Toshiyuki Ojima

Childhood leukemia and magnetic fields in Japan: A case-control study of childhood leukemia and residential power-frequency magnetic fields in Japan

Residential power‐frequency magnetic fields (MFs) were labeled as a possible human carcinogen by the International Agency for Research on Cancer panel. In response to great public concern, the World Health Organization urged that further epidemiologic studies be conducted in high‐exposure areas such as Japan. We conducted a population‐based case‐control study, which covered areas inhabited by 54% of Japanese children. We analyzed 312 case children (0–15 years old) newly diagnosed with acute lymphoblastic leukemia (ALL) or acute myelocytic leukemia (AML) in 1999–2001 (2.3 years) and 603 controls matched for gender, age and residential area. Weekly mean MF level was determined for the childs bedroom. MF measurements in each set of a case and controls were carried out as closely in time as possible to control for seasonal variation. We evaluated the association using conditional logistic regression models. The odds ratios for children whose bedrooms had MF levels of 0.4 μT or higher compared with the reference category (MF levels below 0.1 μT) was 2.6 (95% CI = 0.76–8.6) for AML + ALL and 4.7 (1.15–19.0) for ALL only. Controlling for some possible confounding factors did not alter the results appreciably. Even an analysis in which selection bias was maximized did not fully explain the association. Most of the leukemia cases in the highest exposure category had MF levels far above 0.4 μT. Our results provided additional evidence that high MF exposure was associated with a higher risk of childhood leukemia, particularly of ALL.

Dietary patterns and levels of blood pressure and serum lipids in a Japanese population.

Background Associations between dietary patterns and cardiovascular disease risk factors remain unclear. The objective of this study was to evaluate the association between dietary patterns derived from factor analysis and the levels of blood pressure and serum lipids in a Japanese population. Methods We conducted a cross-sectional analysis among 6886 (in the analysis on blood pressure) and 7641 (in the analysis on serum lipids) Japanese subjects aged 40-69 years. Dietary patterns were identified from a food frequency questionnaire by factor analysis. Associations between dietary patterns and blood pressure and serum lipids were examined after taking potential confounders into account. Results Three dietary patterns were identified: vegetable, meat, and Western. In men, the meat pattern was associated with higher total, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) cholesterol. The Western pattern was associated with higher total and LDL cholesterol. In women, the vegetable pattern was associated with lower systolic and diastolic blood pressure and pulse pressure, and higher HDL cholesterol. The meat pattern was associated with higher total and HDL cholesterol. The Western pattern was associated with higher total, HDL, and LDL cholesterol, and the least intake pattern of Western diet was associated with higher systolic and diastolic blood pressures. Conclusions Dietary patterns of a Japanese population were related to cardiovascular disease risk factors, especially in women.

Use of laboratory data to identify risk factors of giant coronary aneurysms due to Kawasaki disease

Abstract Background : Although some laboratory findings are known to be indicators of the risk of giant coronary aneurysm formation among Kawasaki disease patients, an appropriate cut‐off point to predict aneurysm formation is not clear.

Frequency of Citrus Fruit Intake Is Associated With the Incidence of Cardiovascular Disease: The Jichi Medical School Cohort Study

Background It has been reported that fruit intake protects against cardiovascular disease (CVD). However, most of the relevant studies were conducted in Western countries, and only a few investigated Japanese populations. The present cohort study assessed the effect of citrus fruit intake on the incidence of CVD and its subtypes in a Japanese population. Methods A baseline examination consisting of physical and blood examinations and a self-administered questionnaire was conducted during the period from April 1992 through July 1995. Dietary habits were assessed using a food frequency questionnaire that was divided into 5 categories. Citrus fruit was examined separately due to its frequent consumption by the general Japanese population. Using the Cox proportional hazards model, data from 10 623 participants (4147 men, 6476 women) who had no history of CVD or carcinoma were analyzed to assess the association between frequency of citrus fruit intake and CVD incidence. Results Frequent intake of citrus fruit was associated with a lower incidence of CVD: the hazard ratio for almost daily intake versus infrequent intake of citrus fruit was 0.57 (95% confidence interval: 0.33–1.01, P for trend = 0.04) in men and 0.51 (0.29–0.88, P for trend = 0.02) in women. Frequent intake of citrus fruit was also associated with lower incidences of both all stroke and cerebral infarction, but not hemorrhagic stroke or myocardial infarction. Conclusions Frequent intake of citrus fruit may reduce the incidence of CVD, especially cerebral infarction, in men and women.

