From DEPARTMENT OF CLINICAL SCIENCE, INTERVENTION AND TECHNOLOGY, DIVISION OF PEDIATRICS Karolinska Institutet, Stockholm, Sweden

PHYSICAL ACTIVITY IN SWEDISH AND CHINESE YOUNG CHILDREN AND THEIR PARENTS Elin Johansson

Stockholm 2015

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All previously published papers were reproduced with permission from the publisher. Published by Karolinska Institutet. Printed by Eprint AB 2015 © Elin Johansson, 2015 ISBN 978-91-7676-037-6

PHYSICAL ACTIVITY IN SWEDISH AND CHINESE YOUNG CHILDREN AND THEIR PARENTS

AKADEMISK AVHANDLING som för avläggande av medicine doktorsexamen vid Karolinska Institutet offentligen försvaras i föreläsningssal R64 , Karolinska Universitetssjukhuset Huddinge

Fredagen den 16 oktober 2015 kl. 10.00 Av

Elin Johansson Huvudhandledare: Docent Maria Hagströmer Karolinska Institutet Institutionen för neurobiologi, vårdvetenskap och samhälle Sektionen för fysioterapi Bihandledare: Professor Claude Marcus Karolinska Institutet Institutionen för klinisk vetenskap, intervention och teknik Enheten för pediatrik Professor Ulf Ekelund Norges Idrettshøgskole Seksjon for idrettsmedisinske fag

Fakultetsopponent: Professor Mikael Fogelholm University of Helsinki Department of Food and Environmental Sciences Betygsnämnd: Docent Eva Weidenhielm Broström Karolinska Institutet Institutionen för kvinnors och barns hälsa Enheten för neurologi Docent Maria Ekblom Gymnastik och idrottshögskolan Enheten för prestation och träning Docent Magnus Dencker Lunds Universitet Enheten för klinisk fysiologi och nuklearmedicin

Stockholm 2015

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ABSTRACT Physical activity is believed to affect health, already in childhood. Studies of physical activity in children under the age of three are, however, sparse. The overall aim of this thesis was to explore physical activity and its possible correlates in Swedish and Chinese children, aged one and two, at high and low risk for obesity. Physical activity levels and patterns among parents in Sweden and China were also examined. Study I was a calibration study where children, 15 to 36 months old, were recruited from four preschools in Stockholm, Sweden. Physical activity data, measured with accelerometry, was compared against data from Children´s Activity Rating Scale (CARS). Accelerometer count thresholds for sedentary, low- and high-intensity physical activity was derived (n=26) and cross-validated (n=12). Studies II-IV were explorative cross-sectional studies where physical activity levels, patterns and correlates were examined among one- (Study III) and two-year-old children (Studies II and IV), participating in Early STOPP (Stockholm Obesity Prevention Project) Sweden (Studies II and IV) and China (Studies III and IV). Children and their parents wore an accelerometer for seven days to assess average physical activity (counts per minute) and time spent at different intensities. Differences between weekdays and weekend days were examined as were correlations with sex, body mass index (BMI), motor skills and familyrelated factors. The intensity thresholds developed in Study I were found valid for two-year-old children. Swedish two-year-old children had an intermittent activity pattern with short bursts of high intensity physical activity (Study II). At this age, Swedish children accumulated 2989 (SD 702) counts per minute and spent 57%, 34% and 9% of the day respectively in sedentary, at low- and high-intensity. Chinese children accumulated 1997 (SD 899) counts per minutes and spent 70% of the day being sedentary, 25% at low- and 5% at high-intensity (Study IV). Swedish children varied their activity levels more over the day, compared with their Chinese counterparts (Study IV). In both countries, activity levels were similar on weekdays and weekend days. No association was found between physical activity and sex, BMI, motor skills or any family-related factor at age one (Study III) or two, except for a positive association between fathers’ and boys’ physical activity at age two in Sweden (p