Ichiro Oyama

Industry-based retrospective cohort study of the risk of prostate cancer among rotating-shift workers

Objectives:  The risk of prostate cancer among shift workers was examined in the present industry‐based retrospective cohort study.

An industry-based cohort study of the association between weight gain and hypertension risk among rotating shift workers.

Objectives:We investigated whether the association between shift work and hypertension is independent of weight gain. Methods:Subjects were 10,173 male employees (9209 daytime workers, 964 three-shift workers; mean follow-up period: 12.7 years). Hypertension was defined as systolic blood pressure 140 mm Hg or more or diastolic blood pressure 90 mm Hg or more. The risk of developing hypertension among shift workers was estimated using a Cox proportional hazards model with adjustment for several factors. Results:Analysis revealed that “shift work” (hazard ratio [HR]: 1.85; 95% confidence interval [CI]: 1.68, 2.03), “baseline body mass index” (HR: 1.13; 95% CI: 1.12, 1.15), and “increase in body mass index during follow-up” (HR: 1.15; 95% CI: 1.13, 1.17) were significant independent risk factors for hypertension. Conclusions:Shift work is a significant risk factor for hypertension that is independent of both starting weight and weight gained over years of work.

Retrospective cohort study of the risk of impaired glucose tolerance among shift workers.

OBJECTIVES The aim of this study was to investigate the effect of shift working on the risk of developing impaired glucose tolerance (IGT). METHODS This study comprised 6413 male employees (5608 daytime workers, 512 3-shift workers and 293 2-shift workers) whose work schedules remained constant during the follow-up period (mean follow-up period 9.9 years). IGT was defined as Hemoglobin A1c ≥ 5.9%. The Cox proportional hazards model was used to estimate the risk of developing IGT, after making adjustments for age, smoking, alcohol consumption, leisure-time physical activity, body mass index (BMI) and Hemoglobin A1c (HbA1c) at baseline. Analysis was additionally performed for a sub-cohort of 1625 workers with BMI of 20.0-25.0 kg/m² that did not change by >2.0 kg/m² during the follow up period. RESULTS The risk of developing IGT was significantly elevated among both 3-shift workers [hazard ratio (HR) 1.78, 95% confidence interval (95% CI) 1.49- 2.14] and 2-shift workers (HR 2.62, 95% CI 2.17-3.17). Significant elevations of the risk were still observed at the additional analysis on the sub-cohort (3-shift work: HR 3.55, 95% CI 2.02-6.25; 2-shift work: HR 4.86, 95% CI 2.62-9.01). CONCLUSIONS Both 2- and 3-shift workers were associated with a high risk factor of developing IGT compared to day workers. Moreover, 2-shift workers had a higher risk than 3-shift workers. The risk was observed even among workers whose body mass remained within the normal range.

A cross-sectional study of workplace social capital and blood pressure: a multilevel analysis at Japanese manufacturing companies

Objectives We examined the contextual effect of workplace social capital on systolic blood pressure (SBP). Design Cross-sectional. Setting A conglomerate from 58 workplaces in Japan. Participants Of the 5844 workers at a Japanese conglomerate from 58 workplaces, 5368 were recruited. Individuals who received drugs for hypertension (n=531) and who lacked information on any variable (n=167) were excluded from the analyses, leaving 4735 individuals (3281 men and 1454 women) for inclusion. Primary and secondary outcome measures Systolic blood pressure. Results The contextual effect of workplace social capital on SBP was examined using a multilevel regression analysis with a random intercept. Coworker support had a contextual effect at the workplace level (coefficient=−1.97, p=0.043), while a lack of trust for coworkers (coefficient=0.27, p=0.039) and lack of helpfulness from coworkers were associated with SBP (coefficient=0.28, p=0.002). Conclusions The present study suggested that social capital at the workplace level has beneficial effects on SBP.

Development and validity of a work functioning impairment scale based on the Rasch model among Japanese workers

Development and validity of a work functioning impairment scale based on the Rasch model among Japanese workers: Yoshihisa Fujino, et al. Department of Preventive Medicine and Community Health, University of Occupational and Environmental Health, Japan

Prospective Cohort Study of Work Functioning Impairment and Subsequent Absenteeism Among Japanese Workers.

Objective: This study examined the association of work functioning impairment as measured by work functioning impairment scale (WFun) and subsequent sick leave. Methods: A prospective cohort study was conducted at a manufacturer in Japan, and 1263 employees participated. Information on sick leave was gathered during an 18-month follow-up period. Results: The hazard ratios (HRs) of long-term sick leave were substantially increased for those with a WFun score greater than 25 (HR = 3.99, P = 0.003). The incidence rate ratios (IRRs) of days of short-term absence gradually increased as scores of WFun increased (IRR = 1.18, P < 0.001 in the subjects with WFun of over 25 comparing with those with WFun of 14 or less). Conclusions: Assessing work functioning impairment is a useful way of classifying risk for future sick leave among employees.

Evaluation and simplification of the occupational slip, trip and fall risk-assessment-test

Objective: The purpose of this investigation is to evaluate the efficacy of the occupational slip, trip and fall (STF) risk assessment test developed by the Japan Industrial Safety and Health Association (JISHA). We further intended to simplify the test to improve efficiency. Methods: A previous cohort study was performed using 540 employees aged ≥50 years who took the JISHA’s STF risk assessment test. We conducted multivariate analysis using these previous results as baseline values and answers to questionnaire items or score on physical fitness tests as variables. The screening efficiency of each model was evaluated based on the obtained receiver operating characteristic (ROC) curve. Results: The area under the ROC obtained in multivariate analysis was 0.79 when using all items. Six of the 25 questionnaire items were selected for stepwise analysis, giving an area under the ROC curve of 0.77. Conclusion: Based on the results of follow-up performed one year after the initial examination, we successfully determined the usefulness of the STF risk assessment test. Administering a questionnaire alone is sufficient for screening subjects at risk of STF during the subsequent one-year period.