A brief history of epidemiology in Japan is presented for the sake of convenience in three stages; the period of birth extending to the early 1940s, the period of growth from 1945 to 1964 and the peirod of development from 1965. The future problems facing epidemiology are also described. Even in the Meiji period, outstanding epidemiological studies were conducted by Dr. Kanehiro Takaki and Dr. Masakiyo Ogata, but it was only in 1938 that the first epidemiological research laboratory was formally established. Epidemiology at that time was confined to studies on epidemics of infectious diseases, but in the period of growth from 1945 there began to appear epidemiolgoical studies on non-infectious diseases such as adult diseases and diseases caused by environmental pollution. From the period of development commencing in 1965, the sphere of epidemiological studies was further expanded to include intractable diseases, and with the introduction of information science, epidemiology became actively involved in health services research. There are a number of problems facing epidemiology in Japan, including refinement of risk factors, improved measurements of exposure doses, emphasis on individual characterization aimed at health prediction, and development of new health indices. J Epidemiol, 1996 ; 6 : S3-S7.

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This article summarizes the scientific activities of the Japan Epidemiological Association (JEA). The association was formally inaugurated in January 1991. The major activities of this associatian are (1) holding annual scientific meetings (it has held six meetings since its inauguration) and sponsoring epidemiology seminars ; (2) publishing the official journals (Journal of Epidemiology), news letters and other publications ; and (3) other activities to promote the development of epidemiology. The total membership at present is about 1, 000. The field of specialty of the members are epidemiology, public health, statistics, health administration, clinical medicine, information science, infectious diseases, industrial health, environmental health and other related areas. The association closely collaborates with other Japanese and international organizations (especially with the International Epidemiological Association) in the field of epidemioiogy. J Epidemiol, 1996 ; 6 : S9-S11.

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The present article provides an overview of epidemiological studies in Japan. The origin of modern epidemiology of Japan can be traced back into the late 19th century. Baron K. Takaki at that time made brilliant epidemiological studies on beriberi and was thus able to eradicate the disease long before vitamin B1 deficiency was identified as the cause of the disease. Epidemiological studies really began to flourish in Japan after the end of World War II. Since the most of infectious diseases have been controlled, epidemiological studies on cancer, heart disease, stroke, and other chronic diseases have become the main target of investigations. It may be cautioned that, among infectious diseases, tuberculosis is still a serious health problem today and HIV infection has become a threatening health issue although the number of AIDS patients reported was still about 1, 000 for the whole country in 1995. In contrast to other industrialized countries, heart disease is far less common in Japan, probably reflecting still not- too-rich diet among Japanese. There are a number of unique or unusual epidemiological studies in Japan, including a long-term surveillance of those who were exposed to A-bomb irradiation in 1945. Readers are encouraged to refer to detailed description of each, specific topic presented in this volume. Essential vital statistics are also presented as background information of epidemiological studies in Japan. J Epidemiol, 1996 ; 6 : S13-S17.

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Cancer epidemiology in Japan has been led by the large-scale population based cohort studies. Permanent registration system has made follow-up easier and more efficient. Low cancer incidence and mortality rates led the researchers to investigate possible preventive factors in diet and life style, in addition to the study of risk factors. The on-going large sized prospective cohorts should be a fruitful resource for future cancer epidemiological studies. Various studies of cancer epidemiology are introduced from a methodological aspect. cancer Epidemiology, cancer Registry, Cohort study, Mass-screening, cancer prevantion J Epidemiol, 1996 ; 6 : S19-S29.

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The Special Cancer Research Program was newly established in 1984 within the existing International Scientific Research Program of the Monbusho (Ministry of Education, Science and Culture) as a part of “the Comprehensive 10-Year Strategy for Cancer Control” which was launched by the Japanese Government in 1984. The Comprehensive 10-Year Strategy for Cancer Control ended successfully 1993 and the Second 10-Year Program was started in 1994. When the Special Cancer Research Program started In 1984, the number of projects was 12 and the number of collaborating countries was 18. Since then the numbers of projects and collaborating countries have increased year by year to 27 projects and 30 collaborating countries in 1995. The cumulative (actual) number of projects from 1984 to 1995 was 216 (62) and the total number of collaborating countries was 57. Major topics covered by the Special Cancer Research Program are ; exchanges of scientific information on cancer researches in advanced countries, viruses and parasites related to carcinogenesis, carcinogens/promoters and their inhibitors in the natural environment, migrant studies on cancer, studies on the etiology and prevention of cancers of special interest, and studies on diagnosis and treatment of cancer. J Epidemiol, 1996 ; 6 : S31-S35.

