Published papers

Brain-derived neurotrophic factor (BDNF) is involved in the survival, development, and synaptic plasticity of neurons. BDNF is believed to be associated with the pathophysiology of psychiatric disorders. Several studies have suggested the relevance of DNA methylation in its promoter region with depression. Here, we report different methylation statuses in groups with different depressive scores or undergoing different levels of job-stress. DNA samples were extracted from the saliva of 774 Japanese workers, and the methylation status was determined using the Illumina HumanMethylation 450K Microarray. Depressive symptoms were measured using the Kessler's K6 questionnaire. Job-stress scales were assessed via a self-administered questionnaire. Independent DNA pools were formed based on K6 and job-strain scores, and the methylation levels were compared among these pools. The average DNA methylation rate was significantly decreased in the highest K6 score group compared to the lowest group (methylated signals, 14.2% vs. 16.5%, P=2·16×10 -198 ). This difference remained for the CpG island in the promoter region (10.4% vs. 5.8%, P=3·67×10 -133 ). Regarding the job-strain score, there was a slight increase in the methylation level of the whole gene in the group with the highest score compared to that with the lowest score; however, these groups showed no difference in the promoter region. Our results revealed significant changes in the DNA methylation status of the complete human BDNF gene in persons with depression compared to normal individuals, especially in the promoter region of exon 1. This indicates that DNA methylation in this gene is a promising biomarker for diagnosing depression. © 2014 The Authors.

© 2016 Frontiers Media S. A. The purpose of the study was to investigate the association between parental workaholism and child body mass index (BMI) among Japanese dual-income families. In 2011, 379 dual-income families from urban Tokyo with children aged 0-5 years were recruited for a baseline survey, and 160 (42.2%) were followed up in 2012. Demographics, workaholism, work demands, work control, time spent with children, and parental and child weights and heights were assessed using a questionnaire. Structural equation modeling was performed to determine the association between maternal and paternal workaholism in 2011 and child BMI in 2012, considering the mediating effects of time spent with children. Paternal workaholism showed a direct significant positive association with child BMI after 1 year (standardized coefficient: 0.19; p < 0.001), while maternal workaholism was not associated with child BMI. Both maternal and paternal time spent with children did not mediate the association. Paternal work demands showed a strong positive association with workaholism but paternal work control did not. Paternal, but not maternal, workaholism was associated with an increase in child BMI over 1 year. Interventions that target workaholism by reducing paternal work demands might be effective in preventing overweight in offspring.

© 2019 Japan Society for Occupational Health. Objectives: The aims of the study were to investigate the association between working hours, work engagement, and work productivity, and to examine if work engagement moderates the influence of working hours on work productivity. Methods: We used cross-sectional data from the Japanese occupational cohort survey, which involved 2093 employees in a manufacturing industry. Working hours were self-reported by the study participants. Work productivity was assessed with absolute presenteeism based on the scale of the validated Japanese version of World Health Organization Health and Work Performance Questionnaire (WHO-HPQ). Work engagement was assessed with the Nine-item Utrecht work Engagement Scale (UWES-9). Univariate and multivariable regression analyses were conducted to examine the association of working hours and work engagement with work productivity. We also carried out stratified multivariable regression analysis separately for those with high-work engagement and those with low-work engagement. Results: Working >40 to 50 hours per week and >50 hours per week were significantly positively associated with work productivity in univariate analysis. However, the significant association no longer held after adjusting for work engagement. Work engagement was positively associated with work productivity even after controlling for potential confounders. Working hours were not significantly associated with work productivity among those with high-work engagement or among those with low-work engagement. Conclusions: Working hours did not have any significant associations with work productivity when taking work engagement into account. Work engagement did not moderate the influence of working hours on work productivity, though it attenuated the relationship between working hours and work productivity.

