Classification and nomenclature of nonexperimental epidemiological design have been a "confounded" issue. This paper discusses the problems in existing classifications of nonexperimental epidemiological design from a logical viewpoint including concept, definition and classification dimensions. The author selected, conceptualized and defined the dimensions for a study design classification scheme according to the purposes of the classification, logical consistency, and relative significance of each dimension. This classification includes ten types of basic design distinguished in terms of sampling scheme and order of hypothesized occurrence, which can be grouped into exposure-control, outcome-control and general population designs. More specific concepts may be generated from addition of an additional design features(s) to a basic design. By using the scheme, this classification distinguishes the various existing designs and clarifies some ambiguity. An example is provided to describe the classification scheme. J Epidemiol, 1994; 4 : 113-119.

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To refer to municipal governments employing public health nurses (PHNs), the relationship between the number of PHNs and accomplishment in health care programs was observed. Data regarding accomplishment in health care programs were obtained by a nationwide questionnaire survey sent to all of the municipal governments (cities, towns, and villages). Of the 3, 268 governments, 2, 800 ones or 86% responded the survey. Population sizes and standardized mortality ratios for major causes of death of municipalities were obtained from the Wide-area Information-exchange System for Health and welfare administration (WISH). Results were as follows : The correlation coefficient between the ratios of PHNs and participation rates to stomach cancer examination was 0.63. The correlations were significant and strong in the program achievement of the following ; tracking of non-examinees, registration of stroke patients, activities of local community organizations, participation rates to basic health examination, stomach cancer examination, cervical cancer examination, health education, health counseling, and rehabilitation programs. The results suggest that the number of PHNs in a municipality is one of the important factors to obtain effective achievement of health care programs. Using regression models the author estimated that 1.96-2.72 PHNs per 10, 000 population are required to achieve the target participation rates organized by the Japanese Government. J Epidemioi, 1994; 4 : 121-128.

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From April 1992 to March 1993, we examined the results of a bacterial culture from various clinical aspects in 83 elderly inpatients at a geriatric hospital. A case control study was carried out in order to evaluate the various factors which may influence the occurrence of methicillin-resistant Staphylococcus aureus (MRSA) infection. A univariate analysis revealed that a lower ADL score, a great number of antibiotics administration or the use of the third generation cephems increased the risk for MRSA infection. However, a multivariate analysis revealed that the risk for MRSA infection increased only among the patients who received the third generation cephems (OR: 2.80, 95% Cl : 1.40-5.63). Therefore, in the elderly, the use of third generation cephems seems to pose a great risk factor for MRSA infection.
The level of total cholesterol, serum albumin or hemoglobin did not differ between the MRSA group and the non-MRSA group. However, among the patients who did not receive the third generation cephems, hypoalbuminemia was a risk for MRSA infection (OR: 2.06, 95% Cl : 1.10-3.85). J Epidemiol, 1994; 4 : 129-132.

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In the analysis of stratified person-time follow-up data, the multiplicative incidence rate model requires the rate ratio homogeneity across strata. This homogeneity assumption is statistically convenient but biologically stringent. When we do not have any strong biological models on incidence rate ratio homogeneity, we cannot justify using the estimators for the common (homogeneous) incidence rate ratio without checking the assumption. Given that the homogeneity test has a low power, we at least compare two summary estimators : one based on the homogeneity assumption, and the other not. This paper proposes an equivalence test between the Mantel-Haenszel rate ratio, which is an estimator for the common incidence rate ratio, and the standardized mortality ratio (SMR), which does not require the homogeneity assumption. The proposed test gives a practical choice between these two summary measures. J Epidemiol, 1994; 4 : 133-136.

