Recently the mean birth weight (MBW) of Japan is on the decrease. This phenomenon started in 1976 and continues up to the present as of 1988. Various factors accounting for this phenomenon have been considered and discussed by several researchers. They were interested in social, cultural and economic factors as well as factors influencing community health status. Although the above factors seem to be important, one problem connected with calculation of MBW is worth discussing. The MBW was calculated from a frequency distribution because of a limitation of the source material. The accuracy of calculation of statistics from a frequency distribution depends on the assumption that few frequencies fall on boundaries, but birth weight measurements are apt to fall on figures having 0 at the end because of the properties of weighing scales. Suppose that the exact weight of an infant is 2996g. If his weight is read to the nearest figure having 0 at the end by rounding, it is recorded as 3000g on the birth certificate. Then, in a frequency distribution whose class interval is 500g, his weight is treated as 3250g in calculation of the mean. But some improvements of the methods of weighing, for example, utilization of a scale displaying a digital value of weight may result in a greater chance that his weight is recorded as 2996g. Then, in the same frequency distribution, his weight is treated as 2750g in calculation of the mean. Therefore, an improvement of the method of weighing produces the phenomenon that MBW decreases even if all the original birth weights did not change.
Exact relative frequency, recorded as just 2500g, that is mentioned secondarily in the Vital Statistics of Japan has been decreasing consistently since 1969. This year is the oldest in the above source having frequency distributions of single birth infants. This fact shows that methods of weighing have been improved as the years pass. In this paper we tried to correct MBW by using the relative frequency recorded as exactly 2500g. Two kinds of widths where rounding would be executed were estimated from a frequency polygon. We obtained the following results.
1) The correction equation is represented as ld approximately; where l is a class interval (500g in this paper) and d is calculated by d=Q/(p_a+p_a+1+Z) as a mean value in a certain sense and by d=2Q/(p_a+p_a+1+Z) as a maximum value. In the above equations, Q represents a relative frequency recorded as exactly 2500g, and p_a and p_a+1 represent relative frequencies of the class of 2000-2499g and that of 2500-2999g, respectively. The Z is a very small value calculated under an assumption about relative frequencies recorded as exactly 2000g and exactly 3000g, which are both unknown, and it is neglectable when the relative frequency recorded as exactly 2500g is small as in recent years.
2) Both corrected MBWs of Japan (single births classified by sex) have been changing similarly to the uncorrected MBW.
3) While the MBW of Japan (single births classified by sex) decreased only 63g (male) and 61g (female) from 1976 through 1988, the effect of the decrease of rounding is 11-24% of this decrement. From the above results, we assumed the existence of factors influencing the decrease of MBW of Japan other than rounding.

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To clarify risk factors and groups at high risk of tuberculosis, a study on tuberculosis was conducted in the former coalmining area of Chikuho, where the death rate from tuberculosis was high. The authors analysed 701 newly registered tuberculosis patients during the 5 years from 1982 through 1986 in Iizuka Health Center District in the Chikuho area, studied the geographical distribution of tuberculosis incidence in Fukuoka Prefecture, and compared the trends of tuberculosis incidence in Iizuka Health Center District, all Japan and Fukuoka Prefecture.
The results were as follows:
1) The incidence of tuberculosis in Iizuka Health Center District was higher than those both in all Japan and in Fukuoka Prefecture. The incidence in Iizuka Health Center District has not decreased since 1981. Therefore, the difference in tuberculosis incidence between Iizuka Health Center District, and all Japan and Fukuoka Prefecture has gradually become greater. The incidence of tuberculosis in 1986 was 81.6 (per 100, 000) in Iizuka Health Center District, 58.1 in Fukuoka Prefecture, 46.6 in all Japan.
2) A specific pattern was observed in the geographical distribution of tuberculosis incidence in Fukuoka Prefecture. A high incidence was concenrated in the former coalmining area of Chikuho.
3) The positive rate of tubercle bacilli (38.8%) was the same as that in all Japan. However, the positive rate was higher in age groups 10-49 than that in all Japan.
4) A total of 83.5% of tuberculosis cases were detected when visiting doctors, mainly with complaints of cough, fever and sputum. Only 6.9% of the patients were detected by screening examinations. This result shows that tuberculosis control activities in Iizuka Health Center District are inadequate.
5) Among male patients, 14.8% had pneumoconiosis. Pneumoconiosis appeared to be a risk factor for tuberculosis in those aged 50 and over.
6) In those aged under 60, 33.2% of tuberculosis patients were unemployed at the onset. Thus, socieconomic status seemed to be associated with developing tuberculosis.

