Takashi Izuno

Analysis of factors that influence body mass index from ages 3 to 6 years: A study based on the Toyama cohort study

Abstract Background : The aim of the present study was to elucidate both environmental and behavioral factors that influence body mass index (BMI, kg/m2) among Japanese children from ages 3−6.

Temporal course of the development of obesity in Japanese school children: A cohort study based on the Keio Study

OBJECTIVE To demonstrate the temporal course of obesity development in Japanese school children by conducting a school-site cohort study over 12 years. METHODS From 1981 to 1984, height and weight of 479 subjects (343 boys and 136 girls) were measured every year from entrance into primary school until graduation from high school in Tokyo. Obese children were defined as those with a body mass index (BMI) at or above the age-sex-specific standard value, derived from Japanese nationwide data. RESULTS Approximately 50% of the children who were obese in the primary school period were obese at age 17. Likewise, 40% who were obese in the junior high school period and 70% who were obese in the high school period were obese at age 17. Among 44 children who were obese at age 17, 14 showed tracking of obesity from the preschool period, 14 showed tracking from ages 7 to 11 years, 10 showed tracking from the junior high school period, and 6 showed tracking from the high school period. CONCLUSIONS Among children who were obese at age 17, most tracked from the primary school age or earlier. The earlier the tracking commenced, the greater the BMI at age 17. This indicates the importance of conducting health education for school children at an early age.

Influence of Behavioral and Environmental Factors on the Development of Obesity in Three-year-old Children -A Case-Control Study Based on Toyama Study-

Obesity in children seems to be a risk factor for chronic diseases in adulthood. From the viewpoint of preventive medicine, factors influencing the development of obese children should be removed early in life.The purpose of this study was to the elucidate relationship between obesity in 3-year-old children and both behavioral and environmental factors by conducting a case-control study. Subjects were selected from the Toyama study. Matched-pair comparisons were performed between obese children whose Kaup’s index was 18 or more (N=117) and control children (N=234) . Multivariate stepwised logistic regression analysis also applied to assess influence of confounding factors.The results indicated that the following 6 factors significantly influenced the development of obese 3-year-old children in exact Fisher’s method analysis (p<0.05): person other than the mother responsible for taking care of the child, short sleep duration (9 hours or less), physical inactivity, eating snacks irregularly, overweight father (BMI≥24), and overweight mother (BMI≥24). For both sexes, after adjusting for confounders by multivariate stepwise logistic analysis, overweight mother (OR 2.54, 95 % CI 1.64-3.95), birth overweight (birth weight≥3,500g; OR 1.76, 95 % CI 1.15-2.69), the mother not responsible for taking care of the child (OR 1.65, 95% CI 1.10-2.48), overweight father (OR 1.62, 95%CI 1.09-2.40), eating snacks irregularly (OR 1.56, 95% CI 1.04-2.33), and gender (female;OR 0.51, 95% CI 0.34-0.77) had significant relationships with obesity in childhood. For boys, overweight mother (OR 2.53, 95 % CI 1.47-4.35), birth overweight (OR 2.03, 95%CI 1.22-3.39), eating snacks irregularly (OR 1.94, 95 %CI 1.19-3.18), and birth month (36-41 months; OR 0.47, 95 % CI 0.23-0.96) had significant relationships. For girls, overweight mother (OR 2.62, 1.28-5.35), and short sleep duration (OR 2.24, 1.11-4.52) had significant relationships. In neither Fisher’s exact method nor multivariate logistic models, time to wake up, bedtime, duration of playing outdoors, regularity of meals, care about salty food, or frequency of eating snacks had significant relations with obesity in 3-year-old children (p<0.05).

An indicator quantitatively comparing two treatment effect sizes on responder and non-responder groups – exponential of estimated interaction parameter

Abstract Sometimes a specific treatment is effective in one subgroup but not in another. An indicator allowing quantitative comparison of treatment effect in two subgroups would be useful in clinical medicine. We have developed such an indicator. It is obtained by calculations using Cox’s proportional hazard or logistic model with therapy, subgroup, and confounding explanatory variables. The parameter of the interaction between therapy and subgroup can be estimated and tested statistically. The exponential value of the interaction parameter is what we tentatively call the “hazard ratio ratio”, meaning the ratio between the treatment effects in two subgroups. The 95% confidence interval of the indicator can also be calculated. As a numerical example, the hazard ratio between the survival times of postoperative gastric cancer patients treated by adjuvant immunochemotherapy and patients without adjuvant immunochemotherapy in a subgroup with high serum glycosidically bound sialic acid (SA) level was lower than that in a low-SA subgroup using an estimate for hazard ratio ratio of less than 0.5 with statistical significance. We propose this indicator be used as a “responder/non-responder ratio” of therapy effect.