Objectives:Recent epidemiological research in Europe has reported that two groups of job demands, i.e., challenges and hindrances, are differently associated with work engagement. The purpose of the present study was to replicate the crosssectional association of workload and time pressure (as a challenge) and role ambiguity (as a hindrance) with work engagement among Japanese employees. Methods:Between October 2010 and December 2011, a total of 9,134 employees (7,101 men and 1,673 women) from 12 companies in Japan were surveyed using a self-administered questionnaire comprising the Job Content Questionnaire, National Institute for Occupational Safety and Health Generic Job Stress Questionnaire, short 10-item version of the Effort-Reward Imbalance Questionnaire, short nine-item version of the Utrecht Work Engagement Scale, and demographic characteristics. Multilevel regression analyses with a random intercept model were conducted. Results: After adjusting for demographic characteristics, workload and time pressure showed a positive association with work engagement with a small effect size (standardized coefficient [β = 0.102, Cohen's d [d] = 0.240) while role ambiguity showed a negative association with a large effect size (β =20.429, d = 1.011). After additionally adjusting for job resources (i.e., decision latitude, supervisor support, co-worker support, and extrinsic reward), the effect size of workload and time pressure was not attenuated (β = 0.093, d = 0.234) while that of role ambiguity was attenuated but still medium (β =20.242, d = 0.609). Conclusions: Among Japanese employees, challenges such as having higher levels of workload and time pressure may enhance work engagement but hindrances, such as role ambiguity, may reduce it. © 2014 Inoue et al.

Based on a conceptual analysis, a two-dimensional self-report questionnaire for assessing workaholism (work addiction) is proposed, including (1) working excessively hard and (2) working compulsively. Using independent explorative and confirmative samples that include employees from The Netherlands (N = 7,594) and Japan (N = 3,311), a questionnaire is developed and psychometrically evaluated. Results show that both scales (five items each) are internally consistent and that the hypothesized two-factor structure fits to the data of both countries. Furthermore, convergent validity was shown with measures of excess working time and discriminant validity was shown with measures of burnout and work engagement. Workaholics who work excessively hard and compulsively have a high relative risk on burnout and a low relative risk on work engagement. It is concluded that the two-dimensional measure-dubbed the Dutch Workaholism Scale (DUWAS)-is useful tool in future (cross-cultural) research on workaholism. © 2009 SAGE Publications.

This study among 426 Japanese couples working in different occupational sectors tested the hypothesis that perspective taking moderates the crossover of work engagement. More specifically, we predicted that husbands' work engagement would cross over to their wives, particularly when wives scored high on perspective taking (the spontaneous tendency to adopt the psychological perspective of other people). A similar effect was predicted from wives to husbands. In addition, we hypothesized that the crossover effect would be most pronounced when both partners were high in perspective taking (i.e., a 3-way interaction effect). The results of moderated structural equation modeling analyses confirmed the moderating role of perspective taking, but only for women; women who took the perspective of their partner scored higher on engagement with increasing partner engagement. Moreover, the results showed that engagement crossover was strongest when both men and women were high (vs. low) in perspective taking. This 3-way interaction effect was found from husbands to wives, and vice versa. These findings expand the crossover literature by shedding light on the crossover process. © 2011 American Psychological Association.

