As a condition to achieving an agreement of recognition on the causal relationship in medicine, we firstly explained Hume's problem and counterfactual model. We, however, emphasized that we believe in the existence of causality on medical issues in our daily lives. Therefore, we illustrated conditions when we usually believe in causality. On the other hand, we criticized two well-known key phrases, “lack of mechanism in epidemiology” and “black box in epidemiology”, which have often been used in Japan for skeptic viewpoints against epidemiologic methods even if epidemiology is often used to elucidate a causal effect in medicine in the world. We emphasized that a priori determinations of levels for inference of mechanism is necessary. And, the level and feature of mechanism should be defined in concrete expressions. After explanation of these basic concepts, we mentioned a classic view on specific diseases and non-specific diseases which have not been sufficiently discussed enough yet in Japan. As an example, we used the statements in the Japanese Compensation Law for the Health Effect by Environmental Pollution. In Japan, the classification of these diseases has been confused with that between manifestational criteria of diseases and causal criteria of them. We described the basic concepts to illustrate the causal relationship between non-specific disease and its exposure by using attached figures. Actually, we cannot recognize disease occurrence as a specific disease for several reasons. We indicated that we can recognize the magnitude of effect by causal relationships in medicine as a quantitative continuous variable.

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The exposure to silica and related substances such as silicate (e. g. chrysotile asbestos; 3MgO⋅2SiO₂⋅H₂O) or silicone (-R₂Si-O-)_n, used in plastic surgery, has been known to induce autoimmune diseases. The pathogenesis of autoimmunity induced by such environmental factors, however, needs to be clarified.
On the other hand, details about the relationship between autoimmunity and defective functioning of the Fas-Fas ligand system have been analyzed.
In this report, we intend to summarize our results which suggest a suppressed apoptosis through the Fas-Fas ligand system in silicosis patients, and to speculate on the effects of silica on inappropriate cell survival which could induce the development of autoimmune reactions. We observed elevated levels of serum sFas and an increased expression of sFas mRNA in silicosis patients. sFas instead of membranous Fas binds competitively to the Fas ligand, and consequently, reduces the apoptosis of Fas positive cells.
In addition, we observed polyclonal activation of human T cells by silica and silicate in vitro. In such cases, many autoreactive clones could be activated simultaneously.
From these results, silica and silicate could play an important role in inducing autoimmune reactions by (1) repeated polyclonal activation of human T cells and (2) the suppression of apoptosis inducing the release of sFas into the sera of the patients.

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Serum carotenoid levels among residents with hyperglycemia who were screened in a health check-up program for the inhabitants living in a rural area of Hokkaido were compared with those with normal levels. Serum levels of α, β-carotenes and cryptoxanthin were lower among those with high HbA1c newly detected than among those with a normal level, whereas the serum lipid peroxide (TBARS) level was higher in the former than in the latter for both sexes. Among males who currently smoked and drank alcohol, the intake frequency of carrot or pumpkin was significantly lower for those with high HbA1c than for the others, although no significant differences of serum carotenoid levels were observed. For the diabetes mellitus patients who were consulted in this study, and who have already been under control in the clinic, no significant differences of serum levels of carotenoids, or lipids such as total cholesterol and TBARS were shown compared with other groups.
In conclusion, serum carotenoid levels might be a useful indicator of food intake and oxidative stress for the prediabetic condition since newly detected hyperglycemia tends to show lower serum antioxidant levels such as β-carotene, and higher serum lipid peroxide levels.

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This study was conducted to clarify the genetic and environmental factors for some problem behaviors during sleep in childhood, namely sleep talking, half-sleeping, night terrors and nocturnal enuresis. The subjects were 881 pairs of twins, consisting of 609 monozygotic (279 male-male, 330 female-female) and 272 dizygotic (86 male-male, 84 female-female, 102 opposite-sexed). They were all applicants to the junior high school affiliated with Tokyo University from 1981 to 1998. The twins' mothers had previously completed a medical questionnaire and had been interviewed by three to five interviewers. With regard to the above mentioned four traits, they selected one answer from the choices ‘often’, ‘sometimes’ ‘never’ and ‘unknown’ for each twin. The interviewer checked the answers and, where necessary, explained the meaning of any terms such as “night terrors”. Genetic analysis was performed as follows. First the answers were summarized in the form of a 2×2 contingency table; ‘often’ and ‘sometimes’ were included in one category. Then, tetrachoric correlations of the contingency table were calculated according to zygosity using the program package PRELIS2. Furthermore, covariance structure analysis was performed for several genetic models using the program package LISREL8. The results were as follows. Univariate genetic analysis showed that all four traits were under genetic control. Sleep talking, half-sleeping and night terrors were under strong or moderate genetic control. As to nocturnal enuresis, the genetic effect was moderate and shared environmental factors played an important role. Sex difference was observed in the case of half-sleeping and enuresis. Moreover these traits tended to occur together, and sleep talking, half-sleeping and night terrors shared common genetic and environmental factors in addition to specific genetic and environmental factors.

