0233 Associations Between Actigraphic Sleep Measures and Areal Bone Mineral Density in Adolescents

Abstract Introduction Osteoporosis is one of the leading chronic diseases that can have origins in early life through suboptimal bone accretion. We know that diet and physical activity can enhance bone accretion, and there are emerging data suggesting sleep patterns may also be a determinant of bone accretion. We therefore aimed to evaluate the associations between actigraphic nighttime sleep measures with areal bone mineral density (aBMD) in adolescents. Methods Participants were enrolled in the Sleep and Growth Study 2 (S-Grow2), a cohort of typically developing adolescents in 7th grade (12-13y) recruited from the Philadelphia area. Participants wore a wrist actigraphic sleep monitor (GENEActiv, ActivInsights) for two weeks and the motion data were processed using GGIR to estimate sleep patterns. They also completed a dual energy X-ray (DXA) scan to estimate areal bone mineral density (aBMD) at multiple skeletal sites and expressed as age and sex specific Z-scores. Cross-sectional, multiple regression analyses tested the associations of average nighttime sleep measures (sleep duration, timing, and efficiency) with aBMD Z-scores (total body less head, lumbar spine, total hip, femoral neck, and the distal radius). Models included a quadratic term for sleep measures, and adjusted for sex, race, daily minutes of physical activity, body mass index z-score, and dietary calcium intake. Results Participants (n=302) were 65% white and 47% female. Sleep period duration demonstrated a U-shaped association with aBMD z-scores at the femoral neck (p=.023) and total hip (p=.008), with both shorter and longer sleep durations linked to higher areal bone mineral density. Sleep efficiency showed an inverse U-shaped relationship with aBMD z-scores at the distal radius (p=.01), such that both lower and higher sleep efficiency were associated with lower areal bone mineral density. Sleep timing was not associated with any aBMD measures. Conclusion Our cross-sectional results illustrate non-linear relationships between sleep and areal bone mineral density in adolescents aged 12-13y. This cohort is actively being followed up at 1 year intervals in 8th and 9th grades and future analyses will reveal how changes in sleep impact bone accretion during this developmental window. Support (if any) NIH/NICHD R01HD100421