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Sleep and physical activity can optimize bone health in children

Scientists at the University of South Australia have pinpointed the ideal balance of daily activities for optimal bone health in children. The study shows that children typically need more sleep, more physical activity, and less sedentary time to build strong bones. 

“Children’s activities throughout the whole 24-hour day are important for their bone health, but until now, we haven’t known the perfect combination of exercise, sleep and sedentary time,” explained study lead researcher Dr. Dot Dumuid.

“Higher levels of physical activity are known to be good for children’s bone health, yet we can’t just increase children’s exercise without impacting their other activities.”

“In this study, we looked at the interrelating factors of physical activity (both light, and moderate-to-vigorous physical activity), sedentary time and sleep, finding an ideal combination that delivers the best daily balance.”

To identify the “Goldilocks Day” for bone health and function, the researchers focused on 804 children between the ages of 11 and 13. The participants were selected from the Child Health CheckPoint study, which collected exercise data from activity trackers, bone measurements from QCT scans, and self-reported information on sleep duration. 

According to the analysis, the perfect day for children’s bone health includes: 1.5 hours of moderate-to-vigorous physical activity, such as running or engaging in sports; 3.4 hours of light physical activity like cleaning or walking; 8.2 hours of sedentary time, such as reading or sitting in class; and 10.9 hours of sleep.

“The ‘Goldilocks Day’ tells us the durations of physical activity, sleep and sitting that are ‘just right’ for children’s optimal bone health,” said Dr. Dumuid. “Up to 90 percent of peak bone mass is achieved by age 18-20, which makes this especially important during childhood and adolescence.”

“Optimizing bone health in children is a key protector against osteoporosis, the leading preventable cause of fracture in adults and a major public health problem with considerable economic and societal costs.”

In Australia alone, 1.2 million people suffer from osteoporosis and 6.3 million people have low bone density. Dr. Dumuid said the current research also emphasizes the importance of sleep for bone health, especially among boys.

“We always talk about getting enough exercise to help build bones, but for children, it’s vital that they also get enough sleep,” said Dr. Dumuid. “Curiously, the study also showed that sleep is more important for boys’ bone health than for girls, with boys needing an extra 2.4 hours of sleep a day. However, boys tended to be at earlier stages of pubertal development than girls, causing us to speculate that the need for longer sleep is related to rapidly changing hormonal processes rather than gender.

“By knowing the best balances and interrelations of sleep, exercise and rest, parents and caregivers can guide their child’s daily activities to put them in good stead for future bone health.”

The study is published in the Journal of Bone and Mineral Research.

By Chrissy Sexton, Staff Writer

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