Dietary and smoking habits were examined in 66, 707 participants in a mass screening test for stomach cancer in Saitama, Japan. Eighty-eight participants with stomach cancer, diagnosed by barium X-ray examination and histologically verified after endoscopic examination, were compared with the remaining 66, 619 participants, in a case-control study. In a food consumption frequency questionnaire, dietary habits were investigated on the basis of intake of six individual food items : rice, miso soup, boiled fish, pickled vegetables, nuts, and seaweed ; and seven food groups : potatoes, soybean products (except miso soup), fruits, green-yellow vegetables, white vegetables, raw vegetables, and fish/shellfish (all types) ; together with current cigarette smoking status and individual preference for salty foods. There was no substantial association between the risk of stomach cancer and the consumption of any dietary item, except for the consumption of rice (four or more bowls per day, RR=0.2 ; CI : 0.1 to 0.6). Neither was an increase in risk from cigarette smoking found. The risk score assessment revealed no correlation between risk and risk scores. In spite of the limitations of the present study, our findings seem to support the view that the lifestyles of stomach cancer patients found in the mass study were different from those of stomach cancer patients found in hospitals. J Epidemiol, 1994; 4 : 59-63.

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To explore risk factors for female breast cancer, a hospital-based case-control study was conducted in Tokyo, from 1990 to 1991. Information on potential risk factors was obtained by a selfadministered questionnaire from 5, 084 out-patients. Of the patients, 300 incident breast cancer cases were recruited, and 900 age-matched controls were randomly selected. Following significant findings emerged : (a) A large number of livebirths was associated with a decreased risk in premenopausal women (relative risk (RR) for 3 or more births relative to none : 0.24; 95% confidence interval (CI): 0.08-0.65). (b) In premenopausal women, regular menstrual cycle increased the risk (2.50; 1.16-5.38). (c) Current smokers experienced an increased risk (1.63; 1.11-2.39). (d) Heavy weight was associated with a greater risk of postmenopausal breast cancer: RR for those weighing 70 kg or more relative to those weighing 50 kg or less being 4.82 (1.53-15.2). (e) The later the age at first livebirth, the higher the postmenopausal breast cancer risk (2.85; 1.16-6.99; 3.54; 1.03-12.2 for ages of 30-34 and 35 years and more, respectively). J Epidemiol, 1994; 4 : 65-71.

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Environmental (c²) and genetic (h²) effects on high density lipoprotein (HDL) constituents of children at early adolescence were estimated in 149 Japanese triads composed of the father, the mother and their one fifth-grade schoolchild. Dietary, alcohol drinking, and cigarette smoking habits as well as physical activity were inquired through a questionnaire. Mother-child correlation was significant for all HDL constituents, but father-child correlation was significant only for apolipoprotein (Apo) A-I and spouses' correlation, only for Apo A-II. Children's dietary habits were closer to mothers' than to the fathers'. Among environmental factors significantly related to HDL constituents by multiple regression, however, there was none shared by the family members suggesting that individual rather than shared factors were more influential. When children's HDL constituents were regressed by their environmental factors and parents' residuals obtained as indices for genetic factors, mothers' residuals contributed significantly to HDL cholesterol (HDLG) and Apo A-I, but fathers' did not. For HDLC of children, c² and h² estimated by the coefficient of determination were 0.083 (p <0.05) and 0.097 (p <0.05), respectively. They were 0.075 (p <0, 05) and 0.022 (NS) for Apo A-l and 0.085 (p<0.05) and 0.046 (p<0.05) for Apo A-ll. Thus, HDLC was affected more by genetic factors and less by environmental ones when compared with Apo A-land A-II. J Epidemiol, 1994; 4 : 73-82.

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A population-based cross-sectional study of the association between bone mineral density (BMD) and several physical factors was conducted on the Japanese community elderly in 1991. The study comprised 387 participants living in the urban community of Tokyo. BMD was measured on the third lumbar vertebra with a lateral projection by dual energy X-ray absorptiometry fixed in a van (mobile DXA).
The mean BMD declined with aging in both males and females except at age-group 80-84 in males. Males had significantly higher BMD in average than females in each age-group. In univariate analysis, such many physical factors as height, weight, body mass index (BMI), grip strength, walking speed in maximum walking, serum albumin, serum intact parathyroid hormone (intact-PTH), masticatory ability and age showed significant association with BMD. Multiple regression analysis revealed that age (inversely) and BMI (directly) had significant association with BMD in both sexes. In addition, serum albumin in males and height, intact-PTH and masticatory ability in females remained as significant contributors to BMD. J Epidemiol, 1994; 4 : 83-89.

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Prevalence of low birth weight infants in Japan has been increasing, although infant mortality is the lowest in the world. We conducted a population based case-control study to clarify risk factors for low birth weight infants in Japan. Information was obtained by questionnaire. The response rate was 78.9% from 402 cases and 804 controls.
The majority of low birth weight infants belongs to full-term case group. This is considered to be an important factor for low infant mortality in Japan. We examined potential risk factors by a multiple logistic regression model. Lower maternal academic career and toxemia were identified as significant risk factors for pre-term low birth weight infants, while maternal shorter height, lower prepregnancy weight, maternal smoking and employment during pregnancy and hypertension were identified as significant risk factors for full-term low birth weight infants. The Japanese small physique and prevalent hypertension are considered to be causes for the high prevalence of low birth weight infants. J Epidemiol, 1994; 4: 91-98.

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The hepatitis B virus surface antigen (HBsAg) and its antibody (anti-HBs) were evaluated among 262 chronic hemodialysis patients in two hemodialysis units located in Fukuoka, Japan in 1990. The anti-HBs positive rate was found to be significantly higher in patients with blood transfusion than in those without it (38.0% vs. 25.0%, p<0.05), which suggested that blood transfusion may thus be a major route of Hepatitis B virus (HBV) infection in HD units. However, the ratio of the observed number of anti-HBs positive HD patients and the expected number calculated from healthy inhabitants (O/E ratio) was significantly low (0/E=0.73, p<0.01) while the O/E ratio of HBsAg was significantly high (O/E=2.0, p<0.05). These results therefore indicate that HD patients possess a high risk of becoming HBV carriers. J Epidemiol, 1994; 4 : 99-102.

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Multiple birth rates in entire Japan were analyzed using vital statistics for 1951 to 1968 and 1974 to 1992. The twinning rate per 1, 000 births was 6.4 in 1951 and remained fairly constant until 1968, then decreased to 5.8 in 1974 and gradually increased to 7.5 in 1992. The triplet rate was fairly constant for 1951-1974 (56 per million births), then increased with the year up to 1982 (104), and decreased up to 1984 (87), and suddenly increased thereafter (229 in 1992). The average rate of quadruplets per million births for 1951-1968 was 0.93, then increased to 3.3 in 1974 and 6.5 in 1975, and decreased or remained constant until 1984 and suddenly increased thereafter (19.7 in 1992). The rate of quintuplets was 0.86 per million births for 1975-1989 and 2.89 for 1990-1992. The rate of sextuplets was 0.21 per million births for 1975-1992. The higher multiple birth rates since 1975 have been attributed to the higher proportion of mothers treated with ovulation-inducing hormones and since 1985 partially attributed to in-vitro fertilization. J Epidemiol, 1994; 4 : 103-109.

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