To examine the impact of health-related lifestyle upon medical care utilization and its costs, we conducted a cohort study among all National Health Insurance beneficiaries aged from 40 to 79 years living in the catchment area of Ohsaki Public Health Center, Miyagi, Japan. The baseline survey, using self-completed questionnaire regarding health-related lifestyle, was conducted between October and December 1994. Out of 54, 996 eligible subjects, 52, 029 (94.6%) responded and formed the cohort under study. Medical care utilization (number of outpatient visits and days of inpatient care) and the costs for each subject have been obtained from National Health Insurance Claim History files since January 1995. The baseline characteristics of health-related lifestyle and medical history at the study subjects were consistent with those at our another cohort subjects (so-called Miyagi cohort study; N=47, 605), which included all the residents aged from 40 to 64 years at 14 municiparities in Miyagi Prefecture, Japan conducted in 1990. The medical costs per capita in this cohort was quite compatible with the national average. This prospective cohort study would quantitatively demonstrate the economic impact of health-related lifestyle, thus would lead us to better provision of cost-effective preventive health services. J Epidemiol, 1998 ; 8 : 258-263.
We examined the relationships between preventive health services provided under the Law for Health and Medical Services for the Elderly and the use of inpatient and outpatient care by insured residents aged 40 or older covered by the National Health Insurance in 44 municipalities in Osaka Prefecture. Factor analyses showed that hospital admission rate and inpatient days per 100 insured persons, bed days per insured person, inpatient days per case, mean bed days, the proportion of long-stay (180 days or more), and the rate of long-stay per 1, 000 insured persons accounted for the first factors of inpatient care with factor loadings of more than 0.82. Outpatient utilization rate and outpatient days per 100 insured persons comprised the first factors of outpatient care with factor loadings of more than 0.80. Patient cost per case and the proportion of high patient cost (600, 000 Yen or more for inpatient care and 60, 000 Yen or more for outpatient care) made up the second factors of either type of patient care with factor loadings of more than 0.87. The frequency of use of health check-ups and the numbers of instruction classes and participants in health education and health counseling per 100 residents showed negative correlations with indices of inpatient and outpatient care, except for patient cost per day. The scores for the first and second factors of inpatient care and for the first factor of outpatient care correlated negatively with all indices of the use of preventive health services. More active provision of preventive health services may therefore contribute to reducing the subsequent use of inpatient and outpatient care among residents aged 40 or older. J Epidemiol, 1998 ; 8 : 264-271.
The purpose of this study is to observe the disease-disability association through a cross- sectional study. Between 1994 and 1995, we conducted a questionnaire survey in 5 towns in Japan. Among the items included in the questionnaire, 5 related to ADL (bathing, feeding, dressing/undressing, toileting, and going out socially) were treated as purpose variables; and 5 related to the history of medical treatment received over the past year (diabetes, heart disease, cerebrovascular disease, neuralgia, and bone fractures) were used as explanatory variables. Multiple logistic models were applied to observe the relationship. The history of medical treatment for cerebrovascular disease greatly and unavoidably affects disability related to ADL. Bone fractures, diabetes, and heart diseases contributed to specific ADL disabilities. J Epidemiol, 1998 ; 8 : 272-277.
We estimated the number of patients with chronic renal failure (CRF) but not with end-stage renal disease (ESRD) in Japan by two methods: a nationwide survey and an estimation using incidence rates of ESRD among CRF patients as well as the number of incident ESRD. The former estimated the number of patients with CRF but not with ESRD as 154, 000 (95% confidence interval 139, 000-168, 000), while so did the latter as 142, 000 (133, 000-150, 000). It follows that the number of CRF patients including ESRD could amount to more than 300, 000, which would give a substantial impact on public health in Japan. Despite some own methodological issues in estimation, the two estimates were reasonably in good agreement: supporting their methodological validity in estimation, since sources of errors appeared to be quite independent of each other. J Epidemiol, 1998 ; 8 : 278-284.
