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Researchers Studying Effects of Impaired Sleep on Bone Density in Adolescence
By shafere1 [at] email.chop.edu (Emily Shafer)
Researchers at Children’s Hospital of Philadelphia are going beyond counting sheep while sleeping. They’re using advanced imaging methods to track how sleep patterns may predict changes in bone density and strength from early-to-mid adolescence.
Impaired sleep can have wide-ranging negative effects. This study will determine one more potential consequence: low bone density. Jonathan Mitchell, PhD, assistant professor in the Division of Gastroenterology, Hepatology and Nutrition at CHOP, is leading the project, which is funded by a new grant from the Eunice Kennedy Shriver National Institute of Child Health & Human Development.
Previous research working with animal models and adults linked impaired sleep with lower bone density and increased risk of fracture, according to Dr. Mitchell. However, it is unknown if sleep patterns have an effect on bone gains during childhood, particularly during adolescence, when large amount of bone mass and strength are gained.
“It is important to know the effect of sleep on bone density in children because bone accretion during childhood determines risk for osteoporosis later in life,” said Dr. Mitchell, who is also an assistant professor of Pediatrics at Perelman School of Medicine at the University of Pennsylvania. “The prevalence of osteoporosis is very high, and prevention strategies to optimize bone accretion in childhood are necessary.”
Data has demonstrated a link between the circadian clock genes that regulate sleep-wake patterns, and the dysregulation of both osteoblasts, which are cells that help form bone, and osteoclasts, which are cells that help resorb bone, according to Dr. Mitchell. Osteoblasts are particularly active during adolescence, when children are accruing bone.
Preliminary data from another study Dr. Mitchell conducted revealed an inverted U-shaped association between sleep duration and areal bone mineral density: Both longer and shorter sleep was associated with lower bone mineral density and lower bone strength. The researchers used data from dual energy X-ray absorptiometry (DEXA) scans to determine bone density.
Dr. Mitchell and colleagues will again be using DEXA scans to conduct this prospective, longitudinal study. The study will include adolescents in the seventh grade (ages 12 to 13 years) who are generally healthy and receiving primary care through CHOP. They will undergo DEXA scans to measure bone density and high-resolution peripheral quantitative computed tomography (pQCT) to determine bone strength. The adolescents will undergo these measurements in seventh grade, eighth grade, and ninth grade.
In addition to the DEXA scans and pQCT, the adolescents will wear actigraphy devices to measure their sleep patterns. They will wear the devices for two weeks, which Dr. Mitchell said should give a good snapshot of their usual sleep patterns.
“We can infer sleep patterns based on arm movements and limb movements, and determine various sleep-related measurements, such as how long it takes them to fall asleep, nighttime awakenings, differences in sleep on school nights vs. weekend nights, etc.,” Dr. Mitchell said. “We will use these sleep measures to do an association analysis with how their bone accretion occurs during adolescence.”
There will be three cohorts of children, each with at least 100 children, with a planned sample size of 350 children. The first cohort of children is expected to be enrolled in fall 2020.
“If our early results hold, and we replicate and build on our initial inverted U-shaped associations, then we will have identified a new approach to help optimize bone accretion in childhood,” Dr. Mitchell said. “This will lead us to pursue sleep promotion efforts, and to evaluate in experimental trials if improving sleep patterns does indeed lead to improvement in bone health during critical periods of growth.”