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The authors conducted a case-control study on the relationship between socioeconomic factors and tuberculosis in the former coalmining area of Chikuho where tuberculosis incidence was high.
The cases were 292 newly registered tuberculosis patients in Iizuka Health Center District, in the former coalmining area of Chikuho. Controls were randomly selected from resident cards, matched for sex, age, and place of residence.
The results of comparing the cases with the controls were as follows:
1) Significantly more of the male cases had had long-term employment in coalmining. Exposure to dust is likely to be associated with the high tuberculosis incidence in males aged 50 or over.
2) The cases showed significantly higher unemployment levels and lower educational levels. Among females, more of the cases were unmarried or divorced, and a significantly higher proportion were receiving welfare benefits. The high incidence of tuberculosis is probably related to a low socioeconomic level resulting from closure of coalmines.
3) No difference was observed in working hours, night shifts, smoking rate, and drinking habits. These factors are unlikely to be singly related to the onset of tuberculosis.

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Calcium, phosphorus and vitamin D metabolism were examined in 21 male and 13 female subjects with renal tubular dysfunction in the cadmium-polluted Jinzu River basin in Toyama prefecture, Japan. Multiple proximal renal tubular dysfunction was detected in all subjects showing increased FEβ₂-m and FEua, generalized aminoaciduria and renal glucosuria. Reduced ability of tubular reabsorption of phosphate resulted in hypophosphatemia in 31% of the women. Despite decreased tubular reabsorption of calcium, the level of serum calcium remained normal in all subjects. Serum 1, 25-dihydroxyvitamin-D[1, 25(OH)₂D], which is produced in the proximal tubules through 1α-hydroxylation from 25-hydroxyvitamin-D[25OHD], was normal or increased to more than 60pg/ml. The serum level of 1, 25(OH)₂D was inversely related to creatinine clearance in both the men (p<0.05) and women (p<0.01). Serum iPTH was slightly increased to more than 0.9ng/ml, whereas the levels of other hormones, including 25OHD, calcitonin, thyroxine (T₄) and triiodothyronine (T₃) were normal. The serum alkaline phosphatase activity and serum osteocalcin concentration were significantly increased compared to those of controls in both sexes. Bone loss detected by the measurement of bone density was prominent in female subjects. These results support the hypothesis that the serum phosphate concentration is more important than the serum concentration of 1, 25(OH)₂D for abnormalities of bone metabolism in cadmium-induced renal tubular dysfunction.