"The Checklist for Evaluation of Mental Health Activities at the Workplace" was developed for workplace staff evaluating mental health activities in their own workplace. The validity and reliability of the checklist were examined and criteria for evaluation were developed for workplace/organization/companies with 50 or more employees in Japan. The checklist initially included 33 items covering seven major domains of occupational mental health, with a four-point response option, based on the Japanese Guideline for Worker Mental Health in the Workplace and a relevant literature review. A questionnaire was send to 60 members of the Occupational Mental Health Committee (OMHC) of the Japan Society for Occupational Health to ask their opinions on the checklist and on the minimum requirement for each item on the checklist; 30 (50%) responded. A random sample of 1,335 workplaces from a contractor list of workplaces for worker compensation insurance and a questionnaire was send to the personnel department to fill in the checklist; 412 (31.5%) responded and data from 335 of them with 50 or more employees were analyzed. Some OMHC members felt that one of the items (concerning the Total Health Promotion program) should be dropped; thus the checklist was revised to include 32 items, still covering the seven domains. Based on the workplace survey data, most domain scales showed internal consistency reliability at an acceptable level; explanatory factor analysis yielded a four-factor structure that was well concordant with the hypnotized seven-domain structure. Three levels of adequacy of mental health activities were set for each domain scale: "red" (inadequate), "yellow" (minimal), and "green" (adequate). One third of occupational health professionals from 49 workplaces rated the evaluation result based on the checklist as concordant with their view; 95% of them said the checklist would be useful in promoting occupational mental health activities. The study indicated that the checklist had reliability (based on internal consistency reliability) and content- and construct-validity (based on expert opinions, a factor-structure concordant with empirical data, and evaluation by workplace staff). The checklist seems useful in promoting occupational mental health activities.

An action checklist for improving the workplace environment by means of enhancing mental health of workers (Mental Health Action Check List: MHACL) was developed. The use of the checklist for primary prevention was examined. MHACL was developed through three steps: (1) Review of related references and collection of improvement examples for designing a draft MHACL; (2) pilot application of the draft at industrial workplaces and trials at workshops of occupational health staff; and (3) proposing a new MHACL for general use in industry. Workplace improvement actions related to mental health were listed in eight technical areas. From 84 workplaces in Japan, 201 such actions were collected. Typical improvement action phrases were extracted based on these examples, and a draft MHACL containing 40 generally applicable actions were prepared. This draft was applied to selected workplaces for its use as a tool for group discussion. Then, the utility of the checklist was discussed by 105 occupational health staff working in public service offices. The workshop suggested modifications of the draft MHACL including improved check items and usage procedures and the need to use easy-to-understand actions. The final version of the MHACL comprised 30 items in six technical areas: A) sharing work planning, B) work time and organization, C) ergonomic work methods, D) workplace environment, E) mutual support in the workplace, and F) preparedness and care. A new action checklist was proposed for use as a means of changing existing workplace environments and proposing practical actions for improving it. The checklist was confirmed to be useful for organizing workplace-level discussion for identifying immediate improvements at the workplace. The checklist is expected to be widely applied for promoting primary prevention measures in terms of better mental health.

This study aimed to investigate the reliability and construct validity of a new version of the Brief Job Stress Questionnaire (New BJSQ), which measures an extended set of psychosocial factors at work by adding new scales/items to the current version of the BJSQ. Additional scales/ items were extensively collected from theoretical job stress models and similar questionnaires in several countries. Scales/items were field-tested and refined through a pilot internet survey. Finally, an 84-item questionnaire (141 items in total when combined with the current BJSQ) was developed. A nationally representative survey was administered to employees in Japan (n=1,633) to examine the reliability and construct validity. Most scales showed acceptable levels of internal consistency and test-retest reliability. Principal component analyses showed that the first factor explained 50% or greater proportion of the variance in most scales. A scale factor analysis and a correlation analysis showed that these scales fit the theoretical expectations. These findings provided a piece of evidence that the New BJSQ scales are reliable and valid. Although more detailed content and construct validity should be examined in future study, the New BJSQ is a useful instrument to evaluate psychosocial work environment and positive mental health outcomes in the current workplace. © 2014 National Institute of Occupational Safety and Health.