Low Control at Work and the Risk of Suicide in Japanese Men: A Prospective Cohort Study

Background: Although adverse psychosocial job characteristics are suspected predictors of suicide death, prospective studies based on established stress instruments are limited. Methods: In a multicenter community-based Japanese cohort study, we prospectively investigated the association between psychosocial job characteristics and the risk of death from suicide among male workers. Baseline examination was conducted from 1992 to 1995 to determine the socioeconomic, behavioural and biological variables in addition to the psychosocial job characteristics of 3,125 male workers aged 65 and under and free from major illness. Low job control and high job demands were measured as adverse psychosocial job characteristics according to a job demand-control model questionnaire. Suicide deaths were identified using the Cause-of-Death Register. Results: During the 9-year follow-up, 14 suicides were identified. The suicide death rate was 48.1 per 100,000 person years. Multivariate analysis revealed a more than fourfold increase in the risk of suicide among men with low control at work (relative risk: 4.10; 95% confidence interval: 1.31–12.83) compared with counterpart men after adjustment for age, marital status, educational attainment, occupation, smoking status, alcohol consumption, total cholesterol level, and study area. Job demands were not associated with risk of death from suicide. Conclusions: By using a job demand-control model questionnaire, low control at work was revealed as a predictor of suicide death among Japanese male workers. The finding implies that job redesign aimed at increased worker control could be a worthwhile strategy in preventing, or at least reducing, the risk of suicide death.

Masked Nocturnal Hypertension and Target Organ Damage in Hypertensives with Well- Controlled Self-Measured Home Blood Pressure

It has been reported that masked hypertension, a state in which patients show normal clinic blood pressure (BP) but elevated out-of-clinic BP by self-measured home BP, is a predictor of cardiovascular morbidity much like sustained hypertension. In addition, nocturnal BP is closely associated with cardiovascular disease. This might mean that ambulatory and self-measured home BP monitoring each provide independent information. We performed ambulatory BP monitoring, self-measured home BP monitoring, echocardiography and carotid ultrasonography in 165 community-dwelling subjects. We subclassified the patients according to the ambulatory and self-measured home BP levels as follows: in the masked nocturnal hypertension group, the self-measured home BP level was <135/85 mmHg and the ambulatory nocturnal BP level was ≥120/75 mmHg; in the normotensive group, the self-measured home BP level was <135/85 mmHg and the ambulatory nocturnal BP level was <120/75 mmHg. The intima-media thickness (IMT) and relative wall thickness (RWT) were greater in the masked nocturnal hypertension group than in the normotensive group (IMT: 0.76±0.20 vs. 0.64±0.14 mm, p<0.05; RWT: 0.50±0.14 vs. 0.41±0.10, p<0.05). Even in hypertensives with well-controlled self-measured home BP, elevated ambulatory nocturnal BP might promote target organ damage. We must rule out masked hypertension using self-measured home BP monitoring, and we might also need to rule out nocturnal masked hypertension using ambulatory BP monitoring.

Barriers to health care among the elderly in Japan.

Japan is undergoing a set of health care reforms aimed at cutting rising health care costs and increasing the efficiency of health care delivery. This empirical study used a large-scale community survey on 15,302 elderly people 65 years and older (56.0% women) conducted in seven municipalities in 2006, to reveal clear-cut evidence of barriers to necessary care. The reasons for not getting health care is attributed to health care cost for the elderly with lower income, while higher income counterparts reported being busy or having a condition not serious enough to seek care.