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Population-based cancer registries in Japan were first established in the cities of Hiroshima and Nagasaki in 1957-1958 for assessing radiation effects and in Miyagi in 1959 for promoting epidemiological researches, while most other prefectures in Japan set up cancer registries as a part of their own cancer programs. This resulted in the broader use of registry data in Japan. In 1975, the Reseach Group for Population-based Cancer Registration in Japan was first organized with a research grant under the National Cancer Research Promotion Program. Since then, continuous efforts have been made by the Group to improve the quantity and quality of registry data and to develop methodologies to utilize it. Studies being conducted using registry data cover (1) descriptive epidemiology, (2) analytical epidemiology, (3) evaluation of screening programs, and (4) evaluation of regional cancer medical care. In 1992, 32 regional cancer registries which were operating in Japan set up the Japanese Association of Cancer Registries. However, there are still many difficulties to overcome in order to achieve completeness of reporting in registries. Further improvement of reporting rate, together with standardization of registry data are left for future efforts. J Epidemiol, 1996 ; 6 : S37-S41.

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Japan had the highest mortality from stroke among developed countries in 1960, but experienced rapid changes in diet and other lifestyles with economic growth between the 1960s and the 1980s, which provided an unique opportunity to observe a natural experiment of changes in risk factors and stroke. Blood pressure levels declined due to improvements of drug treatment for hypertension and to dietary improvements such as sodium reduction. An increase in mean values of ethanol intake and body mass index did not correspond with a decline of blood pressure levels. Serum total cholesterol increased with an increased intake of meat, egg, milk and dairy products. Age-adjusted mortality rate of stroke declined 70% between 1960 and 1990. The changes of diet, blood pressure levels and stroke were more evident in rural populations than in urban populations. Risk factors of stroke has been investigated prospectively, and hypertension was found to be the most important risk factor. A low blood cholesterol was associated with the increased risk of intracerebral hemorrhage, which has been confirmed in several Japanese populations, Japanese Americans and Caucasian Americans. Thus, a rise in serum cholesterol suggested to contribute in part to a decline in intracerebral hemorrhage. Risk factors for cerebral infarction include age, atrial fibrillation and hypertensive endorgan effects such as resting electrocardiogram and fundscopic examination. A community-based hypertension control program for stroke prevention has been evaluated ; a larger decline in stroke incidence in the intervention community (69%) than in the reference community (49%, the difference : p<0.001). Effective community programs stimulated the formation of the 1982 national act on health and medical care in which every municipal government is required to conduct health screenings and education for residents aged 40 and over to prevent cardiovascular diseases. J Epidemiol, 1996 ; 6 : S43-S47.

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The age-adjusted death rate from ischemic heart disease in Japan is the lowest among developed countries and the rates have decreased since 1970. The incidences of myocardial infarction in selected populations ranged between 0.12 and 2.56 per 1, 000 for middle-aged males, and between 0.00 and 1.52 per 1, 000 for females. The incidences of sudden death within 24 hours were from 0.00 to 1.58 per 1, 000 for males and from 0.00 to 0.76 per/1, 000 for females. The incidences in Japanese populations appeared to be far below those in Western populations. In the Cox proportional hazard regression model, hypertension and smoking were selected as independent risk factors for myocardial infarction in an agricultural district. It was noteworthy that the level of serum cholesterol was not associated with development of myocardial infarction in rural areas. No positive relation between dietary fat and serum cholesterol was observed in school children, suggesting that growth, sexual maturation and others might be confounding variables between them. The levels of serum cholesterol for females were more affected by menopause than those of blood pressures and body mass index. Although some polymorphisms in selected candidate genes appeared to be associated with some serum lipids and apolipoproteins, the effect of individual RFLP on the inter-individual variations in serum traits was relatively subtle in comparison with that of lifestyle factors. J Epidemiol, 1996 ; 6 : S49-S59.