© 2014 by National Institute of Occupational Safety and Health. This study was aimed to investigate the test-retest reliability and validity of a short version of the New Brief Job Stress Questionnaire (New BJSQ) whose scales have one item selected from a standard version. Based on the results from an anonymous web-based questionnaire of occupational health staffs and personnel/labor staffs, we selected higher-priority scales from the standard version. After selecting one item with highest item-total correlation coefficient from each scale, a 23-item questionnaire was developed. A nationally representative survey was administered to Japanese employees (n=1,633) to examine test-retest reliability and validity. Most scales (or items) showed modest but adequate levels of test-retest reliability (r>0.50). Furthermore, job demands and job resources scales (or items) were associated with mental and physical stress reactions while job resources scales (or items) were also associated with positive outcomes. These findings provided a piece of evidence that the short version of the New BJSQ is reliable and valid.

© Springer International Publishing Switzerland 2016. The present study aimed to investigate the reliability and construct validity of a new version of the Brief Job Stress Questionnaire (New BJSQ), which measures an extended set of psychosocial factors at work by adding new scales/items to the current version of the BJSQ. Additional scales/items were extensively collected from theoretical models of job stress and similar questionnaires in several countries. Scales/items were field-tested and refined through a pilot Internet survey. Finally, an 84-item standard version questionnaire, a 63-item recommended set, and a 23-item short version (141, 120, and 80 items in total when combined with the current 57-item BJSQ) were developed. A nationally representative survey was administered to employees in Japan (n = 1633) in 2010/2011 to examine the reliability and construct validity. As a result, most scales showed acceptable levels of internal consistency (Cronbach’s alpha) and test-retest reliability over one year. Principal component analyses showed that the first factor explained 50 % or greater proportion of the variance in most scales. A scale factor analysis and a correlation analysis showed that these scales fit the proposed theoretical framework. These findings provided a piece of evidence that the New BJSQ scales are reliable and valid. The New BJSQ can be a useful instrument to evaluate psychosocial work environment and positive mental health outcomes in the workplace.

© Kotaro Imamura, Toshi A Furukawa, Yutaka Matsuyama, Akihito Shimazu, Kazuto Kuribayashi, Kiyoto Kasai, Norito Kawakami. Originally published in the Journal of Medical Internet Research (http://www.jmir.org), 10.08.2018. This is an open-access article distributed under the terms of the Creative Commons Attribution License. Background: Previous randomized controlled trials (RCTs) have shown a significant intervention effect of internet-based computerized cognitive behavioral therapy (iCBT) on improving nonclinical depressive symptoms among healthy workers and community residents in a primary prevention setting. Time preference is one's relative valuation for having a reward (eg, money) at present than at a later date. Time preference may affect the effectiveness of cognitive behavioral therapy. Objective: This RCT aimed to test the difference of intervention effect of an iCBT program on improving nonclinical depressive symptoms between two subgroups classified post-hoc on the basis of time preference among workers in Japan. Methods: All workers in one corporate group (approximate n=20,000) were recruited. Participants who fulfilled the inclusion criteria were randomly allocated to either intervention or control groups. Participants in the intervention group completed 6 weekly lessons and homework assignments within the iCBT program. The Beck Depression Inventory-II (BDI-II) and Kessler's Psychological Distress Scale (K6) measures were obtained at baseline and 3-, 6-, and 12-month follow-ups. Two subgroups were defined by the median of time preference score at baseline. Results: Only few (835/20,000, 4.2%) workers completed the baseline survey. Of the 835 participants, 706 who fulfilled the inclusion criteria were randomly allocated to the intervention or control group. Participants who selected irrational time preference options were excluded (21 and 18 participants in the intervention and control groups, respectively). A three-way interaction (group [intervention/control] × time [baseline/follow-up] × time preference [higher/lower]) effect of iCBT was significant for BDI-II (t1147.42=2.33, P=.02) and K6 (t1254.04=2.51, P=.01) at the 3-month follow-up, with a greater effect of the iCBT in the group with higher time preference. No significant three-way interaction was found at the 6- and 12-month follow-ups. Conclusions: The effects of the iCBT were greater for the group with higher time preference at the shorter follow-up, but it was leveled off later. Workers with higher time preference may change their cognition or behavior more quickly, but these changes may not persist.