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For the people who live in cold region, residence quality is especially important to their health, not only from economical aspects such as heating costs in the winter, but also thermal sanitation. Thatched houses are not rare in the district areas. From the climatic or historical implication, old thatched houses are recently improved or rebuilt and people intend to use them. That is, improvements are carried out on such old houses, and the good points are utilized, and reconstruction undertaken, and the example of presenting the house adaptation is also mainly observed. In this study, the thermal sanitation of the indoor environment in the winter was mainly examined on the cases of thatched houses near Fukushima City. The thatched houses used as research objects, are over 100 years after construction and they were previously used as sericulture farmhouses. A temperature and humidity collector and an automatic recording thermo-hygrometer were used in the measurement of the air temperature and humidity. This study was carried out in winter, February and March. The temperature was considerably different according to various parts of the rooms and time, and the air temperature near the ceiling was higher generally than the lower parts of room, near the floor. In the research of the housing where large-scale reconstruction was made, the room temperatures of the living room and kitchen were comparatively high at the time when they were used. In the meantime, room temperatures in the washroom, bedroom, etc. were generally low, showing a changing pattern, which was almost parallel to the change of the outside ambient temperature. In the research of the housing where ceilings had been added and the hearth, etc. had been improved; the room temperatures of most rooms were the lowest in early the morning. The room temperature of the living room rose in the morning and evening where the family gathered, and it was especially higher in the evening, showing air tempemture from 12°C to 18°C. In the bedrooms, which did not use heating appliances such as oil heaters etc., the room temperature was generally low. In the present study, the room temperature of the living room was comparatively high and that of the bedrooms and lavatories in houses with inadequate heating system was low. Even if reconstruction or improvement of old houses is made, the thermal indoor condition is not sufficient. Consideration of thermal facilities of floor heating, etc, is necessary with the air-tightness of houses following reconstruction.

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The intention of this study was to examine the determinants of plasma fibrinogen concentrations in healthy Japanese male workers. A cross-sectional study was conducted in 1998 among 1, 044 (male 975, female 69) employees aged 30-59 years in Osaka, Japan. The overall mean value of plasma fibrinogen concentration was 236.4±47.6mg/dl. There was a dose-response relationship between cigarette smoking and plasma fibrinogen concentration. Plasma fibrinogen concentration was associated with age, body weight, body mass index, white blood cell count and CPITN score, and inversely associated with serum HDL cholesterol in male nonsmokers. Plasma fibrinogen was not related to physical exercise, alcohol consumption or dietary factors.
This study confirms the relationship of known coronary risk factors to plasma fibrinogen concentration in Japanese male factory workers, and suggests that smoking and periodontal disease are related to plasma fibrinogen concentrations.

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In this cross-sectional study, the bone mineral density of the calcaneus was investigated in healthy young (n=35, 22-33 years) and middle-aged (n=49, 45-59 years) men. The relationships among the bone mineral density, body fatness, physical fitness, physical activity in recent and past days, smoking, alcohol, and sex hormones (free testosterone, estradiol, and dehydroepiandrosterone-sulfate; DHEA-S) and sex hormone binding globulin were evaluated. The speed of sound (SOS), broadband ultrasound attenuation (BUA) and stiffness were measured by ultrasonic measurement.
There was no association between age and bone density in each group. In the young group, there was a positive correlation between the body mass index (BMI) and BUA and between the training time during junior high school and BUA, and an inverse correlation between alcohol consumption and SOS after adjustment for the confounding factors using partial correlation analysis. The level of DHEA-S was weakly but not significantly associated with BUA. In the middle-aged group, there was an inverse correlation between the waist to hip ratio and SOS, and between the height of jump and SOS after adjustment for the confounding factors using partial correlation analysis.
These results suggest that different factors may affect bone density in the young and middle-aged men. In young men, the higher BMI and the longer training time during boyhood may have a positive effect, and heavy alcohol consumption may have a negative effect on bone density. In middle-aged men, abdominal fat accumulation has a negative effect and leg muscle power has a positive effect on bone density.

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