A strong inverse association was observed in the relationship between sleeping hours and childhood obesity. Longitudinal research will be required to confirm this causality.

The aim of this study was to clarify the impact of parental obesity and lifestyle factors on obesity in preschool children. The subjects consisted of 8941 children aged 3 years, born in 1989. Anthropometric measurements and questionnaire surveys were conducted between 1992 and 1994. Subjects of body mass index (BMI; (weight (kg))/(height (m))2) more than the age- and sex-specific centiles linked to adult overweight were defined as obese subjects. Parental obesity was defined as BMI of 25 kg/m2 or more. Logistic regression analysis was performed to clarify the strengths of parental and lifestyle factors on childhood obesity, adjusted for possible confounding factors. Odds ratios (ORs) of paternal and maternal obesity for childhood obesity were 1.70(1.43-2.02) and 2.56(2.07-3.17), respectively. There was a dose-response relationship between short sleeping hours and obesity. Compared to subjects taking 11 hours sleep or more, the adjusted OR was 1.20(0.97-1.49) for those taking 10 to 11 hours sleep, 1.34(1.05-1.72) for those taking 9 to 10 hours sleep, and 1.57(0.90-2.75) for those taking less than 9 hours sleep. Eating and exercising habits were not significantly associated with obesity. These results indicate that parental obesity and short sleeping hours are possible risk factors for obesity in preschool children.

It has been observed that obese children receive genetic and environmental effects that are associated with them being overweight. With regard to the latter, lifestyles such as eating habits and physical activity have been focused on. In the present study, the social characteristics which would dominate their lifestyles were investigated as background variables. For this purpose, 9668 Japanese children aged three years who were all born in Toyama prefecture, Japan, in 1998, served as birth cohort subjects. For the comparison between obese (Kaup Index; mass in kg/(height in m)2 > or = 18) and nonobese (Kaup index < 18) children, irregular snack intake, physical inactivity and reduced sleeping hours were chosen as statistically significant obesity-related lifestyle indicators for the children. For social characteristics, family construction (expanded family with grandparents/nonexpanded family), main caregiver (mother/other), attending a nursery school (yes/no) and mother's employment (full-time worker/other) were chosen. These were significantly associated with the obesity-related lifestyles mentioned above using multiple logistic regression analysis adjusted for other variables of social characteristics as well as for gender and birth month (July-December/January-June). The two greatest population-attributable risk percentages were observed for mother as main caregiver (-36.5%) and attending a nursery school (-28.9%) for irregular snack intake. Therefore, these two social characteristics substantially reduced the number of children with irregular snack intake. On the other hand, the two social characteristics were reversed in children with reduced sleeping hours (population-attributable risk percentage of mother as main caregiver: 15.4%; attending a nursery school: 17%). In contrast with favourable effects on snack intake these social characteristics showed an adverse influence on the sleeping habits of children.

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 child's 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 lT or higher compared with the reference category (MF levels below 0.1 lT) was 2.6 (95% CI 5 0.76-8.6) for AML 1 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 lT. Our results provided additional evidence that high MF exposure was associated with a higher risk of childhood leukemia, particularly of ALL. ' 2006 Wiley-Liss, Inc.Key words: residential magnetic fields; childhood leukemia; population-based; case-control study; Japan Exposure to residential power-frequency magnetic fields (MFs) has been suspected to increase the risk of childhood leukemia, although the risk suggested by the first report 1 has not consistently been supported by the following ones.2-10 Recently, however, pooled analyses conducted by Ahlbom et al.11 used geometric means of MF levels and showed that the estimated summary relative risk was 2.00 (95% CI 5 1.27-3.13) when 0.41 lT was compared with < 0.1 lT. Another pooled analysis by Greenland et al.12 used arithmetic means of MF levels and showed that the Mantel-Haenszel odds ratio comparing 0.31 lT with < 0.1 lT was 1.7 (95% CI 5 1.2-2.3).Still, the small number of cases in high-dose ranges remains one of the limitations of these pooled analyses, and the causal inference remains tenuous because of little evidence from animal experiments and lack of appropriate biologic models. Thus, the World Health Organization recommended conducting one or more epidemiologic studies to evaluate the risk with more subjects exposed to high MF levels in 1999, 13 although the International Agency for Research on Cancer (IARC) rated the power-frequency MF as a possible human carcinogen in 2002 14 mainly based on the above finding by the pooled analyses.Thus, the present nationwide case-control study of childhood leukemia was conducted in Japan, where high MF exposures were expected to be ...

Techniques capable of localized imaging of the structure of hydrogen-bearing crystalline materials at the atomic scale have been conspicuously absent. We show that annular bright field scanning transmission electron microscopy enables the direct imaging of hydrogen atomic columns within a sample of vanadium dihydride, VH 2 . The suitability of this technique for quantification of the hydrogen content is discussed.