Shibing Deng

Changes in common activities of 3rd through 10th graders: the CHIC study.

PURPOSE This study was a longitudinal examination of the change in both the activities done and the intensity of those activities from childhood to adolescence. METHODS Common activities were assessed by questionnaire initially on 656 subjects from 21 elementary schools; 50.5% were female, 83.4% were Caucasian, 20.6% African-American, and 6.0% were other races. RESULTS Girls more often reported sedentary activities overall. Weighted least squares analyses showed boys consistently reported more vigorous activities than girls (P < 0.0008). African-American girls reported fewer vigorous activities than Caucasian or other race girls (P = 0.027). Sedentary activities were more frequently reported with increasing age (X2 P < 0.001). The youngest African-American and Caucasian boys reported similar activity patterns. However, boys from other races reported more intense activities until sixth and seventh grades when African-American boys began reporting more sedentary activities than Caucasians or other races (P = 0.004). During sixth-eighth grades, Generalized Estimating Equations (GEE) models show that girls with more advanced pubertal status reported more sedentary activities than girls who were less developed (P < 0.0001). For high school girls, race was a marginally significant predictor (P = 0.05) of activity status. Neither race nor pubertal status were significant factors in activities chosen by middle school boys. However, for male high school students, Caucasians were more likely than African-Americans to report vigorous activities (P = 0.005). CONCLUSIONS Variation in activities by race within gender suggests that establishing activity patterns in youth may be race-specific as well as gender-specific and must be accounted for in designing physical activity interventions. Also, pubertal maturation is a factor in activity choices in middle school girls.

Racial and socioeconomic differences in risk factors for cardiovascular disease among Southern rural women.

BackgroundAfrican American women living in the Southeast experience a higher mortality due to cardiovascular (CV) disease than their White counterparts. It is unclear if this vulnerability to CV disease is due to race, socioeconomic status, or health behaviors. ObjectivesTo examine the disparities in cardiovascular health between Southern rural, African American and White women to determine if a CV Risk-Index differed by race, education, or income levels and if differences persisted when controlling for body mass index (BMI). MethodsSubjects were 1,110 women (27% African American, 73% White) residing in rural North Carolina. Data were collected by mailed questionnaire and analyzed using analysis of variance (ANOVA) and analysis of covariance (ANCOVA). ResultsAfrican American women had significantly lower education and lower income than Whites, higher BMI, and a much greater prevalence of hypertension, angina, and diabetes. In a three-way ANOVA including race, income, and education, education and race were significant predictors of the CV Risk Index, but when adjusted for BMI race was no longer significant (p = .3039); the only significant predictors were BMI and educational level. DiscussionWomen with the least education had the highest CV Risk-Index, regardless of race. These findings suggest the need to focus risk reduction interventions on all Southern rural women with limited education, not only African American women. This supports the current literature that suggests race should be viewed as a risk marker rather than a risk factor.

Cigarette use in adolescents: The cardiovascular health in children and youth study

Tobacco is the leading cause of preventable death in the United States, and its use is increasing in adolescents. To determine the interventions needed to prevent the initiation of smoking, it is important to know the factors related to tobacco use by adolescents. In this study the following factors related to cigarette use were examined: age, gender, ethnicity, self-esteem, physical activity, parental smoking, and socioeconomic status. Participants were 1,207 youth completing a written survey for the Cardiovascular Health in Children and Youth Study (CHIC II). Participants ranged in age from 10 to 15 years, with a mean age of 12.2 years; 64.2% were White, 24.0% Black, 5.8% Hispanic, and 6.0% other races. White and Hispanic youth and youth of other races had significantly higher rates of smoking than did Black youth. Significant risk factors for smoking were: higher grade in school, White race, and for girls only, lower self-esteem. In White youth those in the lowest socioeconomic status were most likely to be current and experimental smokers. Smoking was as common in girls as in boys at these ages. Multivariate analysis showed that neither physical activity nor parental smoking were significant predictors of smoking behaviors. These results suggest that smoking prevention programs for adolescents should specifically target White and Hispanic youth and those from families with low socioeconomic status. In addition, these interventions should include ways to increase self-esteem in girls.

Predicted maximal aerobic power in youth is related to age, gender, and ethnicity.

