Shigeru Sokejima

Working hours as a risk factor for acute myocardial infarction in Japan: case-control study

Abstract Objective: To clarify the extent to which working hours affect the risk of acute myocardial infarction, independent of established risk factors and occupational conditions. Design: Case-control study. Setting: University and general hospitals and routine medical examinations at workplaces in Japan. Subjects: Cases were 195 men aged 30-69 years admitted to hospital with acute myocardial infarction during 1990-3. Controls were 331 men matched at group level for age and occupation who were judged to be free of coronary heart diseases at routine medical examinations in the workplace. Main outcome measures: Odds ratios for myocardial infarction in relation to previous mean daily working hours in a month and changes in mean working hours during previous year. Results: Compared with men with mean working hours of >7-9 hours, the odds ratio of acute myocardial infarction (adjusted for age and occupation) for men with working hours of >11 hours was 2.44 (95% confidence interval 1.26 to 4.73) and for men with working hours of 7 hours was 3.07 (1.77 to 5.32). Compared with men who experienced an increase of 1 hour in mean working hours, the adjusted odds ratio of myocardial infarction for men who experienced an increase of >3 hours was 2.53 (1.34 to 4.77). No appreciable change was observed when odds ratios were adjusted for established and psychosocial risk factors for myocardial infarction. Conclusion: There was a U shaped relation between the mean working hours and the risk of acute myocardial infarction. There also seemed to be a trend for the risk of infarction to increase with greater increases in mean working hours.

Role of taurine supplementation to prevent exercise-induced oxidative stress in healthy young men

Summary. To evaluate the protective effects of taurine supplementation on exercise-induced oxidative stress and exercise performance, eleven men aged 18–20 years were selected to participate in two identical bicycle ergometer exercises until exhaustion. Single cell gel assay (SCG assay) was used to study DNA damage in white blood cells (WBC). Pre-supplementation of taurine, a significant negative correlation was found between plasma taurine concentration before exercise and plasma thiobaribituric-acid reactive substance (TBARS) 6 hr after exercise (r=−0.642, p<0.05). WBC showed a significant increase in DNA strand breakage 6 hr and 24 hr after exercise. Seven-day taurine supplementation reduced serum TBARS before exercise (p<0.05) and resulted in a significantly reduced DNA migration 24 hr after exercise (p<0.01). Significant increases were also found in VO2max, exercise time to exhaustion and maximal workload in test with taurine supplementation (p<0.05). After supplementation, the change in taurine concentration showed positive correlations with the changes in exercise time to exhaustion and maximal workload. The results suggest that taurine may attenuate exercise-induced DNA damage and enhance the capacity of exercise due to its cellular protective properties.

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.

Association between number of comorbid conditions, depression, and sleep quality using the Pittsburgh Sleep Quality Index: results from a population-based survey.

OBJECTIVES Although sleep problems are a serious public concern, it is not clear if the presence of depression or multiple comorbid conditions has an additive or multiplicative effect on sleep quality. METHODS We conducted a population-based, cross-sectional survey in a rural town in Japan. Multivariable-adjusted linear regression models were used to explore the association between the number of comorbid conditions and the Pittsburgh Sleep Quality Index (PSQI) global score. The association between the number of comorbid conditions and presence of depression, as defined by the five-item Mental Health Inventory (scores60), in those with poor quality sleep (PSQI global score>5) was determined using a non-parametric trend test. RESULTS Of 5107 respondents, 3403 (mean age: 51.0years, women: 52.6%) were used for the analysis after exclusion of missing PSQI data. The PSQI global score (mean: 4.9) increased as the number of comorbid conditions increased in a linear and statistically significant manner (p<0.0001). The PSQI global score increased by 0.374 for each additional comorbid condition (p<0.0001). Among those with poor sleep quality, the proportion with depression increased significantly and linearly (p<0.0001) as the number of comorbid conditions increased (37.5% for 0 vs. 59.9% for 4 comorbid conditions). CONCLUSION The number of comorbid conditions correlated positively with poor sleep quality, and as the number of comorbid conditions increased, the proportion of those also suffering from depression increased. Recognizing the signs of depression in patients with multiple comorbid conditions is important because of its exacerbation of poor sleep quality.

Health-related quality of life of mothers of children with leukemia in Japan.

Objective: The study compared the health-related quality of life (HRQOL) of Japanese mothers of children with leukemia to that of mothers of children without leukemia. Method: We used the Medical Outcomes Study 36-item Short-Form (SF-36) to measure the HRQOL of 97 mothers of children (average age 6.2, range 0–14) with leukemia diagnosed between 1999 and 2000, and compared their scores to those of 240 mothers of children without leukemia matched to the children with leukemia. Main results: Of the eight unadjusted domain scores of the SF-36, five were significantly low among mothers of children with leukemia compared to mothers of children without leukemia: ‘role-physical functioning’ (RP), ‘general health perception’ (GH), ‘vitality’ (VT), ‘social functioning’ (SF) and ‘mental health’ (MH). Their SF-36 domain scores, when adjusted for demographic and clinical factors were also significantly low in RP, GH, VT, SF, RE and MH. The MH and SF scores in mothers of children with leukemia requiring hospital care were, respectively, approximately 20 points (1 standard deviation (SD), p < 0.0001) and 30 points (1.5 SD, p < 0.0001) lower than that of mothers of children without leukemia. Conclusion: Mothers of children with leukemia requiring hospital care have poor HRQOL, particularly with regard to mental health and social functioning, and are at a greater risk for depression. These results suggest that the current system for treating leukemic diseases of children in Japan should also include close monitoring of mothers’ mental health, and provision of appropriate treatment and psycho-social support.

