高尾 総司

We discuss the concept of social capital, which has received much attention recently. Social capital is important for the following 2 key reasons:(1) a highly democratic polity and a strong economic performance that attaches great importance to the public good can be achieved on the basis of high social capital;and (2) social capital can effect health status in the human population, and widening of income inequality harms human health through the erosion of social capital. In addition, there are 3 political implications of social capital for Japanese society:(1) social capital has implications for the political decision of whether Japanese society should adopt a “medium burden for medium welfare” or a “low burden for small welfare” model together with the concept of social overhead capital;(2) reciprocity, which is one of the primary components of social capital, is similar to the philosophy underlying the health care system of Japan;(3) Japanese society needs to change from a society that emphasizes the relationships between its members to a society that is open to outsiders and has sufficient opportunities.

To investigate the effect of exclusive breastfeeding on the likelihood of Japanese preschool children being overweight, population-based cross-sectional survey data from M town in Japan were used. Using the population registry of this town, all 616 preschool children were identified, and a self-administered questionnaire was sent to their parents. The exposure variable of interest was exclusive breastfeeding from birth to 6 months, and the outcome variable of interest was the children being overweight at preschool age. Statistical analyses used included logistic regression and sensitivity analyses. In the final analyses, we included 448 preschool children. Although all point estimates indicated a protective effect, logistic regression analyses showed no significant reduction in being overweight due to exclusive breastfeeding in the unadjusted model (odds ratio (OR)0.70, 95% confidence intervals:0.30-1.64), the model adjusted for birth weight (OR0.70, 95% CI:0.30-1.63), the model adjusted for child lifestyle (OR0.71, 95% CI:0.30-1.67), or the model adjusted for parental factors (OR0.46, 95% CI:0.15-1.37). In sensitivity analyses, point estimates were not significant, but a protective effect was observed. In conclusion, our results suggest that breastfeeding might have a protective effect on Japanese preschool children against being overweight, although statistical significance was not observed due to the limitation of the statistical power of the findings.

On February 13, 2002, a public health center in Hiroshima Prefecture, Japan, was notified that many individuals living at the Japan Maritime Self-Defence Force base had symptoms resembling those of food poisoning. Self-administered questionnaires requesting information regarding meal consumption and symptoms were distributed to all 281 members at the base. A case of the illness was defined as a member who had had watery or mucousy stool, or loose stool with abdominal cramps, more than twice a day after consuming dinner on February 12. Control of the illness was defined as a member with no symptoms. The dinner on February 12 was significantly associated with the illness (Mantel-Haenszel odds ratio: 3.59, 95% confidence interval: 1.06-12.20). A case-control study showed that, among the food supplied at dinner on February 12, the braised chop suey was significantly associated with the illness (odds ratio: 12.30, 95% confidence interval: 1.90-521.00). The braised chop suey had been stored in a chafing dish. An environmental investigation indicated that Clostridium perfringens (C. perfringens) in the chafing dish proliferated under an inappropriate heat-retention temperature, and the contaminated braised chop suey could have caused the food poisoning. This study demonstrated that the recommended heat-retention temperature (over 65 degrees C) should be confirmed thoroughly.

Obesity in children is a serious public health problem, and TV viewing is considered a potential risk factor. Since, however, no relevant association studies have been conducted in Japan, we evaluated the association between TV viewing and obesity using a population-based study conducted in a Japanese town. All 616 preschool children in the town were enrolled in February 2008, and a self-administered questionnaire to collect children's and parents' characteristics was sent to the parents. We dichotomized the time spent TV viewing and evaluated associations by logistic regression using a "less than 2h" category as a reference. The questionnaire was collected from 476 participants (77.3%), of whom 449 were available for the final analyses. Among them, 26.9% of preschool children reported 2 or more hours of TV viewing per day and 8.2% were defined as obese. In logistic regression analyses, there was no positive association in unadjusted (odds ratio [OR]1.11, 95% confidence interval [95% CI]:0.50-2.49) or adjusted models for exclusively breastfed status, sleep duration, or maternal factors (OR1.11, 95% CI:0.50-2.51). We also found no positive association between TV viewing and overweight status, possibly owing to the influence of social environment, low statistical power, or misclassification.