Beth Hands

The relationship among physical activity, motor competence and health-related fitness in 14-year-old adolescents

Physical activity, physical fitness and motor competence are important health‐related constructs. However, the relationship among them, particularly for children and adolescents, is still unclear. In this study, motor competence (measured by the McCarron Assessment of Neuromuscular Development), pedometer‐determined physical activity and physical fitness (aerobic fitness, muscle strength, muscle endurance, flexibility and body composition) were examined in a cohort of 1585 adolescents (771 girls, 814 boys) of mean age 14.06 years. Significant gender differences were observed for all measures except motor competence. Apart from hip and shoulder flexibility, males outperformed females. For both males and females, motor competence was associated with all fitness measures, physical activity was associated only with aerobic fitness and aerobic fitness was associated with physical activity, motor competence, BMI and chest pass. Among males, aerobic fitness was also associated with all other fitness tests. The correlations were, in general, moderate to weak. The results challenge the current focus on physical activity rather than physical fitness as the preferred intervention.

The Western Dietary Pattern Is Prospectively Associated With Nonalcoholic Fatty Liver Disease in Adolescence

OBJECTIVES:Poor dietary habits have been implicated in the development of nonalcoholic fatty liver disease (NAFLD); however, little is known about the role of specific dietary patterns in the development of NAFLD. We examined prospective associations between dietary patterns and NAFLD in a population-based cohort of adolescents.METHODS:Participants in the Western Australian Pregnancy Cohort (Raine) Study completed a food frequency questionnaire at 14 years and had liver ultrasound at 17 years (n=995). Healthy and Western dietary patterns were identified using factor analysis and all participants received a z-score for these patterns. Prospective associations between the dietary pattern scores and risk of NAFLD were analyzed using multiple logistic regression.RESULTS:NAFLD was present in 15.2% of adolescents. A higher Western dietary pattern score at 14 years was associated with a greater risk of NAFLD at 17 years (odds ratio (OR) 1.59; 95% confidence interval (CI) 1.17–2.14; P<0.005), although these associations were no longer significant after adjusting for body mass index at 14 years. However, a healthy dietary pattern at 14 years appeared protective against NAFLD at 17 years in centrally obese adolescents (OR 0.63; 95% CI 0.41–0.96; P=0.033), whereas a Western dietary pattern was associated with an increased risk of NAFLD.CONCLUSIONS:A Western dietary pattern at 14 years in a general population sample was associated with an increased risk of NAFLD at 17 years, particularly in obese adolescents. In centrally obese adolescents with NAFLD, a healthy dietary pattern may be protective, whereas a Western dietary pattern may increase the risk.

Physical fitness differences in children with and without motor learning difficulties

Children with motor learning difficulties (MLD) tend to be less physically active than their coordinated peers and one likely consequence is a reduced level of physical fitness. In this study, 52 children with MLD, aged 5 to 8 years, were compared to 52 age‐ and gender‐matched control children across a range of health and skill related fitness components. Analyses of variance revealed significantly lower scores in the group with MLD on the tests for cardiorespiratory endurance, flexibility, abdominal strength, speed and power than the control group. Furthermore, the group with MLD had a significantly higher Body Mass Index (BMI). These findings have implications for educators and allied health professionals working with this age group. Programmes need to teach children with movement difficulties to perform tasks used in fitness assessment and also to work on the development of physical fitness.

Body mass index, adiposity rebound and early feeding in a longitudinal cohort (Raine Study).

Objective:This study examined the influence of type and duration of infant feeding on adiposity rebound and the tracking of body mass index (BMI) from birth to 14 years of age.Methods:A sample of 1330 individuals over eight follows-ups was drawn from the Western Australian Pregnancy Cohort (Raine) Study. Trajectories of BMI from birth to adolescence using linear mixed model analysis investigated the influence of age at which breastfeeding was stopped and the age at which other milk was introduced (binomial 4-month cutoff point). A subsample of linear mixed model-predicted BMI was used to determine BMI and age at nadir for early infant feeding groups.Results:Chi-square analysis between early feeding and weight status (normal weight, overweight and obese) groups found a significant difference between thee age at which breastfeeding was stopped (P<0.001) and the age at which other milk was introduced (P=0.011), with a higher proportion of overweight and obese in the ⩽4-month group, even after controlling for maternal education. Using the linear mixed model, the BMI determined was higher over time for the group that was breastfed for ⩽4 months (P=0.015), with a significant interaction effect with the group in which other milk was introduced at ⩽4 months (P=0.011). Using predicted BMI from the linear mixed model, significant differences for nadirs of adiposity rebound between early feeding groups were found (P<0.005).Conclusions:Early infant feeding was important in the timing of, and BMI at, adiposity rebound. The relationship between infant feeding and BMI remained up to the age of 14 years. Although confounding factors cannot be excluded, these findings support the importance of exclusive breastfeeding for longer than 4 months as a protective behaviour against the development of adolescent obesity.