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During early Meiji era in Japan, there were frequent epidemics of fatal acute communicable diseases such as cholera, dysentery and smallpox, and preventive measures and preparations for acute infectious diseases were urgently needed. Together with improvement of scientific preparations, the Communicable Disease Prevention Law was promulgated in 1897. Then gradually until 1940's, the focus of preventive measures have been shifted from acute infectious diseases to chronic ones, particularly tuberculosis. After the World War II, except the short period of social confusion, major legally-defined communicable diseases had been decreasing rapidly mainly due to the use of antibiotics and improvement of environmental sanitation. At the same time, the introduction of preventive vaccination marked a new era for the prevention of infectious diseases and was largely responsible for the remarkable decrease of infant mortality in Japan. Recently the concept of defense by vaccination against infectious diseases has evolved from group-oriented to individual-oriented, so that the Preventive Vaccination Law was drastically revised in 1994. Currently, effective counter-measures against newly emerged infectious diseases, as viral hepatitis, institution-acquired infection, viral hemorrhagic fever etc., have been implemented. For the future, improvement of infections disease surveillance, vaccine development and expansion of vaccination coverage along with monitoring sideeffects, preventive health education on AIDS/STDs, addressing the special needs of foreigners living in Japan and international collaboration for disease control abroad are all vital to the success of protection of the public's health from infectious diseases in Japan. J Epidemiol, 1996 ; 6 : S61 -S66.

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The data obtained from the national reporting system of acquired immune deficiency syndrome (AIDS) and its causative immune deficiency virus (HIV), the epidemic pattern of AIDS cases and HIV carriers in Japan from 1985 to 1995 could be summarized as follows : 1) the total number of reported AIDS cases and HIV carriers were 1, 154 and 3, 524 which included 167 and 915 foreigners, respectively ; 2) among them the number of HIV carriers in hemophiliacs transmitted through HIV contaminated blood products was 1, 806, including 582 AIDS victims ; 3) excluding these hemophiliacs, there are 572 AIDS cases (167 foreigners) which shared risk factors for heterosexual contacts (37%) and homosexual contacts (31 %), respectively ; 4) on the other hand, more than 50% were heterosexuals and only 20% were homosexuals in 1, 718 HIV carriers (915 foreigners) ; 5) the peak incidence is 33% in the 30s in AIDS, while more than 50% are in their 20s ; 6) male-to-female ratio was 6.8 in AIDS cases but only 1.1 in HIV carriers; 7) the estimated number of HIV carriers in 2000 was 6, 300-8, 500 in Japanese and 700-1, 700 in foreigners, respectively. From the above mentioned epidemic pattern of AIDS/HIV in Japan, we have to recognize that the recent number of HIV infection is actually increasing and the most of current HIV carriers even in foreigners are infected with HIV in our country and general activities for AIDS prevention in Japan and neighboring Asian countries should be promoted. J Epidemiol, 1996; 6 : S67-S74.

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Tuberculosis has decreased so rapidly and has changed its epidemiological feature so markedly in these several decades in Japan, that tuberculosis epidemiologists had done and have to do numerous studies to understand the situations and to adjust tuberculosis control programme of high prevalent country to that of low prevalent country. Main themes of epidemiological research are being focused on 1) the causes of stagnation of the decrease of tuberculosis incidence and estimation of future trend in Japan, 2) risk factors of development of disease at present when more than 95% of diseases are the exacerbation of the remote infection, 3) the efficacy and efficiency of each control measure to improve the existing programme in Japan, 4) the mode of tuberculosis infection in the community using RFLP analysis of tubercle bacilli, 5) epidemiology of tuberculosis in the developing countries where tuberculosis is increasing at present, and so on. Because of the increase of tuberculosis in the world, epidemiological research in tuberculosis is becoming more and more active to-day. It is being expected that epidemiological research on tuberculosis will have more and more fruitful results in near future. J Epidemiol, 1996 ; 6 : S75-S79.

