日本衛生学雑誌 Vol. 72(2017) No. 3

Methylmercury, the causative agent of Minamata disease, can easily penetrate the brain, and adult-type Minamata disease patients showed neurological symptoms according to the brain regions where the neurons, mainly in the cerebrum and cerebellum, were damaged. In addition, fetuses are exposed to methylmercury via the placenta from maternal fish consumption, and high-level exposure to methylmercury causes damage to the brains of infants. Typical patients with fetal-type Minamata disease (i.e., serious poisoning caused by in utero exposure to methylmercury) were born during the period of severe methylmercury pollution in 1955–1959, although they showed no abnormality during gestation nor at delivery. However, they showed difficulties in head control, sitting, and walking, and showed disturbances in mental development, these symptoms that are similar to those of cerebral palsy, during the growth periods after birth. The impaired development of fetal-type Minamata disease patients was one of the most tragic and characteristic feature of Minamata disease. In this review, we first summarize 1) the effects of prenatal methylmercury exposure in Minamata disease. Then, we introduce the studies that were conducted mainly by Sakamoto et al. as follows: 2) a retrospective study on temporal and regional variations of methylmercury pollution in Minamata area using preserved umbilical cord methylmercury, 3) decline in male sex ratio observed in Minamata area, 4) characteristics of hand tremor and postural sway in fetal-type Minamata disease patients, 5) methylmercury transfer from mothers to infants during gestation and lactation (the role of placenta), 6) extrapolation studies using rat models on the effects of prenatal methylmercury exposure on the human brain, and 7) risks and benefits of fish consumption.

The outbreak of itai-itai disease, which is the most severe stage of chronic cadmium poisoning, has occurred in the cadmium-polluted Jinzu River basin in Toyama. In this area, the river was contaminated by slags from a mine upstream; consequently, the soil in rice paddies became polluted with heavy metals including cadmium through irrigation water streams from around 1910 to the 1960s. The inhabitants of the Jinzu River basin used the river water for drinking and cooking until around 1960. In this paper, we review the geographical features of the Jinzu River basin and the endemic area of itai-itai disease, and reevaluated the studies conducted in 1970’s by the Toyama Institute of Health, because these studies have revealed a clear relationship between renal dysfunction or occurrence of itai-itai disease and exposure to cadmium through irrigation water streams.

During the 1960s, the concentrations of air pollutants, particularly that of sulfur dioxide (SO₂), were extremely high in many industrial cities in Japan, and the prevalence of bronchial asthma and chronic bronchitis increased among residents living in the cities. To evaluate the effects of air pollution on respiratory diseases, many epidemiological studies were conducted, and the findings played an important role in the regulatory control of air pollution. After 1970, the concentration of SO₂ has decreased markedly, and its adverse health effects have been minimized. On the other hand, the increasing automobile traffic in Japan has caused considerable increases in concentrations of air pollutants, such as nitrogen oxides (NOx) and particulate matter (PM). The large-scale epidemiological studies conducted in Japan showed that traffic-related air pollution was associated with the development of asthma in school children and the persistence of asthmatic symptoms in preschool children. In recent years, however, the concentrations of NOx and PM have gradually decreased, since control measures based on the Automobile NOx/PM law were enforced in 2001. At present, the adverse health effects of airborne fine particulate matter (PM_2.5) and photochemical oxidants have become a major concern. These air pollutants consist of not only emissions from primary sources but also secondary formations in air, and have spread worldwide. Both short- and long-term exposure to these air pollutants are reported to increase the risk of respiratory and cardiovascular diseases in the population. Therefore, global efforts are necessary to reduce the health risk of these air pollutants.

Objectives: The objective of this study is to examine the factors that influence the operation income and expenditure balance ratio of school corporations running university hospitals by multiple regression analysis.

Methods: 1. We conducted cluster analysis of the financial ratio and classified the school corporations into those running colleges and universities.

2. We conducted multiple regression analysis using the operation income and expenditure balance ratio of the colleges as the variables and the Diagnosis Procedure Combination data as the explaining variables.

3. The predictive expression was used for multiple regression analysis.

Results: 1. The school corporations were divided into those running universities (7), colleges (20) and others. The medical income ratio and the debt ratio were high and the student payment ratio was low in the colleges.

2. The numbers of emergency care hospitalizations, operations, radiation therapies, and ambulance conveyances, and the complexity index had a positive influence on the operation income and expenditure balance ratio. On the other hand, the number of general anesthesia procedures, the cover rate index, and the emergency care index had a negative influence.

3. The predictive expression was as follows.

Operation income and expenditure balance ratio = 0.027 × number of emergency care hospitalizations + 0.005 × number of operations + 0.019 × number of radiation therapies + 0.007 × number of ambulance conveyances – 0.003 × number of general anesthesia procedures + 648.344 × complexity index – 5877.210 × cover rate index – 2746.415 × emergency care index – 38.647

Conclusion: In colleges, the number of emergency care hospitalizations, the number of operations, the number of radiation therapies, and the number of ambulance conveyances and the complexity index were factors for gaining ordinary profit.

Objectives: To grasp the colonization status of Trichophyton in terms of spreading rate, we investigated the intergenerational epidemiological difference in the spreading rate of Trichophyton from teenagers to the elderly aged over 65. In addition, the elderly people were divided into two groups: those living at nursing homes and those living at their homes. We compared the two groups in terms of the difference in the spreading rate of Trichophyton.

Methods: Spreading rate was investigated by identifying the fungi collected by the cotton swab sampling method. The correlation between the responses to the questionnaire survey, which was conducted after the sample collection, and the spreading rate of Trichophyton was analyzed.

Results: The spreading rate of Trichophyton was 23.3%. It was confirmed that the spreading rate in general adults was 9.1%, whereas that in elderly people was 40.8%, which is significantly high. Also, it was confirmed that T. mentagrophytes shows a higher spreading rate among general adults, whereas T. rubrum shows a higher spreading rate among the elderly. Between the elderly living at nursing homes and those living at their homes, although no statistically significant difference was confirmed, the former tended to show a higher spreading rate than the latter. Also, the results of this study showed that spreading rate of Trichophyton and the detachment of the skin of the toes were significantly related.

Conclusions: We found that the risk of spreading of Trichophyton increases with age. Particularly among elderly people aged over 65, taking some actions that prevent the spread of tinea pedis is recommended.

Objectives: We examined the relationship between a physical activity monitor, which measures physical activities and health behavioural factors, and behavioural changes in 70 first-year university students who consented to participate among 80 students (recovery rate, 87.5%).

Methods: We evaluated Pearson’s correlation coefficients using the Mann-Whitney U-test for changes in health behavioural factors and self-efficacy and performed binomial logistic regression analysis with health behavioural factors and self-efficacy as dependent variables and life improvement effects as explanatory variables.

Results: The analysis revealed a positive correlation among five items of expectations of life improvement, health behavioural factors and self-efficacy. The score of “health behaviour and expectations of life improvement effects” was higher than those of health behavioural factors and self-efficacy. Binomial logistic regression analysis revealed that self-efficacy is related to health behavioural factors, health behaviour and expectations of life improvement effects.

Conclusions: Using the physical activity monitor to confirm behavioural science theory, health behavioural factors, self-efficacy and health behaviour are found to be effective for young adults to motivate themselves to maintain healthy behaviours.