Lifecourse Childhood Adiposity Trajectories Associated With Adolescent Insulin Resistance

OBJECTIVE In light of the obesity epidemic, we aimed to characterize novel childhood adiposity trajectories from birth to age 14 years and to determine their relation to adolescent insulin resistance. RESEARCH DESIGN AND METHODS A total of 1,197 Australian children with cardiovascular/metabolic profiling at age 14 years were studied serially from birth to age 14 years. Semiparametric mixture modeling was applied to anthropometric data over eight time points to generate adiposity trajectories of z scores (weight-for-height and BMI). Fasting insulin and homeostasis model assessment of insulin resistance (HOMA-IR) were compared at age 14 years between adiposity trajectories. RESULTS Seven adiposity trajectories were identified. Three (two rising and one chronic high adiposity) trajectories comprised 32% of the population and were associated with significantly higher fasting insulin and HOMA-IR compared with a reference trajectory group (with longitudinal adiposity z scores of approximately zero). There was a significant sex by trajectory group interaction (P < 0.001). Girls within a rising trajectory from low to moderate adiposity did not show increased insulin resistance. Maternal obesity, excessive weight gain during pregnancy, and gestational diabetes were more prevalent in the chronic high adiposity trajectory. CONCLUSIONS A range of childhood adiposity trajectories exist. The greatest insulin resistance at age 14 years is seen in those with increasing trajectories regardless of birth weight and in high birth weight infants whose adiposity remains high. Public health professionals should urgently target both excessive weight gain in early childhood across all birth weights and maternal obesity and excessive weight gain during pregnancy.

The associations between physical activity, screen time and weight from 6 to 14 yrs: the Raine Study.

To examine the strength and direction of the relationship between physical activity level, screen use and BMI in a cohort at ages 6, 8, 10 and 14 yrs as part of a prospective longitudinal cohort study. The sample comprised 1403 males and females who participated in the follow-up survey at 14 yrs of age between 2003 and 2005. Exploratory structural equation modelling was used to examine the interrelationships between physical activity level, BMI and screen time at 6, 8, 10 and 14 yrs. Predictors of BMI at 6, 8, 10 and 14 yrs explained 1.3, 76.1, 80.1 and 73.1 percent of the variances, respectively, with previous BMI the largest predictor [χ(2)=43.082, df=36, p=194]. Increased screen time predicted higher BMI and lower physical activity at 8 and 10 yrs but not 14 yrs. At 14 yrs, physical activity predicted BMI. Sedentary patterns of behaviour in early childhood were predictive of later and concurrent obesity, whereas physical activity was predictive of obesity in adolescence. Different intervention targets are required for children and adolescents.

