Verity Cleland

A prospective examination of children's time spent outdoors, objectively measured physical activity and overweight

Objective: This study aimed to determine whether time spent outdoors was associated with objectively measured physical activity, body mass index (BMI) z-score and overweight in elementary-school aged children, cross-sectionally and prospectively over 3 years.Methods: Three-year cohort study with data collected during 2001 and 2004. Nineteen randomly selected state elementary schools across Melbourne, Australia. One hundred and eighty eight 5–6-year-old and 360 10–12-year-old children. Baseline parent reports of childrens time spent outdoors during warmer and cooler months, on weekdays and weekends. At baseline and follow-up, childrens moderate and vigorous physical activity (MVPA) was objectively assessed by accelerometry, and BMI z-score and overweight was calculated from measured height and weight.Results: Cross-sectionally, each additional hour outdoors on weekdays and weekend days during the cooler months was associated with an extra 27 min week−1 MVPA among older girls, and with an extra 20 min week−1 MVPA among older boys. Longitudinally, more time outdoors on weekends predicted higher MVPA on weekends among older girls and boys (5 min week−1). The prevalence of overweight among older children at follow-up was 27–41% lower among those spending more time outdoors at baseline.Conclusion: Encouraging 10–12-year-old children to spend more time outdoors may be an effective strategy for increasing physical activity and preventing increases in overweight and obesity. Intervention research investigating the effect of increasing time outdoors on childrens physical activity and overweight is warranted.

Trends in children's physical activity and weight status in high and low socio-economic status areas of Melbourne, Victoria, 1985-2001.

Objective: To examine trends in active transport to and from school, in school sport and physical education (PE), and in weight status among children from high and low socio‐economic status (SES) areas in Melbourne, Victoria, between 1985 and 2001.

The longitudinal influence of home and neighbourhood environments on children's body mass index and physical activity over 5 years: the CLAN study

Objective:To determine the independent contributions of family and neighbourhood environments to changes in youth physical activity and body mass index (BMI) z-score over 5 years.Methods:In 2001, 2004 and 2006, 301 children (10–12 years at baseline) had their height and weight measured (BMI was converted to z-scores using Centers for Disease Control and Prevention reference charts; see http://www.cdc.gov/growthcharts) and moderate-to-vigorous physical activity (MVPA) assessed using accelerometers. In 2001, parents reported on the home environment (social support, role modelling, rules and restrictions, physical environment) and perceived neighbourhood environment (local traffic, road safety, sporting venues, public transport), and Geographic Information Systems were used to map features of the neighbourhood environment (destinations, road connectivity, traffic exposure). Generalized estimating equations were used to predict average BMI z-score and MVPA over time from baseline home and perceived and objective neighbourhood environment factors.Results:Among boys, maternal education and heavy traffic were inversely associated, and sibling physical activity, maternal role modelling of MVPA and the presence of dead-end roads were positively associated with MVPA. Having unmarried parents, maternal MVPA role modelling and number of home sedentary items were positively associated with BMI z-score among boys. Among girls, having siblings, paternal MVPA role modelling, physical activity rules and parental physical activity co-participation were positively associated with MVPA. Having unmarried parents and maternal sedentary behaviour role modelling were positively associated, and number of sedentary behaviour rules and physical activity items were inversely associated with BMI z-score among girls.Conclusion:The home environment seems more important than the neighbourhood environment in influencing childrens physical activity and BMI z-score over 5 years. Physical activity and weight gain programmes among youth should focus on parental role modelling, rules around sedentary and active pursuits, and parental support for physical activity. Intervention studies to investigate these strategies are warranted.

Socioeconomic Position and the Tracking of Physical Activity and Cardiorespiratory Fitness From Childhood to Adulthood

This study examined the influence of childhood socioeconomic position (SEP) and social mobility on activity and fitness tracking from childhood into adulthood. In a prospective cohort of 2,185 Australian adults (aged 26-36 years), first examined in 1985 (at ages 7-15 years), self-reported physical activity and cardiorespiratory fitness (subsample only) were measured. SEP measures included retrospectively reported parental education (baseline) and own education (follow-up). There was little evidence of a relation between childhood SEP and activity tracking, but high childhood SEP (maternal education) was associated with a 59% increased likelihood of persistent fitness, and medium childhood SEP (paternal and parental education) was associated with a 33%-36% decreased likelihood of persistent fitness. Upward social mobility was associated with a greater likelihood of increasing activity (38%-49%) and fitness (90%), and persistently high SEP was associated with a greater likelihood of increasing activity (males: 58%) and fitness (males and females combined: 89%). In conclusion, persistently high SEP and upward social mobility were associated with increases in activity and fitness from childhood to adulthood. Findings highlight socioeconomic differentials in activity and fitness patterns and suggest that improvements in education may represent a pathway through which physical activity levels can be increased and health benefits achieved.

