We conducted three prospective cohort studies that examined the association between body mass index (BMI) and health outcomes in Japan. Our studies found statistically significant relationships between excess body weight and increased medical costs, all-cause mortality, and risk of cancer incidence. There was a U-shaped association between BMI and mean total costs. The estimated excess costs attributable to overweight and obesity was 3.2% of the total costs. This 3.2% is within the range reported in studies in Western countries (0.7%-6.8%). We observed statistically significant elevations in mortality risk in obese (BMI≥ 30.0kg/m2) women and lean (BMI<18.5 kg/m2) men and women. Our prospective cohort study found statistically significant relationships between excess weight and increased risk in women of all cancers. The population attributable fraction (PAF) of all incident cancers in this population that were attributable to overweight and obesity were 4.5% in women, which were within the range reported from Western populations, from 3.2% for US women to 8.8% for Spanish women. Our data suggests that excess body weight is a problem not only in Western countries but also in Japan. J Epidemiol 2006; 16: 139-144.
In order to evaluate the accuracy of diagnostic tests based on 2×2 tables, a number of indices were used, some of which are occasionally used inappropriately. This paper demonstrates the characteristics and problems with those indices, and introduces several methods to compare the accuracy of two diagnostic tests. The author summarizes existing indices based on 2×2 tables, agreement rate, kappa (κ), and odds ratio, and reviews their characteristics to find better indices by which to compare two diagnostic tests using hypothetical examples. Because only the odds ratio is not affected by prevalence, the relative odds ratio is the most appropriate index for comparing diagnostic accuracy. In order to decrease selection bias, giving the two tests to the same individuals is preferred. However, no standard method has been established to obtain the standard error of relative odds ratios. In this case, using the newly proposed conditional relative odds ratio (CROR), based on McNemar's odds ratio, the standard error is available. The CROR is a less biased index when the two tests were given to the same individuals, and it is also preferable in light of its ethical and economic advantages. However, a large base population is required for the two tests to be highly accurate and produce few discordant results. J Epidemiol 2006; 16: 145-153.
BACKGROUND: Some observational epidemiologic studies suggest that dietary and serum carotenoids are associated with reduced cardiovascular disease mortality. METHODS: Three thousand and sixty-one subjects (1,190 males and 1,871 females), aged 39 to 80 years, were recruited from residents of Hokkaido, Japan who had attended comprehensive health check-up programs from 1988 through 1995. Serum levels of α-carotene, β-carotene, and lycopene were separately determined by high-performance liquid chromatography. Serum levels of total carotene consisted of the sum of α-carotene, β-carotene, and lycopene levels. Each serum level of α-carotene, β-carotene, lycopene, total carotene, triglyceride, and alanine transaminase (ALT) activity was transformed logarithmically. The hazard ratios of serum α- and β-carotenes, lycopene, and total carotene values were estimated by the Cox proportional hazard model after adjusting for sex, age, and other potential confounding factors. RESULTS: During the 11.9-year follow-up period, 80 deaths (49 males and 31 females) from cardiovascular disease, 40 deaths from heart disease, and 37 deaths from stroke were identified among the cohort subjects. High serum values of carotenoids such as α- and β-carotenes, and lycopene were found to be significantly associated with low hazard ratios for cardiovascular disease mortality. However, a significant inverse association between high serum lycopene value and the risk for stroke mortality was not always observed. CONCLUSIONS: High serum levels of total carotene, comprising α- and β-carotenes and lycopene, may reduce the risk for cardiovascular disease mortality among the Japanese population. J Epidemiol 2006; 16: 154-160.
BACKGROUND: Although several studies have reported increased mortality risk with early menopause, there were no studies examining the relationship between age at menopause and mortality in Japan. The goal of this analysis is to investigate the relationship between age at menopause and all-cause mortality among the Japanese. METHODS: Study subjects were 4,683 postmenopausal females in the Jichi Medical School Cohort Study, a population-based prospective study. Baseline data were obtained by questionnaire and health checkups between April 1992 and July 1995 in 12 rural areas in Japan. Main outcome measures were all-cause mortality derived from death certificates up to December 31, 2002. Cox's proportional hazard models were used to analyze the association of age at menopause with mortality. RESULTS: A total of 215 deaths were observed during the average of 9.2 year follow-up period. After adjusting for age, systolic blood pressure, serum total cholesterol level, serum high density lipoprotein cholesterol level, history of diabetes mellitus, body mass index, smoking habits, alcohol drinking habits, marital status, study area, and types of menopause, the hazard ratios (95% confidence intervals) of allcause mortality were 2.10 (1.07-4.11), 0.68 (0.36-1.26), 0.94 (0.68-1.30), and 1.17 (0.63-2.20) for females with a menopause at ages younger than 40 years, 40-44, 50-54, and 55 or older, respectively, relative to those with menopause at age 45-49 years. CONCLUSIONS: Our data suggest that menopause aged younger than 40 years increases the risk of death from all causes among the Japanese. J Epidemiol 2006; 16:161-166.
BACKGROUND: People under fragile-living conditions show a high rate of interruption of tuberculosis treatment. We examined the social courses of fragile-living urban dwellers with tuberculosis without customary and regular access to a conventional residence and investigated the factors associated with interruption of treatment. METHODS: One hundred and nineteen tuberculosis patients without customary and regular access to a conventional residence who were discharged from a hospital with the largest number of tuberculosis beds in Tokyo between January 1998 and October 2000 were followed up. The associations between demographic, social, and clinical characteristics and interruption of treatment were examined. RESULTS: The subjects (mean age, 51.2 years) were followed up for a median of 342 days. The percentage of cases of interruption of treatment during inpatient care among patients with alcohol problems (56%) was significantly higher than that among patients without such problems (11%). The proportion of cases of interruption of treatment during outpatient care among patients who were literally homeless before admission (40%) was significantly higher than that in others (5%), and that among those who used transient hostels after the initial inpatient treatment (55%) was significantly higher than that in others (4%). The prevalence of drug resistance was higher in cases with than without a history of tuberculosis treatment (P<0.05). CONCLUSIONS: Factors associated with interruption of tuberculosis treatment in patients under fragile-living conditions were identified. Interruption during inpatient care was significantly associated with alcohol problems, and interruption during outpatient care was significantly associated with the use of transient hostels. J Epidemiol 2006; 16: 167-175.