Influenza vaccination of schoolchildren and influenza outbreaks in a school.

BACKGROUND: The objective of this retrospective descriptive study was to determine whether the universal influenza vaccination for schoolchildren was effective in controlling influenza outbreaks in a school. A universal vaccination program for schoolchildren was started in Japan in the 1960s, but the government abandoned the program in 1994 because of lack of evidence that the program was effective in preventing influenza in schoolchildren. METHODS: Influenza vaccine coverage rates, total numbers of class cancellation days, and absentee rates were reviewed in a single elementary school during the 24-year period during 1984-2007. RESULTS: The mean number of class cancellation days and the mean absentee rate in the compulsory vaccination period (1984-1987; mean vaccine coverage rate, 96.5%) were 1.3 days and 2.5%, respectively, and they increased to 8.3 days and 3.2% during the quasi-compulsory vaccination period (1988-1994; vaccine coverage, 66.4%). In the no-vaccination period (1995-1999; vaccine coverage, 2.4%), they were 20.5 days and 4.3%, respectively, and in the voluntary vaccination period (2000-2007; vaccine coverage, 38.9-78.6%), they were 7.0-9.3 days and 3.8%-3.9%. When minor epidemics were excluded, there was a significant inverse correlation between the vaccine coverage rates and both the number of class cancellation days and absentee rates. CONCLUSIONS: The universal influenza vaccination for schoolchildren was effective in reducing the number of class cancellation days and absenteeism in the school.

Reliability of family history of lifestyle-related diseases on questionnaire.

BACKGROUND: Family history of lifestyle-related diseases is an important risk factor and is widely used in epidemiologic studies. To justify its use the validity of the family history needs to be assessed. The aim of the present study was therefore to examine reliability, that is, consistency in repeated measurements, of the family history obtained on questionnaire. METHODS: A questionnaire survey on the family history of lifestyle-related diseases was conducted for 438 high school students about students' parents, grandparents, uncles and aunts, twice with a 1 year interval. The questionnaire was filled in by their parents. Discordance between the two questionnaires in age, age at death and a positive history of lifestyle-related diseases expressed by age at onset by decade age among the family members was examined. Kappa was used as a measure of agreement. RESULTS: The kappas for relatives were high, mostly >0.7 for hypertension and >0.5 for myocardial infarction, angina pectoris, stroke, diabetes mellitus and hypercholesterolemia. The discordance tended to be higher among grandparents than parents, uncles and aunts. The discordance with regard to relatives was mostly <4% for angina pectoris, myocardial infarction, stroke and diabetes mellitus; for hypertension and hypercholesterolemia the discordance was <6%. CONCLUSIONS: The questionnaire provides a reliable and valid method of collecting family history on relatives of high school students. Thus, family history obtained through questionnaires can be used justifiably as a risk factor for lifestyle-related diseases among children and youths.

Potential errors resulting from sex and age difference in assessing family history of coronary heart disease.

BACKGROUND: Coronary heart disease occurs nearly exponentially with age and differently between men and women. Therefore, difference in sex and age of family members yields errors in assessing the family history as a risk factor. The influence of sex and age on the positivity of family history was assessed numerically. METHODS: Through questionnaires filled in by the parents of 2316 high school students, information was obtained on the past history of coronary heart disease among students' parents, grandparents, uncles, and aunts. The sex- and age-specific proportion of a positive history was calculated from the past history among the 24,071 family members. The influence of sex and age on a positive history was estimated as odds ratios by logistic regression analysis of the past history. RESULTS: The odds ratios obtained for sex and age difference were 1.61 (95% confidence interval: 1.42-1.83) and 1.07 (95% confidence interval: 1.06-1.07), respectively. This indicated that a positive history was 1.61 times higher among male members than among female members of the same age, and that a positive history increased by (1.07)y, where y was age difference by year. CONCLUSIONS: Potential errors resulting from disregarding the sex and age of family members can be substantial, judging from the above numerical figures. Some measures to control for the sex and age of family members are required in assessing family history of coronary heart disease.

Height-specific body mass index reference curves for Japanese children and adolescents 5-17 years of age.

BACKGROUND: Body mass index (BMI) reference values in consideration of height variation have not previously been reported. This study established height-specific BMI reference curves for Japanese children and adolescents aged from 5 to 17 years. METHODS: The 2001 nationwide survey data were utilized for the study. First, the range of variation in BMI corresponding to height (mean +/- 2SD) at each age was compared with the range of variation in BMI corresponding to age (from minimum to maximum) at every cm height. Second, various age groups were combined, and percentile values of BMI (3rd, 5th, 15th, 50th, 85th, 95th, and 97th) were calculated for every cm height, regardless of age, and height-specific BMI reference values (males 100-179 cm, females 100-169 cm) were prepared. RESULTS: Variation in BMI due to variation in height at each age was significantly (P <0.05) greater than variation in BMI due to age at every cm height [males, 12.7 +/- 0.4 vs 9.2 +/- 0.4; females, 11.7 +/- 0.8 vs 8.8 +/- 0.3 (mean +/- SE)]. CONCLUSION: Although the use of standard values established in consideration of age and height is desirable for BMI-based guidelines for determining childhood overweight and obesity, to simplify the procedure for practical use, it is necessary to establish standard values by height, not by age. Height-specific BMI reference curves are useful for BMI-based evaluation of childhood overweight and obesity in the school health service and follow-up of obese children until adulthood.

A dose-response relationship between short sleeping hours and childhood obesity: results of the Toyama Birth Cohort Study.

BACKGROUND: Short sleeping hours could cause obesity through increased sympathetic activity, elevated cortisol secretion and decreased glucose tolerance. The aim of this study was to clarify parental and lifestyle factors, particularly sleeping habits, associated with obesity in Japanese children. METHODS: Between June and July 1996, 8274 children (4194 males and 4080 females) aged 6-7 years living in Toyama prefecture, Japan, were investigated by questionnaire survey and the collection of anthropometric data. Subjects with a body mass index (BMI; weight in kg divided by square of height in m) greater than the age- and sex-specific cut-off points linked to adulthood overweight (BMI of 25 kg/m2 or more) were defined as obese subjects. Parental obesity was defined as a BMI of 25 kg/m2 or more. Logistic regression analysis was performed to evaluate the strength of the relationships between parental obesity or lifestyle factors and childhood obesity, adjusted for possible confounding factors. RESULTS: Parental obesity, long hours of TV watching and physical inactivity were significantly associated with childhood obesity. Although wake-up time was not related to obesity, there was a significant dose-response relationship between late bedtime or short sleeping hours and childhood obesity. Compared with children with 10 or more hours of sleep, the adjusted odds ratio was 1.49 (95% confidence interval 1.08-2.14) for those with 9-10 h sleep, 1.89 (1.34-2.73) for those with 8-9 h sleep and 2.87 (1.61-5.05) for those with <8 h sleep, after adjustment for age, sex, parental obesity and other lifestyle factors. CONCLUSION: A strong inverse association was observed in the relationship between sleeping hours and childhood obesity. Longitudinal research will be required to confirm this causality.

Parental obesity, lifestyle factors and obesity in preschool children: results of the Toyama Birth Cohort study.

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.