Association between age at onset of independent walking and objectively measured sedentary behavior is mediated by moderate-to-vigorous physical activity in primary school children

RESEARCH ARTICLE Association between age at onset of independent walking and objectively measured sedentary behavior is mediated by moderate-to-vigorous physical activity in primary school children a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 OPEN ACCESS Citation: Aoyama T, Tanaka S, Tanaka M, Okuda M, Inoue S, Tanaka C (2018) Association between age at onset of independent walking and objectively measured sedentary behavior is mediated by moderate-to-vigorous physical activity in primary school children. PLoS ONE 13(9): e0204030. https://doi.org/10.1371/journal.pone.0204030 Editor: William D. Phillips, University of Sydney, AUSTRALIA Received: March 13, 2018 Accepted: September 1, 2018 Published: September 18, 2018 Copyright: © 2018 Aoyama et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information files. Funding: This work was supported by JSPS KAKENHI Grant Number JP24500832 to CT (https://kaken.nii.ac.jp/en/grant/KAKENHIPROJECT-24500832/) and JP13J07359 to TA (https://kaken.nii.ac.jp/en/grant/KAKENHIPROJECT-13J07359/). The funders had no role in study design, data collection and analysis, decision Tomoko Aoyama ID1☯¤a*, Shigeho Tanaka2☯, Maki Tanaka3¤b‡, Masayuki Okuda4‡, Shigeru Inoue5‡, Chiaki Tanaka6☯ 1 Department of Nutritional Epidemiology and Shokuiku, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, Shinjuku-ku, Tokyo, Japan, 2 Department of Nutrition and Metabolism, National Institute of Health and Nutrition, National Institutes of Biomedical Innovation, Health and Nutrition, Shinjuku-ku, Tokyo, Japan, 3 Department of Child Education, Kyoto Seibo College, Kyoto-shi, Kyoto, Japan, 4 Department of Environmental Medicine, Graduate School of Science and Engineering, Yamaguchi University, Ube-shi, Yamaguchi, Japan, 5 Department of Preventive Medicine and Public Health, Tokyo Medical University, Shinjuku-ku, Tokyo, Japan, 6 Division of Integrated Sciences, J. F. Oberlin University, Machida-shi, Tokyo, Japan ☯ These authors contributed equally to this work. ¤a Current address: Japan Society for the Promotion of Science, Chiyoda-ku, Tokyo, Japan ¤b Current address: Department of Early Childhood Education, Kyoto Bunkyo Junior College, Uji-shi, Kyoto, Japan ‡ These authors also contributed equally to this work. * Abstract Objective Age at onset of walking has been shown as an early predictor of physical activity in infants and children. However, little is known about whether age at onset of walking may predict sedentary behavior (SB). The aim of the present study was to examine the association between the timing of onset of walking and objectively measured SB, and whether this association is mediated by moderate-to-vigorous physical activity (MVPA) in children. Methods The subjects were 388 elementary school children aged 6–12 years. Current weight and height data were collected. Birth weight and the age in months the child first walked independently were reported based on the parents’ recall. Children’s SB and physical activity were objectively measured using a triaxial accelerometer (Active style Pro HJA-350IT, OMRON). The following summary outcome variables were derived from accelerometer data: Time (min/day) spent in SB (1.5 metabolic equivalents [METs]) and MVPA (3.0 METs). Results The mean ± SD time (min/day) spent in sedentary was 376 ± 62 and MVPA was 67.6 ± 20.8. Multiple linear regression analyses revealed that a later age at independent walking was PLOS ONE | https://doi.org/10.1371/journal.pone.0204030 September 18, 2018 1 / 13 Children’s sedentary behavior in relation to independent walking to publish, or preparation of the manuscript. There was no additional external funding received for this study. Competing interests: Dr. Shigeho Tanaka received consigned research funds from Omron Healthcare Co., Ltd. This does not alter our adherence to PLOS ONE policies on sharing data and materials. The remaining authors declare no competing interests. associated with increased time spent in SB (β = 0.15, P < 0.001) and decreased time spent in MVPA (β = -0. 18, P < 0.001) after adjusting for gender, birth weight, current age, body weight, schools, and time spent wearing the accelerometer. When MVPA was introduced as a covariate in the model predicting SB, the association between the age at independent walking and time spent in SB was completely attenuated (β = 0.04, P = 0.215), while MVPA was significantly associated with SB (β = -0.61, P < 0.001). Conclusions Our results indicate that infants who walked at a later age spent more time in SB in childhood, and this association is mediated by MVPA. Appropriate interventions which focus on increasing MVPA and thereby reducing SB may be beneficial in infants who demonstrate a later age at onset of independent walking. Introduction Numerous epidemiological studies have identified consistent associations between physical inactivity, defined as “not performing sufficient amounts of moderate-to-vigorous physical activity (MVPA)”[1], and all-cause and cardiovascular disease mortality [2,3]. Sedentary behavior (SB), defined as “any waking activity characterized by an energy expenditure 1.5 metabolic equivalents and a sitting or reclining posture” [4], has also increasingly been recognized as an important risk factor associated with health outcomes [5]. Recent studies have shown that having a high level of SB negatively impacts health after considering the benefits of MVPA [6]. SB is an independent risk factor for diseases and is therefore worth considering in addition to MVPA. Sedentary lifestyles have become major health problem worldwide, and the identification of factors which determine SB is of great importance to public health. Previous reviews have shown that SBs [7] and physical activities [8] track at moderate levels from childhood, suggesting that SB and physical activity (PA) during childhood may have a particularly important role over an individual’s life course. Thus, a better understanding of the determinants of children’s SB and PA is needed in order to effectively decrease SB and increase PA across the lifespan. Systematic reviews have mainly focused on environmental [9], psychological, social, and behavioral [10,11] factors as correlates of SB and PA during childhood and adolescence. Recent evidence also suggests that early-life factors make a significant contribution to SB [12] and PA [13] in young people, and a few studies have shown that indicators of motor development were an early predictor of PA in children [14–16]. A birth cohort study by Ridgway et al. (2009) reported that an earlier age at standing unaided and walking supported i (...truncated)