Decline in Physical Fitness From Childhood to Adulthood Associated With Increased Obesity and Insulin Resistance in Adults

OBJECTIVE To examine how fitness in both childhood and adulthood is associated with adult obesity and insulin resistance. RESEARCH DESIGN AND METHODS A prospective cohort study set in Australia in 2004–2006 followed up a cohort of 647 adults who had participated in the Australian Schools Health and Fitness Survey in 1985 and who had undergone anthropometry and cardiorespiratory fitness assessment during the survey. Outcome measures were insulin resistance and obesity, defined as a homeostasis model assessment index above the 75th sex-specific percentile and BMI ≥30 kg/m2, respectively. RESULTS Lower levels of child cardiorespiratory fitness were associated with increased odds of adult obesity (adjusted odds ratio [OR] per unit decrease 3.0 [95% CI 1.6–5.6]) and insulin resistance (1.7 [1.1–2.6]). A decline in fitness level between childhood and adulthood was associated with increased obesity (4.5 [2.6–7.7]) and insulin resistance (2.1 [1.5–2.9]) per unit decline. CONCLUSIONS A decline in fitness from childhood to adulthood, and by inference a decline in physical activity, is associated with obesity and insulin resistance in adulthood. Programs aimed at maintaining high childhood physical activity levels into adulthood may have potential for reducing the burden of obesity and type 2 diabetes in adults.

Exercise-Induced Hypertension, Cardiovascular Events, and Mortality in Patients Undergoing Exercise Stress Testing: A Systematic Review and Meta-Analysis

BACKGROUND The prognostic relevance of a hypertensive response to exercise (HRE) is ill-defined in individuals undergoing exercise stress testing. The study described here was intended to provide a systematic review and meta-analysis of published literature to determine the value of exercise-related blood pressure (BP) (independent of office BP) for predicting cardiovascular (CV) events and mortality. METHODS Online databases were searched for published longitudinal studies reporting exercise-related BP and CV events and mortality rates. RESULTS We identified for review 12 longitudinal studies with a total of 46,314 individuals without significant coronary artery disease, with total CV event and mortality rates recorded over a mean follow-up of 15.2±4.0 years. After adjustment for age, office BP, and CV risk factors, an HRE at moderate exercise intensity carried a 36% greater rate of CV events and mortality (95% CI, 1.02-1.83, P = 0.039) than that of subjects without an HRE. Additionally, each 10mm Hg increase in systolic BP during exercise at moderate intensity was accompanied by a 4% increase in CV events and mortality, independent of office BP, age, or CV risk factors (95% CI, 1.01-1.07, P = 0.02). Systolic BP at maximal workload was not significantly associated with the outcome of an increased rate of CV, whether analyzed as a categorical (HR=1.49, 95% CI, 0.90-2.46, P = 0.12) or a continuous (HR=1.01, 95% CI, 0.98-1.04, P = 0.53) variable. CONCLUSIONS An HRE at moderate exercise intensity during exercise stress testing is an independent risk factor for CV events and mortality. This highlights the need to determine underlying pathophysiological mechanisms of exercise-induced hypertension.

A Comparison of Subjective and Objective Measures of Physical Activity and Fitness in Identifying Associations with Cardiometabolic Risk Factors

PURPOSE To compare the ability of alternative measures of physical activity and fitness to quantify associations with health outcomes. METHODS Associations between a range of subjective and objective physical activity and fitness measures and cardiometabolic risk factors were examined using data from 1,631 Australians aged 26-36 years. Anthropometry, fitness, blood pressure, and fasting blood glucose, insulin, and lipids were measured at study clinics. Participants completed the International Physical Activity Questionnaire (IPAQ) and 7-day pedometer diaries; they also reported sedentary behavior (sitting, television viewing). RESULTS In men and women, associations were strongest for fitness, with those in the highest (vs. lowest) fitness quarter having a 75% to 80% lower prevalence of two or more primary risk factors (waist circumference, high-density lipoprotein cholesterol, and insulin resistance). In men, a 60% to 70% reduced prevalence of two or more risk factors was observed across extreme quarters of IPAQ leisure, IPAQ vigorous, sitting duration, and pedometer measures. Similar reductions in prevalence were observed only across extreme quarters of pedometer activity and television viewing in women. CONCLUSIONS Associations between alternative measures and cardiometabolic risk were relatively independent, suggesting that a range of physical activity and fitness measures may be needed to most accurately quantify associations between physical activity and health.

