Longitudinal patterns in objective physical activity and sedentary time in a multi-ethnic sample of children from the UK

Background: Children of South Asian decent born in the UK display lower levels of physical activity than British Caucasians although no longitudinal data are available. Objectives: We aimed to investigate change in activity levels over 1 year in a diverse ethnic sample of children residing in London, UK. Methods: Children were categorized into ethnic groups (Caucasian/mixed, Black, South Asian). At baseline and 1-year follow-up, children’s objective physical activity was monitored (Actigraph accelerometer) for at least 1 day. Mixed models were employed to investigate differences in change in activity levels between ethnic groups. Results: A total of 281 children were included in the analyses. South Asians had a significantly greater increase in time spent sedentary at follow-up than those of a Caucasian/mixed ethnicity (B [ratio sedentary/wear time] = 0.024; 95% confidence interval 0.003, 0.046). South Asian children recorded lower moderate to vigorous physical activity at baseline (B = 6.5, 95% confidence interval, 11.1, 1.9 min d1, p = 0.006) although levels remained relatively stable over follow-up and changes did not differ across ethnic group. Conclusions: In a diverse ethnic sample of children from inner city London, those of a South Asian ethnicity exhibited a significantly greater increase in sedentary time over a period of 12 months in comparison with Caucasian/mixed and Black children.