Are young children with asthma more likely to be less physically active?

The Cross-Sectional and Longitudinal Association Between 24-Hour Movement Behavior Compositions With Body Mass Index, Waist Circumference, and Internalizing and Externalizing Symptoms in 6-Year-Old Children

BACKGROUND

Few studies have examined the association between 24-hour movement behaviors and health in children in their first 2 years of primary school. This study aimed to examine how 24-hour movement behavior compositions at age 6 were related to body mass index (BMI), waist circumference, and internalizing and externalizing symptoms at ages 6 and 10.

METHODS

A subsample of 361 children from the HealthNuts cohort study with valid accelerometer data was included in the cross-sectional analysis. Of these, 279 had longitudinal data for social-emotional outcomes and 113 had longitudinal anthropometric data. Children's 24-hour movement behaviors (ie, sleep, sedentary time, light-intensity physical activity, and moderate- to vigorous-intensity physical activity [MVPA]) were assessed over 8 days using accelerometery and activity logs. BMI z score and waist circumference were assessed using standardized protocols, and parents reported on their child's internalizing and externalizing behaviors. Cross-sectional and longitudinal associations were estimated using compositional data analysis and compositional isotemporal substitution analysis.

RESULTS

Overall, 24-hour movement behaviors were significantly related to internalizing symptoms cross-sectionally and longitudinally and BMI z-score cross-sectionally. Results from compositional isotemporal substitution models indicated that replacing sedentary time or light-intensity physical activity with MVPA was associated with fewer internalizing symptoms at ages 6 and 10. Replacing time spent sedentary and in light-intensity physical activity or MVPA with sleep was associated with lower BMI z score at age 6.

CONCLUSION

Spending more time in MVPA relative to other movement behaviors is associated with fewer internalizing symptoms. In additional, spending more time sleeping is associated with lower BMI z score and waist circumference in children.

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Backyard benefits? A cross-sectional study of yard size and greenness and children's physical activity and outdoor play

BACKGROUND

The home environment is the most important location in young children's lives, yet few studies have examined the relationship between the outdoor home environment and child physical activity levels, and even fewer have used objectively measured exposures and outcomes. This study examined relationships between objectively assessed home yard size and greenness, and child physical activity and outdoor play.

METHODS

Data were drawn from the HealthNuts study, a longitudinal study of 5276 children in Melbourne, Australia. We used cross-sectional data from a sample at Wave 3 (2013-2016) when participants were aged 6 years (n = 1648). A sub-sample of 391 children had valid accelerometer data collected from Tri-axial GENEActive accelerometers worn on their non-dominant wrist for 8 consecutive days. Yard area and greenness were calculated using geographic information systems. Objective outcome measures were minutes/day in sedentary, light, and moderate-vigorous physical activity (weekday and weekend separately). Parent-reported outcome measures were minutes/day playing outdoors (weekend and weekday combined). Multi-level regression models (adjusted for child's sex, mother's age at the birth of child, neighbourhood socioeconomic index, maternal education, and maternal ethnicity) estimated effects of yard size and greenness on physical activity.

RESULTS

Data were available on outdoor play for 1648 children and usable accelerometer data for 391. Associations between yard size/greenness and components of physical activity were minimal. For example, during weekdays, yard size was not associated with daily minutes in sedentary behaviour (β: 2.4, 95% CI: - 6.2, 11.0), light physical activity (β: 1.4, 95% CI: - 5.7, 8.5) or MVPA (β: -2.4, 95% CI: - 6.5, 1.7), with similar patterns at weekends. There was no relationship between median annual yard greenness and physical activity or play.

CONCLUSION

In our study of young children residing in higher socio-economic areas of Melbourne yard characteristics did not appear to have a major impact on children's physical activity. Larger studies with greater variation in yard characteristics and identification of activity location are needed to better understand the importance of home outdoor spaces and guide sustainable city planning.