Dehydroepiandrosterone sulfate (DHEAS) is a major secretory product of the adrenal glands. DHEAS is inversely associated with death from cardiovascular disease in males, but not in females. This cross-sectional study examined the relationships between serum DHEAS levels and atherosclerosis in free living subjects in Japan. We measured the serum DHEAS levels of 990 apparentltly healthy subjects aged 35-81 years old in a rural area in Japan; 431 males and 559 females. The levels were determined by the radioimmunoassay method. The frequency distribution was skewed to a lower value in both sexes. Both unadjusted and age-adjusted mean DHEAS levels were statistically higher in males than in females, A marked linear decline of levels with age was observed in both sexes. DHEAS levels were positively correlated with high density lipoprotein-cholesterol (HDLG), and negatively correlated with low density lipoprotein-cholesterol (LDLC) even after adjustment for age in both sexes. The mean atherogenic index (AI) was significantly inversely correlated with the rise of tertiles of the DHEAS level, both before and after adjustment for age, Total cholesterol (TC), HDLC and Triglyceride (TG). These results suggest high levels of serum DHEAS may have an inhibitory effect on the development of atherosclerosis and have an important role in its etiology and prevention. J Epidemiol, 1998 ; 8 : 285-291.
To estimate the risk of hepatitis C virus (HCV) infection among blood donors, we conducted a retrospective cohort study with 448, 020 HCV-seronegative donors who donated blood more than once between February 1992 and July 1997 in Osaka (a total of 2, 676, 738 allogeneic blood donations). The donors were divided into four age groups according to the age at the initial donation: Group A (16-24 years), Group B (25-34 years), Group C (35-49 years) and Group D (50- 64 years). Fifty-nine donors became infected with HCV among the 448, 020 HCV-seronegative donors who donated blood more than once within a period of approximately five years. In a total of 1, 095, 668 person-years of observation (PYO), the incidence rate was 5.38 per 105 PYO, with the 95% confidence interval (95% C.I.) being 4.10 to 6.95. There was no significant difference in the incidence rate between males and females. Young donors between the ages of 16 and 24 (8.89; 95% C.I., 6.04 to 12.61) had a significantly higher incidence rate of HCV infection than donors between the ages of 35 and 49 (1.81; 0.67 to 3.95). The cumulative risk of HCV infection among donors between the ages of 16 and 64 was estimated to be 0.27% (95% C.I., 0.16 to 0.39) for males and 0.27% (95% C.I., 0.15 to 0.38) for females. Based on the recent age-specific incidence rate, the cumulative risk of HCV infection among blood donors was estimated to be about 0.3% in the Osaka district of Japan. The incidence rate differed among age groups, indicating that HCV infection is associated with age-related behaviors and the need for further epidemiological research towards the eradication of community-acquired HCV infection. J Epidemiol, 1998; 8 : 292-296.
We hypothesized that validity of semiquantitative food frequency questionnaire would be affected by food diversity (variety of foods consumed), because greater food diversity may be related to greater within-individual variation of nutrient intake, which can attenuate the correlation coefficient measuring validity of the questionnaire. We obtained 12 one-day diet records over one year and responses to a semiquantitative food frequency questionnaire from 37 subjects. The food diversity score for each subject was determined by the total number of different foods consumed during the 12 days for the diet records, and the subjects were divided into two groups according to the score. The within- individual variances were similar in those with higher and lower food diversity scores. We never observed a significantly lower correlation coefficient for any nutrient in those with higher food diversity scores. The observed and corrected correlations for most of the micronutrients were higher in those with higher food diversity scores, and the differences were statistically significant for crude fiber, vitamin C, iron, and potassium. The validity of the semiquantitative food frequency questionnaire did not appear to be lowered greatly by greater food diversity. J Epidemiol, 1998 ; 8 : 297-301.