Effects of short-term W-CDMA mobile phone base station exposure on women with or without mobile phone related symptoms

To investigate possible health effects of mobile phone use, we conducted a double-blind, cross-over provocation study to confirm whether subjects with mobile phone related symptoms (MPRS) are more susceptible than control subjects to the effect of electromagnetic fields (EMF) emitted from base stations. We sent questionnaires to 5,000 women and obtained 2,472 valid responses from possible candidates; from these, we recruited 11 subjects with MPRS and 43 controls. There were four EMF exposure conditions, each of which lasted 30 min: continuous, intermittent, and sham exposure with and without noise. Subjects were exposed to EMF of 2.14 GHz, 10 V/m (W-CDMA), in a shielded room to simulate whole-body exposure to EMF from base stations, although the exposure strength we used was higher than that commonly received from base stations. We measured several psychological and cognitive parameters pre- and post-exposure, and monitored autonomic functions. Subjects were asked to report on their perception of EMF and level of discomfort during the experiment. The MPRS group did not differ from the controls in their ability to detect exposure to EMF; nevertheless they consistently experienced more discomfort, regardless of whether or not they were actually exposed to EMF, and despite the lack of significant changes in their autonomic functions. Thus, the two groups did not differ in their responses to real or sham EMF exposure according to any psychological, cognitive or autonomic assessment. In conclusion, we found no evidence of any causal link between hypersensitivity symptoms and exposure to EMF from base stations.

Seismic intensity and risk of cerebrovascular stroke: 1995 Hanshin-Awaji earthquake.

INTRODUCTION No epidemiological data exist concerning the influence of an earthquake on the risk of stroke. Whether the incidence of cerebrovascular stroke increased after the 1995 Hanshin-Awaji earthquake (EQ) in Japan and whether seismic intensity affected stroke risk dose-dependently was examined. METHODS A retrospective cohort study was conducted among residents, who were living in two towns on the island of Awaji and were participants of the National Health Insurance (NHI) program. The two towns were divided into 11 districts and their respective damage and socioeconomic states were investigated. Reviewing the NHI documents issued before and after the EQ, people who had strokes (9th International Classification of Diseases, codes 430-431 or 433-434.9) were identified. Risk of stroke in relation to the seismic intensities, was assessed with the Cox proportional hazard model. RESULTS Among subjects aged 40 to 99 years, 45 of 8,758 (0.514%) had a stroke the year before the EQ 72 of 8,893 (0.810%) had a stroke in the first year following the EQ, and 49 of 8,710 (0.566%) had a stroke in the second year following the EQ. In districts where the earthquakes intensity was < or = 9.5 on the modified Mercalli intensity (MMI), compared with the year prior to the EQ, the relative risk (RR) of stroke was 2.4 (95% confidence interval (CI) = 1.1, 5.0) in the first year following the EQ, after adjusting for age, gender, and income. In that year, compared with MMI of < 8.5-9.0, RRs for 9.0-9.5 and > or = 9.5 were 1.6 (CI = 0.9, 2.1) and 2.0 (CI = 1.1, 3.7), respectively (p for trend 0.02). No trend for the RR was observed in the year before the EQ or in the second year following the EQ. CONCLUSION The incidence of stroke increased in the first year following the EQ. The increase was associated with seismic intensity in a dose-response manner. Results suggest a potential threshold for RR of > or = 2.0 in areas near 9.5 on the MMI scale.

Daily Dietary Tautine Intake in Japan

Our data indicate that dietary taurine intake calculated from 24-hour dietary recalls using the taurine composition tables offoods and using dietary fish and shellfish intake calculated from 24-hour dietary recalls may be useful indexes of dietary taurine intake for nutritional epidemiological studies. Further examination will be required.

Power-Frequency Magnetic Fields and Childhood Brain Tumors: A Case-Control Study in Japan

Background The strength of the association between brain tumors in children and residential power-frequency magnetic fields (MF) has varied in previous studies, which may be due in part to possible misclassification of MF exposure. This study aimed to examine this association in Japan by improving measurement techniques, and by extending measurement to a whole week. Methods This population-based case-control study encompassed 54% of Japanese children under 15 years of age. After excluding ineligible targeted children, 55 newly diagnosed brain tumor cases and 99 sex-, age-, and residential area-matched controls were included in the analyses. The MF exposures of each set of matching cases and controls were measured in close temporal proximity to control for seasonal variation; the average difference was 12.4 days. The mean interval between diagnosis and MF measurements was 1.1 years. The weekly mean MF level was defined as the exposure. The association was evaluated using conditional logistic regression analysis that controlled for possible confounding factors. Results The odds ratios (95% CI) for exposure categories of 0.1 to 0.2, 0.2 to 0.4, and above 0.4 µT, against a reference category of <0.1 µT, were 0.74 (0.17–3.18), 1.58 (0.25–9.83), and 10.9 (1.05–113), respectively, after adjusting for maternal education. This dose-response pattern was stable when other variables were included in the model as possible confounding factors. Conclusions A positive association was found between high-level exposure—above 0.4 µT—and the risk of brain tumors. This association could not be explained solely by confounding factors or selection bias.

The association between socioeconomic status and prevalence of diabetes mellitus in rural Japan.

ABSTRACT The objective of this study is to investigate the association between socioeconomic status and diabetes prevalence. A population-based cross-sectional survey was conducted in Japan. The association between household income tertile, duration of education (<12, 12, >12 years), or occupation (blue collar, white collar) and diabetes prevalence were assessed in 6,197 participants using multivariable-adjusted logistic regression models. Blue collar occupation and middle household income were found to be associated with high prevalence of diabetes mellitus.