Zahl-Thanem Tonje, Steinsbekk Silje, Wichstrøm Lars
NTNU Social Research, Trondheim, Norway.
Department of Psychology, Norwegian University of Science and Technology, Trondheim, Norway.
Front Public Health. 2018 Oct 24;6:305. doi: 10.3389/fpubh.2018.00305. eCollection 2018.
Moderate-to-vigorous physical activity (MVPA) has a range of health benefits across the life span. Although many putative determinants of children's MVPA have been identified, their causal status is uncertain due to difficulties in adjusting for potential confounders. To inform promotion of children's MVPA we therefore aimed to examine well-known child-, family- and contextual predictors of MVPA in middle childhood, by applying a fixed effects regression approach, which rules out the influence of all unmeasured time-invariant confounders. Two birth cohorts of children living in the city of Trondheim, Norway were invited to participate (82.0% consented). The participants were followed-up biennially from age 6 to 10 years ( = 800) between 2009 and 2014. MVPA in children was recorded by accelerometers and child-, family- and contextual factors were obtained through interviews and questionnaires. Predictors included (i) the child's time outdoors, organized sports participation, athletic self-concept, self-reported screen time and objectively measured sedentariness; (ii) self-reported parental MVPA and actively transporting the child to school; and (iii) parental socio-economic status (SES), access to playgrounds and ballparks, traffic safety, and having a garden. A three-wave prospective study was conducted with a hybrid fixed effects regressions analysis adjusting for all time-invariant confounders to examine predictors of MVPA. Children evidenced increased MVPA when they spent more time outside, spent less time being sedentary and when the family had a garden and lived in a traffic-safe area. Adjusting for measured time-varying and all unmeasured time-invariant confounders renders many previously identified child and family factors without impact on MVPA in children. However, several contextual factors may promote MVPA in middle childhood, and efforts to facilitate children being outside in environments that promote physical activity (e.g., being outside, in gardens, or otherwise traffic safe areas) may prove important.
中等强度至剧烈身体活动（MVPA）在人的一生中具有一系列健康益处。尽管已确定了许多儿童MVPA的假定决定因素，但由于难以对潜在混杂因素进行调整，其因果关系尚不确定。因此，为了为促进儿童MVPA提供依据，我们旨在通过应用固定效应回归方法来研究童年中期MVPA的著名儿童、家庭和环境预测因素，该方法排除了所有未测量的时间不变混杂因素的影响。邀请了挪威特隆赫姆市的两个出生队列的儿童参与研究（82.0%同意）。在2009年至2014年期间，对参与者从6岁到10岁每两年进行一次随访（n = 800）。通过加速度计记录儿童的MVPA，并通过访谈和问卷获取儿童、家庭和环境因素。预测因素包括：（i）儿童在户外的时间、有组织的体育活动参与、运动自我概念、自我报告的屏幕时间和客观测量的久坐时间；（ii）自我报告的父母MVPA以及主动送孩子上学；（iii）父母的社会经济地位（SES）、游乐场和棒球场的可达性、交通安全以及拥有花园。进行了一项三波前瞻性研究，并采用混合固定效应回归分析，对所有时间不变混杂因素进行调整，以检查MVPA的预测因素。当儿童在户外花费更多时间、久坐时间减少以及家庭拥有花园且居住在交通安全区域时，他们的MVPA会增加。对测量的随时间变化的因素和所有未测量的时间不变混杂因素进行调整后，许多先前确定的儿童和家庭因素对儿童MVPA没有影响。然而，一些环境因素可能会促进童年中期的MVPA，努力让儿童在促进身体活动的环境中外出（例如在户外、花园或其他交通安全区域）可能会被证明是重要的。