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The surveillance system of infectious disease in Japan started in 1981 and has been providing useful epidemiological information on 27 communicable diseases. The system consists of medical institutions (fixed monitoring stations), institutions of hygienic sciences, health centers, local governments and the ministry of health and welfare. There are two types of information about infectious diseases. One is clinical reports of incidence cases from medical institutions, and the other is laboratory information about etiologic agents. Between health centers, local governments and the department of statistics and information in the ministry of health and welfare, information is transmitted through the on-line network. Collected information is analyzed and submitted by both local and central committees of analysis. From the epidemiological point of view, quality control of the data and integration of other sources of data would be the next goal of the system. J Epidemiol, 1996 ; 6 : S81 -S85.

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In Japan, epidemiological studies on intractable diseases have been undertaken and greatly promoted for more than 20 years by the Research Committee on Epidemiology of Intractable Diseases, with the financial supports from the Ministry of Health and Welfare of Japan. In this paper, chronological history of development of the Research Committee and some scientific accomplishments by the recent Research Committee (1993-1995) were summarized, mainly focusing on descriptive, analytical and other epidemiological studies. Hoped is that the readers are to be acquainted with the recent research activities by the Research Committee and seek for possible international collaborations in epidemiological studies on intractable diseases. J Epidemiol, 1996 ; 6 : S87-S94.

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The Atomic Bomb Casualty Commission (ABCC), the predecessor of the Radiation Effects Research Foundation (RERF), was established in 1947 to conduct long-term, comprehensive epidemiological and genetic studies of the atomic-bomb (A-bomb) survivors. Today this study still depends upon the voluntary cooperation of several tens of thousands of survivors of the bombings of Hiroshima and Nagasaki. An in-depth follow-up study of mortality in the study population of 120, 000 persons, including A-bomb survivors and controls, has continued since 1950. The study of tumor incidence was initiated through record linkage with a tumor registry system in Hiroshima and Nagasaki in 1958. In the same year, biennial medical examinations of 20, 000 individuals began. Follow-up studies also have been conducted on in-utero-exposed persons and first-generation offspring of the survivors. On the basis of these studies spanning nearly half a century, we know that the occurrence of leukemia and cancers associated with A- bomb radiation is higher than among the non-exposed. Among the A-bomb survivors, radiation cataracts, hyperparathyroidism, delayed growth and development, and chromosomal aberrations also occur more often. However, to date no evidence exists of genetic effects in the children of A-bomb survivors. It should be kept in mind that such study results could never be obtained without the cooperation of A-bomb survivors. J Epidemiol, 1996 ; 6 : S95-S105.

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Lifestyle habits and other living conditions in Japanese have progressively been changing after the World War II, and the changing trend has been accelerated since 1970. The frequency and distribution of cancer by site in Japan showed marked secular changes during the past decades, just as reflecting the above changes in environmental factors. A large scaled cohort study on cancer at moment was strongly anticipated in Japan, after the cohort study by Dr. Hirayama et al. had ended around 1980 with unexpectedly fruitful results. However, financial problems and other conditions hindered to start such cohort studies. A multicentered collaborative cohort study had planned among the epidemiologists and epidemiology oriented clinicians who have been working on cancer in the communities, resolving problems on cost and others for long term epidemiological issues. A new cohort with a total of 125 thousands of healthy inhabitants living in the areas scattered throughout country was established in 1988-1990, although they were not randomly distributed in area. Some 30 thousands industrial worker cohort has joined in this study, which will be separately analysed. The study was partly granted by the Ministry of Education, Science, Sports and Culture and largely supported by local government and volunteers in each area for ten years. A research committee on this study was organized and are following up all subjects participated for more than ten years, mainly pursuing mortality status, and incidence of cancer for about half population of the cohort is also under study. About 1, 000 deaths per year were observed in the first four years and more than 30% were due to cancer. The proportion of moved out of town was small being about 1 % per year. The distribution of cancer deaths by site for the first four years was similar to those of general population. This report summarized the study plan and the epidemiological characteristics of the cohort at entry of the study. It also gives a brief account of activities until 1994. J Epidemiol, 1996 ; 6 : S107-S113.

