PROJECT SUMMARY/ABSTRACT Major causes of sleep deficiency affect around 40% of children at some point and 11% through adulthood. Causes of pediatric sleep deficiency are defined by adverse dimensions of sleep health. If untreated, early sleep deficiency can contribute to health, behavior, and learning disparities at kindergarten entry that may persist into adulthood. Yet, early causes of sleep deficiency are grossly underdiagnosed in primary care, and few receive evidence-based treatment. Evidence also suggests that sleep deficiency and downstream outcomes are significantly worse for children with family risk factors such as low income, education, and parent mental health. Because these risk factors are unjustly borne by children who are Black or living in poverty, whose families have few resources to seek help outside of primary care, these sleep health disparities reflect a critical early health inequity. Yet, limited research defines inequities in early childhood sleep health and missing from this work is the examination of the effects of racism, housing instability, peak levels of screen media use, and toxic stress on child sleep health. Our long-term goal is to design and test strategies and health policy to prevent and remedy inequities in early sleep health. Our objective in this proposal is to empirically test the sleep health socioecological framework to define how comprehensive multi-level socioecological factors predict inequities in early childhood sleep health. We propose testing 3 specific and 1 exploratory aims: (1) Evaluate the effect of understudied risk factors (racism, housing insecurity, screen media use, toxic stress) on child sleep health; (2) Evaluate the effect of socio-cultural and neighborhood factors on (a) family factors and (b) children's sleeping environment factors; (3) Define the relationship between multilevel ecologies (socio-cultural and neighborhood, family, child sleeping environment) and children's sleep health; and (4) (Exploratory) Explore child stress as a mediator or moderator of multilevel ecologies on child sleep health. Our central hypothesis is that socio-cultural and neighborhood risk factors increase family risk factors, negatively impacting the child's sleeping environment and consequently predicting worse sleep health. We will test these aims and central hypothesis in a micro longitudinal study (three time points over six months) of 550 racially and economically diverse families of young children (20-48 months of age, when sleep health disparities likely develop) in two geographic sites of the Midwest with rigorous multi-level measures (e.g., Geographic Information Systems [GIS], self-report, ecological momentary assessment [EMA], actigraphy, and physiological biomarkers) using structural equation mediation modeling. The project will provide a critical next step to reduce disparities in young child sleep health problems and their downstream effects. It will also provide the opportunity for an ear...