Cadmium Absorption from Smoking Cigarettes: Calculation Using Recent Findings from Japan

Consumed substances, including food, drink, and tobacco, produced in the environment are exposure sources of Cd. The object of the present study was to estimate Cd exposure and absorption amount from smoking cigarettes, one exposure source of Cd, using recent findings from Japan. The market share of cigarettes produced in foreign countries has increased in Japan, the proportion of tobacco leaves harvested in foreign countries has increased in cigarettes produced in Japan, and the percentage of smokers in Japan has changed. Therefore, obtaining the absorption value of Cd from smoking cigarettes using recent findings from Japan is significant.We collected information on (1) the concentrations of Cd in tobacco leaves by country of harvest and in cigarettes by country of production, (2) the concentrations of Cd in cigarette smoke, (3) the proportion of tobacco leaves harvested in foreign countries used in cigarettes made and sold in Japan, (4) the absorption rate of Cd in the airways for cigarette smoke, (5) the smoking rate by gender, age, and year in Japan, (6) the number of cigarettes sold in Japan by year and country of production, (7) the number of cigarettes smoked by smokers per day according to gender and age in Japan, and (8) the population size in 1998 by gender and age in Japan. The mean amount of Cd absorbed via the airways by smoking for smokers in Japan was calculated to be 0.89–1.78 μg/day from the above information. The values are not small in comparison with the amount of Cd absorbed from the digestive organs.The concentration of Cd in tobacco leaves harvested in Japan and cigarettes produced in Japan is generally higher than that of leaves harvested and cigarettes produced in foreign countries. The increase in the market share of cigarettes produced in foreign countries and sold in Japan and the increase in the proportion of tobacco leaves harvested in foreign countries used in cigarettes made and sold in Japan have decreased the amount of Cd absorbed by smoking for smokers in Japan.

The national burdens of rheumatoid arthritis and osteoarthritis in Japan: projections to the year 2010, with future changes in severity distribution

We projected the national burdens of rheumatoid arthritis (RA) and osteoarthritis (OA) in Japan in the year 2010, together with future changes in severity distribution. The age-, sex-, and in/outpatient-specific prevalence rates of RA and OA from the 1999 National Patient Survey were multiplied by the National Census population projections for 2000 and 2010. The years lived with disability (YLD) of RA or OA in 2010 were adjusted for the projected changes in the summed measure of severity distribution (i.e., the sum products of the percentage distribution and the health-related quality of life score for three severity classes) using the corresponding regression equations. Between 2000 and 2010, the numbers of patients with RA and OA in Japan will increase by 14% (from 0.31 million to 0.36 million) and 27% (from 0.77million to 0.98 million), respectively, and accordingly, the YLD of RA and OA will increase by 3% (from 42.8 to 43.6 per 100 000) and 21% (from 65.8 to 79.1 per 100 000), respectively. Because of the decreasing proportion of severely affected patients, the increase in YLD may be smaller compared with the increase in the number of patients. As in other developed countries, the national burdens of RA and OA in Japan will increase between 2000 and 2010. However, any projection is likely to be an overestimate unless it considers future changes in the severity distribution associated with medical progress.

Recalculation of Summarised Odds Ratios for the Relationship between Passive Smoking and Lung Cancer Based on Data in the EPA Report

We have recalculated the summarised odds ratios, with 95 % confidence intervals (CIs), for the relationship between exposure to environmental tobacco smoke (ETS) and lung cancer based on the odds ratios for the individual epidemiological studies given in the Environmen tal Protection Agency Report in 1992. Using DerSimonians method, the summarised odds ratio, with 95% CI, for all the studies combined was estimated as 1.28 (1.13, 1.46). This method was used as the odds ratios for the individual studies indicated heterogeneity. This heterogeneity may arise because of differences in factors such as socio-economic status, hous ing or occupational environment among the countries where the epidemiological studies were carried out. If so, the summarised odds ratio for all the studies combined may not be an important parameter. Using Sugitas method, which enables us to eliminate publication bias indirectly, the summarised odds ratio, with 95% CI, for the 11 studies in the USA was estimated as 1.11 (0.97, 1.28). Without eliminating publication bias, the value was 1.19(1.01, 1.38). Including odds ratios from two new studies, the summarised odds ratio for the USA was found to be nearly equal to the value with publication bias eliminated. The odds ratios, with 95% CIs, summarised above do not demonstrate whether or not ETS is a significant risk factor for lung cancer. The association between ETS and lung cancer is certainly weak.

Years of potential life lost as the indicator of premature mortality in occupational medicine

Measurement of premature mortality is necessary to plan medical programs and to conduct effective medical activities. The purpose of this study was to compare the years of potential life lost (YPLL) with other mortality indices and to understand the usefulness and limitations of quantitative measurement for premature mortality. Data concerning death during employment were surveyed from 1979 to 1984. One thousand seven hundred twenty-five deaths were observed in 1,504,462 person-years in the study population. Proportionate mortality ratios indicated medical problems concerning malignant neoplasms and heart disease, but they could not identify the problems of suicide and traffic accidents occurring in the relatively younger group. YPLL by a constant end point at 60 years of age could rank these causes next below the major leading causes of death. Thus, YPLL might be a useful indicator of the problems concerning premature mortality in occupational medicine.

Family History of Breast Cancer and Breast Cancer Risk in Japan

We studied 132 families with a family history of breast cancer (familial aggregation cases, FA cases) to assess the breast cancer risk presented by such a family history. For comparison with these FA cases, we randomly selected 132 control families of sporadic cases (SP controls) by adjusting for the age of the proband at surgery. Information on family history was collected for all first-degree female relatives and maternal and paternal grandmothers. Japanese women with a first-degree relative affected by breast cancer were found to have an increased risk of the disease. The odds ratio (OR) for women with a family history of breast cancer was 1.99 (95% confidence interval [CI], 1.48–2.66). The OR for FA-case daughters of women with breast cancer was 1.54 (95% CI, 0.91–2.63). A higher risk was not observed if a woman’s mother had breast cancer. If the proband had a sister with breast cancer, a slightly increased risk of other cancers of the proband was observed (OR, 1.85 [0.87– 3.92]). These results suggest that a family history of breast cancer in Japanese women may affect their risk of developing cancer of the breast and other organs.