The high-risk and population strategy for occupational health promotion (HIPOP-OHP) study: study design and cardiovascular risk factors at the baseline survey.

In order to establish the methodology of a population strategy for improving cardiovascular risk factors, we have planned the High-risk and Population Strategy for Occupational Health Promotion Study (HIPOP-OHP study). This study is a nonrandomized control trial in approximately 6500 participants in six intervention and six control companies. Our population strategy is based on three factors, nutrition, physical activity, and smoking. For each factor, a researcher's working team was organized and has been supporting the intervention. A standardized method to obtain comparable data has also been established. In the baseline survey, urinary sodium excretion in male subjects was higher, and urinary potassium excretion was lower in both genders in the intervention group compared to the control group. The prevalence of hypertension for both genders was also higher in the intervention group. Male subjects in the intervention group had higher serum total cholesterol than controls, while high-density lipoprotein cholesterol was lower in both genders in the intervention group compared to the control group. These differences were reflected by our finding that the predicted relative risk of coronary heart disease for male subjects was significantly higher in the intervention group (relative risk, RR: 1.17; 95% confidence interval, 95% CI.: 1.09, 1.25) and significantly lower in the control group (RR: 0.93; 95% CI.: 0.89, 0.98) compared to a model Japanese population. Similar results were observed in the female subjects. Taken together, these findings indicate that it is possible to compare trends of predicted relative risk for coronary heart disease between two groups.

[Causal inference in medicine--decision making].

In the field of occupational medicine, either when we consider some preventive plans or when we make decisions to compensate for occupational diseases, it has been necessary to discuss causality between work and disease. Furthermore, epidemiologic causality has recently been used in risk assessment in occupational and environmental settings. We have shown that the law of causality in medicine is recognized as probability and continuous variables. Such a law of causality has been recognized in the same way as probability in physics, too, and has been regarded as a model of science. Physicists and mathematicians had claimed the importance of probability in causal inference as well as the principle of uncertainty before it was discovered. We, then, explained Etiologic Fraction (EF), Attributable Proportion for the Exposed Population (APE), Probability of Causation (PC), and so on. The PC has been used to ascertain the conditional probability in an individual case of a disease having been caused by a particular prior exposure, by using the experience of exposed populations to determine the appropriate relative risk, and this has been used for compensation for exposed cases. Next the applicability of information from a population to individuals was presented. Third, we provided a brief historical aspect of epidemiology. The evolutions in Epidemiology have been very rapid, so we pointed out that, in Japan, we could observe many incommensurable phenomena in epidemiologists and physicians depending on the era which was studied by them. Fourth, we discussed judgement and political application based on epidemiologic evidence, using Yanagimoto's classification is also taken or not should be estimated and compared. We presented several examples of reasoning in judgements. Lastly, we discussed several tasks and assignments for the future of epidemiology.

Smoking and mental health: cross-sectional and cohort studies in an occupational setting in Japan.

BACKGROUND: The relationship between smoking and mental health remains unclear. METHODS: We carried out a cross-sectional study and a cohort study on the possible association of smoking and mental health in 782 workers. Using a questionnaire including the 30-item General Health Questionnaire (GHQ-30) and items related to the smoking state, the association between smoking and mental health was evaluated separately in males and females. The subjects were classified into smokers and nonsmokers, and changes in the GHQ score during a 2-year follow-up period were evaluated. To control potential confounding factors, multiple regression analyses were performed. RESULTS: The cross-sectional study showed no difference in the GHQ score between smokers and nonsmokers among males but a significantly higher GHQ score for smokers than nonsmokers among females. This difference among females was confirmed to be significant by multiple regression analysis. The 2-year cohort study showed a decrease in the GHQ score in each group and no reduction in the difference in the GHQ score between smokers and nonsmokers among females. CONCLUSIONS: No difference was observed in mental health between smokers and nonsmokers in males. However, in females, smokers showed poorer mental health than nonsmokers, and this difference remained unchanged even after 2 years.

A case-control study of the relationships among silica exposure, gastric cancer, and esophageal cancer.

