LAUSR

Non-parametric metrics of interdaily stability (IS), relative amplitude (RA), and intradaily variability (IV) characterize between- and within-day rest-activity rhythms. Prior research has reported differences in these metrics by age and race/ethnicity, but these differences have not been widely assessed in children and adolescents. Therefore, we investigated associations of these metrics with sociodemographic factors across the lifespan, including children, in a US-representative cross-sectional study. Rest-activity metrics were derived from actigraphy data (wrist-worn GT3X+ ActiGraph devices) measured over one week in the 2011-2014 National Health and Nutrition Examination Survey (NHANES). Pregnant participants and participants with < 4 days of valid data were excluded; missing activity data were imputed and pooled using Rubin’s rule. Population-weighted linear and ordinal logistic regression (quartiles) models were fit to examine the associations of age, gender, smoking, body mass index (BMI), income-to-poverty ratio, and self-reported race/ethnicity with rhythmicity measures. Stratified analyses by age groups were conducted. There were n=12,526 participants aged 3-80 years. In adjusted analyses, IS and RA (higher: stronger rhythms) decreased with age and were lower among men, whereas IV (higher: weaker rhythm, greater fragmentation) increased with age (p< 0.05). Higher income-to-poverty ratio associated with higher RA (1-unit OR=1.11, 95%CI:1.06,1.16) and IV (1-unit OR=1.10, 95%CI:1.07,1.13). Greater BMI associated with lower RA and IS and higher IV (p< 0.05). Smoking associated with decreased values for all metrics. Compared to the non-Hispanic White group, the Asian, non-Hispanic Black, and Other/Multiracial groups were more likely to have lower RA, lower IS, and higher IV (p< 0.05). Compared to the non-Hispanic White group, the Mexican American (OR=0.83, 95%CI:0.72,0.95) and Other Hispanic (OR=0.83, 95%CI:0.73,0.94) groups were less likely to have higher IV. Analyses stratified by age (≤18, >18 years) resulted in similar patterns among the Asian, non-Hispanic Black, and Other/Multiracial groups (p< 0.05). Rest-activity rhythms differ by age, gender, BMI, income, smoking, and race/ethnicity, representing possible windows for public health intervention and sleep health promotion. Differences in rest-activity measures by race/ethnicity begin in childhood, are evident in early adolescence, and persist throughout adulthood. Future analyses will evaluate the contribution of environmental factors to these differences. NIH-NHLBI T32HL007901, R35HL135818