The measurement of heart rate variability (coefficient of variation of ECG R-R intervals) provides a promising approach for the objective assessment of the autonomic nervous function. It is noninvasive and clinically practical, although it tends to be distorted by confounding factors such as age, tobacco and alcohol. In particular, two components of the respiratory sinus arrhythmia with a high frequency (HF) of 0.15-0.4Hz and Mayer wave related sinus arrhythmia with a low frequency (LF) of 0.04-0.15Hz in the heart rate variability, which were computed by autoregressive spectral and component wave analyses, reflect parasympathetic and sympathetic activities, respectively. This article is intended to present an overview of research, utilizing this frequency domain method, in environmental and occupational health. The available literature, addressing the impact of some chemicals and work-related factors on the human autonomic nervous system, indicates that parasympathetic activity appears to be more vulnerable to these factors than does sympathetic activity. Since decreased cardiac vagal tone is associated with an increased risk of sudden cardiac death or coronary heart disease, attention should be directed to further discovery of hazardous factors in the environment and workplace, which may pose potential autonomic neurotoxic risks.

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Ecological correlation analysis was made between the source of drinking water and standardized incidence ratios (SIRs) of malignant neoplasms registered in Niigata, Japan. The purpose of this study was to find out some clues for generating a working hypothesis that the contamination of drinking water with environmental chemicals especially of endocrine disrupting chemicals in big rivers may be related to the occurrence of cancers.
Sources of drinking water in the year 1974 were classified into two categories; one from the Shinano and Agano and their down-stream rivers, and the other from small rivers flowing into these big rivers, rivers originating from the mountain areas, underground and reservoirs (The other group). After excluding registered cases under 20 years of age, the registry data (1992-94) were sub-divided into two categories according to the source of drinking water.
The SIRs were calculated by using two different standard populations; Niigata total and “The other group”. All of the sites were examined in the former standard. In the latter case, however, 12 and 9 sites in males and females, respectively were selected based on the assumption that the expected numbers in each age group totaled 5 or over when there were more than 200 registered patients as a total. Concerning the judgment for the significant association in the former standard, we considered the presence of positive associations when both of the SIRs in the two categories were significantly different from the Niigata total population (p<0.05 by χ² test).
Of the 33 sites in males, the following sites were correlated with the source of drinking water; tongue, colon, rectum, gallbladder, etc., prostate, kidney, etc. and all sites. Of 35 sites in females, those were the colon, gallbladder, etc., bronchus and lung, breast, corpus uteri, thyroid and all sites.
Of the 12 and 9 respective sites subjected to the second analysis, positive associations were observed in the following: esophagus, colon, rectum, liver, gallbladder, etc., bronchus and lung, prostate, bladder and all sites in males, and colon, rectum, gallbladder, etc., bronchus and lung, breast and all sites in females.
Final conclusion, however, should be waived until the consistency of association can be confirmed by using more reliable incidence data, because the difference in the death certificates only (DCO) rate between the two groups might have played as a bias. The use of mortality data may be an alternative way to evaluate the present findings in terms of the consistency of association.

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Objective: The purpose of this study was to find whether the number of incidents of Creutzfeldt-Jakob disease has increased during the last decade in Japan.
Methods: The chronological trend was observed by examining the data from a nationwide epidemiologic survey conducted by a special committee sponsored by the Ministry of Health and Welfare of Japan in May 1996. The subjects of the survey were patients with Creutzfeldt-Jakob disease who had been diagnosed between January 1985 and May 1996. Although the number of patients reported each year increased continually during the 11-year 5-month period, there were two issues that remained to cast doubt on the accuracy of this apparently obvious chronological trend: (1) the existence of hospitals that did not respond to the survey, and (2) the existence of hospitals where no information was available before a specific time during the observation period. To make up for the incomplete data, the following two methods were proposed: (1) for those hospitals where the precise annual incidence was not known, the average annual incidence for those years when the information was available should be used to make up for the missing data and (2) when a hospital did not have the information for certain years, it would be considered to be a nonrespondent for those years; the response rate should be calculated year-by-year; then the total number of patients should be obtained by the reported number of patients divided by the response rate. The first method underestimates the annual trend if a trend does exist. To evaluate the trend mathematically, linear regression and quadratic regression models were used, in which the independent variable was the calendar year, the dependent variable, the number of patients.
Results: With either method, a trend for increases in incidence was noted. Statistical significance was obtained for the increasing trend in each model. It was found that the quadratic regression model was a better fit than the linear model.
Conclusion: The incidence of Creutzfeldt-Jakob disease in Japan has increased during the last decade.