BACKGROUND: We examined the effect of silica exposure on gastric and esophageal cancer mortality using a cancer control series in a population setting. METHODS: Cases and controls were restricted to male subjects and were drawn from death certificates in the Tobi area of Japan. A control group was selected from a series of deaths due to colon cancer, and cancers of other organs. The Japanese death certificate system is comprehensive because all deaths must be reported to the local office and death certificates are written by medical doctors. Age and smoking habits adjusted the Mantel-Haenszel odds ratios were estimated. RESULTS: For gastric cancer, the age-, smoking-adjusted odds ratios were 1.22 (95% CI 0.74-2.01) for colon cancer and the other cancer control for silica exposure work, and 1. 36 (95% CI 0.76-2.43) for silicosis. For esophageal cancer, the age- and smoking-adjusted odds ratios were 1.53 (95% CI 0.59-3.96) for the cancer control for silica exposure, and 2.33 (95% CI 0.87-6.23) for silicosis, respectively. CONCLUSIONS: The results suggest that gastric and esophageal cancer were related to silica exposure and silicosis in the study area, although they did not reach a statistically significant level because of the small sample size. The estimated odds ratios were higher for esophageal cancer and silicotic patients.

[Achievement of causal inference in the social medicine in Japan].

As a condition to achieving an agreement of recognition on the causal relationship in medicine, we firstly explained Hume's problem and counterfactual model. We, however, emphasized that we believe in the existence of causality on medical issues in our daily lives. Therefore, we illustrated conditions when we usually believe in causality. On the other hand, we criticized two well-known key phrases, "lack of mechanism in epidemiology" and "black box in epidemiology", which have often been used in Japan for skeptic viewpoints against epidemiologic methods even if epidemiology is often used to elucidate a causal effect in medicine in the world. We emphasized that a priori determinations of levels for inference of mechanism is necessary. And, the level and feature of mechanism should be defined in concrete expressions. After explanation of these basic concepts, we mentioned a classic view on specific diseases and non-specific diseases which have not been sufficiently discussed enough yet in Japan. As an example, we used the statements in the Japanese Compensation Law for the Health Effect by Environmental Pollution. In Japan, the classification of these diseases has been confused with that between manifestational criteria of diseases and causal criteria of them. We described the basic concepts to illustrate the causal relationship between non-specific disease and its exposure by using attached figures. Actually, we cannot recognize disease occurrence as a specific disease for several reasons. We indicated that we can recognize the magnitude of effect by causal relationships in medicine as a quantitative continuous variable.

Does smoking cessation improve mental health?

There is a possibility that cessation of smoking improves mental health, but there are no studies that have demonstrated this. A cohort study was performed for 1 year in 18 males who spontaneously stopped smoking (cessation group) and 173 who continued to smoke (smoking group). The mental health state was evaluated using the Japanese version of the 30-item General Health Questionnaire (GHQ-30) before the cessation of smoking and 6 months and 1 year after smoking cessation. Changes in the GHQ score were compared between the cessation and smoking groups. In order to control the effects of confounding factors, multiple regression analyses were performed using the GHQ score after 6 months and 1 year as dependent variables. The GHQ score in the cessation group significantly decreased 6 months and 1 year after smoking cessation (P < 0.04 and 0.01, respectively, by paired t-test). In the smoking group, the GHQ score slightly decreased. Repeated measure analysis of variance revealed that the decrease in the GHQ score in the cessation group was significantly larger than in the smoking group. Multiple regression analysis revealed significant effects of smoking cessation on mental health after controlling for other confounding factors. It can be concluded that smoking cessation may improve mental health.

Women's anxiety in old age and long-term care provision for the elderly.

The purpose of this study was to verify the differences in women's anxiety in old age, the expected long-term care provision, and the expected final location for terminal care for the women themselves and for their parents. In addition, we examined factors that related to their anxiety and needs. The subjects were 1,000 women of the Seikatsu Club customer cooperative association in Chiba; 539 responded to our survey. The subjects were more anxious for their parents than for themselves. They more strongly expected long-term care for their parents to be provided by their family than they expected the same for themselves. Although no differences were observed in the expected location for terminal care, most subjects expected their home to be the terminal location. Analysis by the multiple logistic regression model indicated that the following factors were significantly related to the anxiety in old age: age odds ratio [OR = 1.81], employment [OR = 2.25] for women, and planning to live with parents [OR = 2.42], housing conditions [OR = 0.56] for parents. The following factors were significantly related to the expected long-term care provision: age [OR = 2.22] for women, and age [OR = 2.15], living with parents [OR = 3.58], and employment [OR = 2.33] for parents. Age [OR = 2.14] for women, and planning to live with parents [OR = 2.09] for parents were significantly related to the expected final location of terminal care. This survey showed that women expected long-term care for their parents to be provided by their family, while many expected public long-term care services for themselves. This is the biggest difference in women's outlook on long-term care for their parents and for themselves. Multivariate analysis suggested that women aged 40 years or over, who will need long-term care in the future, tended to expect public home care services for themselves. It is virtually certain that the demand for public home care services will increase in the future.