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Epidemiological studies on several selected topics in occupational health in Japan is introduced in the present paper. Karoushi or sudden death due to overwork was proposed in 1978. Hypertension was suggested to be one of the risk factors for Karoushi, although the risk factors related only to work conditions have not been clarified yet. Epidemiological studies on occupational stress and stress-related diseases have been developed, even with the difficulties of definition or measurement of occupational stress. The depression state and mental state were influenced by occupational stress and personality. A large scale cohort study on 180 thousand radiation workers in Japan has been conducted since 1990 in order to obtain scientific information on the health effects due to low dose protracted radiation exposure. In order to assess occupational cancer risk due to hazardous working environment in Japan, several epidemiological studies were carried out. One cohort study on Japanese forest workers for vibration syndrome showed that the latent interval for the development of vibration induced white finger was 6.2 years. Finally, evaluation studies of mass cancer screening programs in Japan were introduced. It was stressed that the epidemiological approach should be strengthened more in order to obtain more information for prevention of occupational diseases or work-related diseases and for the promotion of workers' health. J Epidemiol, 1996 ; 6 : S115-S120.

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The rapid industrial development that began in the 1950's created environmental problems which consequently led to health hazards among residents of heavily polluted areas in Japan, such as Minamata Disease and Yokkaichi Asthma. Faced with these situations, the Japanese national government and local environmental authorities exerted much efforts to control pollution as well as to provide solutions to health problems. Many studies, including environmental epidemiology, have been conducted, aiming at determining relations between health problems and pollution. The results of environmental epidemiologic studies were prone to conclude associations with pollution and targeted health damages. In the case of the air-pollution related diseases, the government compensated individuals with non-specific respiratory diseases who are residents in the designated special high level air pollution areas. Epidemiological studies played an important role in designating pollution-related diseases and polluted areas. J Epidemiol, 1996 ; 6 : S121-S124.

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Molecular epidemiology of cancer has been developed along with rapid advances in molecular carcinogenesis, introducing new approaches to etiology and prevention of cancer. First, research activities in Japan are briefly reviewed in this issue focusing on studies of genetic susceptibility, DNA damages, and immunological defense. Then we make an estimation of age periods of initiation for several cancer on the basis of multistaged carcinogenesis. The results are discussed in relation to strategies of cancer prevention in molecular epidemiology, introducing our trials previous and on-going as examples. J Epidemiol, 1996; 6 : S125-S129.

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The three-consecutive-day weighing method, in which foods as raw materials are weighed separately before they are cooked, is the most popular dietary assessment method among Japanese dietitians, because this dietary survey method has been adopted in the national nutrition survey for half a century. Under such circumstances, there have been only a few studies aiming to develop and validate a food frequency questionnaire (FFQ) method. The food list of a few FFQs ever used dealt with individual food items alone, but not mixed dishes. Therefore, a frequency questionnaire was very difficult for people not involved in cooking daily to answer. In order to enable subjects to answer a questionnaire more accurately, a new FFQ which has a food list with 122 single foods and recipes was developed. These foods and recipes were identified from 805 24hr-recalls of males and females aged 40-69 years old in Shiso County, Hyogo Prefecture, Japan. During consecutive 56 or 63 days, 67 junior college students in a dietitian course recorded their diet intake. Within a week after the diet record, they answered the newly developed FFQ. Pearson correlation coefficients between energy adjusted nutrient intakes assessed from the FFQ and those from dietary records were calculated. These correlation coefficients ranged from 0.21 for retinol potency to 0.74 for calcium. These data indicate that the newly developed FFQ provides a useful measurement of many nutrient intakes over a two-month period. J Epidemiol, 1996 ; 6 : S131-S136.

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In Japan, the concern about ethical issues in preventive medicine, especially in epidemiological investigation, has been gradually increasing in recent years. In this paper I introduce the following four topics : 1. privacy protection and the computer, 2. informed consent and publication, 3. the attitudes toward ethics among epidemiologists, 4. the attitudes toward epidemiological investigation among examinees. In my opinion, Japanese epidemiologists should give more attention to general ethical principles (Respect for persons, Beneficence) and to the practical methods to apply them in their research works. J Epidemiol, 1996 ; 6 : S137-Sl39.