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A study was carried out to examine the effects of forced running exercise in the growing stage in male ICR mice and of Astragalus membranaceus (As) on their immune functions. The mice were divided at 4 weeks of age into 4 groups. The first group of mice received forced running exercise (E-group), the second group was given As (As-group), the third group received the forced running exercise and was given As (E+As-group) and the fourth group was a control receiving no treatment. The exercise received was forced running at 15m/min on a flat floor without any slope for 60min a day. The mice of groups E and E+As were exercised 5 times a week for 12 weeks. The mice of groups As and E+As were given As p. o. at 200mg/kg per day (5 days/week) for 12 weeks.
The results obtained were as follows:
1. After 12 weeks of forced running exercise, the weight of the anterior tibialis muscle and succinate dehydrogenase activity in the anterior tibialis muscle increased significantly in groups E and E+As compared with the control group. Thymus weight showed a tendency to increase in groups E and E+As as compared with the control group.
2. The potentiation of the phagocytic function of the reticuloendothelial system examined by the carbon clearance method was seen in groups E, As and E+As.
3. Superoxide anion production of peritoneal macrophages significantly increased in groups As and E+As, but not in group E.
4. The acid phosphatase activity of peritoneal macrophages in groups E, As and E+As significantly increased compared with the control group.
5. Interleukin 1 production by macrophages remained in all groups.
6. The proliferation of splenocytes induced by Con A in groups E, As and E+As significantly increased compared with the control group.
These results suggested that forced running exercise in the growing stage in mice and the administration of As enhanced immune functions and that they might also intensify the functioning of the host defense system.

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In order to evaluate factors affecting visual and musculoskeletal symptoms by visual display terminal (VDT) operation, a questionnaire survey was conducted among clerical workers in Chiba university. The results were as follows:
1) Of these workers, 81.9% engaged in VDT operation. For most of the subjective symptoms, the prevalence rates tended to increase with the degree of VDT use.
2) These complaints were combined to give visual and musculoskeletal symptom scores. Both of the scores were higher among females than males, and the musculoskeletal symptom score was significantly higher. No difference was found in regard to age.
3) Analysis using log-linear models was performed to evaluate the effects of sex and age. The results showed that the visual and musculoskeletal symptom scores were significantly higher among the workers operating VDTs for one or more hours per day than among those who did not operate them at all. Analysis of the effects of VDT workloads revealed that VDT use for five or more days per week significantly increased the prevalence rates of both symptoms. Their use for less than fourr days per week affected neither of the symptoms. With regard to operating time per day or length of VDT use, no differences were found.
4) This investigation suggested that the VDT workloads were not so heavy and that the effects on each symptom were minor among the subjects of the present survey. However, it is important that consideration be given to ensure that the workloads for workers who operate VDTs every day not be too heavy.

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The purpose of this study was twofold, 1) to classify the body composition of college women into certain types by combining percent body fat, and lean body mass per unit of height and 2) to clarify the characteristics of physical fitness performance in each group, because we have as yet no reports on physical fitness in such a way.
The subjects were 205 college women (average age 19.1) in Morioka, Iwate, Japan, and we collected data on body forms and physical fitness performance of subjects in 1989 and 1990. We calculated body density by the SUZUKI-NAGAMINE skinfold thickness method for Japanese, and also % FAT by the BROZEK formula. In order to check significant differences of mean values for each type, we employed the t-test, and a statistically significant level of 0.05.
The findings were as follows;
1. We classified the body composition of college women into 9 types; Aa, Ab, Ac, Ba, Bb, Bc, Ca, Cb, Cc by combination of % FAT and unit LBM. Type Aa has much more % FAT and unit LBM, while type Cc has much less % FAT and unit LBM. We observed that each type has a particular body form; for example, type Aa students generally have average height but are heavier, whereas type Cc students are usually shorter and lighter.
2. Type Ba showed the best physical fitness performance of the 9 types. This type has a body composition of average % FAT and much more unit LBM. Type Ab, with much more % FAT and average unit LBM followed type Ba. We observed that a little too much body fat, is not always a negative factor in so far as there is a difinite level of the lean body mass needed for good physical fitness performance of college women.
3. Type Ac showed the worst physical fitness performance of the 9 types. This type has a body composition of much more % FAT and much less unit LBM. Type Cc, with much less % FAT and unit LBM showed considerably bad physical fitness performance as well. We observed that lean body mass is a very important factor, and the body composition with much more body fat and much less body mass is the poorest condition for the physical fitness performance of college women.