The effect of a redistribution system for health care for the elderly on the financial performance of health insurance societies in Japan.

Health care for the elderly in Japan is financed through a pool to which all insurers contribute. We analyzed insurers' financial data to evaluate this redistribution system. Cost sharing affected financial performance substantially. The current formula for cost-sharing redistributes elderly health care costs unequally and should be changed.

Health policy in transition: terminal care and site of death in Japan.

OBJECTIVES: In Japan, hospitals have replaced homes as the predominant site of death, especially for the elderly. Site of death is a reliable indicator of where older people receive care before they die. We conducted a population-based study to identify the factors that determine site of death in a typical rural area in Japan. METHODS: Study subjects were residents of Kawakami town, aged 70 years or older, who died during 1981 and 1990. Death certificates provided information on age, gender, cause of death, duration of illness before death, family members, family occupation, and site of death. RESULTS: Among 455 subjects, 52.7% died at home, while 47.3% died in hospital. Multiple logistic regression analyses indicated that subjects with cancer were 6.1 times more likely to die in hospitals than those with other diseases. Subjects who died in their seventies were 2.3 times more likely to die in hospital than older subjects. Members of non-farming families were 1.7 times more likely to die in hospital than members of farming families. Gender, duration of illness, and the presence of spouse or children in the household were not significantly related to site of death according to multivariate analyses, although trends did exist. CONCLUSION: This case study illustrates the importance of developing geriatric care systems in Japan, utilizing alternatives to hospitals, such as nursing homes and formal home care. This is particularly true for patients with cancer. As the older population rapidly increases in Japan, the need for alternatives in geriatric care grows more critical.

[Causal inference in medicine: a reaction to the report, "incidence of Minamata disease in communities along the Agano River, Niigata, Japan--patterns of the exposure and official diagnosis of patients"].

Kondo's "Incidence of Minamata Disease in Communities along the Agano River, Niigata, Japan (Jap. J. Hyg. 51:599-611;1996)" is critically reviewed. The data of the article were obtained from most of the residents living in the Agano river villages where Minamata disease was discovered in June, 1965. However, sampling proportions were much different between in the population base and in the cases. The method of identification of cases from the data and the reason for the difference were not clearly demonstrated. The citations of reference articles are insufficient despite the fact that other epidemiologic studies on methyl-mercury poisoning have been reported not only in Japan, but also around the world. His "analysis of the recognized patients" is erroneous. Both the sampling scheme of information of hair mercury and the modeling of the analysis are based on Kondo's arbitrary interpretation, not on epidemiologic theory. His "analysis of the rejected applicants" is also erroneous. His calculations of the attributable proportion are incorrect and self-induced in both the assignments of data and analysis of data. Kondo has failed to study the epidemiologic theories in light of changes in the field. Therefore, his article is lacking in epidemiologic theory, a logical base and scientific inference. In Japan, epidemiologic methodology has rarely been used in studies on Minamata Disease in either Kumamoto and Niigata. The government has used neurologically specific diagnosis based on combinations of symptoms to judge the causality between each of symptoms and methyl-mercury poisoning. Epidemiologic data obtained in Minamata, Kumamoto in 1971 indicate that the criteria set by the government in 1977 have produced much more false-negative patients than false-positive patients. As a result, a huge number of symptomatic patients, including those with peripheral neuropathy or with constriction of the visual field, did not receive any help or compensation until 1995. The authors emphasize that the causal relationship between each symptom and methyl-mercury exposure should be reevaluated epidemiologically in Japan.

The relationship between job stress and mental health at work.

In order to evaluate the relationship between job stress and mental health, a cross-sectional study was conducted using a questionnaire relating to demographics, subjective job stress and mental health state. The questionnaire consisted of a 30-item Japanese version of the General Health Questionnaire (GHQ) developed by Goldberg in addition to questions about subjective job stress, to measure mental health and job stress conditions, respectively. All subjects were employees of an electronic company in Japan. Among 782 workers, 763 workers responded to the questionnaire satisfactorily (response rate was 97.6%). People whose GHQ score was more than 7 were classified as having psychiatric problems, while the remaining respondents were considered as having no mental health problems. We employed a multiple logistic regression analysis to estimate the relationship between subjective job stress and mental health, adjusting for gender, age, marital state, familial stress, and physical health state. Subjective job stress was significantly associated with the state of mental health. In particular, the items of "too much trouble at work," "too much responsibility," "are not allowed to make mistakes," "poor relationship with superiors," and "cannot keep up with technology" were significantly related to mental health.