Changes in epidemic patterns of Kawasaki disease in Japan

OBJECTIVE Clustering of cases of Kawasaki disease throughout Japan was noted three times during the period before 1986. During the ensuing 10 years, however, no nationwide epidemic has been recognized. The purpose of this study is to test the hypothesis that local outbreaks have persisted after 1987. METHOD The data on 56 980 patients reported from 1987 through 1996 were classified according to the area of residence. The time trend of the incidence rate was compared by year and by quarter of the year (January to March, April to June, July to September and October to December) in 10 geographical areas in Japan. RESULTS No nationwide outbreaks have been noted since 1987 in Japan, but the existence of local outbreaks of various magnitudes was recognized as occurring in different periods in certain areas. The incidence rates were continuously high in Area 1 between 1987 and 1988 and in Area 4 between 1995 and 1996. In Area 9 local outbreaks were noted on three separate occasions (from 1987 to the first half of 1988, between 1990 and 1991 and from the second half of 1992 to 1993). No clusterings were witnessed in other areas during the 10-year period. CONCLUSION The current annual number of patients ranges from 5000 to 6000, and local epidemics occur in various areas. The current epidemiologic patterns support the infection theory for the etiology of this disease.

Trends in Disability-Free Life Expectancy in Japan, 1995–2004

Background In Japan, life expectancy at birth is currently the highest in the world. However, recent trends in disability-free life expectancy in Japan have not been examined. Methods We used data from Japanese national surveys for the period 1995–2004. These surveys included information on activity status measured by common self-reported instruments. The numbers of expected years with and without activity limitation were estimated by using the Sullivan method. Results The numbers of expected years of life without activity limitation, at birth, in 1995 and 2004 were 68.5 and 69.7, respectively, in males and 72.1 and 73.0 in females. As a proportion of total life expectancy, at birth, these values represent a decrease from 89.7% to 88.6% in males and from 87.1% to 85.3% in females. The proportion of expected years with a limitation of some activities except activities of daily living (ADL) increased in males and females. The proportion of those with an ADL limitation increased in females, but not in males. Conclusions The trends in expected years with and without activity limitation suggest that the duration of life with a light or moderate disability increased in Japanese males and females during the period 1995–2004.

PCDDs, PCdfs and Co-PCBs in human breast milk samples collected in Tokyo, Japan.

Aim: To observe the distribution of PCDD/Fs and Co‐PCBs in samples of human breast milk collected in Japan. Methods: Using high‐resolution gas chromatography, milk samples for poly‐chlorinated dibenzo‐p‐dioxins (PCDDs; 14 congeners), poly chlorinated dibenzofurans (PCDFs; 15 congeners) and coplanar poly chlorinated biphenyls (Co‐PCBs; 12 congeners) from 240 mothers residing in Tokyo were analysed. There were 120 donors each of primiparae and secundiparae, each group including 60 donors aged 25 to 29 y (“the younger group”) and 60 aged 30 to 34 y (“the older group”). Individual milk samples (about 50 ml) were obtained 30 d after delivery in 1999 and in 2000. Results: The mean toxic equivalent (TEQ) level of PCDD/Fs (the sum of PCDDs and PCDFs) was 14.9 pg TEQ/g fat, of Co‐PCBs 10.6 pg TEQ/g fat, and the total sum of PCDD/Fs and Co‐PCBs was 25.6 pg TEQ/g fat. The mean TEQ levels of PCDD/Fs, Co‐PCBs, and total PCDD/Fs and Co‐PCBs were higher in primiparae than in secundiparae. In each of these, the levels were higher in the subgroup of older mothers. In the secundiparae, the mean levels were lower in the group of mothers who had breastfed their first babies than in those who bottle‐fed or partly bottle‐fed their first born.