The challenge
In the last 2-3 decades shorter sleep duration has coincided with emergence of the obesity epidemic, leading to speculation that a causal relationship may exist. However, few studies have investigated if sleep duration predicts body fatness, and vice versa if body fatness predicts sleep duration, in early childhood.
What we have done
Parents were asked to report their child’s sleep duration repeatedly between 1-3 years of age and we measured children’s weight, body fat and waist circumference. We found in South Asian children that longer sleep was associated with less body fat and a smaller waist, higher body fatness was further associated with shorter sleep. No associations were found in White children.
What we need to do next
We need to understand those factors that might explain the ethnic differences found. Do South Asian children need more sleep than White children, or might different sleeping patterns provide an explanation? Our data show that South Asian children go to bed later, and sleep more during the day and less overnight than White children. These sleeping patterns are believed to increase obesity risk.
We also need to investigate the mechanisms that may relate shorter sleep to obesity. Is this simply explained by longer exposure to unhealthy lifestyles, including more opportunity to eat during a longer waking day, or do hormonal factors and tiredness encourage overconsumption of high-fat and high-sugar foods, excess TV-viewing and less physical activity? Might obesity impact on sleep quantity by affecting intermediary behaviours that could aid or obstruct sleep, such as physical activity and screen time?
To shed light on some of these questions we are now collecting sleep data more accurately by asking children to wear sensors around their waist for 24h per day. We are further using improved methods to estimate body composition including specialist scales and scanners.
Link to full research
You can read more about this research in the following paper:
Collings, P.J., Ball, H.L., Santorelli, G., West, J., Barber, S.E., McEachan, R.R., Wright, J., 2017. Sleep Duration and Adiposity in Early Childhood: Evidence for Bidirectional Associations from the Born in Bradford Study. Sleep. 40(2).
Paul's work is focused on describing the levels and patterns of physical activity and sedentary time in children and investigating the causes of obesity and cardiovascular disease. He has a BSc in Sports Science from the University of Portsmouth and an MSc in Sport and Health Sciences from the University of Exeter. Paul graduated top at both institutions. He also has an MPhil in Epidemiology from the University of Cambridge, a course on which he later taught. He completed his doctorate with the MRC Epidemiology Unit (University of Cambridge) in 2014 under the supervision of Professor Ulf Ekelund and Dr Soren Brage. During his PhD, Paul was the beneficiary of a Charter Graduate Scholarship from Homerton College. Paul remained in the Epidemiology Unit as a Career Development Fellow before moving to Bradford. He has reviewed articles for numerous journals including PLoS ONE, MSSE and IJO, and has provided invited scientific commentary for the media. Paul has active scientific collaborations with the Universities of Londrina (Brazil), Swansea, Southampton, Loughborough, Cambridge, and the Norwegian School of Sports Science.