Time to systemic metastases in patients with posterior uveal melanoma.

A total of 116 patients, all of whom had systemic metastases from posterior uveal melanoma, were evaluated to identify potential indicators for time to systemic metastasis. In the multivariate Cox proportional hazards model with clinically available variables, the age at initial treatment for uveal melanoma, gender and diameter of the primary tumor were revealed to be independent predictive factors for time to systemic metastasis. Age older than 60 years, male gender, and diameter of the primary uveal melanoma more than 10 mm were proved to be independent unfavorable factors. The estimated median time to systemic metastasis for the most unfavorable group (age > 60, male, diameter > 10 mm) was 20.2 months in contrast with 76.1 months for the most favorable group (age < or = 60, female, diameter < or = 10 mm). Although the results of this study cannot be applied to all patients with posterior uveal melanoma, predictive factors for time to systemic metastasis in those patients who have recurred supplement the information obtained from prognostic factors for the likelihood of metastasis or survival. They contribute not only to our understanding of the biology of metastasizing posterior uveal melanoma, but also in developing appropriate strategies for follow-up and treatment.

Relation between the instrumental activities of daily living and physical fitness tests in elderly women.

A cross-sectional study was conducted to quantitatively evaluate the relationship between the instrumental activities of daily living (IADL) and various physical fitness tests in elderly women living at home. The study focused on the total population of those women aged 65 years and over living in Y Town, Hyogo Prefecture, Japan, who visited a nursing home for day services. A total of 128 subjects were divided into two groups: dependent in IADL group (n = 49) and independent in IADL group (n = 79). The magnitude of the relation was evaluated by the odds ratio (OR). The following tests showed a significant decrease in IADL: knee-raising test [age-adjusted OR = 4.23, 95% confidence interval (CI) 1.81-9.87], height (age-adjusted OR = 4.09, 95% CI 1.75-9.56), grip strength (age-adjusted OR = 3.68, 95% CI 1.57-8.60), sit-and-reach test (age-adjusted OR = 2.76, 95% CI 1.20-6.34), and standing on one leg with closed eyes (age-adjusted OR = 2.56, 95% CI 1.09-5.97). Multivariate analysis using Hayashi's quantification method I indicated that knee-raising was the test most highly correlated with decreased IADL. These results suggest that measurement of knee-raising ability, muscle strength of the lower extremities and flexibility of hip joint could be the most useful factors to assess the level of instrumental self-support ability.

[The US Health Care and the reform].

Securing access to medical services, controlling costs and improving quality are goals of health care system. Although they are all the same all over the country, each country has its own culture, health care system and health care problems. In the United States, employer-based and individual purchases of private health insurance coverage play a major role, although governmental programs such as Medicaid and Medicare exist for the poor and the elderly. Private health insurance had traditionally secured patients' freedom of choice of health care providers and physicians' professional freedom and had paid providers on a fee-for-service basis. Now, the U.S. has 40 million uninsured persons who do not have access to medical services, although it spends as much as its 14% of GNP on health care. In the early 1990s, this became a major political problem. President Clinton proposed the 'Health Security Act' which would enable any American to have access to comprehensive health care with managed competition to activate the health care market, but it was not enacted. Nevertheless, it is clear that managed care and managed competition will dominate and that traditional fee-for-service plan will be eroded in the health care market. Japan has a universal health care system. We do not have any uninsured or high medical costs. However, it is difficult to improve the quality of health care services within the present system. Japan can learn the system about disclosure of health care information from the managed care in the U.S.

[Causal inference in medicine--a historical view in epidemiology].

Changes of causal inference concepts in medicine, especially those having to do with chronic diseases, were reviewed. The review is divided into five sections. First, several articles on the increased academic acceptance of observational research are cited. Second, the definitions of confounder and effect modifier concepts are explained. Third, the debate over the so-called "criteria for causal inference" was discussed. Many articles have pointed out various problems related to the lack of logical bases for standard criteria, however, such criteria continue to be misapplied in Japan. Fourth, the Popperian and verificationist concepts of causal inference are summarized. Lastly, a recent controversy on meta-analysis is explained. Causal inference plays an important role in epidemiologic theory and medicine. However, because this concept has not been well-introduced in Japan, there has been much misuse of the concept, especially when used for conventional criteria.