Love thy neighbour? Associations of social capital and crime with physical activity amongst women

Using a multilevel study design, this study examined the associations between social characteristics of individuals and neighbourhoods and physical activity among women. Women (n = 1405) recruited from 45 Melbourne (Australia) neighbourhoods of varying socioeconomic disadvantage provided data on social factors and leisure-time: physical activity; walking; and walking in ones own neighbourhood. Individual level social factors were number of neighbours known and social participation. Neighbourhood-level social characteristics (interpersonal trust, norms of reciprocity, social cohesion) were derived by aggregating survey data on these constructs within neighbourhoods. Objective data on crimes within neighbourhoods were obtained from Victoria Police. In bivariable regression models, all social variables at both the individual and neighbourhood level were positively associated with odds of physical activity, walking, and walking in ones own neighbourhood. Associations with individual social participation (associated with all three physical activity variables) and neighbourhood interpersonal trust (associated with overall physical activity only) remained significant in multivariable models. Neither neighbourhood crime against the person nor incivilities were associated with any form of physical activity. These results demonstrate that women who participated in local groups or events and, less consistently, women living in neighbourhoods where residents trusted one another, were more likely to participate in leisure-time physical activity. While redressing macro-level social and economic policies that contribute to neighbourhood inequalities remains a priority, public health initiatives aimed at promoting physical activity could consider focusing on fostering social interactions targeting both individuals and communities. Further investigation of causal mechanisms underlying these associations is required.

Longitudinal examination of the family food environment and weight status among children

OBJECTIVE To examine whether aspects of the family food environment were associated with body mass index (BMI) z-score and weight status in children, cross-sectionally and prospectively over 3 years. METHODS Four aspects of the family food environment (breakfast eating patterns, food consumption while watching television, parental provision of energy-dense foods and child consumption of energy-dense food at home and away from home) were assessed with a questionnaire completed by parents of 161 children aged 5-6 years and 132 children aged 10-12 years in Melbourne, Australia in 2002/03. In 2002/03 and 2006, childrens BMI z-score and weight status (non-overweight or overweight) was calculated from measured height and weight. RESULTS At baseline, 19% of younger and 21% of older children were overweight. Three years later, a greater proportion of younger (now aged 8-9 years) compared with older (aged 13-15 years) children were classified as overweight (28% versus 18%). Few of the family food environment variables were associated with childrens BMI z-score and weight status cross-sectionally and longitudinally. However, among older children, more frequent dinner consumption while watching television was associated with a higher BMI z-score longitudinally (B=0.3, 95% CI=0.0, 0.6), less frequent breakfast consumption was associated with higher odds of overweight longitudinally (OR=2.2, 95% CI=1.1-4.7), and more frequent fast food consumption at home was associated with higher odds of overweight cross-sectionally (OR=3.1, 95% CI=1.4-7.0). CONCLUSIONS This study found few significant associations between aspects of the family food environment and BMI z-score or weight status in a sample of Australian children.

Which domains of childhood physical activity predict physical activity in adulthood? A 20-year prospective tracking study

Purpose It is important to examine how childhood physical activity is related to adult physical activity in order to best tailor physical activity-promotion strategies. The time- and resource-intensive nature of studies spanning childhood into adulthood means the understanding of physical activity trajectories over this time span is limited. This study aimed to determine whether childhood domain-specific physical activities predict domain-specific physical activity 20 years later in adulthood, and whether age and sex play a role in these trajectories. Methods In 1985, 6412 children of age 9–15 years self-reported frequency and duration of discretionary sport and exercise (leisure activity), transport activity, school sport and physical education (PE) in the past week and number of sports played in the past year. In 2004–2006, 2201 of these participants (aged 26–36 years) completed the long International Physical Activity Questionnaire and/or wore a Yamax pedometer. Analyses included partial correlation coefficients and log-binomial regression. Results Childhood and adult activity were weakly correlated (r=−0.08–0.14). Total weekly physical activity in childhood did not predict adult activity. School PE predicted adult total weekly physical activity and daily steps (older females), while school sport demonstrated inconsistent associations. Leisure and transport activity in childhood predicted adult leisure activity among younger males and older females, respectively. Childhood past year sport participation positively predicted adult physical activity (younger males and older females). Conclusions Despite modest associations between childhood and adult physical activity that varied by domain, age and sex, promoting a range of physical activities to children of all ages is warranted.