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The effects of outdoor and indoor nitrogen dioxide (NO2) exposure on pulmonary function were studied in a cohort of children attending eight elementary schools in Chiba Prefecture. A three-year series of annual pulmonary function tests was conducted from 1989 through 1991. NO2 concentration in the living room of each child's home was measured in both the heating period and the non-heating period. Children were classified into four groups according to household annual average NO2 concentration. The indoor NO2 concentration varied with the area of residence and type of heating appliance used. Analyses using log-linear models, including interactions among these environmental factors, were performed to evaluate the association of NO2 exposure with pulmonary function in schoolchildren. Interregional comparison showed that pulmonary function values, adjusted for height and age, were lower among boys living in urban areas, where air pollution levels are high, compared with boys in rural areas. In log-linear models that considered the effect of indoor NO2 concentration, boys in urban areas showed significantly depressed values of FVC and FEV0.75. Indoor air pollution was not definitely associated with pulmonary function among boys, after adjustment for the area of residence. Among girls, high indoor NO2 concentrations were associated with low pulmonary function values, while no significant relationship between area of residence and pulmonary function was shown. Girls in the over-40-ppb group showed significantly depressed values of FVC, FEV0.75 and V25 in the second testing. In the third testing, V25 was the only parameter that was significantly low. These results suggest that pulmonary function is associated with area of residence among boys and with indoor NO2 concentration among girls. However, this study could not reveal the long-term effect of indoor air pollution on pulmonary function, since this association became weaker by the third testing. J Epidemiol, 1994; 4 : 137-146.

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A case-control study on thrombocytopenia with the Rezept files of Tokyo Medical and Dental University Hospital has been carried out. The study explored whether the case-control studies are feasible using files of Rezept system maintained in many Japanese hospitals for health insurance billing. Each of the 100 patients with thrombocytopenia was contrasted with one control case, matched for age, sex, in or out-patient, consultation clinic and year of registration. Of 1, 021 products of drugs registered in the files, 40 products (36 drugs) were associated with the disease. Through medical record review, low platelet count was confirmed in 94.6% of inpatients, while only in 26.9% of outpatients. Thirty-one cases of drug-induced thrombocytopenia were identified, and 29 suspected drugs were listed up. On the basis of the analysis of these data, we conclude that the Rezept files be useful in the case-control studies on adverse drug reactions similar to thrombocytopenia in inpatients. The medical records, however, must be reviewed to confirm the date of disease onset and to obtain information not included in the computerized data. J Epidemiol, 1994; 4 : 147-155.

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To observe whether there is a relationship between smoking habits and socioeconomic factors among Japanese people, we analyzed data from a large population survey with a random sampling method throughout the country. Information of smoking habits (never, current, and former smoking), occupation, length of education, and annual household income was obtained from 1, 454 participants. Prevalence of smokers and socioeconomic status was inversely associated in Japan as well as in other developed countries. However, the association was not so strong as that in other countries. J Epidemiol, 1994; 4 : 157-161.

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To reveal a distribution of lipoprotein (a) (Lp(a)) in Japan and to explore relationships between Lp(a) and conventional cardiovascular risk factors, transaminase (GOT(AST), GPT(ALT)) and γ- gulutamyltranspeptidase (y-GTP), a cross-sectional study in a healthy population was performed. We measured serum Lp(a) of 497 apparently healthy subjects aged 40-69 years old in a rural area in Japan ; 198 males and 299 females. Lp(a) frequency distributions were highly skewed to the low level. Serum Lp(a) level is significantly higher in the females (15.1+/-1.08 mg/dl) than in the males (12.0+/-1.01 mg/dl). Among males the median and mean log Lp(a) levels increased according to age. Pearson's correlation analysis showed statistically significant correlations (p<0.05) between Lp(a) and GOT, GPT, γ-GTP, total cholesterol (TCH), triglyceride, but no statistically significant correlations between Lp(a) and body mass index, blood pressure, high-density lipoprotein cholesterol, blood sugar, corrected TCH for males. On the other hand, the same analysis showed no statistically significant correlation among Lp(a) and each item observed for females. We suppose Lp(a) is not related to conventional cardiovascular risk factors. J Epidemiol, 1994; 4 : 163-169.

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