Early infant feeding and adiposity risk: from infancy to adulthood

Introduction: Systematic reviews suggest that a longer duration of breast-feeding is associated with a reduction in the risk of later overweight and obesity. Most studies examining breast-feeding in relation to adiposity have not used longitudinal analysis. In our study, we aimed to examine early infant feeding and adiposity risk in a longitudinal cohort from birth to young adulthood using new as well as published data. Methods: Data from the Western Australian Pregnancy Cohort (Raine) Study in Perth, W.A., Australia, were used to examine associations between breast-feeding and measures of adiposity at 1, 2, 3, 6, 8, 10, 14, 17, and 20 years. Results: Breast-feeding was measured in a number of ways. Longer breast-feeding (in months) was associated with reductions in weight z-scores between birth and 1 year (β = -0.027; p < 0.001) in the adjusted analysis. At 3 years, breast-feeding for <4 months increased the odds of infants experiencing early rapid growth (OR 2.05; 95% CI 1.43-2.94; p < 0.001). From 1 to 8 years, children breast-fed for ≤4 months compared to ≥12 months had a significantly greater probability of exceeding the 95th percentile of weight. The age at which breast-feeding was stopped and a milk other than breast milk was introduced (introduction of formula milk) played a significant role in the trajectory of the BMI from birth to 14 years; the 4-month cutoff point was consistently associated with a higher BMI trajectory. Introduction of a milk other than breast milk before 6 months compared to at 6 months or later was a risk factor for being overweight or obese at 20 years of age (OR 1.47; 95% CI 1.12-1.93; p = 0.005). Discussion: Breast-feeding until 6 months of age and beyond should be encouraged and is recommended for protection against increased adiposity in childhood, adolescence, and young adulthood. Adverse long-term effects of early growth acceleration are fundamental in later overweight and obesity. Formula feeding stimulates a higher postnatal growth velocity, whereas breast-feeding promotes slower growth and a reduced likelihood of overweight and obesity. Biological mechanisms underlying the protective effect of breast-feeding against obesity are based on the unique composition and metabolic and physiological responses to human milk.

Importance of cardiometabolic risk factors in the association between nonalcoholic fatty liver disease and arterial stiffness in adolescents

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide and is regarded as the hepatic manifestation of the metabolic syndrome. In adults, NAFLD is a determinant of arterial stiffness and cardiovascular risk, independent of the metabolic syndrome. Our aim was to ascertain if NAFLD is associated with arterial stiffness, independent of cardiometabolic factors in a population‐based cohort of adolescents. The 17‐year‐olds (n = 964) from an Australian birth cohort had measures of anthropometry, blood pressure, fasting insulin, glucose, lipids, and NAFLD by ultrasound. Two‐step cluster analysis identified youth at high metabolic risk. Measures of arterial stiffness (pulse wave velocity [PWV] and augmentation index corrected for heart rate [AI@75]) were obtained using applanation tonometry. The overall prevalence of NAFLD was 13.3%. The “high risk” metabolic cluster at age 17 years included 16% males and 19% females. Compared to “low risk,” the “high risk” cluster participants had greater waist circumference, triglycerides, insulin, systolic blood pressure, and lower high‐density lipoprotein (HDL) cholesterol (all P < 0.0001). Those who had NAFLD but were not in the “high risk” metabolic cluster did not have increased PWV or AI@75. However, males and females who had NAFLD in the presence of the metabolic cluster had greater PWV (b = 0.20, 95% confidence interval [CI] 0.01 to 0.38, P = 0.037). Males who had NAFLD in the presence of the metabolic cluster had greater AI@75 (b = 6.3, 95% CI 1.9 to 10.7, P = 0.005). Conclusion: NAFLD is only associated with increased arterial stiffness in the presence of the “high risk” metabolic cluster. This suggests that arterial stiffness related to the presence of NAFLD is predicated on the presence of an adverse metabolic profile in adolescents. (Hepatology 2013;58:1306–1314)

Physical activity measurement methods for young children: A comparative study

Many behavior patterns that impact on physical activity experiences are established in early childhood, therefore it is important that valid, reliable, and feasible measures are constructed to identify children who are not developing appropriate and healthy activity habits. In this study, measures of physical activity derived by accelerometry and pedometry are compared with direct observation of 5- and 6-year-old children (N = 24). The children were monitored for 30 min over 5 consecutive days during a free play session in their preprimary setting. The results for all measures were significantly correlated. When compared to direct observation, the coefficient of determination indicated that the pedometer (R2 = .81) was able to more accurately predict all levels of physical activity compared to the accelerometer (R2 = .59). When the children were grouped into low, moderate, wand high activity levels using observation, the pedometer data were better able to separate the groups than the accelerometer data. These findings indicate that the pedometer is a better measure of free play physical activity in 5- and 6-year-old children compared to the accelerometer.

Lifestyle and demographic correlates of poor mental health in early adolescence.

Aim:  To determine the constellation of lifestyle and demographic factors that are associated with poor mental health in an adolescent population.