. acceleration of the Chinese -or Russian-made rock drills, was 45-55 m/s². According to work observation studies, daily exposure time to vibration was 160-210 min. ISO5349 predicted that this exposure level would be associated with a high risk of HAVS in workers. We found no clear evidence of VWF. There may be several reasons why no worker exhibited VWF: (1) warmer work conditions, (2) younger and less experienced workers, (3) seasonal changes in work operations, and (4) healthy worker effect. On the other hand, 5-10% of rock drill operators might be suffering from moderate HAVS which was sensori-neural type dominant. There may be some characteristic features of HAVS among quarry workers in the tropical area.

View full abstract

A retrospective cohort morbidity study based on standardized incidence ratios (SIRs) was conducted to investigate the possible association between exposure to chlorinated organic solvents and various types of cancers in an electronics factory. The cohort of the exposed group was retrieved from the Bureau of Labor Insurance (BLI) computer database records dating from 1978 through December 31, 1997. Person-year accumulation began on the date of entry to the cohort, or January 1, 1979 (whichever came later), and ended on the closing date of the study (December 31, 1997), if alive without contracting any type of cancers, or the date of death, or the date of the cancer diagnosis. Vital status and cases of cancer of study subjects were determined from January 1, 1979 to December 31, 1997 by linking cohort data with the National Cancer Registry Database. The cancer incidence of the general population was used for comparison. After adjustment for age and calendar year, only SIR for breast cancer in the exposed female employees were significantly elevated when compared with the Taiwanese general population, based on the entire cohort without exclusion. The SIR of female breast cancer also showed a significant trend of period effect, but no significant dose-response relationship on duration of employment. Although the total cancer as well as the cancer for trachea, bronchus and lung for the entire female cohort was not significantly elevated, trend analysis by calendar-year interval suggested an upward trend. However, when duration of employment or latency was taken into consideration, no significantly elevated SIR was found for any type of cancer in either male or female exposed workers. In particular, the risk of female breast cancer was not indicated to be increased. No significant dose-response relationship on duration of employment and secular trend was found for the above-mentioned cancers. This study provides no evidence that exposure to chlorinated organic solvents at the electronics factory was associated with elevated human cancers. Dominant short-term employees may bias the cancer risk toward false positive.

View full abstract

This study presents the results of an investigation of respiratory symptoms, lung function, chest X-ray examinations, analysis of specific IgE antibodies and skin prick tests to fungi on 130 tobacco-processing workers and 112 control workers. Industrial hygiene survey and environmental mycological studies were also performed. The average dust concentrations ranged from 13.76 to 29.55 mg/m³ in the tobacco processing workshops. Also, the numbers of fungi colonies in the processing environments were much higher than those in the control environments. The prevalences of chronic respiratory or nasal symptoms in exposed workers were significantly higher than those in control workers (p<0.05 or p<0.01). The prevalences of lung function abnormalities in the exposed workers were significantly higher than those in control workers (p<0.05). The positive prevalences of specific IgE reactions to fungi (26.92% for A.fumigatus and 51.54% for Rhizopus nigricans) in exposed workers were also significantly higher than those in control workers (p<0.01). The positive prevalences of the skin prick test showed that 18.46% of the exposed workers were positive to A. fumigatus and 23.85% were positive to Rhizopus nigricans. Our results suggested that tobacco processing workers may develop respiratory diseases related to tobacco dust and we consider that fungi might be one of the allergens causing allergic respiratory or nasal diseases in tobacco processing workers.

View full abstract

Merkel cell carcinoma (MCC) is a rare primary neuroendocrine carcinoma of the skin, mostly occurring late in life on sun-exposed body parts. Little is known about the specific etiological factors in the pathogenesis of MCC. A previous report indicated that arsenic exposure might cause MCC, which might be another specific type of skin cancer associated with arsenic exposure. On the southwest coast of Taiwan, high arsenic levels in artesian well water have been documented, and various diseases associated with arsenic exposure have been found to be prevalent in this area. We report two pathologically confirmed cases of MCC in patients who had histories of long-term ingestion of arsenic from drinking water. The tumors were on the anterior chest wall, an area less exposed to the sun, in both cases. The literature on the dose-response relationship between arsenic exposure and MCC is limited. We estimated that the total arsenic ingested by these two cases was around 14.7 and 2.6 gm, respectively. We also tried to assess the cancer risk on the basis of the estimated doses of arsenic exposure and the cancer risk model developed by the U.S. Environmental Protection Agency (EPA). The estimated lifetime target cancer risk was 1.3 × 10^-2 in Case 1 and 2.3 × 10^-3 in Case 2. Both are much higher than the 10^-6 upper limit on lifetime cancer risk put forth by the U.S. EPA health protection standard. We believe that arsenic intoxication played an important role in the carcinogenic process of MCC in our cases.

View full abstract