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In 1993 questionnaires concerning ethical issues were mailed to 34 committee members of the Monbusho research committee of a large-scale cohort study which started in 1988 including 32 rural communities and 4 occupational groups. The questionnaire survey revealed the following results. 1. In all cohorts, “informed consent” for health questionnaires was carried out, though the methods varied. 2. Although the method varied, informed consent for collection of blood was obtained in 28 (77.8%) of the 34 cohorts. The committee decided that the collected specimens without consent is not used for study. 3. The protection of privacy was deliberately planned and has been carefully carried out in the cohort study. 4. The committee members' concerns for ethical issues has increased after joining the cohort study. 5. The attitudes of informed consent for collection of blood at mass screenings showed wide differences among research objects and researchers. These results suggested that the research members had a considerably high concern for ethical issues and that ethical considerations in epidemiological studies should be continued in Japan. J Epidemiol, 1996; 6 : S141-S146.

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Outline of selected ones among a number of nationwide surveys related to health and welfare services (90 surveys as of 1995) conducted mainly by the Ministry of Health and Welfare periodically in Japan is described. That is, history, purpose, coverage, date, contents, data collection procedure, tabulation and publication were explained in regard to : (1) Population Census, (2) Vital Statistics, (3) Patient Survey, (4) Infectious Disease Surveillance System, (5) Comprehensive Survey of Living Conditions of People on Health and Welfare, (6) Census on Medical Care Institutions, (7) Hospital Report, (8) Survey on Physicians, Dentists and Pharmacists, (9) Statiatical Report on Public Health Administration Sevices, (10) Survey on Social Welfare Institutions, and (11) National Nutrition Survey. On-line data service system of the Ministry of Health and Welfare is also briefly mentioned. J Epidemiol, 1996 ; 6 : S147-S157.

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The Health and Medical Services Law for the Aged was implemented from February, 1983 in Japan. This paper describes the present status of health examination programs and cancer screening programs and related issues as follows : methods of the basic health examination and cancer screening, the number of the examinees, detection numbers and rates of targeted diseases, i.e. hypertension, anemia, cancer of the stomach, uterus, lung, breast, and colon etc. The Goals of Japanese Government of the Health Services by the year 2000 are discussed from the several points of view. J Epidemiol, 1996 ; 6 : S159-Sl63.

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In Japan, the spread of immunization and the development of antibiotics and antituberculosis drugs have dramatically decreased the mortality rate from infectious diseases since World War ll. Alterations in health practices, such as decreasing the intake of salty foods and strict management of hypertension, have resulted in prominent decreases in the mortality rate from cerebrovascular diseases, especially from cerebral hemorrhage. However, we still have high death rates from malignant neoplasms and circulatory diseases, which may be partly prevented through improvement of health status. We discuss here about various health promotion activities recently reported in Japan, including prevention of smoking, promotion of exercise, improvement of nutrition, improvement of mental health status, and health risk appraisal. Finally we would like to stress the importance of comprehensive assessment of health status in order to encourage health promotion activities further. J Epidemiol, 1996 ; 6 : S165-Sl68.

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To abstract the health and welfare status of Japan, the essences of related statistics are referred and introduced. Those who want to know more detail are recommended to get a book “Health and Welfare Statistics in Japan” published by the government. J Epidemiol, 1996 ; 6 : S169-S184.

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The health and welfare administration system in Japan is based on the concept of “welfare nation” in the Constitution, and the Ministry of Health and Welfare has prime responsibility for general health and welfare administration. There are two levels of the prefectural governments and municipal governments with their own assemblies. The health centers and the welfare offices are special and first-line organizations for the health and welfare administration, and they are operated by the prefectures or large municipalities in principle. This system has now been experiencing the reform adapted to the aging of population, based on the amendment to the Health Service for the Aged Law and so on in 1990 and the amendment to the Health Center Law in 1994, which is now the Community Health Law. The municipal government is becoming a first-line organization for the health and welfare administration and its responsibility is growing especially in the personal service for the residents. J Epidemiol, 1996 ; 6 : S185-S188.

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The National Nutrition Survey in Japan has played an important role for nutrition policy in this country, by monitoring nutrition and health status of the Japanese since 1946. During those 50 years, diet of the Japanese has remarkably changed, with the proportion of fat intake in total energy being more than 25% and salt intake gradually decreased. The aim of this survey also has shifted from the policy making for food supplies to monitoring the over intake for prevention of diet-related chronic diseases and health promotion. J Epidemiol, 1996 ; 6 : S189-S200.

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