PURPOSE To determine the effects of age, gender, and ethnicity on the predicted aerobic power of youth as they age from 8 to 16 yr. METHODS The sample was a multicohort group of 2540 African Americans (N = 543) and Caucasians (N = 1997), 1279 (50.4%) girls and 1261 (49.6%) boys. Heights, weights, and sum of skin folds (triceps + subscapular) were measured. Aerobic power ((p)VO(2max)), expressed in relative (mL x kg(-1) x min(-1)) or absolute (L x min(-1)) terms, was predicted from a three-stage cycle ergometry test. RESULTS Quadratic mixed-model analysis indicated that boys had higher relative and absolute (p)VO(2max) than the girls (P = 0.0004). The African American subjects had a higher absolute (p)VO(2max) (L x min(-1)) than the Caucasians, but their relative (p)VO(2max) was lower than the Caucasians (P = 0.031). Finally, age had a significant effect on (p)VO(2max) (P = 0.0001). The absolute (p)VO(2max) of the girls increased 9%.yr(-1) until age 14; but their relative (p)VO(2max) declined approximately 1.2 mL x kg(-1) x min(-1) x yr(-1). The absolute (p)VO(2max) for the boys increased yearly by approximately 14% from ages 8 to 16 yr, but the relative (p)VO(2max) of the African American males was stable from ages 8 to 11, then dropped, and stabilized again between ages 12 and 16 yr. The relative (p)VO(2max) of the Caucasian boys declined from ages 8 to 10, but then increased slightly from age 12 to 16 yr. In addition, the interactions of age and gender, and age squared and gender were significant (P < 0.02). CONCLUSION These data indicate that although absolute (p)VO(2max) (L x min(-1)) increases from age 8 to 16 yr, relative (p)VO(2max) (mL x kg(-1) x min(-1)) declines. The decline appears to be related to increased fat mass. Similarly, the higher relative (p)VO(2max) (mL x kg(-1) x min(-1)) of the Caucasian youth compared with the African American youth was related to lower weights and skin folds of the Caucasian youth.

Gender and Ethnic Changes in Physical Work Capacity from Childhood through Adolescence

Abstract This study determined gender and ethnic differences in physical work capacity (PWC170) of 8–16-year-old American youth as they progress from elementary to high school. A multicohort group of 2,540 youth participated: 50.4% girls (21.4% African Americans, and 78.6% Caucasians). PWCI70 was predicted from cycle ergometer testing six times over a 7-year period. The absolute PWC 170 of girls stabilized in early adolescence, while boys increased with each trial. The PWC170 relative to body weight of girls decreased steadily, whereas the boys remained stable. African Americans had greater absolute PWC170 values than Caucasians (p =. 0001). The relative PWC 170 was lower for African American girls than Caucasian girls (p = . 0001), but there were no ethnic differences for boys (p > .05). Although correlations and grouping suggested moderate tracking, girls with high relative PWC170 tended to migrate to lower levels as they aged, where as high-performing boys maintained their PWC170 as they aged.

Leptin and Obesity in Mother-Child Pairs

Defects in the leptin gene or the leptin receptor may be a genetic cause of obesity, but little is known about the familial associations of leptin and obesity. This study compared plasma leptin and measures of obesity in a sample of 248 subjects (124 mother-offspring pairs); 34% were African American and 66% were white. Youth were aged 12 to 16 years. Plasma leptin and body mass index (BMI) were higher in mothers than in their offspring and, among the offspring, higher in girls than boys, even after correcting for BMI or body fat. Racial differences in leptin were present in both mothers and youth when adjusting for percentage body fat but disappeared when adjusting for BMI. In univariate analyses of the associations between mothers and offspring, BMI was associated with leptin in all groups but was most strongly associated in white pairs and in mother-son pairs. In multiple regression analyses, when adjusting for BMI, significant predictors of leptin level for the boys and girls together were gender, BMI, and pubertal status of the offspring; in girls only BMI was significant (R2= 0.72), and in boys the significant predictors were their BMI (R2= 0.66) followed by their pubertal status (R2= 0.06) and the leptin level of their mothers (R2= 0.02). When adjusting for body fat, the predictors were the offspring’s percentage body fat (R2=0.67) and mother’s leptin (R2= 0.03), with similar results in gender-specific analyses. The authors conclude that leptin levels of youth are most closely associated with their degree of obesity or body fat; mother’s leptin and, for boys only, pubertal status also play a small role. Although the small association between maternal leptin on leptin in their offspring could be due to either heredity or shared environment, the results of this study suggest that individual obesity and environmental factors are important predictors of leptin levels in children.