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An investigation on instrumentation of birth weight in obstetric facilities was made in the northern part of Fukuoka Prefecture from March 1989 to January 1991. A distribution of 3000 cases from 100 facilities was analyzed for the purpose of clarifying the reliability of the data.
The following results were obtained.
1) Birth weights measured by analogue scales (1530 cases) showed digit preference in all distributions of the whole, the lower three digits and the lower two digits. But those measured by digital scales (1470 cases) did not show any distortion in these three distributions.
2) There were significant differences among mean birth weights calculated from the intact data, and 50g-, 100g- and 500g-interval frequency histograms in analogue scales (p<0.01). But in digital scales there were no significant differences among mean birth weights. Rounding error was supposed to be one of the main causes of this discrepancy.
Digital scales are superior to other types of scales because they do not show distribution distortion of the data. The reliability of the birth weight data is different among the types of scales. We have to consider which type of scale is used when we refer to annual changes or differences among areas in mean birth weights.

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Using vital statistics (1981-1988) of the Japanese government, the mean birth weight (MBW) classified by sex was calculated from a birth weight distribution of the single births with 500g intervals for all Japan, prefectures and regions. These MBWs were linked with the MBW of 1969-1980 in our previous reports (Ref. 1)2)). The MBWs of single births for twenty years (1969-1988) were investigated and it was pointed out that the MBWs classified by area (all Japan, prefectures and regions) were on the decrease recently and that the areal differences of the MBW were becoming large.
For all Japan a secular change in the MBW was discussed for the term of a standard deviation, a skewness, a kurtosis, and relative frequencies of less than 2500g (weight class 1), those from 2500g to 3999g (weight class 2) and those of 4000g or more (weight calss 3). These investigations revealed that birth weights of Japan have had a tendency to have a small standard deviation, a negative skewness, and a large kurtosis. Weight class 1 decreased until 1976 and increased after this year. Weight calss 2 was on the increase up to 1988, and weight class 3 increased until 1973 and decreased afterward, as if it were accompanied by the MBW.
For the purpose of confirming the contribution of each weight class to the annual change of the MBW, an analytical method for the weight frequency distribution was proposed as follows. Let M, M', p_i and p_i' represent the MBW of a given year (year A), the MBW of an another year (year B), the relative frequency of the i-th weight class in year A and that in year B, respectively. Suppose that M _(i)" represents the MBW when only the i-th weight class has p_i as a relative frequency even in year B. Then, as the result of a fairly simple calculation, the difference between the MBW in year A and that in year B, M'-M, is obtained as follows; M'-M=∑(1-p_i')(M'-M_(i)"). Therefore, the amount (1-p_i') (M'-M_(i)") is able to be considered as a share of the i-th weight class in relation to the difference of M'-M. Acordingly, the share proportioned to the summation of the absolute amount, |(1-p_i')(M'-M_(i)")|/∑|(1-p_i')(M'-M_(i)")|, may represent the degree of the contribution of the i-th weight class to the difference, M'-M.
Dividing the twenty years into an MBW-increasing period (from 1969 to 1976) and an MBW-decreasing period (from 1976 to 1988), the above analysis was performed in these two periods for all Japan by sex. In both periods the change of the MBW was largely due to the change of the class weighing from 3500g to 3999g, and secondarily to the class weighing from 2500g to 2999g, from the point of view of the proportioned share. It is interesting that the third large proportion fell in the class weighing less than 2500g in the MBW-increasing period and that it fell in the class weighing 4000g or more in the MBW-decreasing period. These results were obtained for both males and females. In order to eliminate the bias from the difference of distribution classified by parity, the primiparous birth weight distributions from 1969 to 1988 of males of all Japan were analyzed. In this analysis the same results were obtained. Consequently, it was suggested that the above results were not due to a difference of distribution classified by parity.
Considering that it is important to reduce the number of low-birth-weight infants in maternal and child health practice and to get expectant mothers maintain a proper weight from the viewpoint of maternal and child health guidance, it seems that the change of the birth weight distribution for the last twenty years represents one of the good results of maternal and child health activity.

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