The recruitment and training of early-career researchers are important for the development of science, especially in countries with low birth rates, such as Japan. In several academic societies for social medicine, early-career researchers have formed associations for the purposes of networking and career development. However, to date, little information about the activities of these associations has been shared. Therefore, we organized a symposium at the 93rd Annual Meeting of the Japanese Society for Hygiene (March 4, 2023) to introduce the early-career researcher associations that have been formed within five academic societies namely the Japanese Society for Hygiene, Japan Epidemiological Association, Japan Society for Occupational Health, Japan Society for Medical Education, and Japan Society for Healthcare Administration. In this paper, we summarize the activities, challenges, and future prospects of each association and their strategies for future development and collaboration on the basis of presentations and discussions at the symposium.

Even today, more than 60 years after the discovery of Minamata disease, many controversies continue to arise from various viewpoints. Recently, Dr. Shigeru Takaoka has published a book entitled “Minamata Disease and the Responsibility of Medical authorities” as a summary of his and colleagues’ previous works in which he presented their objections to past academic theories. We, who were also engaged in this research at Kumamoto University, would like to address some substantial viewpoints. Drs. Nishimura and Okamoto clarified why a series of cases that were clearly Minamata disease were found only in the Minamata plant from late 1950 to 1975, even though many acetaldehyde plants have been operating in Japan for many years. Dr. Takaoka ignored this very important issue and we point out the lack of reliability of his data from their health examination of “10,000” people. From the pathology perspective, Dr. Takaoka mis­understood the location and plasticity of neurons. From a clinical viewpoint, he mentioned the poor evidence for the characteristics and courses of the patients’ clinical symptoms.

Objectives: We aimed to investigate the psychosocial factors for postpartum depression as indicated by a high score of the Edinburgh Postnatal Depression Scale (EPDS), including marital relationship and social support. Relevant factors for antenatal depression were also analyzed.

Methods: Thirty-five wife-and-husband pairs who visited University Hospital A for the wife’s antenatal health check-up participated in a questionnaire survey using the Japanese version of the EPDS. Social support from the wife’s husband, kins, and others including friends at the third trimester of pregnancy and 1 month after birth was assessed. The Marital Love Scale (MLS) was also used, and two marital relationship questions were asked regarding the husband’s and wife’s considerate actions toward each other during pregnancy. Binary logistic regression analysis was conducted to determine adjusted associations between higher EPDS scores (≥5 for postpartum depression and ≥7 for antenatal depression) and indicators for social support and marital relationships.

Results: The most relevant factor for higher postpartum EPDS scores was a higher antenatal EPDS score, followed by the couple’s poor communication skills (the wife did not feel any appreciation from her husband) during pregnancy and no support from the wife’s husband during the postpartum period. The wife’s poor marital communication skills and the husband’s low MLS scores during pregnancy were associated (borderline significance) with the wife’s higher antenatal EPDS scores.

Conclusions: A good marital relationship before birth and support by the husband after birth may be important for preventing postpartum depression.

There are several basic prerequisites for the risk assessment of combined exposures to pesticides and dioxins using human health effects as the endpoint. First, all the target chemical substances exert the same toxicity to humans through the same mechanisms. Second, there is a linear dose–response relationship between the toxicity and effects of individual chemicals. With these two prerequisites, the effects of combined exposures are estimated as the sum of the toxicities of individual chemicals. For example, the toxicities of dioxins are calculated using their toxic equivalent quantities (TEQ) by considering the assigned toxic equivalent factor (TEF) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) set individually from their isomers and homologs. In conventional epidemiological studies, when the impact of each of multiple chemical substances is examined, methods such as multiple regression analysis or using a generalized linear model (GLM) have been used on the basis of the same prerequisites. However, in practice, some of the chemicals exhibit collinearity in their effects or do not show a linear dose–response relationship. In recent years, there have been several methods developed in the field of machine learning being applied to epidemiological research. Typical examples were methods using Bayesian kernel machine regression (BKMR) and weighted quantile sum (WQS), and the shrinkage method, i.e., using the least absolute shrinkage and selection operator (Lasso) and elastic network model (ENM). In the future, while taking into account the findings of experimental studies in biology, epidemiology, and other fields, it is expected that various methods will be applied and selected.

The aim of this study was to investigate the relationships of dietary intake, exercise, and menstrual regularity with bone density. In 81 female university students, the osteo-sono-assessment index (OSI) was determined by quantitative ultrasonography. In addition, a questionnaire on the intake of calcium, vitamin D, and phosphorus, exercise experiences in junior high school and high school days, and menstrual regularity was administered. The OSI was higher in the group that had the habit of exercising in junior high school and high school. Furthermore, the higher OSI was associated with higher vitamin D intake and lower phosphorus intake. These findings suggest the importance of exercise and dietary intake for improving bone density.

Many developed countries, including Japan, have capitalist economies based on market principles. In capitalism, businesses try to develop new products and increase their added value, and expand the market in order to generate new profits. Owing to the universalization of capitalist efficiency, our daily lives are becoming condensed to only the necessary things in life. In addition, the advancement of science and technology, which is the driving force behind the expansion of profits, has forced people to become obsessed with new technology and information, and as a result, we have also lost our mental comfort. In this paper, first, we explain the time required to secure the energy necessary for human survival throughout human history. Second, we describe labor productivity with the emergence and development of capitalism. Third, we explain the difference between essential time and pressure-free time, and consider the necessity of pressure-free time during working hours. Finally, we discuss the relationships among pressure-free time, presenteeism, and work engagement.

Objectives: The Ministry of Health, Labour and Welfare (MHLW) states that it is an important issue to realize a work environment where people find their job worth doing, and the MHLW utilizes work engagement as the concept of a job worth doing. In this study, we aimed to clarify the factors related to work engagement in occupational health nurses from both aspects of work environmental and individual factors.

Methods: An anonymous self-administered questionnaire was mailed to 2,172 occupational health nurses who belonged to the Japan Society for Occupational Health and were in charge of practical work. Among them, 720 responded and their responses were analyzed (valid response rate: 33.1%). The Japanese version of the Utrecht Work Engagement Scale (UWES-J) was used to measure their feelings on whether their job is worth doing. Question items at three levels, namely, work level, department level, and workplace level, were selected from the new brief job stress questionnaire as the work environmental factors. Three scales, namely, professional identity, self-management skills, and out-of-work resources, were used as the individual factors. Multiple linear regression analysis was performed to examine the factors related to work engagement.

Results: The mean total score of UWES-J was 57.0 points, and the mean item score was 3.4 points. Among attributes, age, having children, and the position of chief or above were positively correlated to the total score, but the number of occupational health nurses in the workplace was negatively correlated to the total score. Among work environmental factors, work-self balance (positive), which is a subscale at the workplace level, and suitable jobs and opportunities to grow up, which are the subscales at the work level, were positively correlated to the total score. Among individual factors, self-esteem as a professional and self-improvement to be professional, which are the subscales of the professional identity, and problem resolution, which is a subscale of self-management skills, were positively correlated to the total score.

Conclusions: In order for occupational health nurses to find their job worth doing, it is desirable that they will have options to choose diverse and flexible work styles, and that their employers will establish a work-life balance for the entire organization. It is preferable that the occupational health nurses can self-improve, and that their employers will provide opportunities for them to develop professionally. The employers should also establish a personnel evaluation system that allows for promotion. Results also suggest that the occupational health nurses need to improve their self-management skills, and that the employers should assign them to positions suitable to their abilities.