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This study was conducted through anonymous questionnaires in order to compare the smoking habits of nursing school students with those of nursing college students, and to identify factors that might possibly indicate causes of smoking habits, among students of two major courses (a 3-year nursing school course and a 4-year nursing college course) for becoming nurses. The subjects were students in two nursing schools and two nursing colleges in the Tokyo Metropolitan area.
The results showed that the smoking prevalence among nursing school students in the first to the third grades was 26%, and that among nursing college students of the same grades was 12%. As to factors related to smoking habits of the students the smoking patterns of mothers and friends were shown to largely influence those of the nursing students. Among nursing college students, 21% agreed to a smoking ban in their schools, compared with 14% of the nursing school students.

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In 1981, the soil of cadmium (Cd)-polluted rice fields was replaced with new soil in Kashine, a Cd-polluted district located on Tsushima Island, Nagasaki Prefecture, Japan. Consequently, the average dietary Cd intake among the inhabitants decreased from 215μg/day in 1969 to 106μg/day in 1983. The authors investigated the health status of Kashine inhabitants before and after the reduction of Cd intake. Concentrations of β₂-microglobulin in urine (U-β₂-mg) and Cd in urine (U-Cd), hair (H-Cd) and blood (B-Cd) were measured on 35 inhabitants in 1979 and 1996.
The geometric mean of U-β₂-mg concentration for 9 subjects with U-β₂-mg levels≥1, 000μg/g creatinine (μg/g cr) in 1979 increased by approximately 2.5-fold in 1996. Meanwhile there was littl echange in the geometric mean for 26 subjects with U-β₂-mg levels<1, 000μg/g cr in 1996. It was concluded that renal tubular dysfunction among Cd-exposed inhabitants was irreversible and progressive, even after dietary Cd intake decreased.
The geometric mean of U-Cd concentration decreased significantly from 11.0μg/g cr in 1979 to 6.3μg/g cr in 1996. The decrease in U-Cd concentrations was significantly greater among inhabitants with U-β₂-mg levels≥1, 000μg/g cr than among those with U-β₂-mg levels<1, 000μg/g cr (p=0.03). From these results, it was considered that the level of U-Cd was more decreased by the presence of renal tubular dysfunction.
The geometric mean of H-Cd concentration decreased significantly from 109.1μg/kg in 1979 to 55.1μg/kg in 1996. However, it was unclear whether the decrease of H-Cd depended on the decrease of dietary Cd intake, decrease of body burden or both, because U-Cd concentrations also decreased by approximately 43% during this period. H-Cd concentration was weakly and positively correlated with U-Cd (r=0.38∼0.44), an indicator of body burden of Cd. These results suggested that H-Cd concentration was influenced by the body burden of this metal.
The geometric mean of B-Cd concentration in 33 inhabitants was 5.7μg/l in 1996. The geometric mean was signifcantly greater in subjects with initial U-β₂-mg levels≥1, 000μg/g cr than in those with U-β₂-mg levels<1, 000μg/g cr. A close positive correlation was found between B-Cd concentrations and U-Cd (r=0.70, p<0.01). It was suggested that the body burden influenced the levels of B-Cd as well as U-Cd, many years after Cd exposure had decreased.

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The relationship among subjective symptoms of fatigue, subjective fatigue feeling, and life habits of high school and college students
The purpose of this study was to examine the relationship among subjective symptoms of fatigue (SSF), subjective fatigue feeling (SFF), life habits (behavioral patterns (BP) and life-style consciousness (LC)) in male students.
A questionnaire on SSF, SFF, fatigue content, BP and LC was administered to 1802 male students aged 15-20yr, and data from 1792 properly completed questionnaires was analyzed.
The results were:
1) Students experience high SFF from daily activity. Students with a higher SFF tend to have more complaints of SSF, especially symptoms of languor, but the relationship between SFF and symptoms of irritation and physical disintegration are low.
2) Relationships between SFF and BP and LC are relatively low, except for physical condition. Even if the BP is successful, student's SFF is relatively high.
3) Subjective degree of health and physical condition relate highly to SSF. Exercise habits relate to loss of vigor, dietary habits to languor, loss of vigor, drowsiness and a decrease in concentration, and LC to SSF except for languor. It was inferred that SSF is influenced by BP and LC.

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